Module 1(intro To Civil Engg).pdf

Introduction to Civil Engineering

Ramachandran V

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Kerala Technological University which has just come into being in 2014 has formulated a new syllabus for the first and second semester students. One of the compulsory subjects for them is Introduction to Civil Engineering. I was teaching the subject for the last couple of years. Though there are a large number of text books on the subject, the students have to refer to more than one book. It was felt that there was a need to make available all the subject matter in one place and this prompted me to compile the book as per the syllabus of K Tech University. Some topics like cement concrete, RCC etc which have not been included in the K Tech University syllabus have been incorporated in this book for sake of continuity. Attempt has been made to present the topic in a very simple and lucid language with a large number of illustrations. In order to make clear the steps of lay out of buildings, brick masonry (English bond and Flemish bond) few video clips have been included. At the end of each chapter, the main points to be revised and remembered are given as “Points to Ponder”. Also a good number of questions have been given at the end of each chapter for practice. Hope that the students will be able to take full advantage of the book. Comments/suggestions are most welcome!

Ramachandran V

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(As per Kerala Technological University - 2015) 1. General Introduction to Civil Engineering 2. History of Civil Engineering 3. Relevance of Civil Engineering in the Overall development of the country 4. Type and classification of structures : Buildings, Towers, Chimneys, Bridges, Dams, Retaining Walls, Water tanks, Silos, Roads, Railways, Runways, Pipe lines 5. Definition and type of buildings as per National Building Code of India 6. Selection of site 7. Components of buildings and their functions 8. Setting out of a building 9. Stones 10. Bricks 11. Tiles 12. Aggregates 13. Cement mortar 14. Stone masonry 15. Brick masonry 16. Timber 17. Steel 18. Floors 19. Roofs

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Chapter

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Introduction 1. General Introduction to Civil Engineering

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2. History of Civil Engineering

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3. Relevance of Civil Engineering in the development of the country

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4. Types and classification of structures

17

5. Definition and Type of Buildings as per National Building Code

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6. Components of a Residential Building

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Building Materials 7. Stones

48

8. Bricks

53

9. Tiles

64

10. Cement

70

11. Aggregates

77

12. Cement Mortar

86

13. Cement Concrete

90

14. Iron & Steel

101

15. Reinforced Cement Concrete (RCC)

107

16. Timber

111

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Construction 17 Selection of site

122

18 Setting out of a building

125

19. Stone Masonry

127

20. Brick Masonry

134

21. Floors and Flooring Materials

145

22. Roofs and Roof coverings

149

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1. General Introduction to Civil Engineering Engineering is the oldest profession in the technical field and Civil Engineering is the oldest branch of Engineering. Civil engineering deals with the planning, design, construction and maintenance of buildings, roads, railways, airports, seaports, dams, canals, bridges, water supply and sewerage systems. Though in olden times, there was no formal education in the engineering field, construction of various structures like pyramids of Egypt, Taj Mahal of India, Tower of Pisa. Italy were carried out by the local artisans with their traditional knowledge and experience. The well designed towns of Mohanjo Daro and Harappa were built with properly planned and designed roads and sanitary networks around 2600 BC.

. It is reported that our ancestors lived in caves and tree tops. Later on they shifted to huts made of twigs and leaves. In the modern world, it has been recognized that it is the state’s responsibility to provide its citizens the basic amenities like food, shelter (house) and clothing. Civil Engineering has many branches like – Structural Engineering, Geotechnical Engineering, Transportation Engineering, Water resources Engineering, Environmental Engineering, Earthquake Engineering etc. Geotechnical Engineering: This subject deals with soils, rock and foundations of all structures like buildings, roads, railways, dams, tunnels etc. Before starting any work, soil samples are required to be collected from the field, brought to the laboratory and tested to find out the properties of the soils. The foundations are then designed taking into account the load of the structure. Structural Engineering: This discipline deals with the design of different structures. The structure should be safe and should be able to give the service for which it was intended. The load acting on the structure has to be identified and the stresses are to be calculated. The design should be economical also. The loads are dead load, live load, wind load and seismic load. Transportation Engineering: Transportation engineering deals with the construction and maintenance of roads, railways, airways, seaways. For the transportation of men and material a good transportation net work is very essential. This forms one of the essential requirement of the infrastructure development of the country. As far as the roads are connected they connect small villages to the major cities and industrial towns and railways help in trans[porting passengers and goods in large quantities more effectively.. Environmental Engineering: This deals with water supply and sanitary engineering. Water is an essential item for drinking, irrigation, sanitation, hydropower generation etc. The waste 7

accumulated both in solid and liquid form has to be collected, treated and disposed off so that the environment is neat and clean. The atmosphere is now a days polluted due to large scale vehicles on the road, major industries and over population. Necessary steps are to be taken to reduce the effect of pollution. Water Resources Engineering: This discipline of civil engineering deals with the management of quantity and quality of water in the underground and above ground water resources, like rivers, lakes ponds and streams. The availability of water from these sources are to be analysed and actual use planned accordingly. Water as told earlier is required for irrigation, industries, drinking and transportation. Earth Quake Engineering: Earth quakes are certain tremors from the inside of earth which may create the destruction and loss of property and people.. Of course the loss depends on the intensity of earth quake. As such a civil engineer has to design a structure taking into account this seismic load. This will depend upon the actual location of the place. India has been divided into different zones according to the likely severity of the quake. It is not able to predict in advance when and where the quake may happen. The main objectives of earthquake engineering are: *Foresee the potential consequences of strong earthquakes on civil structures *Design, construct and maintain structures to reduce the after effects of earthquakes Construction Engineering: This branch of civil engineering deals with the construction of various structures like buildings, dams, water supply schemes, roads, railways, air ports, sea ports etc. First detailed engineering survey has to be made. Then design the structure and carry out the construction. Proper quality control has to be made by the site engineer so that the structure will be safe and also it should be economical. The work should be completed within the target dates as to avoid cost escalation. So many software packages are available now a days for design, drawing and project planning. Hydraulic engineering: This branch of civil engineering deals with the flow and conveyance of fluids, mainly water and sewage. The knowledge on this subject is required for the design of bridges, dams, channels, canals, water supply and sanitary engineering. Hydraulic engineering is the application of fluid mechanics principles to problems dealing with the collection, storage, control, transport of water and sewage. The hydraulic engineer has to study the effect of scour on bridges and other structures.

Surveying: Before starting a new project a survey has to be made with respect to its alignment, level, feature on the way and surroundings. The project can be a road, railway, airport, dam or other structure.. Surveying is the art of determining the relative position of points on the surface of earth with respect to its direction, magnitude and level. There are different surveys depending on the type of instruments used, purpose of survey etc. The main instruments in this connection are – chain, leveling instrument, theodolite, tachometer, total station etc. After the survey, plans are to be prepared.

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2. History of Civil Engineering It is very difficult to specify the history of the beginning of civil engineering. Our ancestors ate fruits, drank water from streams and slept in caves or on top of trees. Then they felt the need of a house for protection from rain and other atmospheric effects. They cut the trees and using the logs constructed small huts. The construction of Pyramids in Egypt (2700 - 2500 BC) is considered to be the first major civil construction. Ancient historic civil engineering constructions include the Great Wall of China (312 BC), Irrigation projects in China (around 220 BC); Julius Caesar's Bridge over the Rhine River( 55 BC), Taj Mahal (Agra), Red Fort (Delhi), Golden Temple (Amritsar), Hawa Mahal (Jaipur), Ellora Caves( Nasik), Guruvayoor Srikrishna Temple (Kerala), Maha Budha Temple (Gaya), Malankara Orthodox Church (Kerala) in India.

Great wall of China (312 BC)

Pyramids of Egypt (2700-2500 BC)

Tajmahal of india (1632) In the earliest period, the construction of structures were done using mud, stone and lime mortar. Though there was no formal education, they could design and construct such magnificent structure which are still in existence without any serious deterioration. 9

One of the most essential requirements of human beings is food. For raising food crops, irrigation is required. History of Irrigation Development in World Archaeological investigation has identified evidence of irrigation in Mesopotamia and Egypt as far back as the 6th millennium BCE, where barley was grown in areas where the natural rainfall was insufficient to support such a crop. In the 'Zana' Valley of the Andes Mountains in Peru, archaeologists found remains of three irrigation canals dated from the 4th millennium BCE, the 3rd millennium BCE and the 9th century CE. These canals are the earliest record of irrigation in the New World. The Indus Valley Civilization in Pakistan and North India (from 2600 BCE) also had an early canal irrigation system. Large scale agriculture was practiced and an extensive network of canals was used for the purpose of irrigation.

Drawing water from well using bullocks Engineering Education The first engineering school, The National School of Bridges and Highways, France, was opened in 1747. In 1818, world’s first engineering society, the Institution of Civil Engineers was founded in London. The institution received a Royal Charter in 1828, formally recognizing civil engineering as a profession. Its charter defined civil engineering as: “Civil engineering is the application of physical and scientific principles, and its history is intricately linked to advances in understanding of physics and mathematics throughout history. Because civil engineering is a wide ranging profession, including several separate specialized sub-disciplines, its history is linked to knowledge of structures, material science, geography, geology, soil, hydrology, environment, mechanics and other fields.” The first private college to teach Civil Engineering in the United States was Norwich University founded in 1819. The first degree in Civil Engineering in the United States was awarded by Rensselaer Polytechnic Institute in 1835. In India, engineering education started with the opening of School of Survey in 1794, which became the Civil Engineering School in 1858 and was rechristened as College of Engineering in 1859 in Chennai (Madras). The Thomason College of Civil Engineering, Roorkee,(Uttar Pradesh) was started in 1847.whicht was given university status in 1949 and was converted to Indian Institute of Technology (IIT) in 2001.

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3. Relevance of Civil Engineering in the Infrastructure Development of the Country

Civil Engineers have a major role to play in the development of a nation as they have to make the necessary infrastructure in terms of buildings, transportation net work, dams, irrigation canals, power generating stations etc. Infrastructure can be defined as the physical and organizational structures and facilities like buildings, roads etc. needed for the operation of a society. They are required for the economic development of the country. Civil Engineering has got various branches like Geotechnical Engineering, Structural Engineering, Transportation Engineering, Environmental Engineering, Surveying - each discipline dealing with a particular aspect. In general, the functions of a Civil Engineer are Planning, Design, Construction and Maintenance of different Civil Engineering structures. The infrastructure requirements can be broadly grouped under the following categories: Buildings, Roads, Railways, Bridges, Airports, Dams and Canals, Electric Power Stations, Factories, Industrial Town ships

Buildings are required for dwelling, schools, industries, offices, hospitals, factories etc.

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Bridges are required for crossing rivers and other obstacles for both rail and road network.

Food is an essential item for all - rich and poor. Agricultural fields are to be raised and maintained properly.

For raising food production irrigation is to be effective. For this dams are required. The stored water can be used for drinking and hydroelectric power in addition to irrigation.

For transporting men and material from one end of the country to the other end railways are a must.

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For linking villages to towns, cities and industrial towns roads are required

For faster and quicker transport of passengers and goods air transport is the only solution.

Electric power is required for almost are operations – domestic, commercial or industrial purposes. The power is generated though hydro electric, thermal or nuclear power stations.

One of the parameter to measure the progress of a country is its industrial production. This can be the in the small scale sector or large scale sector. Conventional building materials like stone, brick, timber etc are still in vogue, but two materials which have completely revolutionized the construction industry are cement and steel. From a 13

small one room house to a multi- storey buildings, dams, power houses, air ports, rail sleepers, concrete roads, tunnels, bridges etc all are being constructed with concrete and steel. Computers are now extensively used for design, drawing and planning of various civil engineering works. Also micro controllers are being used in various machineries used in construction activities. In the present day world ―going green‖ is on top priority in our society. Reusing materials from existing sites is an upcoming trend in the new environment. Engineers play a very critical role in planning, developing, building and maintaining nation’s infrastructure. Ultimately, the engineering profession uses its expertise, experience and knowledge help to create a safer, more sustainable, and prosperous future for the country. Engineers balance social, environmental and economic considerations to find the best solutions to complex challenges. They have a responsibility to manage the risks associated with their work, and the impacts on the public and on the environment. The progress made by the nation in the successive five year plans is an eye-opener. The progress can be seen in all spectrum - Irrigation, Agriculture, Hydro electric power, Roads, Railways, Air ports, Sea ports, Techno / I T parks, Communication network, Cement, Steel and other heavy and light Industries. Some recent remarkable infrastructure developments in India For any country, its infrastructure is a matter of pride. During the last few years phenomenal change has taken place in sectors like buildings, roads, railways, airports etc leading to world class facilities in various parts of the country. Few such projects are briefly described here. 1. Mumbai’s Eastern Freeway – India’s second largest Fly over - More than 25000 vehicles are expected to take the freeway daily. The 17 km freeway is divided in three parts- 9.29 km elevated road, 4.3 km road-tunnel, and an elevated 2.5 km fly over.

2. Udhampur-Katra rail link (Kashmir) – The work on this line is complete. Pilgrims to Vaishnodevi temple can travel directly to the base camp at Katra. Constructed at an estimated cost of Rs 1050 crores, the route consists of seven tunnels, 30 small and big bridges.

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3. Indore’s BRTS road route- Built at a cost of Rs135 crores, the BRTS consists of physically separated bus lanes and metro like stations.

4. Double decker train from Chennai to Banglore – The fully air- conditioned train started its run on April 25, 2013.

5. India’s first solar park at Caranka village in Gujarath – This is country’s first solar park. Spread across 5000 acres it has 500 MW of generation capacity of both solar and wind energy.

6. Yamuna Expressway (Greater Noida to Agra) – The 165 km long Yamuna Expressway is the longest access controlled six-lane rigid pavements in India.

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7. India’s longest rail tunnel – The 11 km tunnel across PirPanjal mountain range on the Bani hal – Quazigund railway line in Jammu Kashmir.

8. Lulu Mall. Kochi – Constructed at a cost of Rs1600 crores at Edappally, Cochi in 25 lakh square feet complex

9. India’s Life line Express (World’s first hospital train)- Established in 1991, this train has travelled the length and breadth of the country bringing the medical aid to the most farflung inaccessible areas.

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4. Types and Classification of Structures There are different types of structures like buildings, roads, railways, air ports, towers etc. A brief description of these structures is given below: Buildings

A building is a man-made structure with proper foundation, wall, roof and other building services. It may be of mud, stone or cement blocks. The building may be for various purposes – residential, commercial, industrial, educational, religious…..It may be of various sizes and shapes National Building Code of India (2005) defines a building as a structure for any purpose built of any material. The building may be of single storey or multi-storey structure. In the last few years the cost of construction has sky rocketed due to the rise in the cost of building materials as well the increased labour cost. The cost of land has also gone up considerably. Earlier the practice was to construct single storey or two storey buildings. But the trend has completely changed due to the paucity and high cost of land and the increased demand for houses. The old system of combined family has disappeared and the trend is for miniature families. So now multistory residential complexes are being constructed. One factor which has to be taken into connection in this regard

is the Floor Area Index (FAI).

FAI = Covered area of all floors X 100

Plot Area Along with residential buildings. more buildings are required for industries, government offices, private business establishments, educational institutions etc. One important factor is the economy of construction. The space has to be effectively utilized. Green buildings are the requirement of the day. Modern construction techniques and selection of good building materials also will affect in reducing the cost of construction. Towers A tower is a tall structure. There are different towers like clock tower, transmission tower, bell tower, radio tower, communication tower etc. They are not intended for living .but for specific purposes like:

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Eiffel Tower Electricity transmission tower- for distribution of electric power Communication tower- for transmission of communication signals like microwave Radio tower - for transmission of radio signals Bell tower – for hanging bells in churches Tourist tower – As a tourist attraction for the tourists to see (Eiffel tower in Paris, Leaning tower of Pisa, Italy etc)

The towers are normally constructed with steel sections like angle, I section, Channel, square section etc and are connected at the junctions through welding or bolt and nut.

Chimneys

A chimney (flue) is a structure intended for the passing off smoke, hot flue gases

from furnace or fireplace to the outside atmosphere. Chimneys are kept in vertical position so that the gases pass smoothly. Chimneys can be found in buildings, steam locomotives, ships, brick kilns, factories etc.. Since in factories the pollutant gases are passed out through tall towers, the surrounding area is not polluted. In addition, the dispersion of pollutants at higher altitudes can reduce their impact on the immediate surroundings. The cross section of a chimney may be square, rectangular or circular with smooth finish inside. The height of the chimney stack should be at least one meter above the roof level. In big factories, tall chimneys are provided to pass the exhaust gases and smoke at a higher level. The following points must be kept in mind while constructing a tall chimney-

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-Refractory brick lining should be provided inside a chimney when the temperature is expected to exceed 750 degree centigrade. -The total height of the chimney shaft should not exceed 12 times the external diameter at the base or 10 times the least lateral dimension at the base for chimneys of rectangular section. The general practice is to construct the chimneys in lime mortar than cement mortar because cement mortar is likely to disintegrate at high temperature. - Wind pressure must be taken into account when designing a chimney.

Bridges

A bridge is a structure built to cross an obstacle. The obstacle may be a river, railway line, road or canal. Classification Bridges are classified in different ways according to: Material of construction - Timber, Masonry, Steel, RCC, PSC. Purpose (Function) - Railway bridge, Road bridge, Pedestrian bridge, Aqueduct (bridge over a valley), Viaduct (canal over a river) Position - Deck bridge, Through bridge, Semi through bridge Superstructure - Slab bridge, Truss bridge, Suspension bridge, Cable stayed bridge Length - Culvert (less than 6 m, Minor bridge (6 to 60 m), Major bridge (above 60 m) Method of connection of different parts- Rivet, weld, Pin Position - Straight, Skew Selection of site The following points are to be considered in selecting the site of the bridge – The site should be easily approachable, Width of the river should be minimum, Firm and stable banks, Suitable foundation, Right angled crossing The components of a bridge are Abutments, Pier, Deck Slab, Hand- rail, Beam, Bearings, Approaches, Parapet 19

Dams Dams are structures constructed across rivers to store water. The water may be used for drinking, irrigation or hydro electric power generation.

There are different types of dams – Based on functionStorage dam – This is constructed to store water. The stored water may be used for irrigation, drinking or hydro electric power generation. Flood control dam – This is temporarily constructed to store the flood water and release it slowly so that the down- stream side is safeguarded against the damaging effects of floods. Diversion dam - This is constructed to divert the water from the river to a channel. Coffer dam – A temporary structure constructed to divert water so that the new dam or bridge can be constructed. Based on material of construction – Earthen dam , Masonry dam , Concrete dam

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Retaining Walls

Retaining walls are walls made of concrete or masonry to retain soil. Generally they are constructed on the approaches to bridges, for making gardens in sloping grounds and to protect soil from erosion etc. To design a retaining wall, it is required to find out the pressure exerted by the soil on the retaining wall. This can be found out by using Rankin’s theory or Coulomb’s theory. The pressure depends on the unit weight of soil, angle of internal friction, cohesive strength of soil and height of the wall. There is a tendency for the retained material to move down the slope due to gravity. This creates lateral earth pressure behind the wall which is termed as active earth pressure. If the retaining wall yields towards the retained soil. the wall is subjected to passive earth pressure. If there is no movement, the earth pressure is called earth pressure at rest.

Water tanks

A water tank is a container to store and distribute water. The water may be used for drinking ,irrigation or fire suppression. It can be at the ground level or on an elevated stage. They may be of steel, concrete or plastics and of circular or rectangular in shape. Now a days for rain water harvesting also tanks are being used. Rainwater tank (sometimes called a rain barrel ) is a water tank used to collect and store rain water runoff from roof tops via rain gutters. A rainwater catchment or collection (also known as "rainwater harvesting") system can yield 2358 litres of water from 2.54 cm of rain on a 93 m2 roof area. Rainwater tanks are devices for collecting and maintaining harvested rain. These tanks are installed to use rain water for later use. and aid selfsufficiency. Stored water may be used for watering gardens, agriculture, flushing toilets, in washing machines, washing cars, and also for drinking, especially when other water supplies are unavailable.

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Underground rainwater tanks can also be used for retention of storm water for release at a later time.

Silos

Silo is a structure, typically cylindrical in shape in which grain, cement or other materials are stored. There are different types of silos such as the low-level mobile silo and the static upright silo. Mobile silos are normally of capacities from 10 to 75 tons. They are simple to transport and are easy to be set up on site. These mobile silos generally come equipped with an electronic weighing system with digital display and printer. This allows any quantity of cement or powder discharged from the silo to be controlled and also provides an accurate indication of what remains inside the silo. The static upright silos (Tower silos) have capacities from 20 to 80 tons. They are also cylindrical in shape, 4 to 30 m in diameter and 10 to 84 m in height. The stored materials are unloaded into wagons, trucks or conveyors. Silos can be of steel or concrete. The main differences between concrete and steel silos are: 

All steel silo parts are manufactured in a factory, so the quality can be totally controlled, whereas cast in place concrete silos involve more variables such as delivery of concrete and weather.

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The slip frame concrete process is slightly complicated. Also, field supervision plays a really important role in concrete silos: More workers have to be employed and also it takes more time for construction. Ultimately the cost of construction shoots up. Concrete silos can be taller than steel silos. It is easier to erect steel silos and also to install accessories like doors, ladders, samplers, etc. Steel structure is more flexible, so steel silos have better behavior in case of earthquake.

    

Regarding air tightness, both structures are normally airtight if the openings are properly sealed. Steel silos generally give more storage capacity.. They tend to be more cost-effective because of the higher storage capacity.

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It is easier and more effective to do aeration in steel silos.

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Roads

Roads are for the transport of men and material from one part of the country to another part. In India, roads are classified under the following categories - National High way, State Highway, Major District Road, Other District Road and Village Road. There is now a new classification as Express Way. The road structure has the following components – Sub grade, Sub base, Base, Base Coat and Wearing Coat.

Typical X section of a flexible pavement Before upgrading and widening an existing highway, a traffic survey is to be conducted to collect information about the traffic density, direction of movement of vehicles, origin – destination of vehicles, type of vehicles, type of soil, geographic details including anticipated future development. AS far as the geometry of roads are concerned, on curves the outer portion is slightly rais with respect to the inner side. This is known as cant (super elevation). This is provided to counteract the centrifugal force of the vehicle. This will depend on the degree of curvature and speed of vehicle. Also to drain out rain water, side slopes are to be given to the wearing surface.

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Runways

A runway is a rectangular area of land in an airport prepared for the landing and takeoff of aircraft. Runways may be a man-made surface (asphalt, concrete, or a mixture of both) or a natural surface. It is generally paved. Shoulders are provided on either side of a run way. They act as safety zones should an airport move out of the runway during take off or landing. Stop ways are provided at the ends of a run way to accommodate an aircraft that overshoots or undershoots a run way during landing or an aborted take-off. Runways are named by a number between 01 and 36, which is generally the magnetic azimuth of the runway's heading in deca degrees: A runway numbered 09 points east (90°), runway 18 is south (180°), runway 27 points west (270°) and runway 36 points to the north (360° rather than 0°). Air ports are of two types: Civil airports, Military airports The selection of a site for an airport depends on – Economic factors, Commercial factors, Meteorological factors, Physical and Engineering factors.

Typical Layout of Air port

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The capacity of an airport is defined as the number of aircraft operations during a specified interval of time corresponding to a tolerable level of delay. The factors that affect the capacity of an airport are: -The number of runways and whether they are used for both arrivals and take-offs or separately for arrivals and take-offs. - Orientation and configuration of runways -The taxiway -The efficiency of traffic control facilities -Weather conditions A single runway used both for arrival and departure can have an annual capacity of 170,000 to 215,000 air craft operations. In an emergency, military aircrafts may land on Express Highways. Recently this facility was tested by landing and taking off a military aircraft on Delhi Agra Express Highway.

Railways

Railways are the life lines of a nation. For transporting men and material railway net work is very essential. It was in 1853 that the first train started its maiden journey from Bombay to Thana a distance of 15 Kms. Now Indian railways have got 65000 route Kms of track, carrying about 23 million passengers per day by 19000 trains connecting about 8000 stations.. It also runs about 7,000 freight trains carrying about 3 million tonnes of freight every day. It is the largest Government department and is the only department which has got a separate annual budget. Trains run over two rails which are kept at a specific distance .on a transverse member called sleeper. The distance between the two rails is called gauge which is 1676 mm for Broad gauge and 1000 mm for Metre gauge track. Below the rails, there is a layer of broken stones (ballast) of about 20 cm. Previously the sleepers were of wood, steel or cast iron. But now concrete sleepers are being used. Similarly earlier the trains were hauled by steam locomotives but now the same are hauled by diesel or electric locomotives. 25

The railway is administered by the Railway Board composed of Chairman and four other Members. The whole rail network is divided into different zones which are headed by a General Manager. The zone is further subdivided to Divisions. and Sub divisions. For design, development and standardization of railways there is a separate organization under the Ministry of Railways called Research Designs and Standards Organisation (RDSO) based at Lucknow. Pipelines

Pipeline transport is the transportation of goods through a pipe. As per statistics of 2014, total of about 3.5 million km of pipeline is there in 120 countries of the world. The United States has 65%, Russia 8%, and Canada 3%, thus 75% of all pipe line is in these three countries Liquids and gases are transported through pipelines. Pipelines exist for the transport of crude and refined petroleum, fuels - such as oil, natural gas and bio fuels - and other fluids including sewage, slurry and water. Pipelines are useful for transporting water for drinking or irrigation over long distances. Pneumatic tubes using compressed air can be used to transport solid capsules. Oil pipelines are made from steel or plastic tubes which are usually buried underground. The oil is moved through the pipelines by pumping from stations along the pipeline. Natural gas (and similar gaseous fuels) are lightly pressurised into liquids known as Natural Gas Liquids (NGLs). Natural gas pipelines are constructed of carbon steel. Highly toxic ammonia is theoretically the most dangerous substance to be transported through long-distance pipelines. Hydrogen pipeline transport is the transportation of hydrogen through a pipe. Pipelines conveying flammable or explosive material, such as natural gas or oil, pose special safety concerns and there have been various accidents. Pipelines can be the target of vandalism, sabotage, or even terrorist attacks. In war, pipelines are often the target of military attacks. Advantages of transport through pipes:   

Large-scale transportation of natural gas by tanker truck or rail is not feasible Pipelines are a safe and efficient means of transporting large quantities of crude oil and natural gas over land. Pipelines are more cost-effective than the alternative transportation options 26

 

They require significantly less energy to operate than operating trucks or rail and have a much lower carbon footprint Underground pipelines are safe

Points To Ponder

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   

A building is a structure with foundation, walls and roof covering. It is used for dwelling, office, factory, business establishment and other purposes. The size and shape of the building depend on the purpose of the same. Even though there was no formal education, artisans in olden days were able to construct buildings using locally available materials. Some of the structures constructed long back and are still in existence are – The Great Wall of China, Pyramids of Egypt, Leaning tower of Pisa, Tajmahal at Agra, Redfort at Delhi etc. In addition to buildings, there are many other structural elements which are in use like – Chimneys, Towers, Water tanks, Roads, Railways, Airports, Pipe lines etc. Civil engineers have a major role to play in the infrastructure development of the country. For a nation’s development houses, factories, roads, railways, airports, dams, power generating stations etc are required. It is the duty of Civil Engineers to plan, design, construct and maintain these structures.

Model Questions 1.Biefly describe the history of Civil Engineering. 2 What is a building? 3. What is the purpose of a building? 4. What is the role of a civil engineer in the nation building? 5. Briefly explain the following items – Water tanks, Chimneys, Retaining Walls, Silos, Runways, Dams, Towers 6.Explin some of the recent systems in operation as part of India’s infrastructure development.

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5. Definition and Types of Buildings as per National Building Code of India The National Building Code of India (NBC) is a comprehensive building Code. It is a national instrument providing guidelines for regulating the building construction activities across the country. It serves as a Model Code for adoption by all agencies involved in building construction works - the Public Works Departments, other government construction departments, local bodies or private construction agencies. The Code mainly contains administrative regulations, development control rules and general building requirements; stipulations regarding materials, structural design and construction (including safety); and building and plumbing services. Buildings may be classified according to various parameters like occupancy, load transfer, materials used and fire resistance. The National Building Code of India (Part iii 2005) classifies buildings as per occupancy in the following nine groups: Classification of buildings as per occupancyGroup A – Residential Group B - Educational Group C - Institutional Group D - Assembly Group E - Business Group F - Mercantile Group G - Industrial Group H - Storage Group I – Hazardous Group A – Residential Buildings – These are the buildings in which sleeping accommodation is provided for normal residential purposes with or without cooking or dining or both facilities except any building classified under Group C. Group A buildings are further classified as A1 to A5. A1 – Lodging Houses - These are buildings in which under the same management , separate sleeping accommodation for a total of not more than 40 persons on transient or permanent basis with or without dining facilities but without cooking facilities for individuals is provided. A2 – One or two private dwelling houses – These are occupied by members of a single family and have a total sleeping accommodation for not more than 20 persons.

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A3 – Dormitories – These are buildings in which group sleeping accommodation is provided with or without dining facilities for persons who are not members of the same family in a room or a series of closely associated rooms under joint occupancy and single management. Examples – hostels, military barracks A4 – Apartment houses (Flats) –These are buildings under single management in which living quarters are provided for three or more families. A5- Hotels –These are buildings under single management in which sleeping accommodation is provided for hire to more than fifteen persons. Group B: Educational Buildings The buildings used for schools, colleges, or other training institutions that involve assembly during the day for instruction, education are considered educational buildings. Sub divisions B1 – Schools up to senior secondary level with not less than 20 students. B2 – All other training schools with less than 100 students Group C: Institutional Buildings A building or part of a building that is used for the purposes such as medical or other treatment or care of persons suffering from physical or mental illness, disease or infirmity; care of infants, or aged persons in which the liberty of inmates is restricted are categorized as institutional buildings. They normally provide sleeping accommodation for the occupant. They are further sub - divided as: A6 - Hotels (starred) C1- Hospitals and sanatoria C2 – Custodial Institution C3- Penal and mental institutions Group D: Assembly Buildings These shall include any building or part there of where a group of not less than 50 people gather for amusement, recreation, social, religious and for similar purposes. Ex- Cinema halls, theatres, exhibition halls, museums, restaurants etc. These buildings are further sub divided into – D-1: Buildings having stages and fixed seats more than 1000. D-2: Buildings having stages and fixed seats less than 1000

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D-3: Buildings without stages and accommodation for 300 or more persons but no permanent seating arrangements D-4: Buildings without stages and accommodation for less than 300 persons. D-5: All other structures for assembly of people not covered by sub divisions D-1 to D-4. ExCircus tents D-6: Buildings having mixed occupancy providing facilities such as shopping, restaurants etc. D-7: All other buildings for assembly of people not covered under D-1 to D-6 Group E: Business Buildings This group includes any building or part of a building that is used as a shop, store either whole sale or retail. These are sub divided into E1 – E5: Mercantile Buildings F1: Shops, stores markets area upto 50sq m F2: Underground shopping centres, departmental stores with area more than 500 sq m Group G: Industrial Buildings These include buildings or part thereof in which materials of all kinds are manufactured or processed G1- Buildings used for low-hazard Industries: These are buildings where danger to life and property may arise from panic or fire from external sources only. G2- Buildings used for moderate-hazard Industries: The processes in the industries are liable to give rise to a fire that will burn with moderate rapidity. G3- Buildings used for high-hazard Industries; The processes in the industries are liable to give rise to a fire that will burn with extreme rapidity. Group H: Storage Buildings These are buildings used for the storage of goods, vehicles or animals. Group J: Hazardous Buildings These are buildings used for storage, handling, manufacturing of highly explosive materials or products which are liable to burn with extreme rapidity producing poisonous gases or explosions.

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Classification of buildings according to the type of construction: Classification according to method of load transfer Types of structures: Load-bearing structure: The load of roof and floors is transferred to the foundation by thick walls. Framed structure: The load of roof and floors is transferred to the foundation through columns and footings. Walls serve as partitions only. Comparison of load bearing and framed structure: Load bearing structure *Load from roof and floors are transferred to

Framed structure *Transferred through columns and footings

foundation by walls *Walls need foundation throughout

*Footings are required for columns only

*Thickness of load bearing walls should be

*Only exterior walls need 200 mm thick,

at least 200mm *Too many openings for doors, windows and

others need 100 mm thick only * No restriction

ventilators are not permitted *Suited for residential purpose - one or two

*Suitable for multi storey buildings

storey only Classification of buildings according to the materials used RCC structure, Steel Structure, Composite Structure: Classification of buildings according to fire resistance There are four categories in this regard: Type 1, Type 2, Type 3 and Type 4 construction.

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Points To Ponder

    

National building code of classifies buildings into different categories. The two categories are – buildings based on occupancy and buildings based on type of construction Based on occupancy buildings are further classified into 9 groups – A to I These nine groups are – Residential, Educational, Institutional, Assembly, Business, Mercantile, Industrial, Storage, Hazardous According to the type of construction buildings are classified into – Method of load transfer, According to the material used, According to the fire resistance

Model Questions 1. What s National Building Code? 2.What are the parameters of classification of buildings? 3.Based on occupancy what are the classifications? 4.What are the classifications of buildings according to type of construction? 5.What are the classifications of buildings according to method of load transfer? 6.What are the classifications of buildings according to material used? 7.What are the classifications of buildings according to fire resistance?

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6. Components of a Building and their functions Buildings are of different types - residential, commercial, public utility, educational, recreational etc. The type, size, nature of construction etc of the buildings may vary. Before starting the construction of the structure, a plan of the building has to be prepared. Then the approval of local authority – Panchayat, Municipality or Corporation – has to be obtained. The plan of a building has to be prepared in consonance with the building bye-laws of the state. Components of a building The basic components of a building are: Foundation, Plinth, Column, Wall, Lintel, Door, Window, Floor, Stair, Roof Foundation: The foundation is the lowermost part of a building. It is below the ground level. The purpose of a foundation is to distribute the load of the superstructure to the soil below, give stability to the building and to prevent the overturning of the building.

Plinth: It is the portion of a building between the ground level and the ground floor level. A damp proof course is provided at the top of the plinth. Column: These are vertical members which transfer the load from top to the bottom member. The column can be of timber, steel or concrete. It may be of circular, rectangular or square section. Wall: The wall is also constructed to transfer the load from top to the bottom member. It has got the further function of giving protection to the inhabitants from rain, wind etc. and also privacy.Walls partition the building into different rooms / compartments.

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Lintel: It is a small beam provided over window and door openings to transfer the load from above. It can be of wood, steel or RCC. The width of lintel will be that of the wall. Door and Window: A door is provided to get access to the room and also to lock it for safety. Window is provided in the exterior wall to have light and air circulation. The window area should be 15-20 % of the floor area. Floor: The number of floors depend on the height of the building. The lowermost floor is the ground floor. It is prepared by filling the basement with soil and then compacting it. The top is made by marble, tile or stone. The upper floors are generally of RCC. The thickness of slab wil depend upon the span and the load it is subjected to. Stair: Stair is constructed to go from one floor to the other. It will have a number of steps. A landing is normally provided in between the floors. Roof: It is the topmost part of a building. It serves as a cover for protection from rain, wind and sun rays. The roof can be flat or sloping. It should be leak proof and should give a good look to the building. Building Services: The essential building services are: water supply, sanitary fittings and connections, electric connection, rain water drainage system, cup boards, shelves etc. The details of each component of a building are being described here in :

Foundation Foundation is the lowest part of a structure. It is below the ground level. The purpose of the foundation is to transmit the load of the superstructure to the soil below so that the structure is safe. The engineer has to study the properties of the soil and design the foundation accordingly. It should be ensured that the foundation can safely carry the loads. Requirements of Foundation: -The pressure exerted on the soil should not exceed the safe bearing capacity of the soil. -Settlement of the foundation should be with in safe limit. -The foundation should be rigid.

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Types of Foundations 1. Shallow foundation 2.Deep Foundation A foundation is said to be shallow if its depth is less than or equal to its width. Shallow foundations are also called spread footings or open footings. The 'open' refers to the fact that the foundations are made by first excavating all the earth till the bottom of the footing, and then constructing the footing. There are several kinds of shallow footings: Spread footing, individual footing, combined footing , raft foundation etc. Wall footing (Spread footing): The width of the foundation is gradually increased through steps. Trenches are made to the required depth and width. Then a leveling layer of concrete is spread Over that the foundations are constructed in masonry.

Column footing: Columns normally carry heavier loads. Therefore they require footings which can distribute loads to larger areas. The footings of this type are:  Isolated column footing  Combined footing  Cantilever or strap footing  Continuous footing  Raft or mat footing Isolated column footing: This footing is adopted for independent column. The size of the footing will depend on the load on the column and the type of underlying soil.

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Combined Footing: This is a common footing for two columns. This footing can be rectangular or trapezoidal in shape. This type of footing is adopted when one column is very near the boundary of a plot where there is not sufficient space for the footing.

Cantilever (strap footing) This type of combined footing is adopted when the distance between the columns is quite large .A strap beam is provided connecting the slabs under each column.

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Continuous (Strip) Footing: This type of footing is adopted when more than two columns are to be constructed in one line very close to each other..

Raft Foundation

This is also known as mat foundation. In some cases the individual columns may be heavily loaded or the safe bearing capacity of the soil may be low. In that case, the column footings may overlap each other. Raft foundation is adopted in such situations.

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Grillage foundation: In some buildings, steel columns embedded in concrete are to be constructed. The columns may have to carry heavy loads. In such situations, grillage foundation is adopted. It consists of one or more tiers of steel beams inside concrete. A base plate will be provided at the base of the column.

Deep Foundations 1..Pile foundation 2. Pier foundation Pile foundation: A pile is a slender column of wood, steel or concrete. It is driven into the ground or cast in a bore hole. Classification of Piles according to the load transfer: Friction Piles

Bearing Piles

Friction piles transfer the load through friction between the pile and soil. The length of the pile will depend on the frictional resistance. Bearing piles transfer the load through bearing on a hard strata. For this hard strata should be available at a reasonable depth. Classification of piles according to the material used: Timber piles, Steel piles, Concrete piles Bearing Capacity of Soil: It is defined as the maximum load per unit area which a soil can withstand without yielding. First the maximum bearing capacity of the soil has to be determined. There are different methods of determining the bearing capacity. The safe bearing capacity is then calculated by dividing the maximum bearing capacity by a factor of safety which is usually taken as 2 or 3.

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Determination of bearing capacity of soil 1. Field Tests 2. Laboratory tests 1. Field Tests Plate load test The arrangement for plate load test is given in the figure below. Plate load test The arrangement for plate load test is given in the figure below.

Plate load test arrangement For this test, first a pit is made at the desired depth. A test plate is kept at the centre of the pit. The load is applied in steps and the settlement noted. The pressure vs settlement is then plotted. The ultimate bearing capacity is then calculated. The safe bearing capacity is the ultimate bearing capacity divided by factor of safety.( 2 or 2.5) Standard Penetration Test (SPT) The Standard Penetration test (SPT) is an in- situ testing method to determine the engineering properties of subsurface soils. It is a simple test to estimate the relative density of soils and approximate shear strength parameters. In Standard Penetration Test (SPT) a standard thick-walled sampling tube is driven into the ground at the bottom of a borehole by blows from a slide hammer with standard weight and falling distance. The sampling tube is driven 150 mm into the ground and then the number of blows needed for the tube to penetrate each 150 mm (6 in) up to a depth of 450 mm (18 in) is recorded. The sum of the

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number of blows required for the second and third 6 in(150 mm) of penetration is reported as SPT blow value, commonly termed the "N-value". The N-value provides an indication of the relative density of the subsurface soil, and it is used to estimate the approximate shear strength properties of the soils.

Correlation between SPT (N value), friction angle, and relative density Correlation between SPT-N value and friction angle and Relative density (Meyerhoff 1956)

SPT N3 [Blows/0.3 m]

Soil packing

Relative Density [%]

Friction angle [°]

<4

Very loose

< 20

< 30

4 -10

Loose

20 - 40

30 - 35

10 - 30

Compact

40 - 60

35 - 40

30 - 50

Dense

60 - 80

40 - 45

> 50

Very Dense

> 80

> 45

2.Laboratory tests: Undisturbed soil samples are collected from the field and tests conducted in the laboratory to determine the shear strength of soil. Bearing capacity is then calculated. Presumptive Bearing Capacity National Building Code has recommended safe bearing capacity for different soils. Type of soil

Safe bearing Capacity (kN/sq m)

Fine sand, silt Medium clay

150 245

Soft rock

440

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Walls Walls are the vertical elements of a building. They enclose the space within it and also divide that space

Functional Requirements     

strength and stability weather resistance fire resistance thermal insulation sound insulation

The walls are usually constructed of bricks, stones or concrete blocks in cement mortar. Retaining Wall and Breast Wall Retaining wall is constructed to retain soil or other fill material. Breast wall is to prevent slippage of natural slopes .The lateral pressure on the wall is to be calculated and then the design made accordingly. Columns The vertical support which is free from all sides and transfers the load to the floor below is called a column. The column can be of wood, steel or RCC. It can be of circular, rectangular or square in section.

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Beam

Beam is a horizontal structural member supporting the floor above. The beam can be of wood, steel or RCC. Slab is constructed to divide the vertical space into various stories. The topmost slab is the roof slab.

Floors are made of concrete. Steel bars are provided to take up the tensile stresses. The diameter of the bar and the spacing of the bars will depend on the span of the room and the intensity of load.

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Lintel

Lintel is a small beam provided over window and door opening to support the masonry above. The lintel can be of wood, steel or RCC..

Arches

Arches are curved members provided over openings like door and window to support the wall above. Elements of an Arch Keystone: It is the wedge shaped block provided at the crown of an arch. Extrados: it is the outer portion of an arch. Intrados: It is the inner portion of an arch. Voussoirs: They are the wedge shaped units forming the arch. 43

Clear span: It is the horizontal distance between the supports. Rise: It is the vertical distance between the highest point on the intrados and the springing line. Spring line: The imaginary line joining the springing points. Springing points: The points from which the curve of the arch starts. Stairs

A staircase or stairway is one or more flights of stairs from one floor to another. It includes landings, newel posts, handrails, balustrades and additional parts. It can be of wood, reinforced cement concrete, iron or steel. According to their form, the staircases can be with straight flights,

with swinging flights, arched flights or spiral flights. Roof The roof is the topmost part of a building. It serves as a protective cover of the building. It protects the inhabitants from rain, sun, wind and other climatic conditions. There are mainly three types of roofs - Sloping or pitched roofs - Flat or terraced roofs - Folded plate and shell roofs Door

Door

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Doors are openings in the wall at the floor level for entry and exit of persons, safety, security and for light and air. The number of doors in a room should be the bare minimum. Its position should judiciously selected. In genera doors have a frame and one or two shutters. There are different types of doors – Framed and braced door, Panelled door, Glazed door, Flush door, Revolving door, Sliding door, Folding door etc.. Window Windows are openings provided in the wall for light, air and outside view. The window has also got a frame and one or more shutters. There are different types of windows like – sliding window, louvered window, Bay window , Pivoted window. The window frame can be of timber, steel or aluminium.

Lifts Normally in an ordinary house, people go from ground floor to other floors through a stair case. But now a days more buildings are of multi stories whether residential commercial or office building. In such buildings it is very difficult to move up through a stair case. Lifts are used there for moving from one floor to another. It can be told that lLift is a moving platform which moves up and down in a small enclosed space.

Escalator Escalator is a system of movable stairs used to move people upward and downward directions. In public places like airports, railway stations, super markets etc escalators

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are installed for the convenience of general public. The speed of escalators are generally 0.75 m /second..

Points To Ponder

         

The basic components of a building are: Foundation, Plinth, Column, Wall, Lintel, Door, Window, Floor, Stair, Roof The purpose of a foundation is to distribute the load of superstructure to the soil below. There are two types of foundations – Shallow and deep foundation Spread footing, combined footing, grillage foundation etc come under shallow foundation. Pile foundation, Pier foundation and well foundation come under deep foundation. Walls provide security to the in -habitants and also protection from rain, wind and sun Columns are vertical members to transfer the load from top to bottom. Hey may of wood, steel or concrete and may be of square, rectangular or circular in section. There are different floors in a building – ground floor and upper floor. The roof is the topmost floor which provides protection to the building from rain, wind, snow etc. The roof covering may be of tiles, slates or concrete slab. Doors and windows are provided for access to the building, security for inhabitants, light and air. Model Questions 1. 2. 3. 4. 5. 6. 7. 8. 9.

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What are the main components of a building? What is a foundation? What are the different types of foundations? What are the types of walls? What is a column? What is the purpose of a door? What is a lintel? What is a pile foundation? Explain lift and escalator.

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7. STONES

Stones Stones

are blocks of rock and are used for construction of buildings (foundations, walls, columns), flooring, broken stones for roads and concrete. Classification of Rocks 1. Geological Classification a) Igneous Rocks: These rocks are formed by cooling of molten material called magma. These rocks are hard, strong, durable and dense with a crystalline structure. The rocks are formed on the surface of earth or deep below. Examples: Granite, Quartzite, Basalt, Dolomite b) Sedimentary Rocks: Existing rocks are broken down to smaller particles by wind, water and atmospheric gases. This process is called weathering. The smaller particles (sediments) thus formed are transported to other places and deposited there. Gradually the sediments are compressed under their own weight and sedimentary rocks are formed. Example; Sand stone, Lime stone c) Metamorphic Rocks: Igneous and sedimentary rocks when subjected to increased pressure and temperature are transformed to a new type of rock. This rock is called metamorphic rock. Example: Marble, Schist, Slate, Gneiss 2. Physical Classification a) Stratified Rocks: These rocks exist in distinct layers and can be split along these layers. Example: Sand stone, Lime stone b) Un stratified rocks: These rocks do not exist in layers but occur in huge masses. Example: Granite, Basalt 48

c) Foliated Rocks: These rocks have a layered or banded appearance which is produced by exposure to heat and pressure. Example: Gneiss 3. Chemical Classification a) Siliceous Rocks: In this, the main constituent is silica. The rocks are hard, durable and are capable of resisting weathering action. Example: Granite, Quartzite b) Argillaceous Rocks: Argil (clay ) is the main constituent of these rocks. These are hard and durable but are brittle. Example: Slate, Laterite c) Calcareous Rocks: Calcium carbonate is the main constituent of these rocks. Example: Marble, Limestone, Dolomite 4.

Hardness Classification Based on the hardness, rocks are classified as Soft rocks, Medium rocks, Hard rocks and Very hard rocks

Mineral Constituents of Rocks The main chemical constituents of rocks are: Minerals: Alumina, Silica, Lime, Magnesia Alkalies: Soda, Potash Acids: Carbonic acid

Uses of stones - Buildings: Foundations, walls, columns, lintels, floorings - Bridges: Piers, Abutments, Retaining walls - Roads and Railways: As broken stone (ballast) - Concrete: As coarse aggregate (broken stone)

Rubble Rough broken stone as it comes from quarry is called rubble. Rubble may come from Granite, Basalt, Gneiss or Sand stone. It is used in construction of foundations, walls, road work canal protection works etc.

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Laterite Laterite is a sedimentary rock. It is generally found in tropical climate (hot and wet) regions like Kerala, Karnataka, Andhra, Tamil Nadu etc. These are cut from quarries in rectangular blocks. They have to be seasoned (left in air) for about one or two months to attain full strength. The normal compressive strength of laterite is 1.8 to 3.2 N / sq mm. The blocks of stones obtained from quarry is to be dressed (giving proper shape and size). The standard size of laterite stone is 44 cm x 24 cm x 14 cm. Laterite stones are used in walls of buildings and boundary (compound) walls.

Qualities of good stones The qualities of good stones are: Crushing strength, Hardness, Durability, Texture, Appearance a) Crushing strength: It is the load per unit area required to break a specimen of stone under a compressive load. It is expressed in Newton / square mm. Type of rock Granite Laterite Marble b)

Range of crushing strength (N / sq. mm) 90 to 210 2 to 4 80 to 140

Hardness: When stone is used in floors and pavements, it t is subjected to large amount of wear and tear. Hardness is very important in these cases. It is determined by the hardness test.

c) Durability: A good stone should be durable. The durability of a stone depends on chemical composition, physical structure and its resistance to atmospheric action.

its

d) Texture: It is the characteristic physical structure indicated by the size, shape and arrangement of grains in the stone. e) Water absorption: Stones may have pores in it. When stones come in contact with water, it may absorb water. A good stone should not absorb water more than 5 % of its weight. f) Appearance: Stones should have a pleasing appearance specially when used on exteriors. Light coloured stones are preferred to dark coloured. h) Workability: The stones obtained from quarries are to be dressed properly before using it. The process of removing sharp corners, giving proper shape, size and surface finish is called dressing. Some stones like granite and basalt are very hard, tough and therefore are difficult to be dressed easily. i) Weathering: Stones should have the capacity to withstand the effects of weathering action. Otherwise they may disintegrate and decompose easily.

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Deterioration of Stones In course of time, stones may get deteriorated, due to the action of natural agencies like wind, water and temperature. The colour may also fade out giving a bad appearance. Polluted gases containing harmful agents from nearby industries may also add to the deterioration of stones. Preservation of Stones Stones should be protected from weathering action by adopting suitable measures like application of preservatives. A preservative is a solution which has to be applied on to the surface of stone so as to protect it from weathering action. An ideal preservative should be easily applicable, cheap and should penetrate easily into the interior of the stone The commonly used preservatives are paint, coal tar and linseed oil. Commonly used stones The commonly used stones in India are – Granite, Laterite, Basalt, Marble, Sand stone and Lime stone. Quarrying of stones The process of extracting blocks of stones from natural rock bed is termed as quarrying. Methods of quarrying; The following methods are adopted for quarrying. -

Quarrying with hand tools Quarrying with channeling machines Quarrying by blasting

Dressing of stones The stones after quarrying are to be given to correct size and shape. This processing is known as dressing of stones. This may be done at the quarry or the construction site. Testing of Stones To ascertain the qualities of building stones, different tests are conducted. Crushing Strength test: The crushing strength is obtained by testing the specimen in a compressive testing machine. Attrition test: The stones (coarse aggregates) used in road construction work are subjected to grinding action of traffic. Attrition test is conducted to obtain the resistance of stones to abrasion. Acid test: This test is conducted to ascertain the weathering resistance of stones. The stone chips are kept in a solution of hydrochloric acid for seven days and then tested.

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Absorption test: For this test, dried stone chips are kept in distilled water for three days, taken out ,weighed and absorption calculated. Hardness test: This test is conducted in Dorry’s testing machine. Impact test: This test is done in an impact testing machine to find out the toughness of stones.

Points To Ponder          

Stones are blocks of rock. Rocks are formed by the cooling of molten magma. There are different types of rocks – Igneous , Sedimentary and Metamorphic rocks Stones are used for foundation, wall, pavement etc Stones can be classified under geological, physical, chemical and hardness categories.. The commonly used stones are - Granite, Laterite, Marble, Gneiss, Slate, Sandstone Qualities of good stones are - Strength, Durability, Appearance, Water absorption, Fire resistance, Workability Stones can be protected from weathering by application of certain preservatives.(Chemicals) The process of extracting blocks of stones from natural rock bed is termed as quarrying. The process of giving proper size and shape to stones is called dressing. To ascertain the qualities of building stones, different tests are conducted like Crushing strength, Attrition, Absorption, Hardness, Toughness .

Model Questions 1. 2. 3. 4. 5. 6. 7. 8. 9.

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What are the different classifications of rocks? What are the uses of stones? What are the qualities of good stones? How are stones get deteriorated? How are stones preserved? What are the common building stones of India? What is meant by quarrying of stones? What is dressing of stones? What are the tests conducted to ascertain the qualities of building stones?

8. BRICK

Ordinary Brick

Brick is one of the oldest building material.

It is reported that Egyptions, Romans and Chinese used bricks for building construction centuries back. They are extensively used now days also due to its strength, durability, light weight, low cost and easy availability. Bricks are rectangular blocks of clay hardened by burning in kilns . Composition of Good Brick Earth The constituents of good brick earth are: 1) Alumina (Al2O3): A good brick earth may contain about 20% to 30% of Alumina. It imparts plasticity to the earth so that the brick can be moulded to correct size and shape. 2) Silica (SiO2): It exists in the brick earth either free or combined. A good brick earth should contain about 50% to 60% of silica. It prevents the shrinkage, cracking and warping of raw bricks. The durability of bricks depends upon proper composition of silica in brick earth. The excess of silica destroys the cohesion of particles and brick become brittle. 3) Lime (CaCO3): A small quantity of lime of about 5% is desirable in good brick earth. It should be present in a very fine state. The lime prevents shrinkage of the raw bricks. The excess of lime causes brick to melt and therefore its shape may be lost. 4) Oxide of Iron (Fe2O3): Iron oxide helps in fusing of the sand and also provides the red color to the bricks. It is normally kept below 5 to 6% because excess of lime may cause dark blue or black color to the brick. 5) Magnesia: It adds yellow tint to the bricks. A good brick earth may contain about 1 %

magnesia.

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Harmful Constituents of Brick Earth Iron pyrites Iron pyrites in brick earth causes the brick to get crystallized and disintegrated during burning. Also it may discolour the bricks. Alkalis Alkalis exist in brick earth in the form of soda and potash. It causes bricks to fuse, twist and warp. The alkalis remaining in bricks will absorb moisture from the atmosphere. The moisture gets evaporated in course of time leaving grey or white deposits on the surface. This is known as efflorescence. Stone Pebbles and Gravel It prevents uniform and through mixing of clay resulting in weak and porous bricks. Vegetation and Organic Matter Vegetation and organic matter in brick earth assists in burning. But if they are not completely burnt, the bricks may become porous and weak.

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Tests For Determination of Suitability of Brick Earth The following tests are conducted to find the suitability of the earth for the manufacture of bricks: Strength, Soundness, Consistency, Suitability for moulding, Shrinkage and Deformation after burning. Manufacture of Bricks These are the steps in manufacture of bricks: Selection of suitable site for manufacture of bricks The site should be a fairly level ground. Water, firewood, good brick earth and electricity should be available at site. Good road network should be there so that men and materials can be conveniently transported. The site should be slightly away from thickly populated residential areas so that the residents are not subjected to any inconvenience. Preparation of Brick Earth The site is cleared off all rubbish. The upper layer of 20-25 cm thick is removed. The clay is dug out. Vegetable matter, roots, gravel etc if present are removed. Water is then spread on the heap of clay and thoroughly mixed. It is then exposed to atmosphere for few weeks for softening. After adding water again, the clay is kneaded under the feet of a man or cattle. For large scale manufacturing, pug mills are used. This process is known as tempering.

Pug Mill

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Moulding of bricks The thoroughly mixed clay is put in the moulds to give proper size and shape. Moulding can be done by hand or by machine. Hand moulding can be – Ground moulding or Table moulding. Ground moulding: The mould is first dipped in water and kept on a clean and level ground. A lump of clay is then pushed into the mould. The surplus soil is then removed, the mould is then lifted. The process is then repeated. Table moulding: In this case, all the work is done on a specially made table.

Table Moulding Drying The moulded bricks are sun dried by keeping them in open air. in stacks for three to eight days. The drying can be done by artificial methods also. Burning of bricks The dried bricks are burnt in clamps or kilns. For smaller quantities clamps are used while for larger quantities kilns are used. The burning imparts hardness and strength to the bricks.

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Clamps: In this dried bricks and firewood are kept in alternate layers on a specially prepared level ground. The heap of bricks is then plastered with mud. The bricks are then ignited from bottom. The burning is continued for about a month and then allowed to cool for another month. Kilns: There are two types of kilns – Intermittent kilns, Continuous kilns Intermittent kilns: In this type of kiln, burnt bricks will be available only after complete burning. The supply of bricks is not continuous. Continuous kilns: In this type of kiln, it is possible to get bricks at any instant. This is because there are a number of chambers in this kiln.- while in one chamber the bricks may be loading, in another it may be burning and in another it may be cooling. There are different types of continuous kilns. The Hoffman’s Continuous Kiln.

In this there are a number of chambers. There is a central chimney which is connected to all the chambers. At any point of time, loading will be going in one chamber, preheating in another, heating in one, cooling in another and cleaning in another and so on. Cooling and Stacking The bricks after burning are cooled and kept in stacks for further transport to the construction sites.

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Qualities of good bricks - The bricks should be of standard size (19 cm x 9 cm x 9 cm, weight 3 to 3.5 kg) with sharp corners and typical red colour. - The bricks should be properly burnt. - It should not absorb water more than 20 % of its dry weight - When two bricks are struck together, a clear ringing sound should be heard - It should not be possible to make a scratch on the surface with a finger nail. It indicates that

the bricks are sufficiently hard. - The bricks should not be disfigured by the deposition of salt on the surface. This is known as efflorescence. Standard tests for Bricks There are two types of tests - Field tests and Laboratory tests. Field Tests Colour test: The bricks should have typical brick red colour. Hardness test: On the surface of the brick, try to make a scratch with a finger nail; if vno scratch could be made, the brick is hard. Soundness test: Strike two bricks together. If clear metallic sound can be heard, the bricks are considered as sound. Strength test: Drop a brick on a hard flat ground from a height of about one metre. It will not break, if the brick has sufficient strength. For proper quality control of bricks, following laboratory tests are recommended by Bureau of Indian Standards – Compressive strength, Water absorption, Efflorescence, Dimension Tolerances. Compressive strength (IS 1077- 1970) 58

Compressive testing machine -

Take five bricks at random, keep them in water for 24 hours, take out and wipe out water from the surface

-

Spread a layer of cement mortar of 1: 3 proportion, keep them in sacks for 24 hours.

-

After this, keep the bricks in water for a week.

-

Take the bricks out, dry them

-

Test the bricks in a compressive testing machine.

-

Note the load at which the bricks fail.

-

The maximum load divided by the cross sectional area gives the compressive strength.

Water absorption Test (IS 1077- 1970) -Take five bricks at random -Keep them in an oven at 110 degree centigrade for 48 hours -Take the bricks out of oven, cool it and then weigh (W1) -Keep the bricks in water for 24 hours - Take out, wipe the water and weigh again (W2) - Water absorption = W2 – W1

x 100

W1 Efflorescence Test (IS 1077- 1970) Take five bricks at random 59

Keep each brick in a flat bottom vessel. Fill distilled water such that the brick is in water for not less than 2.5 cm deep The water from the vessel may get evaporated and the bricks may be dried. Add fresh water. After the second stage of drying, observe for white patches of salt on the surface (efflorescence) The efflorescence is qualitatively described as – Serious, Heavy, Moderate, Slight, Nil. Dimension Tolerance Test (IS 1077- 1970) This test is done to check the dimensions of bricks- length, breadth and height. Advantages of Bricks over Stones - Bricks can be moulded to any shape - They are marginally cheaper compared to stones - They are lighter in weight - They can be easily handled by mason - They are more fire resistant

Classification of bricks Bureau of Indian Standards (BIS) has classified burnt bricks into four classes- First Class, Second Class, Third Class and Fourth Class.: 1. First Class bricks: Characteristics: Well burnt and having perfect rectangular shape When two bricks are struck each other a ringing sound is produced Compressive strength shall not be less than 140 kg/ sq cm Its absorption of water shall not exceed 20% after 24 hours Appearance, shape and size should be uniform

60

Uses: Suitable for all types of construction in the exterior walls when the plastering is not required. Suitable for flooring 2. Second class bricks Characteristics: Slightly irregular in shape Marginally over burnt Should not absorb water more than 22% Minimum compressive strength 70 kg/sq cm Uses Suitable for internal walls 3. Third class bricks Characteristics: Not burnt properly Moderate efflorescence Should not absorb water more than 24% of its weight Minimum compressive strength 35 kg/ sq cm Uses Used for unimportant and temporary works Fourth class bricks Characteristics: Over burnt, dark in colour, irregular in size and shape

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Uses Used as aggregate in concrete and road works

Special types of Bricks These bricks are not of regular shape and size. Composition of these bricks may also be different from that of ordinary bricks. Some of the special types of bricks are: Hollow brick , Perforated brick, Bull nose brick, Paving brick, Refractory brick, Coping brick.

Perforated Brick

62

Bull nose brick Coping Brick

Points to Ponder



Good brick earth should contain Silica, Alumina, Lime, Iron oxide and Manganese



Harmful ingredients of brick earth are Stone, Pebble, Vegetation and Organic matter.



Recommended field tests to determine the suitability of brick earth are- Consistency, Suitability for moulding, Strength, Shrinkage and Deformation, Soundness



Steps for manufacture for brick are: Preparation of brick earth, Moulding, Drying, Burning and Cooling



Tests for determining the quality of bricks are – Crushing strength, Hardness, Water absorption, Soundness, Shape & size



Bricks are classified as First, Second, Third and Fourth class bricks.



If soluble salts are present in the bricks, it may appear as white patches. This is known as efflorescence



The qualities of good bricks are: Hard, Uniform colour, Free fro cracks, Standard size, Crushing strength > 3.5 N/sq mm, low thermal conductivity, homogeneous structure

Model Questions 1. What are the qualities of good bricks? 2. What are the different steps of manufacture of bricks? 3. What is efflorescence? 4. What are the different laboratory tests to assess the quality of bricks? 5. What are the field tests? 6. What are the advantages of bricks over stones? 7. What are the different classifications of bricks? 8. What is a frog? 9. What is a clamp? 10. How are bricks burnt? 11. What is a Hoffman’s kiln?

63

9.Tiles

A tile is a

piece of hard-wearing material such as ceramic, stone, metal, marble or clay. It is

generally used for covering roofs, floors, walls, showers, and other places. The word tile is derived from the French word tuile, which is, in turn, from the Latin word tegula, meaning a roof tile composed of fired clay. Tiled flooring is commonly used in residential, commercial and office buildings. Tiles are manufactured in factories under controlled conditions.

Points to be taken into consideration while selecting tiles: Appearance, Cleanliness, Durability, Resistance to abrasion, Fire resistance, Initial cost, Maintenance, Dampness resistance. Types of Tiles Floor tiles, Roof Tiles, Wall tiles, Drain tiles

Roof Tile

64

Floor Tile

Ceramic Tiles Wall and floor tile used for interior and exterior decoration belongs to a class of ceramics known as white wares. The production of tile dates back to ancient times. For instance, the Step Pyramid for the Pharoah Djoser, built in ancient Egypt around 2600 B.C., contained colorful glazed tiles. By the beginning of the twentieth century, tile was manufactured on an industrial scale. The invention of the tunnel kiln around 1910 increased the automation of tile manufacture. Today, manufacture of tiles is highly automated. Raw Materials The raw materials used to manufacture tile consist of clay minerals mined from the earth's crust. Natural minerals such as feldspar are used to lower the firing temperature. The raw materials must be pulverized and sorted according to particle size. Primary crushers are used to reduce large lumps of material.

The initial step in ceramic tile manufacture involves mixing the ingredients. Water is added and then ground in a ball mill. The resulting compound is then pressed into the desired shape. Sieves are used to separate out particles in a specific size range. The sieves are kept in a sloped position and are vibrated mechanically or electromechanically . A glaze is a glass material designed to melt onto the surface of the tile during firing, and which then adheres to the tile surface during cooling. Glazes are used to provide moisture resistance and decoration, as they can be colored or can produce special textures.

65

The Manufacturing Process After processing the raw materials, the following steps are taken to obtain the finished product.. These steps include batching, mixing, grinding, spray-drying, forming, drying, glazing, and firing. Many of these steps are now accomplished using automated equipments. Batching *The composition is determined by the type of raw materials. The raw materials also determine the color of the tile, which can be red or white in color, depending on the amount of iron-containing raw materials used. Therefore, it is important to mix the right amounts together to achieve the desired properties. Batch calculations are done taking into consideration both the physical properties and chemical compositions of the raw materials. Once the appropriate weight of each raw material is determined, the raw materials are mixed together. Mixing and grinding 

2 After the ingredients are weighed, they are put together into a mixer. Sometimes it is necessary to add water to improve the mixing of a multiple-ingredient batch as well as to achieve fine grinding. This process is called wet milling and is often performed using a ball mill. The resulting mixture is called a slurry or slip. The water is then removed from the slurry by filter pressing, followed by dry milling.

Spray drying 

3 If wet milling is adopted, the excess water is removed by spray drying. This involves pumping the slurry to an atomizer consisting of a rapidly rotating disk or nozzle. Droplets of the slip are dried as they are heated by a rising hot air column, forming small, free flowing granules that result in a powder suitable for forming. Tile bodies can also be prepared by dry grinding followed by granulation. Granulation uses a machine in which the mixture of previously dry-ground material is mixed with water in order to form the particles into granules, which again form a powder ready for forming.

66

Forming 

4 Most tile is formed by dry pressing. In this method, the free flowing powder containing organic binder or a low percentage of moisture—flows from a hopper into the forming die. The material is compressed in a steel cavity by steel plungers and is then ejected by the bottom plunger. Automated presses are used with operating pressures as high as 2,500 tons.

Drying 

5 Ceramic tiles must be dried (at high relative humidity) after forming, especially if a wet method is used. Drying can take several days. This removes the water at a slow rate to prevent shrinkage cracks. Continuous or tunnel driers are used that are heated using gas or oil, infrared lamps, or microwaves. Infrared drying is better suited for thin tile, whereas microwave drying works better for thicker tile. Another method, impulse drying, uses pulses of hot air flowing in the transverse direction instead of continuously in the material flow direction.

Glazing 

6. After a batch formulation is calculated, the raw materials are weighed, mixed and dry or wet milled. The milled glazes are then applied using one of the many methods available. Dry glazing is also being used. This involves the application of powders, crushed frits (glass materials), and granulated glazes onto a wet-glazed tile surface. After firing, the glaze particles melt into each other to produce a surface like granite.

67

Firing



. 7 After glazing, the tile must be heated in a kiln intensely to strengthen it .



8 After firing and testing, the tile is ready to be packed and shipped. Fixing of Floor Tiles:



First a layer of mortar is spread to a thickness of 25-mm. Then apply cement slurry to the bottom and sides of the tile. The tile is then pressed in position by hitting with a mallet. Then the following day the joints are cleaned of loose mortar, raked up to a depth of 5 mm and then filled up with coloured cement slurry.

Tests of Tiles Bureau of Indian Standards recommends the following tests to determine the quality of ceramic tiles (ISO 10545-1: 1995) Dimensions and surface quality, water absorption, modulus of rupture, impact resistance, abrasion and chemical resistance.

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Points to Ponder



Tiles are materials for covering roof, floor and wall



Points to be taken into consideration while selecting tiles are::



Appearance, Cleanliness, Durability, Resistance to abrasion, Fire resistance, Initial cost, Maintenance and Dampness resistance.



The types of tiles are - Floor tiles, Roof Tiles, Wall tiles and Drain tiles



Tiles are manufactured out of ceramics



The steps of manufacturing bricks are - batching, mixing, grinding, spray-drying, forming, drying, glazing, and firing.



Bureau of Indian Standards recommends the following tests to determine the quality of ceramic tiles (ISO 10545-1: 1995): Dimensions and surface quality, water absorption, modulus of rupture, impact resistance, abrasion and chemical resistance.

Model Questions 1. What is a tile? 2. What for tiles are used? 3. What are the points to be taken into consideration while selecting tiles? 4. What are the steps of manufacturing tiles? 5. What are the tests to be conducted to determine the quality of tiles?

69

10.CEMENT

One material which has completely revolutionized the construction industry is cement. It was in 1824, a mason of England by name Joseph Aspidin developed cement by burning at high temperature a mixture of lime and clay and then grinding it into fine powder. This is known as Ordinary Portland Cement. Composition of Ordinary Portland Cement Ingredient

Average (%)

Lime

62

Silica

22

Alumina

5

Calcium Sulphate

4

Iron oxide

3

Magnesia

2

Alkalies

1

Sulphur

1

Manufacture of Cement There are three operations in the manufacture of cement: 1. Mixing of raw materials

2.Burning

3.Grinding

1. Mixing of raw materials: There are two processes for mixing raw materials1. Dry Process 2. Wet Process

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Dry Process The raw materials lime stone and clay - are air dried and then separately ground into fine powder in ball mills and stored in silos or hoppers.. They are then mixed in correct proportions.

Wet Process The raw materials are crushed separately and are stored in silos. They are then drawn from silos into the wet grinding mills. Water is added and ground to a fine paste (slurry).

71

Wet Process Burning The slurry or the dry mixture is then burnt in a rotary kiln. The rotary kiln consists of a steel tube of diameter of 250-300 cm and of length 60 m to 120m. The kiln rotates about its axis at the rate of one revolution per minute. The slurry is injected at the upper end of the kiln. Hot air is pumped from the lower end. As the dried slurry comes down to the burning zone, it is converted into small lumps which are then converted into clinkers.

Rotary Kiln 72

3. Grinding: The grinding of the clinkers is done in ball mills or tube mills. During grinding 2 to 4 % gypsum is added to control the initial setting time of cement. The finely ground cement is stored in silos, packed in bags and then transported to the market. Properties of Portland Cement and Tests for its Determination The properties can be classified in three categories: Chemical Composition, Physical Properties, Mechanical Properties Chemical Composition: The quality of cement depends on the ratio of the major components like lime, alumina, silica and iron oxide. As per IS 269 (1973), the recommended compositions are: -The ratio of percentage of lime to percentage of silica, alumina and iron oxide shall not be more than 1 and shall not be less than 0.66. -Weight of insoluble residue shall not exceed 1.5% - Weight of magnesia shall not be greater than 5% Physical Properties: Fineness: Finer cement particles impart better quality. It is determined by sieve test or specific surface test. Soundness: It is the capacity of cement to form a hard and strong mass on setting. It is determined by the Le Chatelier test. Setting of cement: When water is added to cement it forms a thick paste. Gradually as time passes, it transforms into a non-plastic rigid mass. The setting time is influenced by the amount of water added to the cement, the temperature at which the cement paste is allowed to set and the humidity of the atmosphere. The setting of cement is identified in two stages, initial setting and final setting. The setting time is determined in the laboratory by Vicat Needle Apparatus As per Bureau of Indian Standards (BIS), for ordinary cement , the initial setting time shall not be less than 30 minutes and the final setting time should not be more than 10 hours.

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Vicat Needle Apparatus

Mechanical Properties: Compressive strength: Cement mortar cubes of size 7.06 cm are made out of mortar of 1: 3 composition ( 1 part of cement to 3 parts of sand) and tested in a Universal compressive testing machine. Normally the tests are done after 3, 7 and 28 days. Tensile strength: Test pieces (briquettes) are made out of cement sand mortar 1: 3 and tested in a standard tensile testing machine after 3, 7 and 28 days. Compressive and Tensile strength as per BIS Ordinary Portland Cement Period

Strength

3 days

Compressive

not less than 115 kg/sq cm

Tensile

not less than 29 kg/sq cm

Compressive

not less than 175 kg/sq cm

Tensile

not less than 35 kg/sq cm

7 days

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Different Types of Cement In addition to Ordinary Portland Cement, there are other types of cements manufactured by changing the composition of raw materials and also by adding some other materials. Rapid Hardening Cement: This is expected to attain maximum strength in 24 - 72 hours. This cement is manufactured by adding slightly more quantity of limestone and also by grinding more finely compared to OPC. This is generally used in situations where strength has to be attained quickly. It attains 7 days strength of OPC in 3 days. Shuttering can be removed early and period of curing is less. Low Heat Cement: Only small amount of heat is generated during setting and hardening of this cement. This is generally used for massive construction like dams. Quick Setting Cement: In this the amount of quantity of gypsum is reduced while small quantity of aluminium sulphate is added. Also the cement is finely ground. This type of cement is used for concreting in stagnant or running water. High Alumina Cement: This contains comparatively large percentage of alumina compared to OPC. This cement can withstand corrosive action of sea water Though its initial setting time is slightly more (about 3.5 hours), its final setting time is less to about 5 hours. Pozzolana Cement:. In this type of cement, pozzolanic materials (powered burnt bricks, fly ash etc) are mixed to add certain qualities to the ordinary cement. It offers great resistance to sulphate and corrosive action of sea water. Also it does not release large amount of heat when reacting with water. As such it is suitable for mass construction work. White cement: It is a special type of cement with a milky white colour. In this type of cement, iron oxide, manganese and chromium are not added. Instead of coal, oil is used in kiln for firing.

Grades of Cement Cement is graded according to its compressive strength. Cement mortar of 1: 3 proportion is made and then cubes of surface area 50 sq cm is made and then tested after 28 days. Cement type

75

Compressive strength (N/sq mm)

Grade 33

33

Grade 43

43

Grade 53

53

Points to Ponder

          

Cement is a widely used construction material It is a mixture of Argillaceous, Calcareous and Siliceous materials There are 3 stages of manufacture of cement They are mixing of raw materials, burning and grinding The mixing can be done in dry or wet condition The burning is done in rotary kiln at a very high temperature The clinker obtained after burning is ground in ball mills/tube mills. The properties of cement can be classified under physical and chemical heads The main properties are strength, soundness. fineness, setting time The main uses of cement are to make cement mortar & cement concrete (Plain and RCC) There are different types of cement – Ordinary Portland Cement, Rapid Hardening Cement, Sulphate Resisting Cement, Quick Setting Cement, White Cement, etc

Model questions

1. What are the ingredients of OPC? 2. Explain briefly the different processes of manufacture of cement. 3. What is meant by setting of cement? 4. What are the mechanical properties of cement? 5. What are the properties of rapid hardening cement? 6. Where is sulphate resisting cement used? 7. How is setting time determined in the lab.? 8. What are the different grades of cement? 9. What is soundness of cement? How is it determined? 10. What are the uses of cement?

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11.AGGREGATES Sand

Sand is a natural aggregate obtained by disintegration of rock. Sand is required for making cement mortar and cement concrete. They range in size from 2 mm to 0.075 mm.

Types of sand: Natural Sand Sands are of three types based on the mode of origin, composition and grain size. - According to mode of origin: River sand, Pit sand, Sea sand -According to size of grains Fine sand, Coarse sand, Gravelly sand -According to shape of grains Angular, Rounded, Flaky Artificial sand (M sand) Due to extensive use of natural sand for construction works, it has become short in supply. This has necessitated the search of alternate sources. Some such alternate sands are: surkhi ( finely ground burnt bricks),coal ash and stone screenings (M sand).

Grading of sand: A group of sand may contain particles of different sizes. Determination of the proportions of various sizes is known as grading. This is done by sieve analysis. Proper grading of aggregates helps in producing dense concrete. Also, it helps in improving workability, strength, economy and durability. The smaller size particles fill the gap (voids) of larger particles.

77

Fineness Modulus: This is an index which gives an idea of the fineness or coarseness of the particles. Higher value of fineness modulus indicates higher coarseness of particles. The fineness modulus is determined by sieve analysis. In this, a known quantity of sand is passed through a set of sieves ( 80 mm to 150 microns) The weight of sand retained on each sieve is noted. Their percentages and cumulative percentages are then calculated. Fineness modulus = (Sum of cumulative percentages retained on sieves) / 100 Based on fineness modulus, sands are classified as – Type

Fineness Modulus

Fine sand

2.2 to 2.6

Medium sand

2.6 to 2.9

Coarse sand

2.9 to 3.2

Field test of sand: Presence of clay: Take a glass of water. Add little sand into it. Thoroughly mix the sand and water and allow it to settle. A distinct of layer of clay will be formed at top if clay is present. Presence of organic matter: Add a solution of sodium hydroxide to a small quantity of sand and mix it. The presence of organic matter is indicated if the colour of solution changes to brown. Presence of salt: Take some sand and taste it.. Presence of mud: Take a small quantity of sand and rub against the fingers. The fingers will be stained if mud is present.

Bulking of sand: The increase in the volume of sand due to surface moisture is called bulking . The increase in volume may range from 20 % to 40% when moisture content is 5 to 10 %.

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Characteristics of Natural sand (IS 650-1966) -It should pass through 2 mm IS sieve and retained on 90 micron sieve. - It should be free from organic matter - It should be free from dirt -It should be of light grey colour

-It should be chemically inert -It should be of sharp, angular, coarse and durable grains -It should be well graded -It should not contain salt

Functions of sand in mortar and concrete Strength - By changing the quantity of sand in the mix, the strength can be adjusted. Shrinkage - It prevents the excessive shrinkage of cement concrete/cement mortar on drying. It also prevents the cracking in the concrete. Surface area - The presence of sand in the cement paste helps to add more surface area. Workability- It gives workability to cement mortar/concrete.

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Points to Ponder

      

Sand comes under fine aggregate. River sand is an example. It should pass through 4.75 mm IS sieve Sand can be natural or artificial ( crushed stone) M sand (manufactured sand) is artificial sand Determination of the various sizes of sand particles is called grading. It is done by sieve analysis Fineness modulus is the value obtained by adding the cumulative percentages of residues retained on IS sieves (80mm to 150 microns) divided by 100.

Model Questions 1. 2. 3. 4. 5. 6. 7. 8. 9.

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What are the different classifications of sand? What are the properties of sand? What are the field tests on sand? What is bulking of sand? What is M sand? What is the purpose of sieve analysis? What is fineness modulus? What is meant by grading of cement? What are the uses of sand?

Broken Stones (Coarse Aggregates)

Crushed stone and natural gravel are the materials generally used as coarse aggregates.

For

majority of works, 20 mm size aggregate is recommended. Aggregates are inert granular materials .For a good concrete mix, aggregates need to be clean, hard, strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete. Aggregates account for 60 to 75 percent of the total volume of concrete. Coarse aggregates are any particles greater than 0.19 inch, but generally range between 3/8 and 1.5 inches in diameter. Crushed aggregate is produced by crushing quarry rock, boulders, cobbles, or large-size gravel. After crushing, aggregates are screened and washed to obtain proper cleanliness and gradation Aggregates strongly influence concrete's properties, mixture proportions and economy. Therefore, selection of aggregates is an important process.

Characteristics: The main characteristics of broken stones that are taken into considered are: Strength, Shape, Size, Grading, Porosity, Abrasion resistance, Durability, Soundness: Strength: Strong aggregates are essential for obtaining strong concrete. Surface texture: It affects the bond to the cement paste and also influences the quantity of water to be added to the mix. Grading: It is the particle size distribution of particles as determined by the sieve analysis. The

grading of aggregate must be so that the workability and density of concrete are not adversely affected .Grading is determined in the laboratory by the fineness modulus test.

81

Porosity (Permeability): It may affect the bond between the aggregates and the cement paste. Organic Impurities: It may interfere with the setting and hardening of concrete. Soundness: It is the ability of aggregates to resist volume change to environmental effects like temperature change and alternate wetting & drying. Abrasion resistance It is also known as resistance to wear. It is of importance when concrete is used for road construction and factory floor works Its vale is determined in the laboratory by Los Angeles test. Aggregate size: Larger the size of aggregates, smaller the surface area to be wetted. This reduces the requirement of water. So for the same workability and cement content, higher strength can be obtained.

Coarse Aggregate Testing The suggested teats for coarse aggregates for roads are: Los-Angeles Abrasion Test, Aggregate Crushing strength test, Aggregate Impact value test, Sieve Analysis/Grading Test of Coarse Aggregates, Specific Gravity and Water Absorption Tests of Coarse Aggregates, Flakiness and Elongation Index, Soundness Test of Coarse Aggregates, Alkali-Silica Reactivity of Coarse Aggregates The main tests are briefly described here: (IS 2386 – Part IV – 1963) Los Angeles Abrasion Test: The aggregate used in surface course of the highway pavements are subjected to wearing due to movement of traffic. When vehicles move on the road, the soil particles present between the pneumatic tyre and road surface cause abrasion of road aggregates. Therefore, the road aggregates should be hard enough to resist abrasion. Resistance to abrasion of aggregate is determined in the laboratory by Los Angeles test machine. The principle of Los Angeles abrasion test is to produce abrasive action by use of standard steel balls. These steel balls are mixed with aggregates and rotated in a drum for specific number of revolutions. It causes impact on aggregates. The percentage wear of the aggregates due to rubbing with steel balls is determined. This is known as Los Angeles Abrasion Value.

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Los Angeles Test Machine Aggregate Crushing value test

Collect the sample passing through 12.5 mm IS sieve and retained on 10 mm sieve. Dry the sample by keeping it in oven at 105-110 degree centigrade; cool the material. Find the weight of the test specimen and then put in the test cylinder. (A). Apply the test load.(40 t).Remove the load, pass the test sample through IS 2.36 mm sieve Find the weight of aggregate particles passed through sieve.(B). Crushing value = (B/A) x 100

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Aggregate Impact Value

Collect the sample passing through 12.5 mm IS sieve and retained on 10 mm sieve. Dry the sample by keeping it in oven at 105-110 degree centigrade; cool the material. Fill the cup of the test machine and find the weight (A). Compact it with a tamping rod. Drop the hammer from the specified height on the specimen. Repeat the test by dropping the hammer 15 times. Remove the sample, sieve it through 2.36 mm IS sieve and find the weight of the passed sample (B). Aggregate Impact value = (B / A) x 100

Grading of Aggregates Grading refers to the particle-size distribution of aggregate. Grading limits and maximum aggregate size affect the amount of aggregate, cement and water as well as workability and durability of concrete. In general, if the water-cement ratio is chosen correctly, a wide range in grading can be used without a major effect on strength.

Shape and Size Matter Particle shape and surface texture influence the properties of freshly mixed concrete. Roughtextured, angular, and elongated particles require more water than smooth, rounded compact aggregate. Therefore the cement content must also be increased to maintain the water-cement ratio. The void content of particles affects the amount of cement paste required for the mix. Angular aggregates increase the void content. Larger sizes of well-graded aggregate and improved grading decrease the void content.

84

Points to Ponder

   *

The main characteristics of broken stones are: Strength, Shape, Size, Grading, Porosity, , Durability, Soundness The recommended main tests on aggregates are - Los-Angeles Abrasion Test, Aggregate Crushing strength test, Aggregate Impact value test Grading refers to the particle size distribution of aggregates Particle shape and surface texture influence the properties of freshly mixed concrete

Model Questions 1.How is broken stones obtained? 2. What are the main charactarestics of good broken stones? 3. What are the tests conducted on broken stones? 4. What is fineness modulus? 5. What is Los - Angeles test? 6. What is grading of aggregates? 7. What are the effects of shape and size of aggregates?

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12. Cement Mortar

Cement mortar is a compound made by mixing cement and fine aggregate (sand) with a specified quantity water. The mortar can be used for jointing of bricks and stone blocks, plastering over brick / stone masonry, flooring etc.. Grades of Cement Mortar Masonry mortars are specified as different grades depending upon their minimum compressive strength, when tested on 28th day. Different grades of cement mortar and their mix proportions are given below. Mortar Mix (by Loose Volume) Grade Name

Compressive Strength on 28th

Cement

Sand

day (in N/mm2)

MM 0.7

1

8

0.7 to 1.5

MM 1.5

1

7

1.5 to 2.0

MM 3

1

6

3.0 to 5.0

MM 5

1

5

5.0 to 7.5

MM 7.5

1

4

Above 7.5

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Procedure of Hand Mixing of Cement Mortar 1. Take one bag of cement, which has a volume of nearly 0.035m3. 2. Measure required quantity of dry sand using a box of volume 0.035m3 3. Spread the measured amount of sand on a water tight platform. 4. Spread the cement over the sand. 5. Mix them dry by turning over by a shovel.. 6. Make a small depression on top of the heap. 7. Add required amount of water at the centre as to get the required consistency. 8. Mix the cement - sand mass thoroughly for 5 to 10 minutes by a shovel. 9. Cement mortar is now ready The mixing can be done by a mixer also. Functions of sand in mortar - To impart strength - To prevent shrinkage - To increase the volume of mortar Properties of good mortar: • should adhere completely to the brick, stone block or other masonry unit to provide stability. • should be workable to set the masonry units right in position • Should rapidly develop strength when hardened. • Should resist the action of environmental factors such as frost and/or abrasion and destructive effects of chemical salts • Should resist the penetration of rain water • Should accommodate irregularities in size of masonry units. • Should provide overall aesthetic appearance. • Should be cost effective

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the

Types of mortar Based on bulk density Heavy mortar: Bulk density should be greater than 15 kN / m^3 Light mortar: Bulk density < 15 kN / m^3 Based on binding material Mud mortar, Lime mortar, Cement mortar, Gypsum mortar Special mortar Light weight mortar, Fire resistant mortar, Sound absorbing mortar

Uses of Mortar - Mortar is used to join bricks and stone blocks. - For plastering of walls - For pointing of brick and stone blocks in walls - To fill cracks in the structure - For flooring of rooms

Precautions in using mortar - Cement mortar should be used immediately after preparation, say with in about 30 minutes - Bricks and stones should be saturated in water before laying - The plastered surface and masonry should be kept wet by sprinkling water for at least one week

Tests for mortar 88

Crushing strength Adhesiveness Tensile strength Setting time

Points to Ponder

    

Cement mortar is a mixture of cement, sand and water It is used Joining bricks and stone blocks, Plastering of walls and Flooring There are different types of mortar based on bulk density and binding material The main properties of mortar are strength, workability, cost effectiveness, good adherence Mortars are specified by different grades as MM 3 like that where 3 stands for 28 days compressive strength in N/ sq mm.

Model Questions 1. What is cement mortar? 2. What are the uses of cement mortar? 3.

How is cement mortar prepared?

4. What are the properties of good mortar? 5. What is meant by MM3 cement mortar? 6. What are the precautions to be taken in using mortar?

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13. Cement Concrete

Cement concrete

is a material which has completely revolutionized the construction industry.

From a small house to a muti-storey building, dams, bridges like that for almost all structures, concrete is a must for its construction. Concrete is a mixture of cement, sand, broken stone and water. The paste, composed of portland cement and water, coats the surface of the fine and coarse aggregates. Through a chemical reaction called hydration, the mix hardens and gains strength to form a rock-like mass known as concrete. The concrete: is plastic when newly mixed but strong and durable when hardened..Concrete’s durability, strength and relatively low cost make it the backbone of buildings and all other infrastructure works. Grades of Concrete As per IS 456-2000, concrete is graded according to the compressive strength of nominal test cubes. The grade is specified by M15, M20. like that where M stands for the mix and the suffix number 15, 20 etc specifies the compressive strength of 15 cm size concrete cubes tested under a compressive load after 28 days of casting. The compressive strength is specified in N / sq. mm. Grades of Concrete and their uses Grade

Proportion

M5

1:5:10

Mass concrete works

M10

1:3:6

Mass concrete Works

M15

1:2:4

Plain cement concrete works

M20

1:1.5:3

General RCC works in buildings

M25

1:1:2

Water retaining structures

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Uses

M35

Design Mix

For pre-stressed concrete works

Proportioning of Concrete This is the process of selecting the quantities of cement, sand, broken stone and water so as to obtain a concrete of required strength, durability and workability. The proportioning is done in two ways: -

Nominal mix

-

Design mix

Nominal Mix In this type of mix, all the ingredients are specified and their proportions are quantified. It is generally used for relatively unimportant and simpler concrete works. Nominal mix concrete may be used for concrete of M-20 or lower. Design Mix It is a performance based mix where choice of ingredients and proportioning are decided by the engineer. The user has to specify only the requirements of concrete in fresh as well as hardened state. The requirements in fresh concrete are workability and finishing characteristics, whereas in hardened concrete these are mainly the compressive strength and durability. Trial mixes are to be made and then tested in the laboratory. Manufacture of concrete The manufacture of concrete involves the following steps - Batching, Mixing, Transporting, Laying (Placing), Compacting and Curing. Batching: In this, the different materials- cement, sand, broken stone, water - are measured and kept separately. Batching is by: a) volume batching b) Weight batching Mixing: The mixing of raw materials can be done manually or mechanically. Manual mixing91

Select a water tight platform of about 3 m x 3m size

-

Spread the measured quantity of sand on the platform

-

Then spread the cement evenly on the sand

-

Mix thoroughly the sand cement mixture with a shovel

-

Add the coarse aggregate and again mix it

-

Add water and mix again with a shovel till a uniform mixture is obtained

In machine mixing, a mixer is used for the process. This is adopted for bigger works and is more efficient. Transporting: The mixed concrete is to be transported to the work site from the mixing plant. For smaller quantities, this can be done as head load in iron pans. Wheel barrows and hand crafts are used for relatively large works, while belt conveyors are employed for very large works. Placing (Laying): Before placing the concrete, the form work should be cleaned and oiled. Care should be taken to see that the concrete is not dropped from a height as otherwise separation may take place. The concrete must be placed in proper layers. Compacting: The laid concrete has to be compacted to remove the entrapped air. If air gets entrapped, it will reduce the strength. Compaction can be done by hand or by vibrators. Curing: The freshly laid concrete has to be kept wet for a brief period to obtain the required strength. This process is called curing. Normally it is done for 14 days. Curing is done by different methods like spraying of water, keeping wet gunning bags over the surface or by applying curing compounds. Properties of Cement concrete - Concrete has high compressive strength; but weak intension - It binds with steel and therefore steel is used to reinforce concrete - It forms a hard surface on setting - There is no appreciable effect of weather on concrete surface - Due to loss of water, concrete may have shrinkage - Concrete hardens with age

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- It can be moulded to any size / shape

Water cement Ratio The ratio of the amount of water to the amount of cement by weight is called water-cement ratio. The amount of water added determines the strength and workability of concrete. When water cement ratio is less, complete hydration of cement particles will not take place which leads to low strength. On the other hand, if the quantity of water added is more, the excess water will get evaporate subsequently creating voids and lowers the strength of the concrete. IS 456-2000 specifies the maximum water-cement ratio for reinforced cement concrete for different degrees of exposure. The suggested ratios are: 0.55 for mild exposure and 0.40 for extreme exposure.

Properties of Green Concrete - Bleeding, Workability, Segregation, Harshness

Bleeding of concrete: When there is excess of quantity of water in the mix, water along with cement particles will rise to the top surface of freshly laid concrete. This is called bleeding. This can be due to excess compaction also. Bleeding causes formation of pores in the concrete making it weak.

Workability of concrete Workability is defined as he relative ease with which concrete can be mixed, transported, placed and compacted in position. Factors affecting workability: 1. 2. 3. 4. 5. 6.

Amount of cement & water Aggregate Grading Nature of Aggregate Particles (Shape, Surface Texture, Porosity etc.) Method of transport, placing and compaction of concrete Temperature of the concrete mix Humidity of the environment

Tests for determining workability The most popular tests are: Slump test and Compacting Factor test

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Slump test: The test is carried out using a mould as shown the figure below. The cone is placed on a hard nonabsorbent surface. This cone is then filled with fresh concrete in three layers. Each layer is tamped using a rod of standard dimensions. At the end of the third stage, concrete is struck off flush to the top of the mould. The mould is then carefully lifted vertically upwards. This subsidence is termed as slump and is measured in mm. Recommended slumps for various works are: Normal RCC work

80 to 150 mm

Mass Concrete

25 to 50 mm

Compacting factor test

Procedure 94

Place the concrete sample in the upper hopper to its top edge and level it.

-

Cover the cylinder

-

Open the trap door at the bottom of the upper hopper. The concrete will fall in to the lower hopper

-

Open the trap door of the lower hopper and allow the concrete to fall in to the cylinder below

-

Remove the surplus concrete above the top level of cylinder and level it.

-

Weigh the cylinder with concrete. This weight is known as the weight of partially compacted concrete (w1).

- Empty the cylinder and then refill it with the same concrete mix in layers; compact each layer and then level the surface. - Weigh the cylinder with fully compacted concrete. This weight is known as the weight of fully compacted concrete (w2). - Find the weight of empty cylinder (w). Compaction Factor = (w1- w2) / (w2-w) Segregation When concrete is dropped from a slightly more height, separation of coarser particles take place. This is known as segregation. Segregation causes reduction of strength. Segregation can be reduced by – Reducing the quantity of water and by Restricting the height of pouring concrete. Harshness Harshness is defined to the resistance offered by freshly laid concrete to surface finishing. This can be due to insufficient quantity of water, lesser quantity of cement and use of poorly graded aggregates.

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Advantages of Concrete Refer to para above- Properties of concrete

Disadvantages of Concrete - Plain cement concrete is weak in tension - Self weight of concrete is relatively high

- It requires considerable time in manufacturing, transporting, laying, compacting and curing of concrete

Admixtures Certain materials are added to the concrete to improve its properties. These are called admixtures. Accelerators: Some times it will be necessary to have the strength of concrete developed quickly. For this, certain chemicals are added. Calcium chloride, aluminium chloride, sodium carbonate etc are some of the chemicals added as accelerators. It has been found that the addition of these chemicals reduce the strength of the concrete. As such its use must be closely watched. Retarders: These are added to get time in setting and hardening. In certain cases, concrete will be made at one place and the same will have to be transported to another place. This may take more time. In these cases, retarders are added to delay the setting of concrete. Gypsum is a good retarder. Plasticizers: These are added to the concrete to make it more plastic without further addition of water. As such, the quantity of water required is less. Air entraining agents: If the concrete contains some air in it in the form of air bubbles, its durability and frost resistance can get improved. The compounds used for this purpose are – resins, aluminium and zinc powders.

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Types of Concrete Reinforced Cement Concrete (RCC): Ordinary concrete has not got the capacity to with stand tensile stresses. As such, steel bars are introduced in the concrete to take up the tensile stresses. Such concrete is called Reinforced Cement Concrete. The diameter of the bars, and the number of bars will depend on the load the member is subjected to. In a building, beams, slabs, columns, lintels etc are subjected to both compressive and tensile stresses and therefore these are made of RCC..

Pre stressed Cement Concrete (PSC) In this, pre stressing is done by pulling the steel wires. This will introduce compressive stresses in the concrete section enabling to take more tensile stresses. With this system, thin sections carry more load. It is used for construction of bridge girders poles, railway sleepers, pipes etc.

Ready Mixed Concrete (RMC): Ordinarily concrete is manufactured at the worksite itself. But in case of ready mixed concrete (premix concrete), the concrete is prepared at a central mixing plant. This ensures better quality control and also work can be done at a faster rate. At certain locations there may not enough space at the work site to set up the plant. There, getting concrete from a central plant will be more ideal.

Fibre Reinforced Concrete (FRC) Fibers are inserted in the concrete to control cracking due to shrinkage. They also reduce the permeability of concrete and also give greater impact resistance in concrete. Fibers do not increase the flexural strength of concrete and so cannot replace structural steel reinforcement. The amount of fibers added to a concrete mix is expressed as a percentage of the total volume of the composite which may range from 0.1 to 3%. The fibres can be of polypropylene, nylon or steel. Steel fibers can Improve structural strength, reduce steel reinforcement requirements, improve ductility, reduce cracks and improve abrasion resistance.

Light Weight concrete Light weight concrete is made by using lightweight aggregate. Lightweight aggregate may consist of processed shale, clay, clinker, or other material. Aggregates which are very absorptive may require pre-wetting prior to concrete batching. Lightweight concrete has a range in unit weight from about 1280 to 1920 kg/m3 depending on the lightweight material used. Where dead weight of the structure is to be reduced , this type of concrete is used. 97

Cellular Concrete: Cellular Concrete is lightweight portland cement concrete containing a high percentage of gas cells created by the addition of foaming agents. The density of this concrete may range from 320 to 1900 kg/m3 . This low density is due to the uniformly distributed non-contiguous air cells. This also gives high workability and thermal conductivity. This concrete is generally used where reduction of load is required.

Form work (Shuttering / centering) Formwork is a temporary structure consisting of planks and supporting members, used as a mould for pouring the fresh concrete. Once the concrete sets and hardens the form work is removed. The construction of formwork takes time and involves expenditure which may go up to 20 to 25% of the cost of the structure . The operation of removing the formwork is known as stripping. Stripped formwork can be reused. Stripping of beams and slabs are normally done after three to seven days. Timber or steel sheets are used for formwork. A good formwork should satisfy the following requirements: It should be strong enough to withstand all types of loads It should be rigidly constructed propped and braced both horizontally and vertically. The joints in the formwork should be tight against leakage of cement paste. Formwork should be so constructed that it should permit removal of various parts in desired sequences without damage. The material used in the formwork should be cheap.

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Points to Ponder



Concrete is a mixture of cement, sand, broken stone and water



Concrete is graded as M5, M10 etc where 5 and 10 are the strength of concrete cubes (N / sq mm) after 28 days.



The different stages of manufacturing concrete are – Batching, Mixing, Transporting, Laying, Compacting and Curing



Curing is the process of keeping freshly laid concrete under wet conditions.



Workability is the ease with concrete can be laid



The workability is determined by Slump test or Compacting factor test



Form work is a temporary support so that the concrete can be laid over it.



Concrete is used for making Floors, Foundation bottom layer, Plastering of walls and RCC.



There are different types of concrete like – Light weight concrete, Fibre reinforced concrete, Reinforced Cement concrete, Pre-stressed concrete, Rapid hardening cement, Cellular concrete etc



Proportioning of concrete is the process of fixing the quantities of cement, sand and broken stone so that concrete of required strength , durability and workability is obtained



Water cement ratio is the amount water to be added to the cement to obtain concrete of good workability and strength.



Certain chemicals are added to the concrete to improve its properties. These are called admixtures.

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Model Questions 1. What is cement concrete? 2.

What are the steps of manufacturing cement?

3. What is water cement ratio? 4. What is workability of concrete? 5. Explain slump test. 6. What are the different types of concrete? 7. What is form work? 8. What is meant by curing of concrete?

9. What are the factors affecting concrete? 10. What is admixture? 11. What are retarders?

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14.Iron & Steel

Iron ores are extracted from earth through mining. This is then melted in a blast furnace and pig iron is generated. The pig iron is then remelted, impurities are removed and cast iron and wrought iron are obtained. Cast iron may contain 2 to 4% carbon while wrought iron may contain 0.15%. Steel is an alloy of iron and carbon with small percentage of sulphur and phosphorus. The main physical properties of steel are strength, elasticity and ductility. These properties are influenced by the amount of carbon and the heat treatment. Pig Iron: It is the basic form of iron. It is impure and raw. After further processing, cast iron, wrought iron and steel are made. Manufacture: The stages of manufacture are – Selection of Ore, Dressing of ore, Calcination, Roasting and Smelting Selection of ore: Natural sources from which iron can be extracted are called iron ores. Common iron ores are: Haematite, Siderite, Magnetite Dressing of ore: The ore as it is extracted from the ground contains lot of impurities and also it is in large lumps. The process of breaking the lumps and removing the impurities is called dressing. Processing of ore: This is done in a blast furnace. Hot air is created and blast into the furnace from bottom. The charge consisting of coke, ore and lime stone is introduced from the top. The molten iron and impurities (slag) is collected at the bottom of the furnace and removed from there. Cast Iron: Cast iron is essentially remelted pig iron. It contains about 2- 4% carbon and small proportions of manganese, silicon and sulphur. The remelting is done in cupola furnace which is similar to blast furnace but smaller in size. The raw materials – pig iron, steel scrap, coke and lime stone are introduced at the top to previously heated cupola furnace. Air is continuously pushed inside. Impurities get oxidized and the slag formed floats on the surface.

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The properties of cast iron are influenced by the amount of carbon and nature in which carbon is present. Properties of Cast Iron: -Hard and brittle; Not ductile; Does not rust; Specific gravity 7.5; Shrinks on cooling; Weak in tension Uses of cast Iron For making columns, Pipes, Sewers, Man hole covers, Parts of machineries Wrought Iron It is the purest form of iron. Pig iron is heated in Puddling furnace. It is a small form of reverbaratory furnace. The charge is heated to 1200 degree centigrade. The impurities form a slag on the top surface which will be removed. Wrought iron is collected at the bottom. Properties of wrought iron High tensile strength, Malleable, Ductile and tough, Density 7.8 g /cubic cm. Uses of Wrought Iron For making plates, sheets, pipes, tubes, railway couplings Steel Steel is a variety of iron containing 0.1 to 1.5 % carbon . It is manufactured by three processes Bessemer process, Open hearth process and Electric process.

Types Steel

Percentage of carbon

1. Mild steel

0.25%

2. Medium carbon steel

0.25% to 0.60%

3. High carbon steel

0.60% to 1.50%

Mild steel is generally used for various works-

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Properties of Mild Steel - it is strong in compression, tension and shear - It can be welded and riveted -It can be permanently magnetized -It is ductile and malleable -It is tough and elastic

Heat treatment The process of heating the metal to high temperature and then cooling to room temperature is called heat treatment. The main heat treatment processes are – Annealing, Normalising, Quenching and Tempering. This is done to improve the properties of steel.

Uses of mild steel - For making structural shapes like angles, channels, sheets, flats etc - As reinforcing bars in RCC - For making various tools and machine pats - For manufacturing roof covering sheets

Marketable forms of steel The rolled steel sections commonly available in market are: Angle, Channel, Round bar, Flat, I section, square bars etc. They are generally used in the construction of roof trusses, transmission towers, beams, columns, foot over bridges, grillage foundations etc. The advantage in using these structural sections are they can be easily fabricated and erected thus saving time and money.

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Advantages of steel as a structural material - High strength - Long life -Can be readily fabricated, erected and dismantled - Steel pipes are gas and water tight

Disadvantages of steel as a structural material - High cost - Likely to be corroded - Low fire resistance

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Points to Ponder

* Metals are classified under two categories - Ferrous metals and Non-ferrous metals * Cast iron, Steel etc are ferrous metals * Aluminium and its alloys come under non - ferrous metals *Pig iron is the basic form of iron. It is manufactured in three stages – Selection of ore, Dressing of ore, Blast furnace treatment. * The main iron ores are Haematite, Magnetite, Siderite * The iron ores are extracted from earth (mines) * The process of removal of impurities and the reduction in size is called dressing. *The charge consisting of ore, coke and lime stone is introduced at the top of furnace, and heated air is blast from the bottom.            

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The molten iron and impurities are collected from the bottom. Cast iron is remelted pig iron. The remelting is done in cupola furnace. The raw materials are pig iron, steel scraps, fuel and fluxes. Cast iron is used in Agricultural machinery, Railway equipments ,Automobile parts Wrought iron is the purest form of iron. There are two forms of manufacture of Wrought iron – Puddling process and Aston process The important properties of Wrought iron are – Strength, ductility, malleability and toughness It is used for making plates, sheets, pipes, tubes etc Steel is a type of iron containing 0.1 to 1.5 % carbon Steel is manufactured by Bessemer process, Open hearth process and Electric process Plain carbon steel is divided into three categories – Low carbon steel, Medium carbon steel and High carbon steel. The process of heating the metal to high temperature and then cooling to room temperature is called heat treatment. The main heat treatment processes are – Annealing, Normalising, Quenching and tempering.

Model Questions

1.What are the two classifications of metal? 2.What are the three stages of manufacture of pig iron? 3.What are the uses of cast iron? 4.What are the important properties of wrought iron? 5. What are the classifications of plain carbon steel? 6. What is meant by heat treatment? 7.What are the uses of steel? 8. What are the main marketable forms of steel? 9. What are the advantages of steel as a structural material? 10. What are the properties of mild steel?

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15.

Reinforced Cement Concrete

As mentioned earlier, plain cement concrete is weak in tension but strong in compression. A structural member is normally subjected to both compression and tension. Therefore steel bars are embedded in concrete to take up the tensile stresses. The diameter of the bars and number of bars will depend on the span of the member and the loads subjected to it. Such a concrete is called reinforced cement concrete.

Advantages of RCC The advantages of RCC (Reinforced Cement Concrete) are. 1. Reinforced Cement Concrete can withstand both compressive stress and tensile stress . 2. It has good fire resistance and weather resistance. 3. RCC protects steel bars from buckling and twisting at high temperature. 4. RCC prevents steel from rusting. 5. RCC is durable. 6. Maintenance cost of RCC is practically nil.

Disadvantages of RCC 1. The structure of RCC is comparatively heavier 2. It takes more time to construct a member with RCC as it involves form work, mixing of cement, aggregates and water, transporting, placing, compacting and curing 107

4.It requires good expertise in designing and constructing the structure

Reinforcement Details

The figure shows the arrangement of steel bars in a RCC beam. The tensile reinforcement bars are provided at the bottom, the anchor bar is provided at the top. The stirrups bind the bars. The diameter and the number of bars will depend on the span and the load to be carried.

Precautions in RCC works - Shuttering should be strong. - The diameter of the bar, number of bars and spacing should be as per the design and drawing - The overlap length should be 50 times the diameter of the bar - The steel bars should have the cover as prescribed in IS 456. -The main reinforcement should be on the tension side of the member

Fibre Reinforced Concrete Fibre reinforced concrete is one in which fibres of steel, nylon, asbestos, coir or, glass are inserted. This type of concrete has the capability to resist cracks. This is used in manufacturing door and window frames, pipes and manhole covers, wearing coats of roads, shell roofs.

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Ferro Cement concrete Ferro cement concrete is one in which wire mesh of metal or any other suitable material is embedded The main properties of ferro-cement concrete are: capacity to resist shock loads, impervious, attractive finish like teak or rosewood, construction with out form work. The uses of ferro cement are – Partition walls, window frames, window shutters, water tanks, pipes, man hole covers, furniture etc.

Pre- stressed concrete (PSC) Since concrete has low tensile strength, cracks may develop in the tensile zone of such structural members. Pre-stressing is done by stressing the steel wires. Concrete in tensile zone only helps to hold the steel wires in position. Pre- stressing helps in utilizing the strength of concrete in tensile zone also. In pre- stressed concrete tension is completely eliminated in concrete. Hair like cracks are eliminated. Therefore more durability is obtained. The deflections are less in PSC members and fatigue strength is high. The disadvantage is that elaborate arrangements are required for pre-tensioning / post tensioning. PSC is commonly used for bridge girders, railway sleepers, poles.

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Points to Ponder

    

Cement concrete in which steel bars are embedded is called reinforced cement concrete.(RCC). Ordinary cement concrete can’t take tensile stresses. It has got good fire resistance and weather resistance. Now a days all structural members like beams, slabs, columns, lintels etc are manufactured with RCC. RCC members are quite heavy, it takes more time to construct and it requires form work.



Model questions 1. 2. 3. 4. 5. 6. 7.

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What is RCC? What are the advantages of RCC? What are the precautions to be taken in RCC works? What is ferro cement concrete? What is pre stressed concrete? Where pre stressed concrete is used? What is fibre reinforced concrete?

16.Timber

Timber is wood for engineering purposes. Timber is one such building material which is being used from time immemorial to construct huts, buildings and make furniture, boats etc. But recently due to paucity of timber coupled with its high cost, its use has been drastically reduced. Large scale felling of trees leads to environmental problems. As such, it’s use is being discouraged while recommending alternate materials to timber. Classification of trees: For engineering purposes, trees are classified according to their mode of growth: .a) Endogenous b) Exogenous a). Endogenous trees: These type of trees is largely confined to tropical semitropical regions. Timber from these trees has very limited engineering applications. Example of endogenous tress is: - Palm, Bamboo. b). Exogenous trees: These trees grow outwards and annual rings are formed in the horizontal section of such a tree. Exogenous trees are further subdivided into – Conifer (evergreen) trees and Deciduous trees. Conifer trees have pointed leaves and their leaves fall when new ones are grown up. Deciduous trees have broad leaves. e g : Teak, Mahogany Classification of Wood Wood can be divided into two groups: a) Hard wood: Teak b). Soft wood: Deodar The classification is based on: Strength (strong, weak), Colour (dark, light), Fire resistance (moderate, poor), Medullary rays (distinct, less distinct), Weight (heavy, light).

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Cross section of a tree trunk

Pith (Medulla): It is the inner most part of a tree. When the tree becomes old, the pith disappears and becomes fibrous and dark. It varies in size and shape. Heart Wood: This is the portion surrounding pith. It is dark in colour and strong. This portion is useful for various engineering purposes. It consists of several annular rings. Sap Wood: It is the layer next to heart wood. It denotes recent growth and contains sap. As the trees grow, sap moves in upward direction. Cambium Layer: It is a thin layer of fresh sap lying between sap wood and the inner bark. It contains sap which is not yet converted into sap wood. If the bark is removed and cambium layer is exposed to atmosphere, cells cease to be active and tree gets extinct.. Inner Bark: It is an inner skin of tree protecting the cambium layer. Outer Bark: It is the outer skin of the tree and consists of wood fibres. Medullary Rays: These are thin radial fibres extending from pith to cambium layer. They hold annular rings together. In some of trees they are broken and some other they may not be so prominent.

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Properties of Timber Strength: Timber should have high strength in bending, shear and direct compression. Fire resistance: A good timber should have high resistance to fire. Hardness: Harder timbers are strong and durable. Warping: Good timber should not warp under changes in environmental conditions. Toughness: Timber should be capable of resisting shocks. Density: Higher density indicates stronger timber. Workability: Timber should be easily workable. Durability: Good timber should be capable of resisting the attack of fungi and insects Defects: Good timber should be free from defects like dead knots, shakes Colour: It should be uniform. Odour: When freshly cut, the odour should be pleasant Soundness: When struck, it should give a clear ringing sound Texture: Texture of good timber is fine and even. Abrasion: Good timber should not deteriorate due to wear. This property is of importance when it is used for flooring. Permeability: Good timber should have low water permeability.

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Seasoning of Timber Fresh timber may contain moisture. The process of removal of moisture from wood is called drying of wood or seasoning of wood. This reduces the chances of decay, improves load bearing properties, reduces weight, makes the timber workable, and improves thermal & electrical insulation properties. Methods of Seasoning

-Natural seasoning -Artificial seasoning Natural Seasoning

Air Seasoning Air seasoning is the traditional method for drying wood. Air seasoning , takes about nine to ten months. For this, logs of wood are stacked in open air in such a manner that air can circulate all around the timbers. The timber pieces should be kept away from vegetation and damp ground. The stack should be properly covered.

Water seasoning In this method, the cut pieces of wood are kept in the running water of a river for about two to four weeks. The sap will be washed away during this period. The cut pieces are then taken out of water and allowed to dry in air. Natural seasoning is simple, cheap and does not require skilled supervision. But the drying of different surfaces may not be uniform and also the space required for stacking is quite large. Artificial seasoning The artificial methods of seasoning are: Boiling, Chemical seasoning, Kiln seasoning and Electrical seasoning. Seasoning by boiling: The timber is kept immersed in water in a vessel. The water is heated to boiling temperature. It is kept boiling for four to five hours. The timber is then taken out of water allowed to dry in air. Chemical seasoning: The timber pieces are quoted with a chemical solution like sodium chloride, sodium nitrate or urea. Then the timber is exposed to natural drying.

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Kiln seasoning: The timber pieces are dried in specially designed kiln. Here there is perfect control over temperature, humidity and circulation of air. The process is comparatively costly but the quality of seasoning is quite high. Electrical seasoning: .High alternating current is passed through green timber pieces. The heat generated dries out the moisture. This technique is costly as costly equipments are to be installed and also the consumption of electricity is high. Comparison of Natural Seasoning and Artificial Seasoning In natural seasoning, it is difficult to control moisture content, while in artificial seasoning the moisture can be reduced to any extent. Natural seasoning is simple and economical while artificial seasoning is comparatively costlier. Natural seasoning is a slow process while artificial seasoning is fast. Natural seasoning requires more space while for artificial seasoning the requirement of space is less. Defects in timber The defects which are likely to occur in timber are due to: (i) Natural forces (ii) Defective seasoning (iii) Conversion (iv) Attack of insects and fungi The natural forces cause the following defects. Knots, Shakes, Wind cracks, Upsets a) Knots: When branches are cut off or broken from the tree, knots are formed. Knots are dark and hard spots. Grains are distorted in this portion. Figure below shows some varieties of knots. If the knot is intact with surrounding wood, it is called live knot. If it is not held firmly it is dead (decayed) knot.

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b) Shakes: The shakes are cracks in the timber which are caused due to excessive heat, frost or twisting due to wind during the growth of a tree. Depending upon the shape and the positions shakes, are classified as star shake, cup shake, ring shakes and heart shakes.

c) Wind Cracks: These are the cracks on the outside of a log due to the shrinkage of the exterior surface. They appear as shown in Fig. below. .

(d)

Upsets: Figure shows a typical upset in a timber. This defect is due to high compression in the tree when it was young. Upset is an injury by crushing. This is also known as rupture.

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(ii)

Defects due to Defective Seasoning: If seasoning is not uniform, the converted timber may warp and twist in different directions and even cracks may appear. This type of defect is more common in case of kiln seasoning. (iii) Defects due to Conversion During conversion of timber to commercial sizes and shapes, the following defects are likely to occur: chip marks, torn grain, diagonal grain etc. (iv) Defects due to Fungi and Insects Attack: Fungi are very complex multi cellular organisms. These attack wood when the moisture content is above 20%.. Wood becomes weak and stains appear on it. Beetles, marine borers and termites (white ants) are the insects which eat wood and weaken the timber.

Common Indian timber Aini: It is strong and yellowish brown in colour. It is used for doors, windows, rafters, purlins, furniture etc. Bamboo: It is an endogenous tree. Bamboo is generally used for thatched roofs, scaffoldings etc. Mahagony: It is reddish brown in colour, durable and possesses good workability. It is used for doors, windows, furniture, ship building and railway sleepers. The forests are there in Kerala, Madhya Pradesh, Tamil Nadu and Mysore. Coconut: It is reddish in colour, difficult to saw, outer portion hard and inner portion soft. It is used for posts, furniture and form work. Teak: The teak wood is hard, strong, and durable. Teakwood is suitable for all types of structural work, furniture , railway sleepers etc. Irul: It is strong, durable and hard wood with less workability. It is used for railway sleepers, agricultural tools. Jack: It is yellow coloured, lacks workability. It is used for door frames, and panels, furniture. Mango: It is moderately strong and workable. It is generally used for furniture, door and window panels and packing boxes. 117

Rosewood: It is strong, hard, durable and costly. It is used for furniture and ornamental carvings. Sal: Sal is hard and close-grained. It is of dark brown colour. It is durable and can resist termites attack. It is used in building construction, bridge construction and ship building. It is found in U P Bihar and Assam. Tamarind: It is durable, dark brown coloured. It is used for form work in concrete construction.

Preservation of Timber The purpose of applying preservatives on the surface is to protect the timber from the attack of insects and fungi and thus prolong the life of the components / systems made of timber. The different methods of preservation are: Painting, Tarring, Creosoting, Application of ASCU powder developed by Forest Research Institute of India.

Type of timber suitable for various purposes Door and Window frames-

Rosewood, Teak, Jack

Door and window panels-

Jack, Mango, Teak

Furniture

Rosewood, Teak, Mango, Jack

Form work

Mango, Coconut tree

Packing case

Mango

Railway sleepers

Teak, Irul

Special Timber Products Veneer (Ply): Veneer is a thin sheet of timber with a maximum thickness of 6mm. They are made out of timber logs by sawing, slicing or rotary cutting. Veneers are used for the manufacture of plywood and laminated board. Ply wood: It is a special type of processed wood containing thin sheets (plies) glued together. Plywood panels may consist of any odd number of plies. It is extensively used in various civil engineering applications like roofs, furniture, ceilings etc. Laminated timber: It is another type of processed wood. In this selected wood sheets (veneers), are glued together in such a way grains of all sheets are parallel longitudinally. It is manufactured in three grades – Industrial, Architectural, and Premium grades.

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Fibre boards: These are made by pressing together fibrous materials which are first heated and pressed hard. On cooling, a rigid material of light density is obtained. These are used for flush doors, wall panels, insulation boards etc.

Points to Ponder

     

Timber is wood for engineering purposes Timber is obtained from trees Trees are of two types – Exogeneous and Endogeneous Exogeneous trees are further classified as conifer (evergreen) and deciduous trees Another classification is soft wood and hard wood The main parts of a tree are – Roots, Stem (trunk) and Crown (branches and leaves

)        

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The cross section of a tree shows the following components – Bark, cambium layer, sap wood, annual rings, heart wood, medullary rays, pith. The factors to be taken into account before felling a tree are – age of tree, time / season of felling, method of felling. Conversion is the process of cutting and sawing the wood for planks, battens etc. Seasoning is the process of removing moisture from freshly cut timber. A defect is an irregularity or abnormality in or on the wood which may lower its strength, durability or utility. Timber is said to be decayed if it loses its value as an engineering material. Preservation of timber is done to protect it from attack of insects, fungi etc. The common tests conducted on timber are to ascertain compressive strength, moisture content, specific gravity, shrinkage and swelling

Model questions 1 What are the different types of trees? 2. Draw the cross section of a trunk of a tree and mark the parts? 3. What is seasoning? What are the different methods of seasoning? 4. What are the defects found in timber? 5. Suggest suitable types of timber for: Furniture, Door and Window frames and panels, Railway sleepers, Packing cases 6. What is seasoning of wood? 7.What are the special timber products? 8. What are the common Indian timbers? 9. What is conversion of wood? 10. What are the main properties of wood?

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Building construction

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17.Selection of the site for a building

There are many factors which must be taken in to account while selecting a site for a commercial, industrial l or a residential building. Some of these factors are given below. 1. 2. 3. 4. 5.

Purpose of the building Shape of the Plot Location of the plot Availability of amenities Water Table

A. Residential Building

1.Purpose of the building First the purpose for which the building is being constructed should be identified. If it is for residential purpose, it is ideal that the building is away from main business centre of the city. If it is for a factory, it should be near to a place where raw materials are available in the vicinity.

2. Shape of the plot: Geometry of the plot for any kind of construction is very important which can largely effect the appearance of the structure. Shape of the plot should be such that the construction can be easily made with out incurring much expenditure. And also there must be space for future expansions.

3. Location of the plot: The site should be located in a fully developed place. It is desirable that there are no major industries in the vicinity so that the environment is not polluted. The site should be slightly elevated so that there is no chance for stagnation of water. The soil at the site should be of good quality so that the bearing capacity of it is comparatively high.

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4. Availability of Amenities: Plot for a residential building should be taken in the area provided with amenities like electricity, telephone, Internet, Gas, School, Colleges, University, Hospital etc Another important facility is the good and fast transport system..

5. Availability of Water: The water should be available from wells in the vicinity or other wise it must be available through pipes provided by local government agencies.

6.Orientation of the site: Orientation of the site has some bearing on its selection. Site should be such that early morning sun and late evening sun is available in the building. 7. Good Landscape: The site should have a good landscape to promote a peaceful and serene environment. 8. Good surroundings: For a happy and comfortable living, the residents in the neighbourhod should be of almost equal status. B. Industrial Building 1. The factory site should be away from residential locality. 2. There must be space for future expansion 3. Raw materials should be available in the neighbor hoods. 4. It is preferable that the site is on an elevated plot so that the rain water will not get stagnated. 5. The site should be well connected by road, rail and air. 6. Electric power is readily available. 7. There must be facility for treatment of the effluent before discharging out. 8. Availability of local trained labour

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C. Educational Building: 1. The site should be away from the main city centre 2. The site should be well connected by road 3. The surroundings should be neat and clean with out noise pollution 4. Drinking water should be available through out the year 5. It is preferable that the building site is slightly elevated so that water will not get stagnated 6. Natural light is available 7. There must space for play ground as well as for future expansion.

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18.Setting out of a Building Plan On Ground Before starting the excavation for the foundation, the centre line and outline of excavation should be clearly marked on the ground. Procedure:

Fig.1: Example plan to be set out on the ground 1. From the plan (fig 1), the centre line of the walls are calculated. Then the centre lines of the rooms are set out by setting perpendiculars in the ratio 3:4:5. Suppose the corner points are A, B, C, D, E, F and G which are marked by pegs with nails on top. 2. The setting of the corner point is checked according to diagonals AC, BD, CF and EG. 3. During excavation, the centre points A,B,C,D,E,F,G may be removed. Therefore the centre lines are extended and the centre points are marked about 2m away from the outer edge of excavation. Thus the points A1, A2, B1, B2 and like wise, are marked outside the trench. Centre line are shown clearly by stretching thread or rope. The centre points fixed 2m away from the excavation are marked with sit out pegs.

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4. From the plan details, the width of excavation to be done is also marked by thread with pegs at appropriate positions. 5. The excavation width is then marked with lime or with furrow by spade. See the video clip for setting out a building-Part 1,2,3 https://www.youtube.com/watch?v=Lyb20DhmT90 For detailed information about setting out visit the site: http://www.tcd.ie/civileng/Staff/Brian.Caulfield/3A1/3A1%20Lecture%2011.pdf

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19. Stone Masonry

Stone masonry refers to the construction of various structures like buildings, compound walls, retaining walls etc using blocks of stone joined together with mortar. Materials for stone masonry The materials required for stone masonry are: Mortar, Stones Mortar: Mortar consists of binding material and sand in specified proportions. The binding material may be mud, lime or cement. Generally cement – sand mortar (1: 3) is used for stone masonry. Stones for the Masonry Granite: It is of igneous rock, strong and durable. It is available in Kerala, Karnataka, Kashmir, UP, MP, Punjab, Assam etc. Sandstone: It is of sedimentary rock. It is easy to work and sufficiently strong. These stones are available in almost all states of India. Marble: This is of metamorphic rock. They are available in different colours and are available in Rajasthan and Maharashtra. Laterite: This is found in coastal areas of Kerala, Karnataka, Tamilnadu and West Bengal. When freshly cut, they will be soft but in due course hardens on exposure to atmosphere. They are porous and as such they must be plastered with cement mortar to protect it from rain. Limestone This is of calcareous rock. It is available in different colours and is easy to work. It is available in almost all states. It easily gets disfigured in acidic atmosphere. Dressing of Stones After quarrying, the stones are to be cut to proper size and surface finishing done. This process is known as dressing. This may be done at the quarry site or construction site. Types of stone masonry: Stone masonry is of two types: 1. Rubble Masonry 2.Ashlar Masonry. 127

The masonry in which either undressed or hammer dressed stones are used is called random rubble masonry. Random rubble masonry is divided into the following types:

Rubble Masonry Un coursed random rubble masonry: The random rubble masonry in which stones are laid without forming courses is known as un coursed random rubble masonry. This is the roughest and cheapest type of masonry and is of varying appearance. The stones used in this masonry are of different sizes and shapes. Before laying, all corners of stones are slightly knocked off. Joints are filled with mortar and flushed. Large stones are used at corners and at jambs to increase their strength. Through stone is used for every square meter of the face area for joining faces and backing. 128

Suitability: Used for construction of walls of low height in case of ordinary buildings. Coursed random rubble masonry: The random rubble masonry in which stones are laid in layers of equal height is called coursed random rubble masonry. In this masonry, the stones are laid in somewhat level courses. Headers of one coursed height are placed at certain intervals. The stones are hammer dressed. Suitability: Used for construction of residential buildings, godowns, boundary walls etc.

Square Rubble Masonry : In this type of masonry, stones are given straight bed and sides by hammer dressing. Polygonal Rubble Masonry: In this type of masonry, stones are arranged in such a manner to give a polygonal shape. The stones are hammer dressed. Flint Rubble Masonry: In this type of masonry flints of varying thickness and length are used. The thickness may range from 50 mm to 75 mm and length from 150 mm to 300 mm. Dry Rubble Masonry: In this rubble masonry stones are laid without using any mortar. It is an ordinary masonry and is recommended for constructing walls of height not more than 6m. (compound walls)

Dry Rubble

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Ashlar Masonry

In Ashlar masonry, finely dressed stones are laid in cement or lime mortar. The courses are of uniform height, all the joints are regular, and have uniform thickness. Since the stones are to be properly dressed, it takes time and as such is this type of masonry is more costly. This masonry is mainly used for architectural buildings, abutments of bridges etc. Ashlars masonry is further sub divided into the following types: i. ii. iii. iv. v. vi. vii.

Ashlar fine tooled masonry Random course ashlars masonry Rough tooled ashlar masonry Rock or quarry faced ashlars masonry Chamfered ashlars masonry Block in course masonry Ashlar facing

- Ashlar fine tooled masonry: In this type of stone masonry, stone blocks of same height in each course are used. Every stone is fine tooled on all sides. Thickness of mortar is uniform through out. It is an expensive type of stone masonry as it requires more skilled labour Wastage of material while dressing is also more. - Random coursed ashlar masonry: This type of ashlar masonry consists of fine or coursed ashlar. The courses are of different thicknesses, depending upon the type of the building.

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Coursed Ashlar - Rough tooled ashlar masonry: In this type of ashlar masonry the sides of the stones are rough tooled and dressed with chisels. Thickness of joints is uniform. - Rock or quarry faced ashlar masonry: This type of ashlar masonry is similar to rough tooled type but the margin is left rough on the face. - Chamfered ashlar masonry: It is similar to quarry faced. But the edges are bevelled or chamfered.

Chamfered Ashlar - Block-in course masonry: It is a type of ashlar masonry which is in-between rubble and ashlar. The stones are all squared and properly dressed. It resembles to coursed rubble masonry or rough tooled ashlar masonry. - Ashlar facing: Ashlar facing is the best ashlar masonry. This type of masonry is very expensive. So it is commonly used in works of great importance and strength. For economy the facing is built in ashlar and the rest in rubble. Quality control of stone masonry construction

- Stones should be hard and durable and free from cavities. - Stones should be laid on their natural bed - Stones should be immersed in water before use. - Verticality of the wall should be checked. - Vertical joints should be staggered. - The height of the masonry should be raised uniformly - Mortar used should be of correct proportion

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Maintenance of Stone Masonry

- In course of time, cracks may develop in the masonry. Small cracks should be cleaned by wire brush, and then filled with cement paste. If the cracks are wider, first remove the loose material and then fill it with 1:2 cement mortar. - Due to leakage of water through masonry, sometimes layers of white soluble salts get deposited on the surface of masonry. This should be removed by scrubbing with a brush and water. - To prevent leakage of water through masonry, waterproofing materials should be applied on the surface. - Oil stains should be removed by scrubbing with benezene or petrol.

Points to Ponder

        

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Stone masonry means construction of structures using stone blocks and mortar. Mortar is a mixture of binding material and sand. The binding material can be mud, lime or cement. The common types of stones used in India are – granite, marble, laterite, sand stone, slate. The cutting the sharp corners of stone blocks, cutting it to proper size and giving the finishing touch is called dressing. There are mainly two types of masonry – rubble masonry and ashlar masonry. In ashlar masonry, stones are cut to proper size , sharp corners removed and finishing touch is given while in random rubble masonry stones of irregular shapes are used. Proper quality control should be followed during the construction. The following maintenance works are suggested for old masonry – water proofing, removal of efflorescence, removal of stains and repair of cracks.

Model Questions 1. Define masonry. 2. What are the two types of masonry? 3. What are the main building stone blocks used in stone masonry? 4. What is dressing? 5. Explain quality control of masonry construction 6. How should stone masonry be maintained?

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20. Brick Masonry

Bricks were used from time immemorial for construction of buildings. Even now bricks are being used as a construction material to a large extent. Brick masonry is constructed with brick and mortar. The mortar can be of mud, lime or cement. Bricks are manufactured by moulding clay to proper size, drying and then burning in kilns. The standard size of bricks is 190 x 90 x 40 mm. Some Definitions Stretcher: It is a brick with its length in the direction of the wall. Header: A brick is called a header if its shorter side is exposed. Closer: It is the portion of the brick cut in the longitudinal direction.

Queen closer: It is a half brick in the longitudinal direction. King closer: It is a portion of a brick with one corner chopped off. Bevelled closer: It is a portion of a brick with one portion removed as shown in the sketch above. Bull nose Brick: Bull nose brick is a special type of brick which has one, some or all of its corners rounded off. These bricks are used to create soft and attractive curved edges to steps, sills, or in capping walls. Bat: It is a portion of a brick cut across its width. The length of the brick may be half or threefourth of its original length. 134

Bond Bond is the method of arranging the bricks so that the individual bricks are joined together in layers (courses) and that the vertical joints do not come in the same line. Rules for bonding: The lap should be at least ¼ th brick along the length and ½ brick across the thickness of wall. Brick bats should be used for the minimum. All bricks should be of same size and shape. The vertical joints in alternate layers should be in the same line. 13.4 Method of brick laying Brick laying is an art. Only a skilled mason can do the work efficiently. First clean the surface over which the wall is to be built. Then spread 15 mm thick cement mortar over the area. The corner of the wall is marked. The first brick is laid at the corner over the mortar and pressed well. The other bricks are laid subsequently. The corners are raised first and then the inbetween portion is raised. 13.5 Types of Brick Bonds The different types of brick bonds are: 1. English-bond 2. Flemish bond, 3. Stretching bond, 4. Heading bond, 5. Garden wall bond, 6. Facing bond, 7. Raking bond, 8. Dutch bond, 9. English cross-bond, 10. Zig-Zag bond, 11. Silver lock’s bond. 135

English Bond English bond consists of alternate courses of headers and stretches. In the English bond arrangement, vertical joints in the header courses come over each other while the vertical joints in the stretcher course are also in the same line. For the breaking of vertical joints in the successive course it is essential to place a queen closer, after the first header in each heading course. Walls having their thickness equal to an even number of half bricks, i.e., one brick thick wail, 2 brick thick wall, 3 brick thick wall and so on, present the same appearance on both the faces, i.e. a course consisting of headers on front face will show headers on the back face also. Isometric view of 1½ brick wall in English bond , and plans of 1, 1 ½, 2, 2 ½, 3 brick walls are shown below,

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See the video showing the procedure of laying bricks in English bond

https://www.youtube.com/watch?v=qn9Y5FpYn1Q

Flemish Bond In this arrangement, stretchers and headers are placed alternately in the same course. There are two types of Flemish bond: 1.Double Flemish bond 2. Single Flemish bond 1 .Double Flemish Bond: In this type of bond, headers and stretchers are alternately placed in each course in front as well as back. In the case of single Flemish bond, the front is made in Flemish bond and back in English bond.

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Comparison of English bond and Flemish bond -

The Flemish bond has a better appearance than English bond The strength of a wall in English bond is more than that of a wall in Flemish bond The construction cost of Flemish bond is more .

See the video showing the procedure of laying bricks in English bond

https:// www.youtube.com/watch?v=7UGYc9uzEMA 3.Stretching bond: In this arrangement, all the bricks are laid as stretchers. Each alternate course is commenced with a half brick bat. Stretching bond is used for half brick wall only. This bond is also termed as running bond It is commonly used for the construction of half brick thick leaves of cavity walls, Partition walls etc.

4. Header bond : In header bond all the bricks are laid as headers on the faces. The overlap is obtained by keeping a three-quarter bat in each alternate course at quoins. This bond permits better alignment. Therefore it is used for walls curved on plan.

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. 5.Garden wall bond: This type of bond is generally adopted for garden wall of one brick thick wall. This type of bond is not strong as English bond. As such, it is used to construct dwarf walls or other similar types of walls. . There are two types of garden wall bond, (a) English garden wall bond (b) Flemish garden wall bond (a) English garden wall bond. In this bond bricks are arranged in similar to that of English bond. But the heading courses are inserted at every fourth or sixth course. Usually the arrangement consists of one course of headers to three courses of stretchers.

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(b) Flemish garden wall bond. In this, alternate course is of one header to three or five stretchers in series. Each alternate course will have a three quarter bat placed next to the quoin header and a header is laid over the middle of each central stretcher.

6.Facing bond: This bond is adopted for thick walls, where the facing and backing are to be constructed with bricks of different thicknesses. In this bond, heading and stretching courses are so arranged that one heading course comes after several stretching courses. The number of joints in the backing and the facing are different. This may cause unequal settlement of the of the wall. 7.Raking bond: In this bond, bricks are laid at any angle other than zero or ninety degrees. This arrangement increases the longitudinal stability of thick walls built in English bond. This bond is kept at different intervals along the height of a wall. There are two types

of

raking

bond

;

(a) Herringhone-bond (b) Diagonal bond. (a) Herring-bone bond. This type of bond is ideal for very thick walls. In this, bricks are laid in course inclined at 45° in two directions from the centre. This bond is also generally used for pavings.

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(b) Diagonal bond. This bond is used for walls of 2 to 4 brick thick. This bond is kept at fifth or seventh course along the height of the wall. The bricks arc kept end to end.

8.Dutch bond: In this bond alternate courses are of headers and stretchers. Each stretching course starts at the quoin with a three-quarter bat and every alternate stretching course has a header placed next to the three-quarter brick bat at the quoin.

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9.English cross-bond: This is similar to English bond. But queen closer is introduced next to quoin headers and each alternate

stretching

course

has

header

placed

next

to

quoin

stretcher.

10. Zig-Zag bond: This is similar to herring-bone bond. But the bricks are laid in a zig-zag fashion. This is generally adopted for paved flooring.

Points to be observed in Brick Masonry - Bricks should be of good quality - Bricks should be soaked in water before laying - Walls should be raised uniformly 142

- Brick masonry wall should be cured for about two weeks - Verticality of the wall should be maintained - Brick bats should be used for the bare minimum - Hold fats of doors and windows should be embedded firmly in the wall Comparison of Stone Masonry with Brick Masonry Bricks are light Thinner walls can be constructed with bricks Dead weight of brick masonry is less Strength of brick is less Brick masonry has a tendency to absorb moisture

Stone blocks are heavy Thinner walls can’t be constructed Dead weight is more Strength is more No tendency to absorb moisture

Defects in brick masonry

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  

Poor quality bricks may absorb moisture, thus weakening the structure With the absorption of moisture, the brickwork may swell. When the brickwork comes in contact with water, white crystals may appear on the surface creating a bad appearance.

 

By using inferior quality bricks, the structure may settle leading to cracks In cold regions due to frost action , cracks can develop in brick construction

Points to Ponder



joined

Brick masonry is the civil construction with bricks and mortar. Bond is the method of arranging the bricks so that the individual bricks are together in layers (courses) and that the vertical joints do not come in the same line.

There are different types of bonds; but the most common are English bond and Flemish bond  In English bond alternate courses are of headers and stretchers while in Flemish bond in each course there are alternate stretchers and headers.  The main points to be observed in brick masonry works are – use of good quality bricks, mortar to be of proper mix, brick masonry to be cured for two weeks by sprinkling water, bricks to be soaked in water before use…….

Model Questions 1. Define stretcher and header. 2. What is bond? 3. What are the main bonds? 4. Compare brick masonry with stone masonry. 5. What are the main points to be observed in the brick masonry construction? 6. What are the main defects in brick masonry?

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21.Floors and Flooring Materials

A floor is the bottom surface of a room. In a building, there is the ground floor, first floor, second floor like that. Floors may be of stone, wood, concrete or any other material that can support the expected load. The levels of a building are often referred to as floors although a more proper term is story. Floors typically consist of a subfloor for support and a floor covering used to give a good walking surface.

Requirements of a floor - It should be durable - It should have an attractive finish It should be impervious -

The floors should be strong enough to with stand the load It should not be too costly

-

The maintenance cost should not be high It should have a level surface

Factors to be taken into the selection of flooring materials Durability, Appearance, Damp resistance, Fire resistance, Resistance to abrasion, Initial cost ,Maintenance Types of Flooring Mud, Brick, Cement Concrete, Terrazzo, Mosaic , Marble, Tile, Timber, Rubber, Linoleum Construction of floor Ground Floor First the soil is compacted. A layer of broken stones or brick bats is then pressed into it. Then a layer of concrete of 1:4:8 mix is laid for about 150 mm thick as base course. The floor finish is then laid. The floor finish generally adopted is – Terrazzo, Mosaic, Marble, Tiles, Timber. 145

Upper Floors The upper floor are supported on walls and columns. The floors have to withstand self weight and live load. Therefore they are designed for strength, limiting the deflection to the allowable limits. The types of floorings are listed above. Cement Concrete Flooring The most commonly adopted flooring is of cement concrete. For the construction of the floor, soil is first filled up in the basement and compacted. Then the whole area is divided into convenient sizes of squares or rectangles. These bays are then filled with concrete, compacted and finished smoothly. After curing, the floor is washed and cleaned.

Mosaic Floor First the base course of concrete is laid. Over which a layer of 3040 mm thick mortar is spread. Broken pieces of marble chips are set on this layer. After drying for a day, the top surface is rubbed with carborandum stone to get a polished surface.

Mosaic Floor Timber Floor

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Timber boards may be placed directly on the concrete bed or over a timber frame work. Timber floor is costly. It is generally provided in auditoriums.

Timber Floor

Tiled Floor

Tiles of clay, cement or terrazzo are manufactured in factories. These tiles are fixed on a base of about 25-30 mm thick cement mortar. Apply a layer of cement slurry on the sides and bottom of the tile and then press it into the base of mortar. The next day, the joints are cleaned filled up with coloured cement slurry.After curing for seven days, grinding and polishing are done.

Tiled Floor Maintenance and repair of concrete Floor Cracks may develop in the floor. The cracks may be surface cracks or structural cracks, The structural cracks may start from the base and extend to the surface while the surface cracks may be in the surface only. Structural cracks are caused due to shrinkage, temperature variations or settlement. For repairing structural cracks, that portion will have to chipped off and then filled up with fresh concrete. Hair cracks can be repaired by filling it with some varnish.

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Points to Ponder

   

Floor is that part of a building over which people stay and move. The bottom most floor is the ground floor. The upper floors are there at the correct levels as first floor , second floor like that. The base floor is generally of cement concrete. The floor finishes are of marble, tiles, stone, wood, rubber, mosaic, terrazzo etc.

Model Questions 1. What is a floor? 2. What are the requirements of a floor? 3. What are the common floor finishes? 4. What are the factors to be taken into the selection of flooring materials? 5. How is a concrete floor repaired? 6. Describe the procedure of construction of a concrete floor.

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22.Roofs and Roofing Materials

Roof is the topmost part of a building. It serves as a cover protecting the inhabitants from rain, sun and wind. The roof can be pitched or flat; tiled or of concrete. Requirements of a good roof     

It should be leak proof It give protection from sun and rain It should be durable It should be fire resistant It should be structurally stable

Types (Classification) of Roofs   

Flat or terraced roofs Sloping or pitched roofs Folded plates or shell roofs

Flat roofs are used where rainfall is low to moderate, sloping roofs are used in places of heavy rainfall. Folded plates and shell roofs are used to cover large column free areas such as auditoriums. Flat Roofs Flat roofs are horizontal but with a slight slope to drain out rain water. Advantages -The roof can be converted into a floor by constructing another storey -Over head water tanks and other services can be installed -The roof can be used as a terrace for recreational purposes

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Disadvantages - There is a chance for leakage of rainwater - The dead weight is more - The initial cost of construction is high -

Construction time is more

Types of flat roofs - RCC roofs - Madras terrace roofs - Bengal terrace roofs - Punjab terrace roofs

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RCC roofs These type roofs are commonly used now. The thickness of slab, diameter of bars, spacing of bars etc will depend on the load and span of the room. A typical cross section of slab and plan is shown in the above figure. Pitched (sloping) roofs Sloping roofs are adopted in places of heavy rain fall. It consists of a structure over which roofing materials like tiles, GI sheets, AC sheets are fixed. The slope of the roof varies from 10 degrees to 60 degrees. This type of roofs are generally adopted for large span buildings like factories, work shops, auditoriums etc. There are three types of pitched roofs: Single, Double and Trussed roofs. Single roofs: These roofs consist only common rafters which are fixed on to the wall plate and ridge. There are four types of single roofs – Lean-to roof, Couple roof, Couple- close roof, Collar-beam roof

Couple close roof

Lean – to roof

Double roofs: These roofs are also known as purlin roofs. The purlins act as intermediate supports to rafters.

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Purlin Roof Trussed Roof: A truss is a triangulated system of straight interconnected structural elements The external forces applied to the system and the reactions at the supports are generally applied at the nodes. The principal force in each element in a truss is axial tension or compression. For shorter spans wooden trusses and for larger spans steel trusses are used. Tiles, GI sheets are used as covering over the roof truss. There are different types of trusses but the most common trusses are- King post truss and Queen post truss.

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Steel Truss

Steel Truss v/s Timber truss In olden times mainly wooden trusses were used. But now, due to scarcity of timber and its high cost, steel trusses are being used. Steel truss have the following advantages –     153

They can be fabricated in any shape They can be easily erected They are stronger and durable They are fireproof

 

No chance for attack of thermites They are of light weight

Roof covering for pitched roof Tiles, Thatch (straw), Slates, AC sheets, GI sheets Folded plate and Shell roofs Folded plate roof is a slab with a number of folds.

Folded Plate roof

Shell Roof

Shell roofs are curved roofs. These can be built to cover large areas with out columns. Comparison of shell roof with conventional roof Advantages -Shell roofs have good aesthetic view -Less material is required - Large column free area can be obtained - Form work can be removed early Disadvantages -Analysis of shell roof more tedious -Form work is costly -The top surface is curved

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Comparison of shell roof with folded plate roof Advantages -Folded plate requires simple frm work -Design of folded plate is simple -Movable form work can be employed Disadvantages -Folded plate roof requires more material than shell roof

Points to Ponder

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Roof is the topmost part of a building. It protects the inhabitants from rain, sun, wind etc. There are three types of roofs – Sloping, Flat and shell & folded plate Flat roofs are generally made of reinforced cement concrete. Sloping roofs are covered with tiles, slates, GI / Asbestos sheets Truss is a frame work of slender members The more popular wooden trusses are – King post and Queen post truss Now a days trusses are of steel rather than timber For column free halls, folded plate /shell roofs are adopted Model Questions

1. What is a roof? 2. What are the types of roofs? 3. What is a king post truss? 4. Compare steel truss roof with timber truss? 5. What is a folded plate truss? 6. What are the materials commonly used for covering sloping roof?

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Acknowledgement In compiling this text, a large number of publications from the print media as well as from the internet have been referred to and the same is kindly acknowledged herewith.

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About the Author Ramachandran V is presently working as Professor of Civil Engineering, KMCT College of Engineering, Kozhikode. He has five decades of experience in teaching, design and construction of Buildings, Roads, Railways, Software Development & Training. Earlier he has worked for Research Designs and Standards Organisation, (Ministry of Railways) Lucknow, RITES ( A Government of India Undertaking), New Delhi, CRIS (A Government of India Undertaking), New Delhi and SNTF ( Government of Algeria).He has taken M Tech in Civil Engineering from HBTI, Kanpur and Diploma in Expert Systems from M I University, Iowa, USA. He is a Member of the Institution of Engineers (India), Indian Geotechnical Society, Computer Society of India and Institute of Rail Transport. He has published few papers in print media as well as web sites.

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