Te Reviewer Midterm.docx

Chapter 1: Introduction

Advantages of Concrete: • Ability to be Cast

Concrete - cement (11%), fine aggregates (26%), coarse

• Fire resistant

aggregates (41%) and water (16%) and air (6%).

• On-site fabrication • Aesthetic properties.

Concrete - most commonly used man made construction material.

Process - responsible for quality of concrete.

• Low maintenance. • Can be reused or recycled.

Limitations of Concrete: • Low tensile strength

Cement - most important and costliest ingredient of concrete

• Low ductility • Volume instability

Aggregate - give volume to the concrete

Fine aggregate - 30-35% of the mixture Coarse aggregate - 40-45% of the mixture

• Low strength-to-weight ratio

Progress in Concrete Technology: • Lightweight Concrete • High-Strength Concrete

Water - indispensable because it is required for hydration. Admixture - optional ingredient which is used for specific purpose.

• High Work-ability or Flowing Concrete • Shrinkage Compensating Concrete • Fiber-Reinforced Concrete

Two distinct activity on production of concrete: 



• Concrete Containing polymers

Material

• Heavyweight Concrete



Selection

• Mass Concrete



Proportioning

• Roller-Compacted Concrete

process 

Mixing



Transportation



Placement



Compaction



Curing

Basic ingredients of concrete: Cement Aggregate Water Admixture

1824 - Joseph Aspdin of England invented Portland cement.

Chapter 2: Portland Cement

Cement - material used to bind aggregates. Cement paste - act as glue which makes a cohesive mass with all aggregates. Hydraulic Cement - Modern day cement. Clinkers - 20-30% of material fuses together spherical balls due to intense heat. Heat of hydration - heat generated when cement and water react.

Composition of modern day cement: Calcareous Material

: Limestone of chalk

Application of Aggregates:

Argillaceous Material

: Clay/Shale

• Portland cement concrete

Siliceous Material

: Silica

• Asphalt concrete • Base materials for roads

Chemical Properties of Portland Cement:

• Ballast for railroads

Chemical analysis

• Foundations

• Compound composition

• Plaster, mortar, grout, filter materials, etc.

• Chemical limits

The relative quantities of each of these phases affects: • setting time

Classification of Aggregates: 

According to origin of aggregates

• rate of strength development



Natural Mineral Aggregates

• overall strength



Synthetic Aggregates

• durability



Recycled Aggregates

• color 

According to weight of aggregates

Physical Properties of Portland Cement:



Normal Weight

• Fineness



Light Weight

• Soundness



Heavy Weight

• Consistency



• Setting time • False set and flash set

Properties of Aggregates: 

Inherited Properties:

• Compressive strength



Chemical and mineral composition

• Heat of hydration



Specific Gravity

• Loss on ignition



Hardness

• Density



Strength

• Bulk density



Colour

• Sulfate expansion



Acquired Properties 

Aggregate Shape

Setting time tests:



Rounded

Initial setting time - is the time from moment water is added until the paste ceases to be fluid and plastic.



Angular



Elongated



Flaky



Irregular

Final setting time - is the time from moment water is added for the paste to acquire a certain degree of hardness.

Chapter 3: Aggregates for Concrete



Aggregate Size



Surface Texture





Smooth texture



Rough texture



Water Absorption 

Bone dry



Air dry



Saturated surface dry



Moist

Phases of Concrete: Paste Phase Aggregate Phase

Significance of Gradation



Physical durability – exposure to freezing and thawing, wetting and drying, physical wear. 

Soundness: if volume changes accompanied with environmental changes lead to the deterioration of concrete –unsoundness.



Volume changes: alternate freezing and thawing, repeated wetting and drying – internal stresses –volume increase.



Wear resistance: abrasion and wear.

Strength Shrinkage Finish ability

Maximum Aggregate Size (MSA) - It is the smallest sieve opening through which the entire sample passes.

Bulking of sand - property of sand by virtue of which its apparent volume increases when some water is added to it.

Quality of Aggregates: Deleterious Material Salt contamination Alkali reaction

Durability of Aggregates

Causes of Durability:

to

surface

Chemical Durability - results from a reaction between reactive silica in aggregates and alkali compounds contained in the cement.

Economy Consistency

resistance

Tests on Aggregates Bulk Density (ASTM C 29) Relative Density (Specific Gravity) Absorption and Surface Moisture