Sab 2112 - L2 Cement
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Do It Yourself……..
CEMENT
At the end of class students should understand…… 1) 2)
3) 4)
Raw materials in cement manufacturing process Chemical compositions of Portland cement and their functions Hydration process of cement Types of Portland cement and their applications
CEMENT
Ingredients Manufacturing process Chemical compositions Type of cements
Hydration process Testing of cement
CEMENT Is the product obtained by grinding clinker formed by burning rawmaterials (argillaceous and calcareous) primarily consisting of lime (CaO), silicate (SiO2), alumina (Al2O3), and iron oxide (Fe2O3)
Characteristics of cement
Setting and hardening when mix to a paste with water
Cohesive and Adhesive
History of Portland Cement
1824 – patented by Joseph Aspdin Materials to produce cement were found on the English Isle of Portland Thus, called PORTLAND CEMENT
Brands of Cement
Cement
Argillaceous + Calcareous Silica (SiO2 -60%) Lime (CaO -20%) Alumina (Al2O3 -10%) Ferum oxide (Fe2O3)
Argillaceous – clay, sandstone, shale Calcareous – limestone, chalk, oyster shells
Cement
Hydraulic cement – able to set and harden in the presence of water e.g. OPC Non-Hydraulic cement – requires no water to harden, only require air to harden e.g. lime
Manufacturing Process Two types of process: Wet Process – softer materials (clay + chalk)
Dry Process – harder materials (shale + limestone)
Steps in manufacturing process 1)
2) 3) 4)
Grinding and mixing of raw materials Burning in a rotary kiln Cooling, grinding and sieving Storing, packing and distributing
Wet Process 1)
Materials being ground and mixed with the correct proportions
2)
The mixture in a slurry form is fed into a rotary kiln where it is heated/burnt to a temperature of 1500 °C to form clinker
1. Grinding Raw Materials
2. Mixing
3. Burning
Burning
100 °C – water is driven off 850 °C – limestone changes to calcium oxide and CO2 is liberated 1500 °C – CaO reacts with SiO2 to form Calcium Silicate (CS) CaO reacts with other compounds to form Calcium Aluminate (CA) and Calcium Aluminoferite (CAF)
4. Grinding Why clinker need to be ground?
Wet Process 3)
4)
Cooling and grinding – Gypsum [Ca(SO)4] is added during the grinding process to prevent flash setting Storing – stored in silo
Final Products - cement
Dry Process
The process is relatively the same as wet process except in dry process the raw materials (harder materials) are mixed in dry condition. Small amount of water is added to form 12mm in diameter ‘balls’ The ‘balls’ are burnt in a rotary kiln and the chemical reactions are the same as wet process
CHEMICAL COMPOSITION OF PORTLAND CEMENT
Will affect: Strength of cement Rate of hydration Amount of heat of hydration Durability of cement
Chemical Composition of Portland Cement Abb.
Compound
Oxide
C3 S
Tricalcium silicate
3CaO.SiO2
45-60%
C2 S
Dicalcium silicate
2Cao.SiO2
15-30%
C3 A
Tricalcium Aluminate
3CaO.Al2O3
C4AF
Tetracalcium Aluminoferrite
4CaO.Al2O3.Fe2O3
Others
Percent
6-12% 6-8% 8%
Others of Minor Compounds
Magnesium oxide Titanium oxide Manganese oxide Sodium oxide Potassium oxide Minor – refers to quantity not importance
Alkalis in Cement
Sodium oxide (Na2O) and Potassium oxide (K2O)
May cause problem – Alkali Silica Reaction
HYDRATION PROCESS OF PORTLAND CEMENT
Is the chemical reaction between the compounds of cement and water that yields products that achieve the binding property after hardening Two stages: setting and hardening
Hydration Process of Cement
Cement + H2O → C-S-H gel + Ca(OH)2 It is an exothermic process where heat is liberated (heat of hydration) The silicates, C3S and C2S, are the most important compounds, which are responsible for the strength of hydrated cement paste C3S provides the early strength and liberated higher heat of hydration
Set –
reaches a state in which its form cannot be changed without rupture
Setting
Flash set – rapid development of permanent rigidity of the cement paste – along with high heat False set – rapid development of rigidity without the evolution of heat
Hydration of cement
C-S-H gel and Ca(OH)2
C-S-H gel
Ca(OH)2
Cont.
C2S reacts slowly, provide later strength, highly chemical resistance (sulphate, chloride) C3A is undesirable, contribute little or nothing to the strength of cement except at early ages, and when hardened cement paste is attacked by sulphates, the formation of sulphoaluminate may cause disruption
Hydration of C3A
Cont.
C4AF does not affect the behaviour of cement hydration significantly. However, it reacts with gypsum to form calcium sulphoferrite and its presence may accelerate the hydration of silicates
Hydration Process
Rate of Hydration
Effect on porosity
W/C effect on porosity
Strength vs porosity
TYPES OF PORTLAND CEMENT
Types of Portland Cement 1) 2)
3)
4) 5)
6)
7) 8)
Ordinary Portland Cement (OPC) – Type I Rapid Hardening Portland Cement (RHPC) – Type III Sulphate Resisting Portland Cement (SRPC) – Type V Modified Portland Cement (MPC) – Type II Low Heat Portland Cement (LHPC) – Type IV Portland-Blastfurnace Cement (PBC) – Type IS Portland-Pozzolan Cement (PPC) – Type IP Others
Effect of chemical composition
Cement differing in chemical composition may exhibit different properties when hydrated
Strength, durability, rate of strength gain, heat of hydration
Ordinary Portland Cement (Type I)
By far the most common (60%) cement used in general concrete construction when there is no exposure to sulphates in the soil or groundwater Minimum fineness of 225 m2/kg Rate of hardening is moderate Standards: BS 12:1991, MS 522,ENV 197-1:1992
Rapid Hardening Portland Cement (RHPC – Type III)
Rapid strength gain due to higher C3S content (70%) Minimum fineness of 325 m2/kg Used when: formwork is to be removed early for reuse or where sufficient strength for further construction is required quickly
Should not be used in mass concrete construction or in large structural sections because of its higher rate of heat development
RHPC (cont.)
For construction at low temperatures, the use of RHPC may provide a satisfactory safeguard against early frost damage The setting time and chemical composition of RHPC and OPC is relatively the same
Sulphate Resisting Portland Cement (SRPC – Type V)
This cement has low C3A (3.5%) content so as to avoid sulphate attack from outside the concrete Minimum fineness of 250 m2/kg Active salts are magnesium and sodium sulphates – increase in volume, cause concrete crack
Sulphate attack is greatly accelerated if accompanied by wetting and drying (splash zone) The heat develop by SRPC is not much higher than the low-heat cement, which is an advantage
Sulphate attack
Severe damage
Portland-Blastfurnace Cement
Made by inter-grinding or blending Portland cement clinker with granulated blast-furnace slag Known as slag cement Slag contains lime, silica and alumina, but not in the same proportions as in Portland cement Minimum fineness of 275 m2/kg Early strength are generally lower than OPC but later strength are similar or even higher
Cont.
Typical uses are in mass concrete because of low heat of hydration and in seawater construction due to better sulphate resistance ( lower C3A content) than with the OPC The amount of slag replacement between 25 to 70% of the mass of the mixture
Portland-Pozzolan Cement
Made by inter-grinding or blending pozzolans with Portland cement A pozzolan is a siliceous or siliceous and aluminous material which itself possesses little or no cementitious value BUT in finely divided form and in the presence of moisture, chemically react with Ca(OH)2 liberated during the hydration of Portland cement to form compounds possessing cementitious properties
Cont.
Portland-Pozzolan cement gain strength slowly and therefore require curing over a comparatively a long period, but the long-term strength is high Amount replacement between 25 to 40% More durable than OPC
Concrete with silica fume
DENSE CONCRETE
Normal plain concrete
What to consider? Materials? Cement? Type of construction?
Discussion
What are the main materials used for the manufacture of cement? What is the purpose of adding gypsum to cement? Why clinker (cement) needs to be ground? What are the chemical composition of Portland cement? Different types of OPC and applications.
Summary
Cement ingredients Manufacturing process Chemical compositions Hydration process Types of cement and application
Thank You
CEMENT
At the end of class students should understand…… 1) 2)
3) 4)
Raw materials in cement manufacturing process Chemical compositions of Portland cement and their functions Hydration process of cement Types of Portland cement and their applications
CEMENT
Ingredients Manufacturing process Chemical compositions Type of cements
Hydration process Testing of cement
CEMENT Is the product obtained by grinding clinker formed by burning rawmaterials (argillaceous and calcareous) primarily consisting of lime (CaO), silicate (SiO2), alumina (Al2O3), and iron oxide (Fe2O3)
Characteristics of cement
Setting and hardening when mix to a paste with water
Cohesive and Adhesive
History of Portland Cement
1824 – patented by Joseph Aspdin Materials to produce cement were found on the English Isle of Portland Thus, called PORTLAND CEMENT
Brands of Cement
Cement
Argillaceous + Calcareous Silica (SiO2 -60%) Lime (CaO -20%) Alumina (Al2O3 -10%) Ferum oxide (Fe2O3)
Argillaceous – clay, sandstone, shale Calcareous – limestone, chalk, oyster shells
Cement
Hydraulic cement – able to set and harden in the presence of water e.g. OPC Non-Hydraulic cement – requires no water to harden, only require air to harden e.g. lime
Manufacturing Process Two types of process: Wet Process – softer materials (clay + chalk)
Dry Process – harder materials (shale + limestone)
Steps in manufacturing process 1)
2) 3) 4)
Grinding and mixing of raw materials Burning in a rotary kiln Cooling, grinding and sieving Storing, packing and distributing
Wet Process 1)
Materials being ground and mixed with the correct proportions
2)
The mixture in a slurry form is fed into a rotary kiln where it is heated/burnt to a temperature of 1500 °C to form clinker
1. Grinding Raw Materials
2. Mixing
3. Burning
Burning
100 °C – water is driven off 850 °C – limestone changes to calcium oxide and CO2 is liberated 1500 °C – CaO reacts with SiO2 to form Calcium Silicate (CS) CaO reacts with other compounds to form Calcium Aluminate (CA) and Calcium Aluminoferite (CAF)
4. Grinding Why clinker need to be ground?
Wet Process 3)
4)
Cooling and grinding – Gypsum [Ca(SO)4] is added during the grinding process to prevent flash setting Storing – stored in silo
Final Products - cement
Dry Process
The process is relatively the same as wet process except in dry process the raw materials (harder materials) are mixed in dry condition. Small amount of water is added to form 12mm in diameter ‘balls’ The ‘balls’ are burnt in a rotary kiln and the chemical reactions are the same as wet process
CHEMICAL COMPOSITION OF PORTLAND CEMENT
Will affect: Strength of cement Rate of hydration Amount of heat of hydration Durability of cement
Chemical Composition of Portland Cement Abb.
Compound
Oxide
C3 S
Tricalcium silicate
3CaO.SiO2
45-60%
C2 S
Dicalcium silicate
2Cao.SiO2
15-30%
C3 A
Tricalcium Aluminate
3CaO.Al2O3
C4AF
Tetracalcium Aluminoferrite
4CaO.Al2O3.Fe2O3
Others
Percent
6-12% 6-8% 8%
Others of Minor Compounds
Magnesium oxide Titanium oxide Manganese oxide Sodium oxide Potassium oxide Minor – refers to quantity not importance
Alkalis in Cement
Sodium oxide (Na2O) and Potassium oxide (K2O)
May cause problem – Alkali Silica Reaction
HYDRATION PROCESS OF PORTLAND CEMENT
Is the chemical reaction between the compounds of cement and water that yields products that achieve the binding property after hardening Two stages: setting and hardening
Hydration Process of Cement
Cement + H2O → C-S-H gel + Ca(OH)2 It is an exothermic process where heat is liberated (heat of hydration) The silicates, C3S and C2S, are the most important compounds, which are responsible for the strength of hydrated cement paste C3S provides the early strength and liberated higher heat of hydration
Set –
reaches a state in which its form cannot be changed without rupture
Setting
Flash set – rapid development of permanent rigidity of the cement paste – along with high heat False set – rapid development of rigidity without the evolution of heat
Hydration of cement
C-S-H gel and Ca(OH)2
C-S-H gel
Ca(OH)2
Cont.
C2S reacts slowly, provide later strength, highly chemical resistance (sulphate, chloride) C3A is undesirable, contribute little or nothing to the strength of cement except at early ages, and when hardened cement paste is attacked by sulphates, the formation of sulphoaluminate may cause disruption
Hydration of C3A
Cont.
C4AF does not affect the behaviour of cement hydration significantly. However, it reacts with gypsum to form calcium sulphoferrite and its presence may accelerate the hydration of silicates
Hydration Process
Rate of Hydration
Effect on porosity
W/C effect on porosity
Strength vs porosity
TYPES OF PORTLAND CEMENT
Types of Portland Cement 1) 2)
3)
4) 5)
6)
7) 8)
Ordinary Portland Cement (OPC) – Type I Rapid Hardening Portland Cement (RHPC) – Type III Sulphate Resisting Portland Cement (SRPC) – Type V Modified Portland Cement (MPC) – Type II Low Heat Portland Cement (LHPC) – Type IV Portland-Blastfurnace Cement (PBC) – Type IS Portland-Pozzolan Cement (PPC) – Type IP Others
Effect of chemical composition
Cement differing in chemical composition may exhibit different properties when hydrated
Strength, durability, rate of strength gain, heat of hydration
Ordinary Portland Cement (Type I)
By far the most common (60%) cement used in general concrete construction when there is no exposure to sulphates in the soil or groundwater Minimum fineness of 225 m2/kg Rate of hardening is moderate Standards: BS 12:1991, MS 522,ENV 197-1:1992
Rapid Hardening Portland Cement (RHPC – Type III)
Rapid strength gain due to higher C3S content (70%) Minimum fineness of 325 m2/kg Used when: formwork is to be removed early for reuse or where sufficient strength for further construction is required quickly
Should not be used in mass concrete construction or in large structural sections because of its higher rate of heat development
RHPC (cont.)
For construction at low temperatures, the use of RHPC may provide a satisfactory safeguard against early frost damage The setting time and chemical composition of RHPC and OPC is relatively the same
Sulphate Resisting Portland Cement (SRPC – Type V)
This cement has low C3A (3.5%) content so as to avoid sulphate attack from outside the concrete Minimum fineness of 250 m2/kg Active salts are magnesium and sodium sulphates – increase in volume, cause concrete crack
Sulphate attack is greatly accelerated if accompanied by wetting and drying (splash zone) The heat develop by SRPC is not much higher than the low-heat cement, which is an advantage
Sulphate attack
Severe damage
Portland-Blastfurnace Cement
Made by inter-grinding or blending Portland cement clinker with granulated blast-furnace slag Known as slag cement Slag contains lime, silica and alumina, but not in the same proportions as in Portland cement Minimum fineness of 275 m2/kg Early strength are generally lower than OPC but later strength are similar or even higher
Cont.
Typical uses are in mass concrete because of low heat of hydration and in seawater construction due to better sulphate resistance ( lower C3A content) than with the OPC The amount of slag replacement between 25 to 70% of the mass of the mixture
Portland-Pozzolan Cement
Made by inter-grinding or blending pozzolans with Portland cement A pozzolan is a siliceous or siliceous and aluminous material which itself possesses little or no cementitious value BUT in finely divided form and in the presence of moisture, chemically react with Ca(OH)2 liberated during the hydration of Portland cement to form compounds possessing cementitious properties
Cont.
Portland-Pozzolan cement gain strength slowly and therefore require curing over a comparatively a long period, but the long-term strength is high Amount replacement between 25 to 40% More durable than OPC
Concrete with silica fume
DENSE CONCRETE
Normal plain concrete
What to consider? Materials? Cement? Type of construction?
Discussion
What are the main materials used for the manufacture of cement? What is the purpose of adding gypsum to cement? Why clinker (cement) needs to be ground? What are the chemical composition of Portland cement? Different types of OPC and applications.
Summary
Cement ingredients Manufacturing process Chemical compositions Hydration process Types of cement and application
Thank You
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