The radius of a arch, R ={H2 + (B/2)2 } / 2H
Where, R= radius of the arch
H= height of the arch
B= width of the arch
ARCH
মঙ্গলবার, ২৮ সেপ্টেম্বর, ২০১০
LEARN
What is cement?
Cement is a binding material.
What are the physical properties of cement?
1. Fineness (OPC- minimum 225 sq.m/kg
PPC- minimum 300 sq.m/kg
PSC- minimum 225 sq.m/kg)
2. Setting time (initial setting time not less than 45 minutes and final setting time not more than 8 hours.)
3. Soundness ( not more than 10mm)
4. Compressive strength
5. Tensile strength
What are CEM-I and CEM-II?
CEM-I: Ordinary Portland Cement.
CEM-II: Portland Composite Cement.
What are the constituents of Portland composite cement (PCC)?
Clinker, fly ash, blast furnace slag, gypsum.
Why gypsum is added to cement?
To control the flash setting i.e. to control the setting time.
Why fly ash is important?
About 0.87 ton CO2 is generated in per ton cement which causes pollution. But we can reduce this pollution by using fly ash because of its low carbon content. Moreover, using of fly ash reduce the heat of hydration and reduce the formation of hair crack. Fly ash also important to produce higher strength later.
Which are the chemical compounds those responsible for setting and hardening of cement paste?
1. tri-calcium silicate(C3S)
2. di-calcium silicate(C2S)
3. tri-calcium aluminate(C3A)
4. tetra-calcium alumino ferrite(C4AF)
What is hydration?
The reaction between cement and water is called hydration.
What is soundness of cement?
Due to hydration cement undergoes volumetric change which causes expansion. If expansion is excessive crack will develop. Soundness of cement means measurement
of expansion. The expansion should not exceed 10mm.
What are the effects of Ca(OH)2 in cement?
Due to hydration of tri-calcium silicate and di-calcium silicate a gel like compound CaO.SiO2.H2O (C-S-H gel) and Ca(OH)2 form. C-S-H gel has cementitious nature but Ca(OH)2 is unimportant (the only importance is due to alkaline in nature maintain the pH value around 13 and protect the corrosion of steel.) rather due to its solubility in water it makes the concrete permeable and effects the durability of concrete which is undesirable. To reduce its quantity finely grinded siliceous material like fly ash is added which react with Ca(OH)2 and forms C-S-H gel.
What are the field tests of cement?
1. The colour of the cement should be greenish grey.
2. There should be no visible lump in cement.
3. It should give you a smooth and not gritty feeling if you feel it between fingers.
4. The particles should float before sink if you throw it on a bucket full of water.
5. Take a sample of cement on a steel plate and burn for about 20 minutes if it is adulterated the colour will change otherwise remain unchanged.
What is Portland Slag Cement (PSC)?
It is obtained by mixing clinker, gypsum and blast furnace slag.
What are the advantages PSC?
1. Reduce heat of hydration.
2. Reduce permeability.
3. Increase resistance chemical attack (resistance to chloride, soils and water containing excessive amount of sulphates or alkali metals, alumina and iron, as well as, to acidic water.
4. Refinement of pore structure.
Why PCC is better than OPC?
Though 7 days strength of PCC is lower than OPC, PCC provides higher strength in later age.
As fly ash reacts with Ca(OH)2 the durability of concrete increases.
OPC + WATER → C-S-H GEL + Ca(OH)2
PCC + WATER → C-S-H GEL + Ca(OH)2
Ca(OH)2 + FLY ASH → C-S-H GEL
Generate lower heat of hydration for which it is useful for mass concrete construction.
What is bleeding of cement?
The tendency of water to rise to the surface of freshly placed concrete is called bleeding. Excessive water in concrete causes bleeding.
How can we control the heat of hydration?
The reaction between clinker and water generates excessive heat. In case of mass concrete the excessive heat causes crack in the concrete. To control this heat a suitable amount of clinker is replaced by fly ash. As fly ash reacts slowly the generation of heat is lower.
How concrete act as human body ?
In case of micro cracks the unreacted cement particles expose to the surface. When these particles come in contact with water the paste from again and seal those micro cracks. This is called self healing behaviour of cement. This is like self healing behaviour of human body when scratched.
Cement is a binding material.
What are the physical properties of cement?
1. Fineness (OPC- minimum 225 sq.m/kg
PPC- minimum 300 sq.m/kg
PSC- minimum 225 sq.m/kg)
2. Setting time (initial setting time not less than 45 minutes and final setting time not more than 8 hours.)
3. Soundness ( not more than 10mm)
4. Compressive strength
5. Tensile strength
What are CEM-I and CEM-II?
CEM-I: Ordinary Portland Cement.
CEM-II: Portland Composite Cement.
What are the constituents of Portland composite cement (PCC)?
Clinker, fly ash, blast furnace slag, gypsum.
Why gypsum is added to cement?
To control the flash setting i.e. to control the setting time.
Why fly ash is important?
About 0.87 ton CO2 is generated in per ton cement which causes pollution. But we can reduce this pollution by using fly ash because of its low carbon content. Moreover, using of fly ash reduce the heat of hydration and reduce the formation of hair crack. Fly ash also important to produce higher strength later.
Which are the chemical compounds those responsible for setting and hardening of cement paste?
1. tri-calcium silicate(C3S)
2. di-calcium silicate(C2S)
3. tri-calcium aluminate(C3A)
4. tetra-calcium alumino ferrite(C4AF)
What is hydration?
The reaction between cement and water is called hydration.
What is soundness of cement?
Due to hydration cement undergoes volumetric change which causes expansion. If expansion is excessive crack will develop. Soundness of cement means measurement
of expansion. The expansion should not exceed 10mm.
What are the effects of Ca(OH)2 in cement?
Due to hydration of tri-calcium silicate and di-calcium silicate a gel like compound CaO.SiO2.H2O (C-S-H gel) and Ca(OH)2 form. C-S-H gel has cementitious nature but Ca(OH)2 is unimportant (the only importance is due to alkaline in nature maintain the pH value around 13 and protect the corrosion of steel.) rather due to its solubility in water it makes the concrete permeable and effects the durability of concrete which is undesirable. To reduce its quantity finely grinded siliceous material like fly ash is added which react with Ca(OH)2 and forms C-S-H gel.
What are the field tests of cement?
1. The colour of the cement should be greenish grey.
2. There should be no visible lump in cement.
3. It should give you a smooth and not gritty feeling if you feel it between fingers.
4. The particles should float before sink if you throw it on a bucket full of water.
5. Take a sample of cement on a steel plate and burn for about 20 minutes if it is adulterated the colour will change otherwise remain unchanged.
What is Portland Slag Cement (PSC)?
It is obtained by mixing clinker, gypsum and blast furnace slag.
What are the advantages PSC?
1. Reduce heat of hydration.
2. Reduce permeability.
3. Increase resistance chemical attack (resistance to chloride, soils and water containing excessive amount of sulphates or alkali metals, alumina and iron, as well as, to acidic water.
4. Refinement of pore structure.
Why PCC is better than OPC?
Though 7 days strength of PCC is lower than OPC, PCC provides higher strength in later age.
As fly ash reacts with Ca(OH)2 the durability of concrete increases.
OPC + WATER → C-S-H GEL + Ca(OH)2
PCC + WATER → C-S-H GEL + Ca(OH)2
Ca(OH)2 + FLY ASH → C-S-H GEL
Generate lower heat of hydration for which it is useful for mass concrete construction.
What is bleeding of cement?
The tendency of water to rise to the surface of freshly placed concrete is called bleeding. Excessive water in concrete causes bleeding.
How can we control the heat of hydration?
The reaction between clinker and water generates excessive heat. In case of mass concrete the excessive heat causes crack in the concrete. To control this heat a suitable amount of clinker is replaced by fly ash. As fly ash reacts slowly the generation of heat is lower.
How concrete act as human body ?
In case of micro cracks the unreacted cement particles expose to the surface. When these particles come in contact with water the paste from again and seal those micro cracks. This is called self healing behaviour of cement. This is like self healing behaviour of human body when scratched.
VISIT THE SITE AND LEARN SOMETHING ABOUT ONLINE INCOME
http://www.infotechse.info/jobs/idevaffiliate.php?id=7651
SOMETHING ABOUT CEMENT
What is cement?
Cement is a binding material.
What are the physical properties of cement?
1. Fineness (OPC- minimum 225 sq.m/kg
PPC- minimum 300 sq.m/kg
PSC- minimum 225 sq.m/kg)
2. Setting time (initial setting time not less than 45 minutes and final setting time not more than 8 hours.)
3. Soundness ( not more than 10mm)
4. Compressive strength
5. Tensile strength
What are CEM-I and CEM-II?
CEM-I: Ordinary Portland Cement.
CEM-II: Portland Composite Cement.
What are the constituents of Portland composite cement (PCC)?
Clinker, fly ash, blast furnace slag, gypsum.
Why gypsum is added to cement?
To control the flash setting i.e. to control the setting time.
Why fly ash is important?
About 0.87 ton CO2 is generated in per ton cement which causes pollution. But we can reduce this pollution by using fly ash because of its low carbon content. Moreover, using of fly ash reduce the heat of hydration and reduce the formation of hair crack. Fly ash also important to produce higher strength later.
Which are the chemical compounds those responsible for setting and hardening of cement paste?
1. tri-calcium silicate(C3S)
2. di-calcium silicate(C2S)
3. tri-calcium aluminate(C3A)
4. tetra-calcium alumino ferrite(C4AF)
What is hydration?
The reaction between cement and water is called hydration.
What is soundness of cement?
Due to hydration cement undergoes volumetric change which causes expansion. If expansion is excessive crack will develop. Soundness of cement means measurement
of expansion. The expansion should not exceed 10mm.
What are the effects of Ca(OH)2 in cement?
Due to hydration of tri-calcium silicate and di-calcium silicate a gel like compound CaO.SiO2.H2O (C-S-H gel) and Ca(OH)2 form. C-S-H gel has cementitious nature but Ca(OH)2 is unimportant (the only importance is due to alkaline in nature maintain the pH value around 13 and protect the corrosion of steel.) rather due to its solubility in water it makes the concrete permeable and effects the durability of concrete which is undesirable. To reduce its quantity finely grinded siliceous material like fly ash is added which react with Ca(OH)2 and forms C-S-H gel.
What are the field tests of cement?
1. The colour of the cement should be greenish grey.
2. There should be no visible lump in cement.
3. It should give you a smooth and not gritty feeling if you feel it between fingers.
4. The particles should float before sink if you throw it on a bucket full of water.
5. Take a sample of cement on a steel plate and burn for about 20 minutes if it is adulterated the colour will change otherwise remain unchanged.
What is Portland Slag Cement (PSC)?
It is obtained by mixing clinker, gypsum and blast furnace slag.
What are the advantages PSC?
1. Reduce heat of hydration.
2. Reduce permeability.
3. Increase resistance chemical attack (resistance to chloride, soils and water containing excessive amount of sulphates or alkali metals, alumina and iron, as well as, to acidic water.
4. Refinement of pore structure.
Why PCC is better than OPC?
Though 7 days strength of PCC is lower than OPC, PCC provides higher strength in later age.
As fly ash reacts with Ca(OH)2 the durability of concrete increases.
OPC + WATER → C-S-H GEL + Ca(OH)2
PCC + WATER → C-S-H GEL + Ca(OH)2
Ca(OH)2 + FLY ASH → C-S-H GEL
Generate lower heat of hydration for which it is useful for mass concrete construction.
What is bleeding of cement?
The tendency of water to rise to the surface of freshly placed concrete is called bleeding. Excessive water in concrete causes bleeding.
How can we control the heat of hydration?
The reaction between clinker and water generates excessive heat. In case of mass concrete the excessive heat causes crack in the concrete. To control this heat a suitable amount of clinker is replaced by fly ash. As fly ash reacts slowly the generation of heat is lower.
How concrete act as human body ?
In case of micro cracks the unreacted cement particles expose to the surface. When these particles come in contact with water the paste from again and seal those micro cracks. This is called self healing behaviour of cement. This is like self healing behaviour of human body when scratched.
Cement is a binding material.
What are the physical properties of cement?
1. Fineness (OPC- minimum 225 sq.m/kg
PPC- minimum 300 sq.m/kg
PSC- minimum 225 sq.m/kg)
2. Setting time (initial setting time not less than 45 minutes and final setting time not more than 8 hours.)
3. Soundness ( not more than 10mm)
4. Compressive strength
5. Tensile strength
What are CEM-I and CEM-II?
CEM-I: Ordinary Portland Cement.
CEM-II: Portland Composite Cement.
What are the constituents of Portland composite cement (PCC)?
Clinker, fly ash, blast furnace slag, gypsum.
Why gypsum is added to cement?
To control the flash setting i.e. to control the setting time.
Why fly ash is important?
About 0.87 ton CO2 is generated in per ton cement which causes pollution. But we can reduce this pollution by using fly ash because of its low carbon content. Moreover, using of fly ash reduce the heat of hydration and reduce the formation of hair crack. Fly ash also important to produce higher strength later.
Which are the chemical compounds those responsible for setting and hardening of cement paste?
1. tri-calcium silicate(C3S)
2. di-calcium silicate(C2S)
3. tri-calcium aluminate(C3A)
4. tetra-calcium alumino ferrite(C4AF)
What is hydration?
The reaction between cement and water is called hydration.
What is soundness of cement?
Due to hydration cement undergoes volumetric change which causes expansion. If expansion is excessive crack will develop. Soundness of cement means measurement
of expansion. The expansion should not exceed 10mm.
What are the effects of Ca(OH)2 in cement?
Due to hydration of tri-calcium silicate and di-calcium silicate a gel like compound CaO.SiO2.H2O (C-S-H gel) and Ca(OH)2 form. C-S-H gel has cementitious nature but Ca(OH)2 is unimportant (the only importance is due to alkaline in nature maintain the pH value around 13 and protect the corrosion of steel.) rather due to its solubility in water it makes the concrete permeable and effects the durability of concrete which is undesirable. To reduce its quantity finely grinded siliceous material like fly ash is added which react with Ca(OH)2 and forms C-S-H gel.
What are the field tests of cement?
1. The colour of the cement should be greenish grey.
2. There should be no visible lump in cement.
3. It should give you a smooth and not gritty feeling if you feel it between fingers.
4. The particles should float before sink if you throw it on a bucket full of water.
5. Take a sample of cement on a steel plate and burn for about 20 minutes if it is adulterated the colour will change otherwise remain unchanged.
What is Portland Slag Cement (PSC)?
It is obtained by mixing clinker, gypsum and blast furnace slag.
What are the advantages PSC?
1. Reduce heat of hydration.
2. Reduce permeability.
3. Increase resistance chemical attack (resistance to chloride, soils and water containing excessive amount of sulphates or alkali metals, alumina and iron, as well as, to acidic water.
4. Refinement of pore structure.
Why PCC is better than OPC?
Though 7 days strength of PCC is lower than OPC, PCC provides higher strength in later age.
As fly ash reacts with Ca(OH)2 the durability of concrete increases.
OPC + WATER → C-S-H GEL + Ca(OH)2
PCC + WATER → C-S-H GEL + Ca(OH)2
Ca(OH)2 + FLY ASH → C-S-H GEL
Generate lower heat of hydration for which it is useful for mass concrete construction.
What is bleeding of cement?
The tendency of water to rise to the surface of freshly placed concrete is called bleeding. Excessive water in concrete causes bleeding.
How can we control the heat of hydration?
The reaction between clinker and water generates excessive heat. In case of mass concrete the excessive heat causes crack in the concrete. To control this heat a suitable amount of clinker is replaced by fly ash. As fly ash reacts slowly the generation of heat is lower.
How concrete act as human body ?
In case of micro cracks the unreacted cement particles expose to the surface. When these particles come in contact with water the paste from again and seal those micro cracks. This is called self healing behaviour of cement. This is like self healing behaviour of human body when scratched.
এতে সদস্যতা:
মন্তব্যসমূহ (Atom)