Definition of cement
Cement is defined as the binding medium in concrete in which both have cohesion and adhesion property. All types of cement are obtained by grinding the clinker.
Clinker is obtained by burning the mixture of calcareous and argillaceous group material in definite proportions.
Let us describe all Types of cement used for construction.
Types of cement
- Ordinary Portland cement
- Rapid hardening cement
- Extra rapid hardening cement
- Sulphate resistance cement
- Blast furnance slag cement
- Super sulphate cement
- Low heat cement
- Portland pozzolana cement
- Air entraining cement
- Colored cement
- Hydrophobic cement
- Masonry cement
- Expansive cement
- Oil-well cement
- Radi-set cement
- High alumina cement
- Acid resisting cement
- It is the most common cement used in the concrete industry.
- It is suitable in general concrete work where it is not exposed to sulphate in soil and in groundwater.
- Initial setting time = 30 minutes and final setting time = 10 hours.
Rapid hardening cement
- It is a modified OPC with high early strength.
- High early strength is obtained by increasing C3S content and reducing C2S content as well as finer grinding.
- Three days strength hardening cement will be equal to seven days’ strength of OPC.
- It evolves a larger amount of heat hydration.
- Rapid Hardening Cement may be advantageous in colder regions or weather.
- It is used when rapid strength development is required.
- Rapid hardening cement may not be appropriate for mass concreting because of large heat is librated during hydration.
- It is costly in comparison with OPC (10%).
- It is also known as high early strength cement.\Initial setting time = 30 minutes and final setting time = 10 hours.
Extra rapid hardening cement
- It is obtained by inter grinding CaCl2 and RHC clinker.
- Concrete mixed prepared by this cement should be placed, compacted, and finished within 20 minutes.
- Its early strength is about 5% higher than RHC.
- It is suitable for cold weather.
- At 90 days, the strength of this cement will be nearly equal to OPC.
- The use of this cement in prestressed concrete is prohibited.
Sulphate resisting cement
- A Portland cement with low C3A (Lesser than 5%) and C4AF content is effective in sulphate attack.
- It has a high silica content.
- Sulphate attack causes expansion in the volume of concrete.
- It may be used in marine construction, sewage treatment plant, in foundation or basement where soil contains sulphate.
Blast furnace cement
- It is obtained by grinding the mixture of OPC clinker, gypsum, and granulates blast furnace slag in a suitable proportion.
- Its rate of hardening is slower than OPC.
- Blast furnace cement has a low heat of hydration.
- This cement also solves environmental problems.
- Blast furnace slag should be 25% to 65% of total weight.
Super sulphate cement
- It is obtained by grinding mixture of 80-85% granulated slag, 10-15% hard burnt gypsum, and also 5% OPC clinker.
- Low heat cement is finer than OPC.
- It has a low heat of hydration.
- The water-cement ratio shall not be less than 0.5.
- It is suitable for mass concrete.
- Initial setting time = 4 hours and final ssetting time = 4 hours & 30 min.
Low heat cement :
- It is obtained by increasing C2S and reducing C3S and C3A in the content of OPC.
- Low heat cement was developed in America during 1930 for the use of mass concreting such as in the dam.
- It produces low heat during hydration.
- It gains strength at a slower rate.
- It is obtained by intimately grinding a mixture of OPC clinker and gypsum with mineral additives (pozzolana ) or inerts (Non-pozzolanic) material such as limestone, dolomite, carbonated sludge, etc and air-entraining agent in suitable proportion.
- Fineness is higher than OPC.
- It is suitable for masonry work.
- The cement which does not shrink while hardening and thereafter but expands slightly with the time is known as expansive cement.
- Expansive cement is obtained by mixing about 8 to 20 parts of sulpho aluminate clinker with 100 parts of the OPC clinker and 15 parts of the stabilizer.
- This cement suffers no overall change in volume on drying.
- This cement requires experience and a skilled hand to use this type of cement.
- Used for grouting anchor bolts or grouting machine foundation.
- These types of cement are obtained by inter-grinding OPC clinker, fly ash, gypsum, and certain admixture in suitable proportion.
- The cement slurry is used to seal the annular space between steel casing and rock strata or any other cavities in the sedimentary rock layer.
Portland pozzolana cement
- It is produced either by grinding together Portland clinker & pozzolana with the addition of gypsum or by intimately and uniform blending Portland cement and fine pozzolana.
- Portland pozzolana cement produces low heat of hydration.
- It provides better resistance to the attack of impurities in water.
- The strength of cement is the same as OPC.
- 10 to 25% pozzolana by weight of Portland cement is kept.
Air entraining cement
- It is made by mixing a small amount of an air-entraining agent with OPC clinker while grinding.
- Types of air-entraining agent used are ( alkali salts of wood resin, synthetic detergent of the alkyl-aryl sulphonate, etc)
- The agents are found in powder or liquid form.
- It is costly than OPC.
- It is used in the precast concrete industry for the repair of rigid pavement for high early strength.
- It is very poor for sulphate attack.
High alumina cement
- It is obtained by fusing a mixture of alumina and calcareous material in suitable proportion and grinding the product to a fine powder.
- Raw materials for this cement are limestone, bauxite.
- It is comparatively more expansive.
- It is more reactive and produces very high early strength.
- About 80% of strength is obtained at the age of 24 hours.
- Initial setting time 4 hrs and final setting time is 5 hrs.
- It is suitable for undersea or underwater construction.
Hence, These are the different types of cement used in construction.