Types of Cement
Many types of cement are available in markets with different compositions and for use in different environmental conditions and specialized applications. A list of some commonly used cement is described in this section:
Ordinary Portland cement
Ordinary Portland Cement (OPC) is mostly used for common structures and also for important civil works. In India, about 70% of cement is of this category. It has mainly three grades. Grade means mortar cube strength in N/mm2 after 28 days Lets know more about the Ordinary Portland Cement.
- This type of cement used in construction when there is no exposure to sulphates in the soil or ground water.
- Lime saturation Factor is limited between i.e. 0.66 to 1.02.
- Free lime-cause the Cement to be unsound.
- Percentage of (AL2O3/Fe2O3) is not less than 0.66.
- Insoluble residue not more than 1.5%.
- Percentage of SO3 limited by 2.5% when C3A < 7% and not more than 3% when C3A >7%.
- Loss of ignition -4%(max)
- Percentage of Mg0-5% (max.)
- Fineness -not less than 2250 cm2/g.
Rapid hardening Portland cement
- It is firmer than Ordinary Portland Cement
- It contains more C3S are less C2S than the ordinary Portland cement.
- Its 3 days strength is same as 7 days strength of ordinary Portland cement.
Low heat Portland cement
- Heat generated in ordinary Portland cement at the end of 3days 80 cal/gm. While in low heat cement it is about 50cal/gm of cement.
- It has a low percentage of C3A and relatively more C2S and less C3S than O.P. Cement.
- Reduce and delay the heat of hydration. British standard ( B S. 1370: 1974 ) limit the heat of hydration of this cement.
Sulphate resisting Portland cement
- Maximum C3A content by 3.5% and minimum fineness by 2500 cm’/g.
- Firmer than ordinary pot land cement.
- Sulphate forms the sulpha-aluminates which have expensive properties and so causes disintegration of concrete.
Sulphate resisting Portland cement
- For this cement, the silage as obtained from blast furnace is used
- The clinkers of cement are ground with about 60 to 65 percent of slag.
- Its strength in early days is less and hence it required longer curing period. It proves to be economical as slag, which is a Waste product, is used in its manufactures.
- As per Indian standard, the proportions of Pozzolana maybe 10 to 25 % by weight. e.2. Burnt clay, shale, Fly ash.
- This Cement has higher resistance to chemical agencies and to seawater because of absence of lime.
- It evolves less heat and initial strength is less but final strength is 28 days onward equal to ordinary Portland cement.
- It possesses less resistance to the erosion and weathering action.
- It imparts a higher degree of water tightness and it is cheap.
White Portland cement
- Grey colour of O.P. cement is due to the presence of Iron Oxide. Hence in White Cement Fe, O, is limited to 1 %. Sodium Alumina Ferrite (Crinoline) NavAlF6 is added to act as flux in the absence of Iron-Oxide.
- It is quick drying, possesses high strength and has superior aesthetic values and it also cost lee than ordinary Cement because of specific requirements imposed upon the raw materials and the manufacturing process.
- White Cement is used in Swimming pools, for painting garden furniture, moulding sculptures and statues etc.
- The Cement of desired colour may be obtained by mixing mineral pigments with ordinary Cement.
- The amount of colouring material may vary from 5 to 10 percent. If this percentage exceeds 10percent, the strength of cements is affected.
- The iron Oxide in different proportions gives a brown, red or yellow colour. The coloured Cement is widely used for finishing of floors, window sill slabs, stair treads etc.
- This type of cement is produced by adding an expanding medium like sulphoaluminate and a stabilising agent to the ordinary cement.
- The expanding cement is used for the construction of water retaining structures and for repairing the damaged concrete surfaces.
High alumina cement
- This cement is produced by grilling clinkers formed by calcining bauxite and lime. It can stand high temper lures.
- If evolves great heat during setting. It is therefore not affected by frost.