Different Types of Cement
What is Cement?
Cement is a binding material called a binding agent. We know cement is the main ingredient of building materials.
Cement is a commonly used binding material in construction. The cement is obtained by burning a mixture of calcareous (calcium) and argillaceous (clay) material at a very high temperature and then grinding the clinker so produced to a fine powder. It was first produced by mason Joseph Aspdin in England in 1924. He patented it as Portland cement.
TYPES OF CEMENT :
There are many varieties of cement apart from ordinary Portland cement. Important varieties are briefly explained below:
- White Cement: White cement is the cement when made free from colouring oxides of iron, manganese and chromium. In the manufacture of this cement, oil fuel is used instead of coal for burning. White cement is used for floor finishes, plastering, ornamental works etc. It is used for fixing marbles and glazed tiles. In swimming pools white cement is used to replace glazed tiles.
- Coloured Cement: The cement of desired colours is produced from ordinary cement by intimately mixing pigments with it. The chromium oxide gives green colour. Cobalt produces a blue colour. Iron oxide with different proportions produces a brown, red or yellow colour. The addition of manganese dioxide gives black or brown coloured cement. These cements are used for giving finishing touches to floors, walls, window sills, roofs etc.
- Quick Setting Cement: While mixing a low percentage of gypsum and adding a small amount of aluminium sulphate while manufacturing the cement, quick setting cement is produced. Finer grinding also adds to the quick setting property. This cement is used to lay concrete under static or slowly running water. It takes 5 minutes to cement start setting after adding water and becomes a hard mass within 30 minutes.
- Rapid Hardening Cement: This cement can be produced by increasing lime content and burning at high temperatures while manufacturing. It is very necessary to grind it to very fine. It gains strength in the early days as the initial and final setting time of this cement is the same as that of Portland cement. This property helps in the earlier removal of formworks and speeds up construction activity.
- Low Heat Cement: In mass concrete works like the construction of dams, the heat produced due to the hydration of cement will not get dispersed easily. This may cause to rise more cracks. Hence in such constructions, it is preferable to use low-heat cement. This cement contains a low percentage (5%) of tricalcium aluminate (C3A) and a higher percentage (46%) of dicalcium silicate (C2S).
- Pozzolana Cement: Pozzolana is a volcanic powder found in Italy. It can be processed from shales and certain types of clay. In this cement, only 10 to 30 per cent is pozzolana material. It’s used for mass concrete works. Also used in sewage line works. It can resist the action of sulphate and releases less heat during the setting. It imparts a higher degree of water tightness. The tensile strength of this cement is high but the compressive strength is comparatively low.
- Expanding Cement: The main property of this cement is that it expands as it sets and this is the reason it is used for filling the cracks in concrete structures. This property is achieved by adding expanding media like sulpha aluminate and a stabilizing agent to ordinary cement.
- High Alumina Cement: It is manufactured by calcining a mixture of lime and bauxite. Resistant to sulphate is more acid attack. Develops almost full strength within 24 hours of adding water. It is used for underwater work.
- Acid Resistant Cement: It is produced by adding acid-resistant aggregates such as quartz, quartzite, sodium silicate or soluble glass. The benefit of this cement is that it has good resistance to the action of acid and water and this is the reason it is commonly used in the construction of chemical factories.
- Blast Furnace Cement: Slag is the waste product which comes from the manufacture of pig iron. While grinding clinkers of cement along with about 60 to 65 per cent of slag, this cement is produced. It is quite similar to ordinary but it is cheap since it utilises waste products. This cement is durable but it gains strength slowly and hence needs a longer period of curing.
- Sulphate Resistant Cement: This cement is produced by keeping the percentage of tricalcium aluminate C3A below five per cent in ordinary cement. It is used in the construction of structures which are likely to be damaged by alkaline conditions. Examples of such structures are canals and culverts.
- Fly Ash Blended Cement: Fly ash is a by-product of thermal stations. The particles of fly ash are very minute and fly in the air, and can cause creating air pollution. Thermal power stations have to spend a lot of money to arrest fly ash and dispose of it safely. It is found that one of the best ways to dispose of fly ash is to mix it with cement in controlled conditions and derive some of the beneficiary effects on cement. Most of cement factories nowadays produce fly ash in their own thermal stations or borrow it from other thermal stations and further process it to make it suitable to blend with cement. 20 to 30 per cent of fly ash is used for blending.
- Fly ash blended cement has superior quality of resistance to weathering action. The ultimate strength gained is the same as that with ordinary Portland cement. However, the strength gained in the initial stage is slow. Some of the brand names of blended cement are Birla plus, Birla star, A.C.C. Suraksha etc.