Types of Cement
In addition to ordinary Portland cement there are various varieties of cement. Significant varieties are briefly explained below:
(i) White Cement: The cement when made free from coloring oxides of iron, chlorium and maganese results into white cement. In the manufacture of this cement, the oil fuel is utilized rather than of coal for burning. White cement is utilized for the, plastering, floor finishes, ornamental works etc. In swimming pools white cement is utilized to replace glazed tiles. It is utilized for fixing marbles and glazed tiles.
(ii) Colored Cement: The cements of preferred colors are produced by intimately mixing pigments along with ordinary cement. The chlorium oxide gives green color. Cobalt gives blue color. Iron oxide with different proportion gives brown, red or yellow color. Addition of manganese dioxide produces black or brown colored cement. These cements are used for giving finishing touches to,walls, floors window sills, roofs etc.
(iii) Quick Setting Cement: Quick setting cement is generated by reducing the percentage of gypsum and adding a small amount of aluminium sulphate at the time of manufacturing of cement. Finer grinding also adds to quick setting property. This cement begin setting within five minutes after adding water and becomes hard mass within 30 minutes. This cement is utilized to lay concrete under static or slowly running water.
(iv) Rapid Hardening Cement: This cement can be generated by increasing lime content and burning at high temperature whereas manufacturing cement. Grinding to very fine is also essential. Although the initial and final setting time of this cement is the similar as that of Portland cement, it gains strength in early days. In earlier removal of form works and speed in construction activity this property helps.
(v) Low Heat Cement: In mass concrete works as construction of dams, heat generated due to hydration of cement will not get dispersed easily. This can give rise to cracks. Therefore in such constructions it is preferable to use low heat cement. This cement contains higher percentage (46%) of dicalcium silicate (C2S) and low percentage (5%) of tricalcium aluminate (C3A) and
(vi) Pozzulana Cement: Pozzulana is a volcanic power found in Italy. It may be processed from shales and definite types of clay also. In this cement pozzulana material is 10% to 30%. It may resist action of sulphate. It releases less heat at the time setting. It imparts higher degree of water tightness. Its tensile strength is good but compressive strength is low. It is utilized for mass concrete works. It is also utilized in sewage line works.
(vii) Expanding Cement: This cement expands as it sets. This property is gained by adding expanding medium like sulpho aluminate and a stabilizing agent to ordinary cement. This is utilized for filling the cracks in concrete structures.
(viii) High Alumina Cement: It is composed by calcining a mixture of lime and bauxite. It is more resistant to acid attack and sulphate and. It develops nearly full strength within 24 hours of adding water. It is utilized for under water works.
(ix) Blast Furnace Cement: In the manufacture of pig iron, slag comes out as a waste product. This cement is produced by grinding clinkers of cement with about 60% to 65 %of slag. The properties of this cement are more or less same as ordinary cement, but it is cheap, as it utilize waste product. This cement is durable but it gains the strength slowly and therefore needs longer period of curing.
(x) Acid Resistant Cement: This cement is generated by adding acid resistant aggregated like quartz, quartzite, soluble glass or sodium silicate. This cement has good resistance to action of acid and water. This is commonly used in the construction of chemical factories.
(xi) Sulphate Resistant Cement: this cement is produced by keeping the percentage of tricalcium aluminate C3A below 5% in ordinary cement. It is utilized in the construction of structures which are likely to be damaged by alkaline conditions. Instance of such structures are culverts, canals etc.
(xii) Fly Ash Blended Cement: Fly ash is a byproduct in thermal stations. The particles of fly ash are minute and they fly in the air and creating air pollution problems. Thermal power stations ought to spend lot of money to arrest fly ash and dispose safely. It is establish that one of the best ways to dispose fly ash is to mix it along with cement in controlled condition and derive some of the beneficiary effects on cement. Now-a-days cement factories generate the fly ash in their own thermal stations or borrow it from other thermal stations and further procedure it to make it appropriate to blend with cement. 20% to 30% fly ash is used for blending.
Fly ash blended cements have superior quality of resistance to weathering action. The last strength gained is the similar as that with ordinary Portland cement. Though strength gained in the initial stage is slow, Birla star,Birla plus A.C.C. Suraksha are some of the brand name of blended cement.