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Some countries have only one grade of cement whereas others prescribe different grades.This question is relevant for countries whose standards prescribe different grades.

The main  advantage (some people say: the only advantage ) in using higher grade cement is the faster rate of gain in strength during the initial two or three weeks.

Als, though a bit  costlier than low grade cement, it is claimed that they offer 10-20% saving in cement consumption.

However  a faster rate of hydration results in higher heat, increased shrinkage, and lower later-age strength. There are many other disadvantages also  in using higher grade cements. Higher grade cements are promoted by the industry as economical cements as less quantity of cement is required. Reduction in the amount of cement, when the quantity of water is based on workability, leads to higher water to cement ratio and more voids in concrete.

Further, without adequate quantity of fine material the concrete becomes unworkable. A reduction in the quantity of cement in ordinary concrete produces a harsh mixture, honey combing, and more voids. Moreover, concrete exposed to humidity and moisture requires a minimum cement content to prevent the corrosion of steel reinforcement. This means exposed structures should be made with a minimum quantity of cement, independent of the grade of cement to make them durable.

It can be said that Higher Grade Cements do not have much  utility for normal construction works & their use is generally recommended only for   higher grades of concrete say M30 and above .

The usage of higher grade cement is becoming more & more popular. In fact 33 grade cement is now almost out of market in many countries.

However, the use of a high grade cement should not be taken for granted to yield high grade (strength) concrete as the strength of concrete depends on the mixture of cement, sand, coarse aggregate and water. In fact, the cement's grade has no relationship to the strength of concrete. It is possible to produce concretes of wide-ranging strengths using a particular grade of cement, as it is done in the West using ASTM Type 1 cement.

Moreover, the term 'grade' has nothing to do with quality; increase in the grade does not increase the quality of the cement. The quality guarantees a set of minimum standards prescribed. Two cements of different grades can have the same quality.

Every structure has to satisfy the requirements of strength and durability. Strength is the ability of the structure (or its elements) to with stand load. Durability refers to the period of trouble-free life.

A structural element of concrete may possess high strength, but may deteriorate sooner than expected, making it a material of poor quality. Here the quality is with reference to-concrete and not that of cement. But if a brand or grade of cement is directly responsible for producing bad quality of concrete, the cement can be blamed as that of low quality. But any grade or brand of cement that satisfies the minimum requirements prescribed by the code, generally, should produce concrete of desired properties if the mix proportioning is done properly.

To put it in a proper perspective, a brand or grade of cement can be said to be of good quality if the concrete made with it satisfies both the strength and durability requirements.

The strength requirements (that is, the strength of concrete) is satisfied by choosing the proper amount of cement, limiting the amount of water, consolidating the mixture well, and curing the hardened concrete as long as possible.

It may be stated that manufacture of  higher grade cement has been made possible by modern equipment/plants, better quality control on processes/products, using superior quality limestone, finer grinding, better particle size distribution & better packing.