“2. The total percentage of C2S and C3S in all types of Portland cements is around 70 per cent, so that even though the strength development of two cements at early stages may be different, the final strength obtained after long periods of time may not be different. However, removal of formwork, prestressing of concrete depends to a large extent on the early strength of concrete. 3. When producing low-heat Portland cement the percentage of C2S is increased and that of C3S and C3A is decreased. This type of cement is of particular use in construction of dams, massive foundation, etc. to reduce the production of heat. 4. Reducing C3A increases sulphate resistance but the 7 day and 28 day strengths also get lowered as compared to the ordinary Portland cement. Sulphate-resisting Portland cement has less than 5% C3A. This type of cement is recommended for sewer works. 5. Rapid hardening cements compared to ordinary cements have more or less the same composition except that the latter is more finely ground and may sometimes contain higher percentage of C3S. The increased fineness increases the 7 day strength.”