This cement is similar to ordinary Portland cement. As the name indicates it develops
strength rapidly and as such it may be more appropriate to call it as high early strength cement. It is pointed out that rapid hardening cement which develops higher rate of development of strength should not be confused with quick-setting cement which only sets quickly. Rapid hardening cement develops at the age of three days, the same strength as that is expected of ordinary Portland cement at seven days.
The rapid rate of development of strength is attributed to the higher fineness of grinding (specific surface not less than 3250 sq. cm per gram) and higher C3S and lower C2S content.
A higher fineness of cement particles expose greater surface area for action of water and also higher proportion of C3S results in quicker hydration. Consequently, capid hardening cement gives out much greater heat of hydration during the early period. Therefore, rapid hardening cement should not be used in mass concrete construction.
The use of rapid heading cement is recommended in the following situations:
(a) In pre-fabricated concrete construction.
(b) Where formwork is required to be removed early for re-use elsewhere,
(c) Road repair works,
(d) In cold weather concrete where the rapid rate of development of strength reduces the vulnerability of concrete to the frost damage.
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