Trade Journals for the Concrete Industry

Rapid hardening cement (type CEM I 42.5 or 52.5R) is often added to get a desired strength in a shorter time. However, it has an effect on the workability also, which can make addition of plasticisers necessary, because adding water can lead to lower strengths at all ages. Rapid cement as well as plasticisers cost more than normal hardening portland cement (type CEM II or CEM III N). Therefore, determination of opti- mal dosing of rapid cement, normal portland cement and superplasticisers is worthwhile. Besides the cements, superplasticiser, water and aggregates, there might often be other admixtures or additives including microsilica, fly ash or blast furnace slag, accelerators, etc. which affect the strength of concrete. All these have to be taken into account while determining optimal compositions of concrete depending on the strength required at a given time, or time required to achieve a specified strength.