COMPARISON OF THE PROPERTIES OF PORTLAND CEMENT AND PORTLAND-LIMESTONE CEMENT

Abstract

A study was made in a cement factory in Dar es Salaam, Tanzania, where OrdinaryPortland Cement (CEM I 42.5N) and Portland-limestone cement (PLC) which has thebrand name Twiga Cement Extra (CEM II/A-L/32.5R) are produced and conforming to theTanzania Standard TZS 727 (Part1): 2002, which is equivalent to EN 197 published by thecommittee for European normalization (CEN). A comparison was made between the twotypes of cements in terms of physical, chemical and mechanical properties. It was foundout that they all complied with the standards, that there was no significant difference intheir setting times and that the Portland cement had higher strengths than the PLC. It wasalso observed that there was a slightly lower water demand for the same consistency whencompared to OPC and hence there is an improvement of the cohesiveness of a concrete mixwhen PLC is used. It was concluded, however, that the two cements are different and thatusing the two cements interchangeably as is done in Tanzania is wrong because they donot have equivalent strengths and therefore equivalent performance since the PLC is notoptimized. Portland-limestone cement (PLC) is known to offer significant energy savingsand green house gas (GHG) reduction (up to 10% GHG savings) over conventionalPortland cement while at the same time providing comparable performance if optimized.