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 Ordinary
Portland Cement (CEM I 42.5N) and Portland-limestone cement (PLC) which has the
brand name Twiga Cement Extra (CEM II/A-L/32.5R) are produced and conforming to the
Tanzania Standard TZS 727 (Part1): 2002, which is equivalent to EN 197 published by the
committee for European normalization (CEN). A comparison was made between the two
types of cements in terms of physical, chemical and mechanical properties. It was found
out that they all complied with the standards, that there was no significant difference in
their setting times and that the Portland cement had higher strengths than the PLC. It was
also observed that there was a slightly lower water demand for the same consistency when
compared to OPC and hence there is an improvement of the cohesiveness of a concrete mix
when PLC is used. It was concluded, however, that the two cements are different and that
using the two cements interchangeably as is done in Tanzania is wrong because they do
not have equivalent strengths and therefore equivalent performance since the PLC is not
optimized. Portland-limestone cement (PLC) is known to offer significant energy savings
and green house gas (GHG) reduction (up to 10% GHG savings) over conventional
Portland cement while at the same time providing comparable performance if optimized.