Influencers of strength
Over the years several factors that influence the strength of cement have been determined. These include mineralogy, chemistry, microstructure and process.
Figure 1: central irregular alite growth with many inclusions surrounded by clearer alite growth
The various influences on the strengths achieved by Portland cements has been the subject of a number of research projects in the laboratory as well as analyses of industrially-produced materials over the years. A useful method of prediction of commercial cement strengths is to perform a regression analysis that uses historical data to predict the potential strengths before any physical testing has been carried out. This was described in a previous article in ICR.1 The method identified small variations in a few selected parameters that were observed to have the greatest effect on cement performance and predicted changes which would occur following the experiencing of these normal run of the mill variations. The predictions can be very useful in the normal running of a cement factory and have been used at several places by this author with success and benefit to customers. However, the equations resulting from the regression analysis will only be reliable within the range of data values present in the original data set. If a significant change occurs to any of the factors in the equation, the analysis will no longer be relevant to the new situation.
