Modified testing of clay-bearing aggregates

A suite of tests have been performed on a variety of aggregates with the intention of predicting the presence of clay minerals and evaluate their suitability. The results of methylene blue adsorption, liquid limit, linear shrinkage and plasticity index on ground rock powder together with petrographic analysis of stained thin sections of rock fragments/particles have been used in this study to predict the presence of clay minerals in the aggregates. It is concluded a.o. that clay minerals can be found in any type of rock aggregates regardless whether they are fresh or weathered. Simple and cheap tests like methylene blue, plasticity index and liquid limit together with petrographic analysis of stained thin sections habe the ability to predict and quantify the presence of clay minerals especially those which are present in a small amount. Petrographic analysis is essential in any research dealing with the suitability of the aggregates.