An Examination of the Use of Lime and Pulverized Fly Ash to Stabilize Clay Materials

Abstract

Clay soils frequently present difficulties in construction operations. One of the means by which the engineering behaviour of clays can be improved is to stabilize them by the addition of cementitious materials. However, one of the problems with stabilization of clay soils is their range of mineralogical composition, which means that some are more easy to stabilize than others. In order to investigate this problem, three of the principal components found in clays, namely, kaolinite, montmorillonite and quartz, were chosen. These three components were treated with varying amounts of lime and pulverized fly ash (PFA). As stabilization of clay soils has most frequently been used in relation to road construction, the soil materials were subjected to the types of tests used in the design procedure for road pavements, namely, Atterberg limit tests, compaction tests, California bearing ratio tests, unconfined compressive tests, and tests to determine Young's modulus. Samples for testing, except those for consistency limits, were prepared with optimum values of moisture content and maximum dry density and were cured for different periods of time. The results of the various tests were compared, especially to see if there was an optimum amount for a particular addition which would bring about maximum enhancement of engineering performance of the components concerned. In all cases lime gave a greater enhancement in the soil property concerned than did PFA. When mixtures of lime and PFA were used, that with the highest lime ratio gave the best improvement.