REDUCTION OF EXPANSIVE INDEX OF KAOLINITE AND BENTONITE CLAY BY USING SAND AND FLY ASH MIXTURES

Expansion or swelling behavior of expansive soil has always created problems in the field of geotechnical engineering. When any construction has been carried out on expansive soil without pre-knowledge of their properties under various environmental conditions, the damage is severe. One of the methods to find out swelling potential of expansive soil is the expansive index (EI). The present study investigates the reduction of EI for the two commercially available expansive soils i.e., kaolinite and bentonite when mixed with Ottawa sand and Class C fly ash. The percentages of Ottawa sand and Class C fly ash mixed with kaolinite and bentonite were 0 to 50% by weight. The results show that there is a significant reduction in the swelling properties of expansive soil with the addition of Ottawa sand and Class C fly ash. The reduction in expansive index ranged approximately from 10 to 50% and 4 to 49% for kaolinite and bentonite, respectively. Also the maximum swelling pressure of kaolinite and bentonite soil decreased approximately 93% and 64%, respectively with the addition of various percentages of Ottawa sand and Class C fly ash. These results help to identify the swelling potential and swelling pressure of expansive soil with different percentages of sand and fly ash which will be beneficial to the geotechnical engineer. Standard index properties test such as liquid limit, plastic limit and shrinkage limit test was conducted to see the characteristic of expansive soil when mixed with less expansive sand and Class C fly ash. Also, for these expansive soils one dimensional (1-D) consolidation characteristics was studied with sand and Class C fly ash mixtures and the results were compared with pure kaolinite and bentonite soil. Pre-consolidation (Pc) behavior, compression index (Cc) and recompression or swelling index (Cs) properties were also studied for the different percentages of sand and Class C fly ash with expansive soil