EFFECT OF THE CLAY FRACTION ON SOME MECHANICAL PROPERTIES OF LIME-SOIL MIXTURES

Artificially prepared, lime-treated mixtures of sand-clay were studied in the laboratory. The experimental programme was arranged with two types of clay mineral (kaolinite and montmorillonite), three levels of clay content (10,30 and 50 per cent), four levels of lime content for the kaolinite soils (0,2,4,8 per cent) and five levels for the montmorillonite soils (0,2,4,8,12 per cent). Two periods of curing (seven and 28 days) were employed. Firstly the maximum dry density optimum moisture content relationships for the 27 different mixtures were determined using one compactive effort. Test specimens for these mixtures were then fabricated at their corresponding optimum compaction conditions. The effect of the type and content of the clay fraction on the specimens' compressive strength, Q, cohesion, C, angle of internal friction, phi, and elastic modulus, e, was determined. The results showed that regardless of the clay content in the soil, increases in the values of q, C, and e due to lime-treatment are significantly higher for the montmorillonite than for the kaolinite specimens. Generally the most significant increase in any of these parameters occurs at two per cent lime for the kaolinite specimens, while for the montmorillonite specimens these strength parameters tend to develop progressively with lime content up to about eight per cent or even beyond. The pattern of increase in the angle of internal friction due to lime treatment is comparable for the two types of soil. The most significant increase occurs mostly up to two per cent lime where it reaches about 10 degrees. Good correlations between unconfined compressive strength and both cohesion and elastic modulus were observed. Linear regression equations for the prediction of and e for lime-treated soils from known values of g were accordingly established. (Author/TRRL)