Stabilisation of highly swelling clay using lime–sand mixtures

Stabilisation of expansive soil using lime or sand is an effective improvement technique as it reduces the swelling ability of the soil. The aim of this paper is to study the influence of different lime fractions and lime–sand mixtures on the behaviour of highly expansive clay by performing swelling and strength tests on each mixture. Calcium (Ca)-bentonite is utilised as highly expansive clay. All samples were remoulded according to the results of the modified compaction Aashto test. Non-treated bentonite possesses high values of swelling and strength. Mixing lime and sand with clay causes significant reductions in swelling characteristics. The reductions increase effectively with the increase in lime and sand content. The swell potential and the swelling pressure of the clay almost vanish when stabilised by 10% lime and 50% sand. Generally, adding only lime into clay leads to an increase of its California bearing ratio (CBR) and unconfined compressive strength (UCS), whereas mixing clay with both lime and sand leads to an increase in the CBR values. The CBR values increase significantly with the increment of their content. For a >30% sand content, the UCS of the lime–clay mixtures decreases on increasing the sand fractions, whereas the UCS values increase with a longer curing time. The CBR and UCS-56 d curing time of the stabilised clay with 10% lime and 50% sand increase to twice the values for the non-treated clay.