Reducing the collapsibility of clay using a cement–polymeric fibre admixture

The collapsibility of soils is one of the various phenomena by which soils pose threats to structures built upon them. This behaviour is more pronounced in clays and some silty sands in arid and semi-arid zones. In this study, an attempt was made to decrease the collapsibility of three different clay soils (soil I, soil II and soil III with different clay content and plasticity indices) by treatment with cement–polymeric fibres as an admixture at various percentages (1, 2, 3, 4 and 5%). The collapsibility potential of all soils was found to be ‘moderate to high’ in the remoulded initial state. Standard double oedometer tests were conducted to measure the collapsibility of the soils before and after stabilisation. It was found that an increase in the cement:fibre ratio and/or the admixture content percentage significantly decreased the collapse strain at inundation. Moreover, the collapsibility index decreased on increasing the admixture content beyond 3% for soil I and 2% for soils II and III. For an admixture content of <2–3%, the reduction in the collapsibility index was found to be negligible. For all soils used in this study, with a 5% admixture content and a cement:fibre ratio of 6:1 by weight, the soils were found to change from the very high collapsibility range to the almost no-collapsibility range.