Effect of brown coal fly ash on dispersive clayey soils

Abstract

Dispersive soils exhibit erosive behaviour in contrast to normal clayey soils. Several chemical stabilisers have been identified as being capable of stabilising these soils. However, the effect of brown coal fly ash (BFA) on the stabilisation of dispersive soil has not yet been investigated adequately. BFA is known to be a weak contributor to strength development. In this work, the stabilisation mechanism of BFA for strength improvement and erosion resistance over time was investigated using two different dispersive soils. The experimental results revealed that the selected BFA is an effective stabiliser in enhancing the erosion resistance of the tested dispersive soils in the short-term. On the other hand, it was found that the addition of hydrated lime further enhanced the strength development of dispersive clayey soils and facilitated early strength gain. Furthermore, soil samples treated with an effective combination of BFA and hydrated lime were investigated at the micro-level by means of energy dispersive x-ray spectroscopy and scanning electron microscopy. The micro-level investigations revealed that the cation exchange rate was higher in soils with a low calcium/sodium ratio.