Soils with lower CBR values are rejected in most of civil engineering applications such as road and construction sector applications.
Therefore, the soil has to be improved or removed. There is a considerable amount of water treatment plants in Sri Lanka. The larger amount of sludge was produced by them. This sludge is not used as profitable manner.
Fly ash is also a huge waste in the thermal power plants in Sri Lanka. This attempt was made to make use both sludge and fly ash in a productive manner. Also, this proposal is a cost effective and environmentally friendly solution.This study concludes that lower characteristics of soil can be enhanced with fly ash with an optimum value at 30%.
Although there was not a considerable amount of improvement in MDD there was huge improvement of CBR value compared to the original sludge about 211.55% after 28 days curing. But this enhancement is not yet satisfactory to RDA conditions. (Liquid limit < 40%, Plasticity index 1750 kg/m3 and CBR > 30%). So, this cannot be used in the road sector without further improvement.
However, there are other applications for this kind of soil like land filling purposes.