Improvement of peaty soils with municipal solid waste fly ash

Municipal solid waste fly ash is one of the products in the incineration process of solid waste and is usually disposed of in a landfill. The high lime content present in municipal solid waste fly ash indicates a possibility of using it to improve poor quality soils. Peaty soils are found at shallow depths in Singapore. These soils are generally excavated and disposed of in a landfill. This paper investigates the possibility of improving the peaty soil using municipal solid waste fly ash and also evaluates the environmental impact of the use of the latter. Test results showed that the shear strength of peaty soil can be improved by a few times by mixing with municipal solid waste fly ash. Leaching tests conducted on peaty soil-municipal solid fly ash mixes showed that the effluent element concentrations are below the limits set for trade effluent discharged into an uncontrolled watercourse but are generally above the limits set for drinking water and trade effluent discharged into a controlled watercourse. Therefore, peaty soil-municipal solid waste fly ash mixes should not be used at sites where there is a possibility for the effluent to discharge into controlled watercourses.