Utilization of Fly Ash in Road Construction in South Africa: Environmental Assessment

Abstract

Using fly ash as alterative material in place of conventional materials is continually gaining interest over decades. This results from its international recognition as non-hazardous construction material. However, fly ash composition varies and thus it cannot be generalized that every fly ash is non-hazardous. In South Africa, fly ash is produced in large quantity, yet its utilization on annual basis remains at 6 percent which is majorly utilized in cement and concrete production. Thus, this study focuses on investigating leaching of major elements in South Africa Class F fly ash when used as a stabilizer in road construction. Three different specimens of fly ashes, namely; Kendal Dump Ash, Durapozz and Pozzfill enhanced with different cements were used as stabilizer for G5 soil use in road construction. Using an X-Ray spectrometry analyser the samples were tested for any possible leach elements. Leach tests results show that fly ash enhanced with cement as soil stabilizer in road construction is not harmful as the fly ash constituents‘ exhibit limited mobility. However, results also indicated that fly ash left in dump sites can be harmful, if some of the leached elements find their way to the ground water. Thus, utilization of fly ash for road construction is an environmental sustainable option and has engineering advantages when properly used for soil stabilization.