Use of incineration fly ash as a substitute for cement in geotechnical applications

Abstract

Singapore’s waste disposal trends have been on the rise in the last decade. The current primary solution for waste disposal is through incineration, that can reduce the waste volume by up to 90%. As a by-product of incineration, incineration fly ash has little usage currently, and is often transported to Singapore’s only landfill to rest.

Singapore is abundant in marine clay, with the purpose of reusing incineration fly ash, incineration fly ash is being explored for the feasibility of incorporating it as a partial replacement of cement in the deep mixing process in Singapore. The three main constituents in this study are incineration fly ash, marine clay, and cement. There is little data on marine clay treatment specifically using an incineration fly ash cement admix, thus this study hopes to bridge the gap and extend its usefulness elsewhere.

Using unconfined compression test and direct shear test, the study analyses and discusses the unconfined compression strength and shear strength of the incineration fly ash-cement-marine clay sample. From the experimental results, increasing the percentage of incineration fly ash present in the cement mix leads to decreases in both compressive and shear strength. Lastly, incineration fly ash is still suitable for use in specific geotechnic applications when its percentage in the cement mix is kept below 20%, where the unconfined compression and shear strength are within acceptable range, allowing for a way to reuse incineration fly ash.