Recycling of municipal solid waste incineration by-product for cement composites preparation

In this study, the feasibility of application of municipal solid waste incineration (MSWI) fly ash and bottom ash as a supplementary cementitious material for the preparation of blended cement was evaluated. For this purpose, the cement composites with 10-50 wt% of cement replaced by the equivalent amount of washed MSWI fly ash and bottom ash were prepared, together with water needed for normal consistency, setting time for the blend, strength and hydration characteristics of MSWI ash-cement composites were investigated. The results show that the washed MSWI fly ash and bottom ash have some cementitious activity, but the activity is relatively lower than Portland cement. The behavior of the addition of composites of washed MSWI fly ash and bottom ash were observed to be different with respect to water demand and setting time. Addition of washed fly ash and bottom ash were found to have a deleterious effect on the mechanical strength of cement composites and the maximum replacement by washed MSWI fly ash and bottom ash should be limited to the range of 40 wt% and 20 wt%, respectively to ensure the mechanical properties of composites. Besides, the hydration characteristic of cement blended with washed MSWI fly ash and bottom ash was also measured by using X-ray powder diffraction (XRD) and scanning electron microscope (SEM). Finally, the environmental and economic impact of the as-derived cementitious materials was also evaluated. It was found that the recycling of MSWI fly ash and bottom ash for the cement production can achieve a significant economic and environmental benefit at the same time.