Municipal solid waste incineration bottom ash : a potential supplementary cementitious material

Abstract

Concrete is the most used building material in the world. It might have a positive effect in expanding urbanism, however it has a negative environmental impact as its manufacturing process is a major cause of CO2 emission. This empowered scientists to come up with ways that aimed to reduce the CO2 gas generation, one of which is the substitution of cement by supplementary cementitious material (SCM). This substitution insures a reduction in the cement quantity therefore a reduction in CO2 generation. This project aims to study the potential use of municipal solid waste incineration bottom ash MSWI BA to substitute cement as SCM. So far, no recycling method was found to be eco-effective and cost-efficient at once. This study aims to maximize the amount of MSWI BA that could be recycled in concrete while maintaining desirable mechanical properties. Previous studies did not achieve the desirable mechanical properties of the treated bottom ash. The project was time consuming and was not cost efficient. Therefore, the aim of this study is to compare the untreated bottom ash samples to the treated ones and find out if the treatment was beneficial and to what extent. The materials used for this study are Ordinary Portland Cement (OPC) (CEM I 52.5 N-SR3), MSWI BA, standard sand, and distilled water. The MSWI BA has been characterized by X-ray Diffraction (XRD) and X-ray Fluorescence (XRF). Full observation and evaluation of the study are achieved through replacement of cement by MSWI BA with different proportions (0%, 5%, 10%, and 15%) where each mixture is tested for compressive strength and flexural strength for four different durations (2, 28, 90 and 180 days). The mineralogical composition of cement paste with 15% MSWI substitution has been characterized by mercury porosity and XRD and compared to reference without MSWI BA. The results obtained showed that the compressive strength difference was not large enough to dismiss the fact that untreated MSWI BA was in fact a promising SCM.