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

Abstract

This study consists of testing and evaluating the possibility of recycling municipal solid waste incineration bottom ash (MSWI BA) and using it as supplementary cementitious material (SCM) to replace a certain amount of cement in mortar samples. 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. Sodium Hydroxide (NaOH) solution treatment was performed on MSWI BA to account for a chemical reaction that occurs between the metallic aluminium present in MSWI BA and cement paste, which results in hydrogen gas generation and high porosity of concrete. The materials used for this study are Ordinary Portland Cement (OPC) (CEM I 52.5 N-SR3), MSWI BA, limestone, standard sand, and distilled water. 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 for four different durations (2, 28, 90 and 180 days). In addition, cement paste samples are tested for mercury porosity, thermogravimetric analysis (TGA), and X-ray diffraction (XRD) to determine mineralogical compositions of used materials. At short term, the compressive strength of mortars containing MSWI BA treated by Eddy current showed significant improvement compared to 0% cement substitution mortars, due to development of pozzolanic reaction, and higher results than MSWI BA – treated by NaOH washing – mortars. The NaOH treatment was found to be slightly inconvenient at short term and might have changed the chemical composition of MSWI BA. Further investigation is needed regarding the effects of the treatment on MSWI BA at long term.