Effect of partial replacement of cement by MSWIBA on the properties of mortar

Abstract

Municipal solid waste is currently a pressing challenge in Lebanon. This problem has been aggravated recently due to an increase in population resulting from the flow of Syrian refugees to the country. Incineration is a common technique to treat the solid waste resulting in the formation of a well-known residue: Municipal solid waste incineration bottom ash (MSWIBA). Those residues can be either dumped in landfills leading to environmental concerns or used in construction materials as a sustainable, resource efficient and economic approach in both solid waste management and construction. The goal of this study is to explore this option. For this purpose, mortar specimens were prepared with amounts of 10, 20, 30 and 40% weight of cement replaced by MSWIBA obtained from incinerators. Three tests (compressive strength, ultrasonic pulse velocity (UPV) and total water absorption (TWA)) were performed for each mixture at different curing durations: 1, 3, 7, 14 and 28 days. Results indicate that MSWIBA has a limited cementitious activity and a deleterious effect on the compressive strength of mortar cubes. From the analysis of the pozzolanic activity index, it was found that the maximum replacement of cement by MSWIBA should be limited to 10%. UPV results show that the curing duration is of paramount importance for the mortar quality and any increase in the MSWIBA beyond the 10% replacement level leads to significant drop in the UPV results. Finally, the evaluation of TWA results indicates the presence of MSWIBA in mortar is not the main factor affecting its absorption.