Sustainable use of different size fractions of municipal solid waste incinerator bottom ash and recycled fine aggregates in cement mortar

The demand for recycled fine aggregates (RFA) is increasing daily, and researchers are continuously looking for cheaper and local alternative fine aggregates. The increasing growth of municipal solid waste (MSW) incineration plants has led to the accumulation of incinerated bottom ash in the vicinity of cities. There can be a possibility to utilize this municipal solid waste incinerated bottom ash (MSW-BA) as a partial replacement of recycled fine aggregated to achieve sustainable and economical mortars. This study analyzed the feasibility of incorporating different grain sizes, fine fraction (0.15-0.3 mm), medium fraction (0.3-0.6 mm), and coarse fraction (0.6-4.75 mm)) of MSW-BA and RFA in sustainable cement mortars with replacement amounts of 10 %, 20 % and 30 %, respectively. In addition to assessing the mechanical properties of the sustainable mortar, Mercury Intrusion Porosimetry was carried out. Based on the filler effect combined with its mineralogy and pozzolanic properties of MSW-BA, a medium fraction at 10 % replacement showed the highest compressive and flexural strength of 31.05 MPa and 5.07 MPa, respectively. After exposure to the 1 mol/liter sodium hydroxide (NaOH) solution, the largest reduction of compressive strength by 7.92 MPa was found in 10 % medium fraction replacement of MSW-BA. Porosity was also reduced when smaller grain sizes of MSW-BA was replaced with RFA, and leaching tests have confirmed leaching of heavy metal are under limits. Results showed that adding MSW-BA can improve the compressive strength of concrete up to a certain extent, but over-addition of MSW-BA can lead to a detrimental effect on strength.