Strain hardening cementitious composites incorporating high volumes of municipal solid waste incineration fly ash

Abstract

This paper reports the potential use of municipal solid waste incineration fly ash (IFA) as cement supplement for the production of strain hardening cementitious composites (SHCC). Results showed that IFA is not a conventional pozzolan according to ASTM C618. Certain chemical reaction; however, occurred when IFA is used together with cement as evidenced by the formation of Friedel’s salt in IFA-SHCCs. As a result, the compressive strength as well as tensile ductility of IFA-SHCCs can be maintained when up to 20% cement was replaced by IFA. At higher replacement level, however, excessive alkali metal chloride may leach out from the matrix leading to porous honeycomb microstructure of matrix which results in reduced compressive strength but enhanced tensile ductility of IFA-SHCCs. Leaching tests showed that almost all heavy metals concentration complied with the limits set in the Dutch Soil Quality Decree for construction materials. This suggests SHCC binder can effectively immobilize heavy metals in IFA potentially due to the low water-to-binder ratio of IFA-SHCCs matrix. Preliminary evaluation indicates that IFA may be used to replace cement in the production of SHCC. Further studies are necessary to investigate the long-term environmental impact of IFA-SHCCs.