Novel recycling application of high volume municipal solid waste incineration bottom ash (MSWIBA) into sustainable concrete.

Since municipal solid waste incineration bottom ash (MSWIBA) contains some heavy metals that are harmful to the groundwater and soil, this study proposes an effective and new approach to deal with high-volume MSWIBA. Selecting 70% MSWIBA, 10% ordinary Portland cement (OPC), 10% fly ash/ground granulated blast furnace slag (FA/GGBFS), and 1% volume of polypropylene (PP) fiber as the raw materials, this project designed and manufactured cold-bonded fiber aggregates (CBFAs) and applied them into sustainable concrete. It was found that the water absorption of CBFAs was between 12 and 14%, the bulk density was between 900 and 1100 kg/m, and the compressive strength of single particle was greater than 1.8 MPa. And it was found that the mechanical strength and bulk density of CBFAs were positively correlated, while the mechanical strength and water absorption were negatively correlated. The leaching behaviors of CBFAs on Cu, Pb, Cd, and Cr were successfully suppressed to less than 1% of that originally from MSWIBA, which can be in line with the Chinese standards. Additionally, it is also found that the green concrete with adding GGBFS-CBFAs has higher overall fluidity and better mechanical properties than the concrete with FA-CBFAs. The mechanical properties of concrete were the best under the replacement rate of 60% of CFBAs, and the strength of green concrete added with GGBFS-CBFAs reached 96% of that of ordinary concrete. In this study, the rapid chloride ion penetration test, mercury intrusion and electron microscope tests found that the bonding effect between the CBFAs and the green concrete matrix was better, and the pore structure in the transition zone of the surrounding interface was refined. The proportion of transition pores in the pore structure was up to 59%. This shows that the concrete added with CBFAs has better resistance to chloride ion diffusion, and has some improvement on the durability. This research suggests that CBFAs including high volume MSWIBA has the potential to be successfully applied as the alternative to natural aggregates in sustainable concrete, and this can also advance waste recycling, and solidify high volume heavy metals in infrastructures.