Mechanical and microscopic properties of concretes made with municipal solid waste incinerator bottom ash (MSWIBA) exposed to freeze-thaw cycles

Recently, owing to the over-exploitation of natural river sand, escalating amounts of waste incinerated, limited landfill space, and the imperative of achieving a circular economy, there has been a growing interest in exploring applications for municipal solid waste incinerator bottom ash (MSWIBA). This study investigates the influence of the MSWIBA substitution rate for natural river sand and freeze-thaw (F-T) cycles on the macroscopic performance response, microscopic morphology, and pore structure characterization of concretes. The results indicate that the addition of MSWIBA can effectively refine the pore structure of concrete specimens. However, the addition of MSWIBA leads to increased porosity and decreased density during the F-T cycles, resulting in lower concrete strength. Higher MSWIBA content exacerbates these negative effects, diminishing concrete durability, particularly frost resistance. In summary, incorporating a small amount of MSWIBA refines concrete pore structures, but excessive amounts intensify internal expansion stress and disharmony during F-T cycles, resulting in the expansion of micropores and the crack propagation. Concrete specimens exhibit optimal performance when the MSWIBA substitution rate for natural river sand ranges from 0 % to 41.3 %. Notably, the substitution rate of 24.8-41.3 % demonstrates high-value utilization of MSWIBA.