Impacts of milling duration on construction and demolition waste (CDW) based precursor and resulting geopolymer: Reactivity, geopolymerization and sustainability

Using construction and demolition waste (CDW) as the geopolymer precursor is gaining increasing interest. The milling process is required in the production of CDW-based precursor. This paper aims to investigate the impacts of milling duration on CDW-based precursors and resulting geopolymer paste. Results show that prolonged milling enhances the reactivity of CDW precursors by changing the particle size, crystal structures and surface group. A longer milling duration promotes the formation of the Si-rich gel, resulting in a higher reaction degree and a more densely packed structure of CDW-based geopolymer. Benefiting from the higher strength, geopolymer derived from CDW with longer milling can achieve a lower CO2 emission per unit strength. However, the reactivity enhancement of CDW became less apparent with the increasing milling duration since the particle aggregation and activated phases on the surface could prevent further activation. The milling for CDW-based precursor production is suggested to be appropriately prolonged but not exceed 2 h. [Display omitted]