Performances of cement-based materials incorporating new SCMs produced by the co-calcination of construction wastes with waste dolomite powder

In this study, new types of supplementary cementitious materials (SCMs) were manufactured by the calcination of construction wastes such as engineering muck (EM) and waste brick (WB) in the presence of waste dolomite powder (WDP). The impacts of calcined dolomite-muck (CDM) and calcined dolomite-brick (CDB) on the performances of Portland cement were investigated, the reaction mechanism of CDM and CDB in pastes was also analyzed. Results showed that the mineral compositions of CDM and CDB are β-C ₂ S, periclase, quartz and merwinite. The incorporations of CDM and CDB decreased obviously the hydration heat and strengths of cement-based materials at early stages. However, the blended cement mortars with 10-20% CDM and CDB obtained similar or higher strengths at later stages compared to the control mortar. This is attributed to the hydration of β-C ₂ S in CDM and CDB, resulting in the pore structure densification and the lower porosity at later ages. In addition, the mortars with CDM and CDB also produced gentle expansions attributed to the hydration of periclase in CDM and CDB, which is beneficial for mitigating the shrinkage.