Role of partial limestone calcination in carbonated lime-based binders

Most carbonation reactions are characterized by products encasing unreacted particles, leading to incomplete reactions and consequently lower material utilization efficiency. This study introduces a novel approach for preparing gradient carbonated materials by partially calcined limestone (PCL), which is calcined below full calcination temperatures to maintain some original limestone while partially transforming into lime. The mechanical strength, phases evolution and microstructure were investigated. The results indicated that the mechanical properties of the materials improve continuously and porosity markedly decreases as the calcination degree of PCL increases, peaking at around 35 %. However, excessive calcination degree impedes the formation of a compact structure. Simultaneously, the carbonation process yields CaCO₃ with a lower decomposition temperature, exhibiting two distinctive microstructural features: an encapsulating layer on the surface of unreacted limestone and the tiny particles (<5 μm) scattered between the layers. This study presents a promising approach to carbonated material design, demonstrating that through controlled partial calcination of limestone, opening avenues for more efficient material utilization.