Utilization of Carbide Slag in Autoclaved Aerated Concrete Preparation

Lime is one of the main raw materials necessary for the production of autoclaved aerated concrete (AAC). The preparation of lime by calcining limestone directly and indirectly emits a large amount of CO2 due to the limestone decomposition and energy consumption. In this study, AAC was made using modified carbide slag (MCS) instead of lime, which effectively can utilize solid wastes and reduce the CO2 emission. Results showed that in the first 2 h of hydration, the heat release rate of MCS was higher than that of lime, and the cumulative hydration heat of lime and MCS within 30 h was 206.1 and 204.3 J/g, respectively. MCS not only can improve the fluidity of slurry, but also can enhance the gas-foaming rate. Cumulative pore volume increased with the increase of MCS content in AAC. Tobermorite, quartz, katoite, anhydrite, and calcite were the main minerals in the AAC. With the increase of MCS content, the density and strength of AAC decreased and the thermal insulation performance increased. When the MCS content was 100%, the AAC density was 594 kg/m3, the compressive strength was 3.6 MPa, and the thermal conductivity was 0.141 W center dot m-1 center dot K-1, which meet in the requirements of the Chinese standard.