Microwave preparation and carbonation properties of low-carbon cement

•Microwave sintering can significantly decrease the sintering temperature of γ-C2S.•When carbonated, microwave sintered low-carbon cement exhibited excellent compressive strength.•The main carbonation products of low-carbon cement are calcite and silica gel. Low-carbon cement (LCC) with a main phase of γ-C2S exhibits excellent carbonation activity in the presence of moisture, but its sintering temperature in a conventional furnace is about 1400 °C, which consumes a huge amount of energy. To address the sustainability issues facing the preparation of γ-C2S, microwave sintering is increasingly recognized as a potential alternative due to its volumetric heating nature. In this study, LCC was prepared in a microwave furnace and a conventional furnace, respectively, and then followed by carbonation. Results show that microwave sintering can lower the sintering temperature by about 100 °C compared to the samples prepared in a conventional furnace. Moreover, when subjected to carbonation for 8 h, the sample prepared in the microwave furnace (M1250) developed higher compressive strength than that prepared in the conventional furnace (C1350). The main carbonation products of LCC are calcite and silica gel, which combine with uncarbonated particles to form flocculent and fibrous structures. The outcome will provide a reference for preparing low-carbon cementitious materials.