Preparation of calcium oxide–C₂S–C₄A₃$S¯$ clinkers for autoclaved aerated concrete

High-belite calcium sulfoaluminate cement (HBCSA) is a low carbon dioxide binder but suffers from slow early strength development due to its low hydration rate. Adding calcium oxide (CaO) can increase the hydration rate, but the synthesis of HBCSA clinker containing a designed amount of calcium oxide remains unexplored. In this study, a method was developed to produce calcium oxide–C₂S–C₄A₃$S¯$ (CBCSA) clinkers for autoclaved aerated concrete (AAC). Experiments were performed to systematically examine the effects of the calcination temperature, retention time and minor oxides on the mineral composition of the clinkers, along with the influence of the mineral composition on the slurry properties and the physical–mechanical performance of the AAC. The results indicated that the optimal calcination temperature was 1230–1290°C and the optimal retention time was 30–60 min. The CBCSA clinker prepared with 26.5% calcium oxide, 8.8% C₄A₃$S¯$ and 44.7% C₂S produced an AAC slurry with well-matched foaming and thickening rates, shortening the pre-curing time. The resulting AAC blocks achieved a bulk density of 724 kg/m³ and a compressive strength of 7.00 MPa, demonstrating that the CBCSA preserved environmental benefits while enhancing the production efficiency of AAC.