Abstract: Foam concrete has good heat insulation and sound insulation properties, but the drying shrinkage is large, and it is easy to crack in practical engineering applications. In this study, slag was used to replace part of cement. By adding anhydrous calcium sulfate to regulate the concentration of sulfate in slurry, the crystallization of ettringite was promoted to form transition structure, and the synergistic regulation of matrix compressive strength optimization and drying shrinkage reduction was realized. The results show that when the content of calcium sulfate is 1%~15% (mass fraction), the fluidity of foam concrete slurry increases first and then decreases with the increase of calcium sulfate content, and the settlement distance and drying shrinkage of foam concrete slurry increase first and then decrease with the increase of calcium sulfate content. When the content of calcium sulfate is 5%, compared with the control group, the fluidity of foam concrete slurry increases by 4.1%, the settlement distance of slurry at 90 min is the smallest (0.13 mm), the compressive strength at 28 d increases by 17.4%, and the drying shrinkage rate reduces by 28.0%. Appropriate amount of ettringite crystals can reduce the drying shrinkage by forming a transition structure, thereby reducing the cracking risk of foam concrete. This study provides a theoretical basis and technical path for the preparation of calcium sulfate used for anti-dry shrinkage foam concrete.

Key words: foam concrete, slag, ettringite, anhydrous calcium sulfate, drying shrinkage, transitional structure