Effect of Fly Ash on Bonding and Shrinking Behaviors of High-Belite Sulphoaluminate Cement–Based Foam Concrete

A sandwiched foam concrete (FC) layer with good bond and thermal properties is crucial to the overall performance of a prefabricated insulation panel. In this study, the effects of grade and the dosage of fly ash (FA) on the dry density, specific strength, thermal conductivity, bonding strength, shrinkage, and moisture loss rate of high-belite sulphoaluminate cement (HBSC)–based foam concrete (HBFC) were investigated. The shrinkage differences between HBFC and portland cement-based foam concrete (PCFC) were also compared. The results show that the bonding strengths of HBFC doped with Grade-I and Grade-II FA are higher than that doped with Grade-III FA. When the Grade-III FA dosage is less than 5%, or the Grade-I and Grade-II FA dosage are less than 15%, the bonding strengths of HBFC meet the requirements of the prefabricated insulation wall panel. The shrinkages and moisture loss rates of HBFC in all groups increase fast within 24 h of curing. The 672 h shrinkages of the HBFC doped with all grades of FA increase with the FA dosage, which are still much lower than those of PCFC. The shrinkages of HBFC doped with Grade-I and Grade-II FA are lower than that with Grade-III FA, and the rule is the same as the moisture loss rates of the HBFC. HBSC doped with a 15% dosage of Grade-II FA is the most suitable binder for a preparing cost-effective HBFC panel with the dry density, specific strength, thermal conductivity, bonding strength, and 672 h shrinkage of being 302.9 kg/m3, 1,276.6 N·m/kg, 0.0791 W/m·k,0.128 MPa, and 2.930 mm/m, respectively, and the corresponding cost for preparing 1 m3 of HBFC is about $41.30.