Modification of super-sulfated cement based foamed concrete with nano-ettringite

Super Sulfate Cement (SSC) has great potential to replace Portland cement in the preparation of foam concrete (FC). However, SSC presents the problem of low early strength and easy carbonation, and these problems would be more serious in FC, limiting its practical application. In this study, nano-ettringite (NE) was utilized as a foam stabilizer and a hydration accelerator to improve the stability of precast foam and the properties of SSC-FC. The influence of NE on the stability of foams was studied; A series of techniques were employed to study the properties, hydration process, and microstructure of FC, respectively. The results demonstrated that NE limited the coalescence and disproportion of the bubbles by increasing the viscosity of the cell walls, which enhanced the stability of the foam. Furthermore, NE enhanced the compressive strength of SSC-FC and optimized its pore size structure. At 28 d, the compressive strength of SSC-FC without NE-stability foam was only 3.44 MPa, and SCC-FC with 8%NE-stability was 5.06, increasing by 48%. This was attributed to two aspects: on the one hand, a more uniform and smaller pore structure was produced by adding NE. On the other hand, NE promoted the generation of hydration products through nucleation induction, which made the pore walls of the SSC-FC denser. Additionally, NE similarly improved the thermal insulation, drying shrinkage, and carbonization resistance of SSC-FC. These results proposed a novel method to improve the properties of SSC-FC.