Study of macro-/micro-properties and in-situ mineralization mechanism of CO2 foam concrete based on solid waste-derived SAC-gypsum composite

Abstract

CO₂ foam concrete (CFC) has a promising application in the field of building energy conservation and carbon reduction. The cement-based composite is critical to the mechanical performance, microstructure, and CO₂ sequestration of CFC. In this paper, a solid waste-derived sulphoaluminate cement (SAC)-gypsum composite with high strength and water resistance properties was explored using solid waste-based SAC, hemihydrate desulfurization gypsum and supplementary cementitious materials. Then, the SAC-gypsum composite and CO₂ foam were used to prepare CFC with high strength, steam-free curing and low thermal conductivity, and the influence of different CO₂ concentrations, CO₂ gas flow rates and CO₂ foam dosages on CFC preparation was investigated. The prepared CFC showed properties of high strength, steam-free curing and low thermal conductivity. The compressive strengths of CFC were 6.55–9.45 MPa (1.54–1.96 times of air foam concrete). Meanwhile, CFC achieved CO₂ sequestration of 2.05 wt% of the raw material, and the comprehensive carbon emissions was 90.90–115.27 kg CO₂/ton. It was found that the in-situ CO₂ mineralization reaction in CFC had completed in early-age, and the mineralization products i.e., CaCO₃ and amorphous gel on the foam wall enhanced the early-age and later-age performance of CFC. This study provides a promising approach towards green, low-carbon and high-performance foam concrete, as well as sustainable construction.