CO₂ 矿化燃煤灰渣基加气混凝土配方研究

In order to realize the utilization of coal-fired solid waste and captured carbon dioxide, the effects of ratio of solid waste, mineralized curing pressure and mineralized curing temperature on the compressive strength and carbon fixation rate of aerated concrete were studied, with the coal-based waste, coal ash and desulfurization gypsum as the main raw materials and slag as the supplementary cementitious material. The crystal phase structure and micro morphology under different mineralized curing conditions were analyzed by XRD and SEM, and the effect of different mineralized curing conditions on the pore structure of aerated concrete was studied by MIP. The experimental results show that the appropriate residual water/ slag ratio is helpful to improve the CO₂ fixation rate and early compressive strength of aerated concrete. When the CO₂ curing pressure increases from 0.05 MPa to 1.00 MPa, the carbon fixation rate increases by 24.8%, and the compressive strength increases first and then decreases. When the curing pressure is 0.1 MPa, the maximum compressive strength is reached. With the CO₂ curing temperature rising from 25 ℃ to 105 ℃, the carbon fixation rate and compressive strength increases first and then decreases. The carbon fixation rate reaches maximum of 7.21% at 45 ℃, and the compressive strength reaches maximum of 3.53 MPa at 65 ℃. According to analysis of XRD and SEM, the major mineralized products are CaCO₃, which mainly exist in the form of calcite and vaterite. Higher curing pressure (≥0.2 MPa) is likely to cause micro-cracks at the product interface. With the increase of curing temperature, the mineralized products and hydrated products appear simultaneously. According to MIP analysis, the influence of mineralized curing on the pores of aerated concrete can be divided into two aspects: on the one hand, CaCO₃ and other products with small particle size can fill the pores of 10-50 nm, on the other hand, reaction heat of mineralization and volumetric expansion of products can cause the increase of 30 - 60 μm pores. The microstructure can be optimized by increasing the curing temperature, which can make the distribution of pores more uniform.