CO_(2)矿化燃煤灰渣基加气混凝土配方研究

Study on formulation of aerated concrete by CO_(2) mineralization using coal ash

为实现燃煤固体废弃物和捕集后CO_(2)的资源化利用,以煤基废弃物燃煤灰渣、脱硫石膏为主要原料,以矿渣为补充胶凝材料,研究了固废配比、矿化养护压力、矿化养护温度对加气混凝土抗压强度和CO_(2)固定率的影响。通过XRD、SEM分析了不同矿化养护制度下的晶相结构和微观形貌,通过压汞法研究了不同养护工况对加气混凝土孔隙结构的影响。结果表明,合适的剩余水灰比有助于提高加气混凝土的CO_(2)固定率和早期抗压强度;CO_(2)养护压力由0.05 MPa上升至1.00 MPa时,加气混凝土的固碳率提高24.8%,抗压强度先上升后降低,养护压力在0.1 MPa时达到峰值;CO_(2)养护温度由25℃上升至105℃时,加气混凝土固碳率和抗压强度先上升后下降,固碳率在45℃时达到最大值7.21%,抗压强度在65℃时达最大值3.53 MPa;通过XRD和SEM分析可知,主要矿化产物为碳酸钙,并以方解石和球霰石的形态存在,较高养护压力(≥0.2 MPa)易导致产物界面出现细微裂缝,而随养护温度升高,矿化产物与水化产物同时出现;通过MIP分析可知,矿化养护对加气混凝土孔隙的影响可分为两方面,一方面,粒径小的碳酸钙等产物可填充10~50 nm孔隙,另一方面,矿化放热及产物体积膨胀会导致30~60μm孔隙增加,提高养护温度可优化微观结构,使孔隙分布更加均匀。

In order to realize the utilization of coal-fired solid waste and captured carbon dioxide,the effects of ratio of solid waste,miner⁃alized 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 cementi⁃tious 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 ex⁃perimental results show that the appropriate residual water/slag ratio is helpful to improve the CO_(2) fixation rate and early compressive strength of aerated concrete.When the CO_(2) 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 CO_(2) curing temperature rising from 25℃to 105℃,the carbon fixation rate and compressive strength in⁃creases first and then decreases.The carbon fixation rate reaches maximum of 7.21%at 45℃,and the compressive strength reaches maxi⁃mum 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 influ⁃ence 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 30-60μm pores.The microstructure can be optimized by increasing the curing temperature,which can make the distribution of pores more uniform.