钢渣-粉煤灰固废复合碱激发胶凝材料矿化养护

Mineralization maintenance of steel slag-fly ash solid waste composite alkali-inspired cementitious materials

针对钢渣固废占用资源、污染环境的问题,将钢渣与CO_(2)矿化封存技术相结合可实现工业固废和CO_(2)的资源化利用。通过研究钢渣–粉煤灰复合碱激发胶凝材料在自然和矿化养护条件下,不同CaO和水玻璃掺量、水玻璃模数、矿化养护压力和时长对样品固碳率和抗压强度的影响,发现当添加质量分数15%CaO、4%模数为2.2的水玻璃时,样品的固碳率和抗压强度分别可达7.86%和158 MPa,有最佳综合性能。其中,CaO掺量与样品的固碳率呈正比,当不添加CaO时,固碳率仅0.35%;当CaO掺量升至15%时,固碳率可达7.86%。可见,CaO对固碳率的提升起决定作用。随着矿化养护压力升高,固碳率由4.82%升至7.86%。当矿化养护时间由0.25 h增至1.5 h时,固碳率增幅124%。XRD结果表明,矿化养护28 d后,Ca(OH)_(2)衍射峰消失,方解石含量显著上升,可见Ca(OH)_(2)与CO_(2)发生碳酸化反应,生成大量具有较良好稳定性的方解石,有效实现CO_(2)封存。SEM测试结果表明,矿化养护后样品生成的大量方解石与C-S-H凝胶和粉煤灰玻璃体紧密地附着在一起,利于提高抗压强度。通过压汞测试测定CO_(2)养护前后孔隙分布,相较自然养护,矿化养护后样品的孔隙大幅下降,矿化产物起好填充作用,使样品的强度得到明显提升。结合经济性分析发现矿化钢渣–粉煤灰碱激发胶凝材料有好的综合性能与经济效益。

Aiming at the problems of steel slag solid waste occupying resources and polluting the environment,the combination of steel slag and CO_(2)mineralisation and sequestration technology can achieve the resourceful use of industrial solid waste and CO_(2).Through the study of steel slag-fly ash composite alkali-inspired cementitious materials in the natural and mineralisation maintenance conditions,different CaO and water glass dosing,water glass modulus,mineralisation maintenance pressure and length of time on the samples of the carbon sequestration rate and compressive strength of the samples,under the condition that the mass fraction of CaO and the modulus of the water glass of 2.2 are 15%and 4%respectively,it is found that the samples of carbon sequestration and compressive strength of the carbon sequestration rate and compressive strength of the samples are up to 7.86%and 158 MPa,respectively,with the best overall performance.Among them,CaO doping and the carbon sequestration rate of the samples are positively proportional to each other,when the doping mass fraction of CaO was 0,the carbon sequestration rate was only 0.35%.When the doping mass fraction of CaO was increased to 15%,the carbon sequestration rate was up to 7.86%,which shows that CaO plays a decisive role in the enhancement of carbon sequestration rate.With the increase of mineralisation maintenance pressure,the carbon sequestration rate increases from 4.82%to 7.86%.When the duration of mineralisation conditioning was increased from 0.25 h to 1.5 h,the increase of carbon sequestration rate was 124%.XRD results show that after 28 d of mineralisation maintenance,the diffraction peak of Ca(OH)_(2) disappeared and the calcite content increased significantly,which shows that Ca(OH)_(2) carbonates with CO_(2),generating a large amount of calcite with better stability and effectively realizing CO_(2)sequestration.The results of SEM test show that a large amount of calcite generated from the samples after mineralisation conditioning is closely attached with C−S−H gel and fly ash vitreous body,which is conducive to the improvement of compressive strength.The pore distribution before and after CO_(2)conditioning is determined by mercury compression test.Compared with natural conditioning,the pore space of the samples after mineralisation conditioning decreases dramatically,and the mineralisation products play a good role in filling up,so the strength of the samples is significantly improved.Combined with the economic analysis,it is found that the mineralised steel slag-fly ash alkali-inspired cementitious material has good comprehensive performance and economic benefits.