建筑垃圾-粉煤灰基胶结充填体强度机理研究

Study on the Strength Mechanism of Construction Waste-Fly Ash Cementitious Filling Material

为实现城市建筑垃圾与粉煤灰的无害化利用,研发矿山采空区回填用低原料成本与性能最优胶结充填材料,设计4因素3水平正交试验确定充填体的最优参数配比,分析充填体的强度机理。结果表明,料浆质量分数、胶砂比、Ca(OH)2掺量与充填体抗压强度和屈服应力呈正相关,而与扩散度、塌落度和凝结时间呈负相关。正交试验中料浆质量分数影响最大,最优参数为:胶砂比为1∶3,粉煤灰与水泥质量比为8∶2,Ca(OH)_(2)掺量为10%,料浆质量分数为70%。硬化机理为:充填体样品中粉煤灰受Ca(OH)_(2)碱激发作用,发生火山灰反应生成水化硅酸钙(C-S-H)凝胶,并且生成较多的钙矾石及中间水化产物硅酸二钙(C_(2)S)与硅酸三钙(C_(3)S),28 d总水化产物失质量达5.39%。充填体的建筑垃圾颗粒被水化产物覆盖,结构更加密实且孔隙减少。

To achieve the harmless utilization of urban construction waste and fly ash,a low-cost,high-performance cementitious filling material for mine goaf backfilling was developed.A four-factor,three-level orthogonal experimental design was used to determine the optimal parameters for the filling material and elucidate its strength mechanism.The results showed that slurry concentration,sand-cement ratio,and Ca(OH)_(2) content were positively correlated with the compressive strength and yield stress of the filling material,while consistency,slump,and setting time were negatively correlated.Among the factors,slurry concentration had the greatest impact.The optimal parameters were as follows:sand-cement ratio of 1∶3,fly ash to cement mass ratio of 8∶2,Ca(OH)_(2) content of 10%,and slurry concentration of 70%.The hardening mechanism involved the activation of fly ash by Ca(OH)_(2),leading to the formation of C-S-H gel,calcium aluminate,and intermediate hydration products C_(2)S and C_(3)S,resulting in a 28 d total hydration product loss of 5.39%.The construction waste particles in the filling material were covered by hydration products,resulting in a denser structure with reduced porosity.