活化煤矸石-粉煤灰-水泥三元复合胶凝材料水化硬化特征研究

Hydration properties of activated "coal gangue-fly ash-cement" ternary compound cementitious material

  • 摘要: 为提高煤矸石的利用率,将煅烧煤矸石按设计比例与粉煤灰均匀混合后取代30 % 水泥,研究热活化煤矸石-粉煤灰复合胶凝材料部分取代水泥后对砂浆流动度和力学性能的影响,并结合水化热、XRD、TG和SEM分析复合水泥水化机理。结果表明: 随着活化煤矸石掺量的增加,水泥砂浆流动度和力学性能呈先增大后减小的趋势,当活化煤矸石掺量占复合粉体总量20 % 时,砂浆28 d抗压强度可达52.27 MPa; 活化煤矸石和粉煤灰的加入,改变复合水泥体系中矿物成分和化学成分占比,消耗水泥水化生成的氢氧化钙并形成额外的C-(A)-S-H凝胶,同时还导致AFt相向AFm相转变; 活化煤矸石在改善水泥砂浆力学性能时,物理充填效应和成核效应大于火山灰作用。

     

    Abstract: Coal gangue is a solid waste generated from coal selection and washing. This study proposes to improve its utilization rate by enhancing its activity through calcination and mixture with fly ash in a designed proportion to replace 30 % of cement. We investigated the effect of coal gangue-fly ash composite cement on the fluidity and mechanical properties of mortar after replacing cement, and analyzed the hydration mechanism of the composite cement using water heat generation, XRD, TG, and SEM. Results show that with the increase in the amount of activated coal gangue, the fluidity and mechanical properties of the cement mortar first increased and then decreased. When the activated coal gangue accounted for 20 % of the total composite powder, the 28-day compressive strength of the mortar reached 52.27 MPa. The addition of activated coal gangue and fly ash altered the proportion of mineral and chemical components in the composite cement system, consumed the calcium hydroxide generated during cement hydration, and formed additional C-(A)-S-H gel. It also induced the transformation of the AFt phase into the AFm phase. When the mechanical properties of cement mortar is improved, the activated coal gangue exhibits more significant physical filling effect and nucleation effect than its pozzolanic activity.

     

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