Study on the Proportion Optimization and Hardening Mechanism of Slag-Based Filling Materials Regulated by Finely Ground Fly Ash
In order to achieve the efficient utilization of fly ash and blast furnace slag,as well as develop the low-cost and high-performance cemented filling materials for mining,a series of orthogonal ratio optimization experiments were conducted.The effects of fly ash content,Ca(OH)2 content,Na2SO4 content,and slurry mass concentration on the compressive strength,fluidity,and setting time of the slag-based cemented filling materials were explored,so as to obtain the optimal parameter proportion.At the same time,the regulation mechanism and hardening mechanism of finely ground fly ash on slag-based materials were studied by thermogravimetric differential thermal analysis and scanning electron microscopy.The results show that the compressive strength of the backfill at 7 days and 28 days in the orthogonal experiments exceeds 2.6 MPa and 6.8 MPa,respectively.The alkaline activation of Ca(OH)2 plays a crucial role in enhancing the compressive strength at 3 days,while the fly ash content has a significant effect on the overall compressive strength of the backfill.The optimal parameter proportion of filling materials(Y sample)is:30％finely ground fly ash content,15％Ca(OH)2 content,5％Na2SO4 content,and 80％slurry mass concentration.The analysis of the hardening mechanism indicates that the addition of finely ground fly ash increases the endothermic peak of the hydration products such as C-S-H and ettringite around 110 ℃ in the slag-based cemented filling materials.The weight loss of Y samples at 3 days and 28 days is 4.80％and 4.96％,respectively,which indicates continuous reactions within the filling materials,resulting in the formation of more C-S-H and ettringite.The interconnection and growth of these products lead to a denser structure and reduce porosity in the filling body,contributing to higher compressive strength.
Finely ground fly ashFilling material proportionHardening mechanismFluidityCompressive strength
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