Analysis on Physical and Mechanical Properties of Coal based Solid Waste Filling Material in Early Age

Zheng WuLizhen Xu^*Chang XinWen Zhang

• Xi 'an University of Science and Technology, Xi 'an, China

Fly ash filling materials play a vital role in coal mining, but their widespread application is hindered by limitations such as low early age strength, poor fluidity, and severe water segregation. This study aims to optimize the mixing ratio and improve the performance of fly ash filling materials by investigating their physico-mechanical properties, as well as hydration reactions, during the early age with different mixing ratios. Five distinct mixing ratios of fly ash filling materials were examined, focusing on the temporal evolution of their physical and mechanical parameters during the early age, accompanied by an in depth analysis of their hydration reactions. The findings reveal a close correlation between the microstructure, mechanical characteristics of the filling materials, and factors like water binder ratio and fly ash content. Specifically, fly ash, to some extent, suppresses the early age strength of the material. When the fly ash content is reduced from 75% to 50%, the 48 hours uniaxial compressive strength and elastic modulus of the filling material increase by 3.06 times and 6.80 times, respectively. Additionally, by adjusting the mix ratio and incorporating additives, we found that a filling material with a water binder ratio of 0.63 and a fly ash content of 50% has a high hydration rate, high compactness, and high early age strength. By adjusting the mixing ratio and using additives reasonably, the early strength of fly ash filling materials can be significantly improved, minimizing material waste and enhancing engineering safety.