Experimental study on mechanical properties, hydration kinetics, and hydration product characteristics of aeolian sand paste-like materials

Abstract

Using fly ash (FA), aeolian sand (AS), cement, and mixing water as filling materials for making the paste-like filling mining can not only effectively control the surface subsidence and solve the “three-underground mining” coal pressure but also solve the environmental problems caused by the solid wastes, so as to realize the sustainable utilization of solid waste. The utilization of a large amount of AS resources can control land desertification, and the sale of aeolian sand can bring considerable economic benefits to Yuyang district. Hence, in this study, different ASPM samples were produced by varying the content of FA (0–30 wt%) and the curing times (3, 7, 14 and 28 days). The mechanical strength test, hydration kinetics test and microscopic test of aeolian sand paste-like materials (ASPM) was studied. The results showed that, according to the typical underground mining, the uniaxial compressive strength (UCS) of the backfill, cured for 28 days, was generally between 0.7 and 2.0 MPa, which can provide good roof support. In this study, the minimum strength of the ASPM reached 4.43 MPa (C-FA0), so the ASPM met the requirements of strength performance. Secondly, the hydration exothermic process of ASPM was divided into five different stages, and the influence of FA content on hydration kinetics was analyzed. For example, in the acceleration stage of ASPM, there was a positive correlation between the FA content, exothermic heat, and exothermic rate. The possible reason was that the particle size of FA was finer than that of AS, and the hydration reaction was more sufficient. In addition, the microscopic morphology and the characteristics of hydration products of ASPM were also studied. It is an important prerequisite for industrial field practice to study the mechanical properties, hydration characteristics and hydration product of ASPM.