A potential way for improving the dispersivity and mechanical properties of dispersive soil using calcined coal gangue

This paper investigated the improvement behaviors on dispersivity, water stability and mechanical properties of dispersive soil by calcined coal gangue (CCG) at 700 °C, and analyzed the modification mechanism. Dispersive soil specimens with different content of CCG (varying from 1 % to 10 %) were prepared and cured for 0–28 days. The dispersivity of the soil was determined by three different dispersivity determination tests. The tensile strength and compressive strength of the dispersive soil were determined by mechanical property tests. SEM, EDS, TG and XRD analytical methods were employed to reveal microstructure and mineral changes during modification. The results of the study show that the admixture of CCG and the prolongation of curing time contributed favorably to suppressing the dispersivity of the soil and enhancing the water stability, the compressive strength and tensile strength of the dispersive soil. With the increasing of CCG content and the prolongation of curing time, the dispersive soil gradually transforms into non-dispersive soil. Microstructural and mineral analysis indicate that CCG has pozzolanic activity, and the production of pozzolanic reaction products significantly increase the friction and cohesion among soil particles. The results show that the utilization of CCG as an admixture to improve the dispersive soil not only solves the disposal problem of waste gangue, but also optimizes the undesirable characteristics of the dispersive soil. And the modification effect of CCG on dispersive soil in practical engineering is confirmed by validation test.