Reaction mechanisms of the hydration products of solidified sulfate saline soils in the long-term solid waste period

To ensure effective utilization of saline soils in cold and arid areas as engineering materials, we used calcium carbide slag along with slag, slag + fly ash, and fly ash as the cementitious materials to solidify sulfate saline soil. We then studied the effects of the salt content, calcium carbide slag content, and aging period on the compressive strengths of solidified soil samples containing different compositions of the active cementitious materials. The hydration products of the solidified soil samples were characterized under different conditions by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, thermogravimetric analysis, and mercury intrusion porosimetry. The results of these analyses showed thast the salt and calcium carbide slag contents significantly affected the strengths of the solidified soil samples. When the salt content was 3.1% and calcium carbide slag content was 7%, the synergistic effects were found to be maximal in the solidified soil system containing different active cementitious materials. Moreover, under high salt content and a lengthy aging period, we found that stronger activities of the cementitious materials were not linked to higher strengths of the solidified soil samples. Through experimental evaluations, we found that the influence of high salt content on the solidified soil was reflected in changes in the amounts of hydration products formed and the corresponding pore structure.