Properties and microstructure of soil solidified by titanium slag-flue gas desulfurized gypsum-Portland cement composites as solidifiers

Abstract

Using Portland cement for soil solidification has sustainability issues due to high energy-consumption and carbon emissions. An innovative approach suggests using titanium slag and flue gas desulfurized gypsum as substitutes for Portland cement for soil solidification. This study systematically evaluates the effects of titanium slag-flue gas desulfurized gypsum-Portland cement composite (TS-FGD-OPC composite) solidifier on the performance of solidified soils. The evaluation includes assessing the unconfined compressive strength (UCS), elastic modulus, moisture content, and leachate pH value. Additionally, the hydration process and microstructure development of the solidified soils are characterized through the XRD, TG-DSC, BET, and SEM tests. The results indicate that the although its compressive strength is much lower, TS-FGD-OPC composite can be used as soil solidifier. With the titanium slag content increase, the TS-FGD-OPC composite solidifier brings the solidified soils to have lower UCS, elastic modulus and leachate pH value, and higher plastic deformation and moisture content. However, to get the same UCS, the utilization of the TS-FGD-OPC composite solidifier can bring the significant reduction of the Portland cement consumption. At the same dosage, the TS-FGD-OPC composite incorporating 50% titanium slag and 20% flue gas desulfurized gypsum yields an UCS achieving up to 92.5% of that in pure Portland cement solidified soil. This is attributed to the filling of pores between soil particles with hydration products and unhydrated particles, resulting in the densification of the solidified soils and the cohesion increase of soil particles. The findings confirm the feasibility of substituting Portland cement with titanium slag and flue gas desulfurized gypsum to prepare an effective and environmentally friendly soil solidifier, to reduce the demand for Portland cement in soil solidification.