Application of steel slag composite grout for strengthening expressway photovoltaic slope

Steel slag composite grout (SSCG) was prepared by a large amount of steel slag (SS) to reinforce expressway photovoltaic (PV) slopes and reduce carbon emission. Laboratory tests were conducted to investigate SSCG properties, including flowability, effective water-solid ratio (W/S), stone rate, initial and final setting time, as well as flexural strength (FS), unconfined compressive strength (UCS), FS/UCS ratio and microstructure of SSCG stone body. Ordinary Portland cement (OPC, 42.5) and sulphoaluminate cement (SAC, 42.5) grouts were selected to make contrasts. Based on the performance results, the recommended SSCG composition for engineering application is 40 % SS + 25 % blast furnace slag (BFS) + 20 % silicate cement clinker (CC) + 10 % fly ash (FA) + 5 % flue gas desulfurisation gypsum (FGDG). and the recommended admixture is: 6 % AA + 2 % bentonite + 0.4 % FND-C. With the above SSCG and related grouting techniques for slope soils, the soil cohesion was increased by 7.3–12.2 % and the angle of internal friction was increased by 10.2–19.7 %. To further validate the beneficial effects of SSCG on slope stability and the safe application of PV systems, numerical modelling calculations were conducted based on the soil sample test results. The simulations demonstrated the positive effect of SSCG in enhancing slope stability and facilitating the secure installation of PV systems on expressway slopes. The successful operation of grid-connected PV systems provided compelling evidence for the technical applicability of SSCG and it contributed to the application feasibility of PV systems to expressway slopes. The innovative use of SSCG in this study not only ensures the safety of construction projects but also contributes to environmental sustainability through the application of industrial slags.