Mechanical behavior and microstructural investigation of loess sustainable stabilization using nanosilica and GGBS

Loess, characterized by its high porosity, low strength, and sensitivity to weather conditions, presents significant challenges for sustainable infrastructure development. Conventional stabilization methods using lime and cement contribute substantially to greenhouse gas emissions and embodied energy. This study proposes a novel and eco-friendly approach for loess soil stabilization by incorporating nanosilica (NS) and ground granulated blast-furnace slag (GGBS), an industrial byproduct, to enhance mechanical performance while minimizing environmental impact. Special attention was given to sustainability aspects, including waste valorization, carbon emissions reduction, embodied energy, and practical feasibility. GGBS was combined with NS to improve the mechanical performance of the soil. Different NS contents (0.4%, 0.7%, 1%, and 1.3%) were evaluated, with 1% NS providing optimal pore filling and uniform dispersion. Subsequently, GGBS was added at varying concentrations (5%, 10%, 15%, and 20%) to the NS-treated loess. The samples cured for 7 and 28 days were subjected to freeze-thaw cycle testing. Experimental characterization included unconfined compressive strength (UCS), ultrasonic pulse velocity (UPV), collapse potential (CP), and microstructural analyses (SEM, XRD, FTIR, and BET). The optimal mix increased UCS by up to 24 times, with only a reduction of 9% after 10 freeze-thaw cycles. Microstructural analyses confirmed the formation of C-S-H and C-A-S-H gels, which led to soil densification. A quantitative sustainability assessment showed the reduction of carbon emissions by over 60% compared to traditional stabilization methods, along with decreased costs, emphasizing significant environmental and economic benefits. This method not only improves mechanical performance but also values industrial waste, thereby providing a scalable, cost-effective, and environmentally sustainable solution for loess stabilization.