This study aims to assess the effectiveness of an industrial residue-based soil stabilizer (GDP) and recycled fine aggregate (RFA) in enhancing the properties of soft clay. The GDP is composed of ground granulated blast furnace slag (GGBS), desulfurized gypsum (DG), and Portland cement (PC). The optimal formula for GDP and the appropriate amount of RFA needed to reinforce the soft clay were determined through unconfined compressive strength (UCS) testing. The microscopic characteristics and reinforcement mechanism of the GDP-RFA-reinforced soft clay were then analyzed using X-ray diffraction (XRD), Fourier transform infrared (FTIR), thermogravimetry (TG), and scanning electron microscopy (SEM) techniques. The effectiveness of utilizing GDP and RFA as reinforcement additives in soft clay ground was also validated through field testing. The experiments showed that using GDP instead of cement significantly increased the strength of soft clay, with the optimal mass ratio of GGBS, DG, and PC in GDP being 6:1:3. The strength of the GDP-reinforced sample initially increased and then decreased as the RFA content increased, reaching its peak at a RFA content of 30 %. The formation of C-S-H and C-A-H gels, along with AFt crystals, in the GDP-RFA-reinforced sample greatly enhanced its mechanical properties. RFA helped to form more hydrated products and provide effective mechanical support, but excessive RFA could lead to large pores in the matrix. The use of GDP and RFA in reinforcing soft clay ground significantly improved its specific penetration resistance, bearing capacity, and compressive modulus. A significant linear correlation was found between the compressive modulus of reinforced clay and its specific penetration resistance or UCS. As a result, an empirical model has been developed to predict the compressive modulus of reinforced clay based on this correlation.

This study comparatively investigated the performance of mortar prepared using excavated soil recycled fine aggregate (ESRFA), which mainly included fine aggregate obtained by sediment separation equipment and sieving. Scanning electron microscopy (SEM) was used to analyse the size and shape of ESRFA particles. The particle size distribution of ESRFA was uneven and its sphericality was lower than that of river sand. Two series of rendering mortar mixes were prepared using identical water/cement and aggregate/cement ratios of 0.55 and 3, respectively, using river sand as fine aggregate. ESRFA was used to replace 30%, 50%, 70%, and 100% of the river sand in each mixture. The experimental results showed that the flowability of the mortar prepared with ESRFA was lower than that of the aggregate-based mortar, but the porosity, water absorption, and mechanical properties (compressive strength, flexural strength, and drying shrinkage) increased and then decreased upon increasing the ESRFA content. In conclusion, ESRFA shows potential as a partial replacement for river sand in mortar, particularly at lower substitution rates. Further research is needed to optimize the processing and application of ESRFA in concrete to enhance its performance and sustainability.