Strength and permeability performance of excavated waste mud stabilized with ternary industrial byproducts

To address the dual challenges of improving strength and reducing permeability in solidified soils produced from excavated waste mud, this study develops a sustainable stabilization method using industrial by-products. A ternary solid waste-based cementitious material (SWC), consisting of ground granulated blast furnace slag (GGBS), steel slag (SS), and desulfurization gypsum (DG), was optimized through an extreme vertex mixture design. The results demonstrate that, under appropriate mix proportions, the solidified soil using SWC can achieve comparable unconfined compressive strength (UCS) at 7 d and superior strength at 28 d compared to ordinary Portland cement (OPC). Specifically, the mixture containing 60 wt% GGBS, 30 wt% SS, and 10 wt% DG, referred to as G60S30D10, achieved a 28 d UCS of 3.22 MPa, representing an increase of approximately 105% over OPC, and a permeability coefficient of 1.94 × 10⁻⁸ m/s, an order of magnitude lower than that of OPC, which indicates excellent water resistance. Microstructural analysis, including X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and mercury intrusion porosimetry, reveals that the primary hydration products in the SWC solidified soil include ettringite (AFt), C-S-H, C-A-H, and C-A-S-H. Compared to OPC, the AFt content increased by 22-83%, and the combined action of expansive AFt crystals and dense C-(A)-S-H gels effectively fill interconnected pores, leading to a substantial reduction in detrimental macropores (> 1 μm) from 15% in OPC to 2-3% in the SWC matrix. This refined pore structure substantially contributed to the observed reduction in permeability. These findings offer valuable insights into the performance and mechanisms of low-carbon, high-efficiency solidified soils using industrial by-products.