To investigate the potential application of geopolymer materials in pile foundation post-grouting engineering, this study utilized industrial solid wastes such as fly ash (FA), slag (SL), and steel slag (SS) to prepare geopolymer grouting materials (GGMs) with various mix proportions. The fluidity, setting time, bleeding rate, and mechanical properties of these materials were evaluated to determine the optimal mix proportions for pile foundation grouting. Furthermore, the influence mechanisms of different maintenance conditions on material performance were investigated, including unconfined compressive strength, flexural strength, and microstructural changes. The results indicated that when the SL-to-FA ratio was 1:1, the GGMs satisfied the requirements for pile foundation grouting, and their mechanical properties significantly improved with extended curing time. Under Yellow River water maintenance conditions, the materials formed a dense three-dimensional network of hydrated products, notably enhancing their mechanical characteristics. Additionally, field tests confirmed that GGMs effectively improved the shear strength of the pile-soil interface. The grout distribution pattern on the pile side exhibited a compaction-splitting mechanism. These research findings provide theoretical support for applying geopolymer materials in pile foundation grouting engineering.

To achieve environmental and economic goals in ground improvement, a one-part geopolymer (OPG), synthesized from binary precursors (fly ash [FA] and granulated blast furnace slag [GGBFS]) and a solid activator (solid sodium silicate [NS]), was used to replace ordinary Portland cement (OPC) for stabilizing high-water-content soft clay. The effects of different initial water content (50%, 80%, 100%, and 120%) and various OPG binder content (10%, 20%, 30%, and 40%) on the strength development of the OPG-stabilized soft clay were investigated through unconfined compressive strength (UCS) and unconsolidated undrained (UU) triaxial tests. Additionally, the microstructure evolution and the distribution of pores in the OPG-stabilized soft clay were examined by the utilization of mercury intrusion porosimetry (MIP) and scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS) techniques, respectively. The life cycle assessment (LCA) methodology was then used to analyze the environmental and economic advantages of employing an OPG binder for soil stabilization. It was revealed that the optimal content of OPG binder was contingent upon the water content of soft clay, with variations in requirements for strength development. Specifically, for soft clay not demanding early strength, a maximum binder content of 20% is proposed. Conversely, for soft clay that necessitated rapid strength gain, the OPG binder content escalated with increasing water content of the soft clay, in which soft clays with different water contents had corresponding required amounts of OPG binder. For soil with water content ranging from 50% to 80%, the recommended OPG binder content is 20%. While for soil with 100% and 120% water content, the designed OPG binder content is suggested to be 30% and 40%, respectively. The environmental assessment demonstrated that the utilization of OPG as a binder for the stabilization of soft clay reduces costs and carbon emissions in comparison to OPC. The present study provides substantial theoretical validation for the utilization of OPG as a novel binder to stabilize soft clay with elevated water content, which holds promise as an eco-friendly and cost-effective solution in ground improvement.