Preparation of eco-friendly geopolymer anchor grouting material using water-quenched iron slag: performance, multi-objective optimization, and engineering applicability

Cement and resin are currently the most prevalent grouting materials for ground anchors. However, their utilizations are accompanied by significant drawbacks, including high energy consumption and environmental pollution. By contrast, geopolymer possesses sufficient potential to serve as an alternative. In this study, water-quenched iron slag (WIS) was utilized to produce geopolymer anchor grouting material. Twenty-five groups of tests were designed through orthogonal experiment theory. Macroscopic performances of the geopolymer grouting material were tested and discussed, including workability (consistency and setting time) and mechanical properties (compressive strength and elastic modulus) at curing ages of 3d, 7d, and 28d. Microstructural morphology and reactive mechanism were analyzed based on the results of SEM, EDS, XRD, and MIP. Response surface models were developed to predict the macroscopic performances. A population-evolved grey wolf optimization (PEGWO) algorithm was proposed, the convergence speed, stability, and global optimization capability of which are superior to those of GWO and PSO algorithms. The PEGWO algorithm was used to develop a multi-objective (cost, carbon emission, and strength) optimization method for determining the best proportion of the geopolymer grouting material. A series of element-scale pullout tests was conducted for the geopolymer and cement grouted anchors embedded in two types of soils. The shear strength over the geopolymer grout-soil interface is approximately equivalent to that of the cement grout-soil interface, and even slightly superior, which verifies the engineering applicability of the developed WIS-based geopolymer anchor grouting material. • An eco-friendly geopolymer anchor grouting material was produced using waste water-quenched iron slag. • Macroscopic performance and microstructural morphology of the geopolymer grouting material were systematically investigated. • Response surface models were proposed for predicting the workability and mechanical properties of the geopolymer grouting material. • PEGWO algorithm were developed for the multi-objective (cost, CO 2 emission, and strength) intelligent optimization of mix proportion. • Engineering applicability of the geopolymer grouting material was assessed through a series of element-scale pullout tests.