# Diffusion and Consolidation of Slag-Based Geopolymer for Concrete Payment Rehabilitation
## 5 Conclusions  
A new visual indoor grouting test system was developed to study the diffusion and consolidation characteristics of the slag-based geopolymer under different gradation aggregate conditions, and SEM was used to observe the reactants and consolidation. Moreover, the consolidation effect of the slag-based geopolymer on a weak road base was studied through on-site grouting tests. The main conclusions are as follows:  
As the size of the aggregate decreased, the diffusion depth of the slurry gradually decreased, and a relatively complete specimen only formed at a high grouting pressure. The 9.5-4.75 mm aggregate formed a complete cylindrical specimen under a grouting pressure of 0.4 MPa; when the grouting pressure was 0.2 MPa, 20 mm to 50 mm grout splitting surfaces would form at the lower part of the grout bulb. However, the 4.75-2.36 mm aggregate only developed a bulb and some slurry veins, and a pressure filtration effect occurred. The 2.36-1.18 mm aggregate did not develop slurry veins, and the grouting bulb was also very small; moreover, the pressure filtration effect was more significant. In the diffusion consolidation grouting test, the strength of the specimens consolidated by the 9.5-4.75 mm aggregate met the requirement of 28 d strength, and the diffusion depth of the other two aggregates also increased. Due to the fact that the blast furnace slag powder was rich in CaO and SiO\({}_{2}\), a large number of gel products were generated by the polymerization of geopolymer materials. The geopolymer slurry with a water-slag ratio of 0.4 would promote the hydration and  
Figure 26: Test pit excavation for geopolymer grouting test: (**a**) consolidated slurry at the bottom of the slab; (**b**) consolidation slurry at the top of the road base; (**c**) exploration pit excavation; and (**d**) consolidation of loose granular materials and consolidated geopolymer slurry layer. dissolution reaction in the early stage, but the pores of the structure would increase, and shrinkage cracks appeared in local positions of the reactants. However, the size of the cracks was not large, and the polymerization reaction of the geopolymer was relatively complete, without any residual flake-shaped calcium hydroxide crystals. As the size and porosity of the aggregate increased, the diffusion depth of the geopolymer slurry also increased, resulting in a better consolidation effect on the aggregate. Under a 1.0 MPa grouting pressure, the consolidated 2.36-1.18 mm aggregate was slightly loose, and there were many granular gels on the surface. Under a 0.8 MPa grouting pressure, the geopolymer filled the pores of the 4.75-2.36 mm aggregate, and the consolidated structure was relatively dense. Fine cracks appeared locally at the bonding interface between the aggregate and the slurry. Under a 0.4 MPa grouting pressure, the diffusion of the slurry in the pores of the 9.5-4.75 mm aggregate was better, and the solidified slurry was denser. The slurry consolidated coarse aggregate shrank slightly, and the interface cracks were relatively wider compared to the fine aggregate, but it could still meet the actual engineering needs. The diffusion and consolidation characteristics of the geopolymer obtained through indoor tests provide a certain guidance for the formulation of on-site grouting schemes. The geopolymer slurry effectively penetrated the voids beneath the concrete slabs and within the road base layers, enhancing the overall structural stability. The average deflection of the driveway decreased from 104.8 (0.001 mm) to 48 (0.001 mm). The geopolymer materials consolidated quickly, and generated dense fillers between the weak road base layers, which could significantly improve the road base load-bearing capacity. Conceptualization, W.L. and B.L. ; methodology, J.Y. ; software, W.L. ; validation, W.L. and B.L. ; formal analysis, W.L. ; investigation, J.Y. ; resources, B.L. ; data curation, W.L. ; writing--original draft preparation, W.L. ; writing--review and editing, B.L. ; visualization, W.L. ; supervision, W.L.