# Diffusion and Consolidation of Slag-Based Geopolymer for Concrete Payment Rehabilitation
## 3 Results and Discussion
### Diffusion and Consolidation Test  
For studying the consolidated strength of aggregates with different particle sizes of 9.5-4.75 mm, 4.75-2.36 mm, and 2.36-1.18 mm after diffusion, the three single-graded aggregate grouting tests were conducted under different initial conditions. Slightly different from the previous grouting tests, the bottom flange plate valve of the test mold was first opened, and then the air pump valve was opened for grouting. The valve at the bottom of the mold was immediately closed when the slurry flowed out. We started timing after closing, and the grouting test ended after 1 min. Among the three types of single-graded aggregate, complete cylindrical specimens with the sizes of 4.75-2.36 mm, and 2.36-1.18 mm were not consolidated and formed, while only the 9.5-4.75 mm-particle-size aggregate consolidated and formed complete cylindrical specimens. The consolidation specimen of the 4.75-2.36 mm aggregate under 0.8 MPa pressure is shown from the front view and top view, as shown in Figure 11. In the consolidation test of the aggregate with a 4.75-2.36 mm particle size, the complete cylindrical specimen was not consolidated, but the diffusion depth was 80 mm, and the slurry bulb appeared ellipsoidal. There were also many slurry veins at the lower part of the slurry bulb. In addition to the multiple veins in the center, there were also multiple slurry veins on the outer cylindrical surface of the specimen, with a diameter of about 30 mm. Since the bottom valve was opened at the beginning, the diffusion resistance of the geopolymer slurry was relatively low, resulting in an increase in the depth of diffusion and consolidation, as well as an increase in the number of grout veins. It could be seen in Figure 12 that the aggregate with a 2.36-1.18 mm particle size also did not solidify into a complete cylindrical specimen. The consolidation depth of the slurry was about 15 mm, and the slurry bulb was still very small, with a maximum diameter of 90 mm. Because the internal porosity of the aggregate with a 2.36-1.18 mm particle size was small, even if the bottom flange valve was open at the beginning, under high grouting pressure conditions, the influence on the diffusion depth of the slurry was still very small. The consolidated specimens of the 9.5-4.75 mm aggregates and the 28 d compressive strength are shown in Figure 13. The aggregate with a 9.5-4.75 mm particle size was consolidated into complete cylindrical specimens under pressures of 0.2 MPa, 0.3 MPa, and 0.4 MPa. When the grouting pressure was 0.4 MPa and 0.3 MPa, the surface of the specimen was relatively smooth. However, when the pressure was 0.2 MPa, the structure of the bottom of the specimen was loose with some pores. It could be seen that, as the grouting pressure decreased, the compactness of the consolidated specimen gradually decreased. The basic principle of the compressive strength test was based on \"Testing Methods of Cement and Concrete for Highway Engineering\" (JTG 3420-2020) [33]. Under the three grouting pressures, the 28 d compressive strength of the 0.4 MPa grouting specimen was the highest, while the 28 d compressive strength of the 0.3 MPa grouting specimen was the  
Figure 10: The pressure filtration effect of slurry using 2.36-1.18 mm aggregate: (**a**) 0.8 MPa; (**b**) 0.9 MPa; and (**c**) 1.0 MPa. second highest, and the 28 d compressive strength of the 0.2 MPa grouting specimen was the smallest. Although the 28 d compressive strength of the 0.2 MPa grouting specimen was the lowest, it was still higher than that of the geopolymer slurry with a water-slag ratio of 0.4. It could be seen that the geopolymer slurry had a good consolidation performance for the loose aggregate. Through drilling, it was found that, in the concrete pavement rehabilitation using micro-cracking homogenization, in the local weak roadbed sections, the loose aggregates are mostly fine aggregates, with a few slightly larger-particle-size aggregates.