Early strength and durability of tannery sludge metakaolin based geopolymer concrete pavement repair material

In this study, approaches to synthesizing rapid tannery sludge/metakaolin geopolymer repair materials were explored to investigate tannery sludge treatment and utilization. The setting time and 1-d compressive strength were taken as indicators for evaluating the performance of the geopolymer as a repair material. The effects of the Si/Al ratio, Na/Si ratio, water/cement ratio, and tannery sludge content were determined, and the durability of the geopolymer was also studied. The optimum formula met the requirements of a pavement repair material when the Si/Al ratio, Na/Si ratio, water/cement ratio, and tannery sludge content were 2.58, 0.33, 0.67, and 10%, respectively. The final setting times of this formula were 102 min. The 1-d compressive strength was 21.0 MPa, and the chromium leaching concentration was 7.52 mg·L−1. Additionally, the geopolymer exhibited good resistance to high temperatures and acid rain, and freeze-thaw processes. Therefore, a geopolymer repair material that exhibited high strength in the early stage and stable performance in the later stages was synthesized. XRD, FT-IR, MIP, and SEM were also conducted for micro-analysis, and it was found that the decrease in geopolymer gelation, and increases in the pore size and porosity resulted in a decrease in the properties of the repair materials.