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

Approaches to synthesising rapid geopolymer repair materials made from tannery sludge (TS) and metakaolin (MK) were explored to investigate the treatment and utilisation of TS. The setting time and 1-day compressive strength were taken as indicators for evaluating the performance of the TS/MK geopolymer as a repair material. The effects of the silica/alumina molar ratio (A), sodium oxide/silica molar ratio (B), water/cement (w/c) ratio (C) and TS content (D) were determined, and the durability of the geopolymer was also studied. The optimum formula (A = 2.58, B = 0.33, C = 0.67 and D = 10%) met the requirements for a pavement repair material. The final setting time of the optimum formula was 102 min, the 1-day compressive strength was 21.0 MPa and the chromium leaching concentration was 7.52 mg/l. The geopolymer also exhibited good resistance to high temperatures, acid rain and freeze–thaw processes. A geopolymer repair material that exhibited high early strength and stable performance at later stages was thus synthesised. Microstructure was examined using X-ray diffraction, Fourier transform infrared spectroscopy, mercury intrusion porosimetry and scanning electron microscopy, and it was found that a decrease in geopolymer gelation and increases in the pore size and porosity resulted in a decrease in the properties of the repair material.