Calcined clay’s effect on the performance and mechanism of natural hydraulic lime grouting material

The physical and mechanical properties of grouting material are critical indicators to assess its compatibility to earthen archaeological sites as a fissure repair material. This study activated the clay from Huangshan Archaeological Site by calcination to explore how calcined clay enhances the age performance of grouting material with various temperature and admixture dosage. The results revealed calcined clay’s effect of improving water retention and density of the slurry and reducing shrinkage and colour difference of grouting material. The mechanical strength increased first and then decreased with rising calcination temperature, as clay’s mineral activity was altered by phase transformation. Microstructural analysis demonstrated that skeletal minerals, such as SiO2, intertwined with hydration products, like CSH and C4AH13, densifying the pores in the concretion. This modified grouting material with calcined clay demonstrates feasibility for earthen site restoration by controlling mineral activation.