Development of a Novel Injection Grout Based on Traditional Hot-Mix Technique for Historic Masonry Consolidation

Grout injection is widely used to consolidate historic masonry. As an irreversible intervention, grouts must ensure adequate injectability and compatibility, while developing hydraulic setting under high humidity and limited air circulation within masonry cores. Although natural hydraulic lime grouts satisfy these requirements, limited availability in some regions increases cost and restricts widespread use. Hydrated lime — pozzolan grouts offer an alternative based on locally available raw materials; however, slow pozzolanic reactions may delay setting and strength development. To address this limitation, this study develops a hot-mix quicklime — pozzolan grout and compares it with hydrated lime — pozzolan mixtures. Fresh, physical, and mechanical properties were assessed, and pozzolanic reactions were analyzed by XRD, FTIR, and TGA/DTA. All mixtures remained injectable within the targeted workability window. Compared to hydrated lime — pozzolan grouts, the hot-mix grouts exhibited faster stiffening; however, continuous agitation maintained adequate flowability. The hot-mix grouts demonstrated enhanced pozzolanic reactivity and reduced carbonation, resulting in improved physical and mechanical performance. Chemical compatibility was ensured through the lime — pozzolan binder system. Porosity and water absorption remained consistent with traditional masonry materials, and sufficient strength was achieved without excessive stiffening. Overall, the laboratory results indicate promising performance and potential as an alternative consolidation material.