Feasibility of producing hot-mix injection grouts for sustainable restoration of historic masonry

Grout injection is a widely used technique for the consolidation of historic masonry, where adequate flowability, injectability, stability, and mechanical performance are required simultaneously. This study investigates the feasibility of producing hot mix injection grouts for historic masonry consolidation using quicklime, hydrated lime, and different mineral constituents. Three formulation series were designed to examine the effects of quicklime content, mineral composition, filler type, and the combined use of quicklime and hydrated lime. Metakaolin, silica fume, pumice, and brick powder were incorporated in different proportions within the grout formulations. Fresh state performance was evaluated through Marsh funnel, mini-slump, bleeding, heat development, and sand column injectability tests, together with 28-day flexural and compressive strength measurements. The results showed that grout performance depended on quicklime content, mineral composition, and filler characteristics. High quicklime contents were associated with greater heat development and poorer injectability, whereas lower quicklime contents improved injectability. Pumice generally resulted in lower bleeding and higher strength than brick powder, while brick powder favored flowability. The results provide an initial basis for the development of hot mix injection grouts, showing that quicklime content and the proportions of the mineral constituents govern fresh state behavior, injectability, and early mechanical performance.