Grouts for Injection of Historical Masonries: Influence of the Binding System and Other Additions on the Properties of the Matrix

Abstract

Grouting of historical masonries has been a widely used technique for regaining their integrity or strengthening them. Since cement-based grouts proved very strong, and in some cases destructive for these old masonries, grouts based on a lime-pozzolan binding system have been developed by researchers as an alternative, meeting compatibility issues required for repair interventions. In this paper, a number of grout compositions based on lime and other traditional binders are studied, with and without additions of limestone filler and nanoparticles of silica. In some, a small quantity of white cement (15 wt.%) was incorporated into the system. Apart from the different constituents of the binding system, the addition of admixtures was used for improving the properties of grouts. Rheological properties, such as fluidity, volume stability and penetrability of the grouts, were measured in the fresh state. Mechanical properties of dried grouts and grouted sand were checked. Volume changes due to drying shrinkage of grouts were recorded after demoulding and up to 28 days. The microstructure of the dried grouts of the control mixture and of that with silica nanoparticles was examined by stereoscope, image analysis, and DTA-TG methodology.