Experimental characterization of injection grouts incorporating hydrophobic silica fume

This paper puts forward a new hydrophobic silica fume and assesses its contribution to the performance improvement of grouts for stone masonry consolidation. The experiments were conducted using different dosages of hydrophobic silica fume with natural hydraulic lime grouts in the presence of a polycarboxylate-based high-range water reducer. Results revealed that the effects of hydrophobic silica fume on properties of natural hydraulic lime grouts optimize the use of ordinary silica fume. Remarkable rheological performance was obtained in the presence of hydrophobic silica fume: the plastic viscosity and yield stress were reduced compared with the ordinary silica fume. For mechanical strength aspects, it was found that hydrophobic silica fume slightly affected the flexural and compressive strength; however, the values obtained are suitable for the old stone masonry consolidation purposes. It was also observed that water capillarity was substantially reduced as a result of the water-repellent behavior of hardened grouts. This study suggests that the promising effectiveness of this new silica fume for injection grouts opens the way for it to be used in many other applications.