Low-pressure silica injection for porosity reduction in cementitious materials

The durability of building materials is related to the presence of cracks as they provide a fast pathway to the transport of liquid and gases through the structure. Restoration and preservation of historic buildings has been investigated through the application of novel cementitious materials, using nanoparticles such as nano-silica and silica fume. The small particle size range and the high reactivity of nanoparticles allow them to interact with calcium sources naturally present in construction materials, forming binding and strengthening compounds such as calcium silicate hydrate. Nanoparticles act as a crack-filling agent, reducing the porosity and increasing the durability of existing materials. In this study we describe the injection of nano-silica using low water pressure in hydrated cement paste. This novel technique can tailor mechanical and hydraulic properties of existing building materials using a simple and non-destructive procedure.