Use of nanosilica- or nanolime-additioned TEOS to consolidate cementitious materials in heritage structures: Physical and mechanical properties of mortars

Tetraethoxysilane or tetraethyl orthosilicate (TEOS), also known as ethyl silicate, traditionally applied to consolidate stone, has recently begun to be used on Portland cement mortars and concrete with promising results. TEOS not only fills the pores in the substrate, but reacts with the cement favouring the precipitation of new C-S-H gels that densify and strengthen the materials. This study explored the effectiveness of new TEOS-based treatments bearing nanosilica (NS) or nanolime (NC) and their compatibility with cement materials found in the built heritage, given the participation of the various products in the pozzolanic reactions that may induce additional C-S-H gel. The physical and hydric properties (mechanical strength, porosity, surface gloss and colour, water vapour permeability and low pressure water absorption) of a Portland cement mortar were determined before and after applying the consolidants. Ethyl silicate alone or in conjunction with nanolime (4:1) proved to most effectively raise material strength and improve water repellence while conserving the original colour and gloss.