1 October 2020

In April 2020, the partners UCA and CSIC published an article entitled “Producing C-S-H gel by reaction between silica oligomers and portlandite: A promising approach to repair cementitious materials”. The article was published inside the journal “Cement and Concrete research” and it talks about the research activity performed in laboratory by the researchers of the University of Cadiz and the Eduardo Torroja Institute for the development impregnation treatments for concrete-based monuments.

Impregnation treatments are one of the alternatives to protect concrete-based building and monuments from weathering degradation. However, it is important to consider the chemical compatibility of the reaction products with the building material. The impregnation product studied here consists of a silica oligomer able to polymerize, by a simple sol-gel process, inside the pore structure of concrete. In this work, we investigate the ability of this impregnation treatment to produce C-S-H gel in contact with cement paste. A complete characterization of the reaction products demonstrated that the silanol groups from silica oligomers react with the portlandite present in the cement paste generating a material with the chemical, structural and morphological features of C-S-H gel. Simultaneously, the ²⁹Si NMR results indicate that the SiO units are incorporated into the existing C-S-H, increasing its chain length. These results open the way for a simple concrete structures repairing procedure.