  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 CS-H gel. Simultaneously, the 29Si NMR results indicate that the Si-O 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.
