Preliminary study of the application of a novel hydrophobic photo-polymerizable nano-structured coating on concrete substrates

In order to improve of the durability of concrete from the attack of aggressive environments, a solvent-free hydrophobic photo-polymerizable organic-inorganic (O-I) nano-structured coating, indicated as HEP, was experimented on different concretes. The nano-structured hybrid product was already proved to act as an excellent hydrophobic protective coating for different natural stones. The outstanding properties of this novel system refer to the high reactivity of HEP at low-moderate temperatures, its eco-compatibility, being solvent-free, and preservation of its performance even after a severe environmental aging. The hybrid system was obtained starting from methacrylic-siloxane monomers, through a process involving hydrolysis and condensation steps. The cross-linking reactions of the acrylic monomers took place via free radical photo-polymerization reactions, activated by a suitable UV photo-initiator. The suitability of the un-reacted fresh system to be applied on concrete was first assessed through rheological analysis. Then, the liquid mixture, after its application on a glass substrate, was subjected to a dual curing procedure, consisting in a UV-polymerization step followed by a thermal stage. Different properties (i.e. Tg, transparency, scratch and surface hardness) were evaluated on the experimental coating. HEP was, then, applied on concrete substrates and its surface and protective characteristics were measured. Two different concretes were selected, i.e. based on Portland-limestone and pozzolanic cements.