Influence of hydrophobisation on surface free energy of hybrid fiber reinforced ultra-high performance concrete

The aim of the research presented in the paper was to evaluate the feasibility of using hydrophobic preparations based on organosilicon compounds for protection treatment on the hybrid fiber reinforced ultra-high performance concrete (FRUHPC) surface. Three polisiloxanes agents were deposited onto the seven types of concretes, with a steel-polypropylene fiber content ranging from 0% to 1%. In this investigation, the surface free energy (SFE) of the coatings was calculated using the Owens-Wendt, Neumann, Wu, and Fowkes methods. In order to examine the contact angle, three measuring liquids were used: distilled water, glycerine and diiodomethane. It has been shown that the Neumann method with one polar and the Owens-Wendt method with a pair of polar liquids gave the most reliable results.