Surface free energy of hydrophobic coatings of hybrid-fiber-reinforced 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 the protection treatment of hybrid-fiber-reinforced high-performance concrete (FRHPC) surfaces.The wettability of concrete has a direct effect on the durability and corrosion resistance.The wetting properties of FRHPC were evaluated through the measurement of the contact angle between the surfaces of these materials with either water or glycerine used as probe liquids.On this basis, the surface free energy (SFE) was determined.The polar and disperse components of SFE were obtained by means of the Owens-Wendt method.Three different siloxane preparations were deposited onto seven types of concrete with the fiber content ranging from 0 % to 1 %.In order to investigate the effect on the strength, the granodiorite aggregate in concrete mixes 5, 6, 7 was replaced with granite.The basic characteristics of the concrete strength were examined: the tensile splitting strength, the compressive strength, the modulus of elasticity.A SEM examination of the coated concrete surfaces confirmed that preparations A-C can effectively cover the voids and pores present in the concrete surfaces.The presented results indicate that the surfaces of the concrete with a silane film had a wide range of SFE, depending on the kind of agent.SFE depended on the chemical reactivity of the silanes used, the type of solvent, the viscosity and surface tension of the solution.The evaluation of the contact angle and SFE helped to efficiently select the most appropriate preparation.