Microstructural and Surface Energy Evaluation of Concrete Coatings Modified with Methyl Ester and Stearic Acid

The purpose of this paper is to determine the influence of the stearic acid and methyl esters on the properties of protective coatings applied to reinforced concrete objects. The evaluation of protective effectiveness included compositional analysis (XRD, XRF), surface properties (contact angle, surface energy, UV resistance), soiling resistance, roughness, and surface morphology (SEM). The scanning microscopy SEM images showed a relatively uniform distribution of resin on the concrete surface. The lateral dimensions of the epoxy-rich surface domains ranged from 8 μm to 40 μm. All analysed samples exhibited a very similar chemical composition, in which SiO2 was the dominant component. In situ tests were conducted on an operating reinforced-concrete cooling tower. Among the investigated coating systems, ER1 + SA exhibited the highest observed mean apparent static water contact angle (CA) of 131°. A strong inverse empirical relationship was observed between the apparent contact angle and average surface roughness. UV ageing caused small numerical decreases in contact angle for most systems. After one year of operation, the ER2 epoxy coating modified with methyl esters was the best-preserved of the analysed variants.