Testing and Modeling Composite Coatings with Silanes for Protecting Reinforced Concrete in Saltwater Environment

Abstract

There is increasing interest in developing relatively quick test procedures to evaluate the effectiveness of composite coatings to reduce the infiltration of water and salt solutions into concrete structures to rapidly rehabilitate and extend the service life of reinforced concrete structures. In this study, concrete was first treated with two different types of silanes and then coated with a latex-based coating to investigate the sensitivity of the test procedure to resist the diffusion of water and 15% NaCl salt solution into concrete at room temperature. The concrete used in this study had a compressive strength of 36.5 MPa, with about 1.6% water absorption capacity in 21 days. The performance of concrete with composite coatings was investigated by using the immersion test, followed by the drying test. On the basis of 21 days of immersion test in water, the weight increase in specimens coated with one type of silane and latex coating was 1.21%, which was half of what was observed with the other silane and latex coating. Similar trends were observed with 15% salt solution, and hence, the test method adopted in this study was sensitive in selecting the composite coating. A new thin-film model was developed to predict the weight change of coated concrete cylinders during the drying phase. Finite-element (FE) modeling of the weight-change phenomenon showed that the initial rate and total weight change after 21 days of immersion testing was governed by the effective mass transfer coefficient, thickness, and a saturation parameter of the composite coating.