An experimental characterization of the properties of graphene oxide—Waterborne epoxy resin coating of concrete after chloride erosion

Abstract

The durability of concrete surfaces is frequently compromised by adverse external factors, such as freeze-thaw cycles and ionic corrosion among others. This study aims to investigate the comparative performance of three concrete coating techniques independently applied uniformly to concrete surfaces, namely the Graphene Oxide—Waterborne Epoxy Resin Coating (GO-WEP) coating and two commercially available WEP coatings (S1, S2). The corrosion resistances of the coatings were evaluated under various conditions: chloride drying-wetting cycles, chloride freeze-thaw cycles, and chloride immersion tests. In this study, the changes in color difference and adhesion of the coating after chloride erosion were studied. And after five drying-wetting cycles, the GO-WEP coating exhibited a color difference value approximately 56 % and 45 % lower compared to S1 and S2 coatings respectively. The S1 and S2 coatings demonstrated adhesive strength below 1.50 MPa after the 3rd and 4th cycles respectively, indicating a loss of protective capabilities. Conversely, the GO-WEP coating maintained adhesive strength greater than 1.50 MPa after five cycles, implying sustained protective capabilities. Following freeze-thaw cycles, the color difference value in GO-WEP was about 16 % and 7 % lower than S1 and S2 coatings respectively. S1 and S2 coatings lost their protective ability after the 4th and 5th cycles respectively, while GO-WEP maintained an adhesive strength greater than 1.50 MPa. Furthermore, following chloride immersion, the GO-WEP coating had a color difference value approximately 20 % and 17 % lower than S1 and S2 respectively. The adhesive strength reduced by 39.7 %, 46.4 %, and 43.1 % for the three coatings respectively, signaling the superior performance of GO-WEP in all tested properties. The surface morphology and compressive strength variations of the coated concrete were also studied. As the experimental cycles progressed, both S1 and S2 coatings suffered noticeable surface damage, while the GO-WEP coating demonstrated no significant changes until the end of the experimental cycles. During the chloride drying-wetting and chloride immersion tests, the concrete specimens showed an increase in strength. Initially, uncoated concrete showed a faster rate of strength increase than coated concrete. However, this rate slowed down and even reversed in later stages. Coated concrete on the other hand, exhibited a steady increase in strength over the experimental cycles, with GO-WEP coated concrete showing the slowest growth rate. In the chloride freeze-thaw cycle test, concrete strength decreased progressively. And by the fifth cycle, the compressive strengths of GO-WEP, S1, and S2 were 31.5 MPa, 30.8 MPa, and 30 MPa, respectively, a 9 %, 6 %, and 3 % improvement over the 29 MPa of uncoated concrete. These findings further reinforce the superior protective effect of the GO-WEP coating on concrete.