PROTECTIVE ABILITY OF AN ACRYLIC-BASED SURFACE COATING SYSTEM AGAINSTCHLORIDE AND CARBONATION PENETRATION INTO CONCRETE

The majority of concrete structures, particularly those in coastal env ironments, often suffer from both chloride and atmospheric carbonation attacks. Application of polymer-based concrete surface coating is one of the solutions available for the long-term protection of the reinfo rcement steel from corrosion. This paper deals with the performance of concrete slabs coated with acrylic-based coating against chloride and atmospheric carbon dioxide attacks. For this purpose, fully and parti ally surface-coated slabs were exposed to repeated cyclic wetting by s odium chloride solution followed by drying. After completion of the cy clic exposure regime, the slabs were exposed to laboratory drying envi ronment and then were subjected to experimental investigations. The ex perimental results showed practically no chloride penetration into the concrete beneath the acrylic-based surface coating even after long-te rm exposure. On the other hand, for the uncoated concrete, the amount of chlorides and their depth of penetration into the concrete were fou nd to be dependent on the water-cement ratio of the concrete. The amou nt of chlorides penetrating laterally, and the distance they penetrate from the uncoated concrete into the adjoining concrete below the acry lic-based surface coating is also a function of the w/c of concrete. F urther, both x-ray diffraction studies and phenolphthalein spray tests showed the acrylic-based coating to be very effective in controlling the carbonation of the concrete below it, especially when the coating was applied by spraying. The coating maintained good adhesion with the substrate concrete even after the long-term repetitive wetting and dr ying cycles.