Various Surface Impregnation Treatments for Pre-conditioned Concrete Subjected to Seawater Immersion Tests

This paper performed a five-month seawater immersion test for concrete specimens treated with various surface impregnation materials. Six types of surface impregnation materials that belonged to two popularly used series in Japan, namely silane-based water repellent agent and sodium silicate (water glass)-based sealer, were selected to treat pre-conditioned concrete specimens. The six types of materials include liquid silane, liquid silane/siloxane, silane-based cream, silane-based gel, sodium silicate, and acrylic/sodium silicate. Concrete specimens before the surface impregnation had been exposed in air for three years and were found to be carbonated within a certain thickness. To simulate the actual port environment, the concrete specimens were pre-set three different levels of moisture contents. Time-dependent water absorption was monitored during the seawater immersion test, at the end of which the penetration depth of water repellent agents in the treated specimens and the chloride penetration profiles in the treated and untreated specimens were evaluated. Sodium silicate sealers were found to have marginal effects in preventing the concrete from water absorption and chloride penetration. However, the applicability of using silane-based surface impregnation as a chloride barrier and a water reducer for concrete has been verified in this paper even under severe environment. Cautions should be paid to that the pre-conditions in concrete such as the carbonation and the degree of water saturation may influence interactively the reaction and penetration effectiveness of surface impregnation materials in the concrete. In addition, according to the obtained chloride penetration profiles, for which the concrete specimens were cut in to slices 5mm in thickness, it was found that higher chloride contents observed in the first 5mm thick concrete from the surface usually corresponds to steeper descending branches forward, and vice versa. However, it seems necessary to obtain accurate and more realistic chloride penetration profiles based on analyzing slices with a thickness much smaller than 5mm to clarify the chloride transport mechanisms behind these test results