Carbonation of water repellent concrete

Water repellent treatment (WRT) has been considered an effective preventive method for concrete structures. In reality, however, many concrete structures are exposed to conditions with high risk of carbonation deterioration. In this contribution, one type of ordinary concrete had been prepared by surface impregnation with 400 g/m2 silane cream, 100 g/m2 and 400 g/m2 silane gel, by integral water repellent treated adding 2 % silane emulsion, followed by submitting to carbonation for 7, 28 and 72 days, to study the influence of WRT on carbonation of concrete. Results show that surface impregnation reduced carbonation depth of concrete under relative humidity of 70 %, but integral treated concrete had more carbonation. At the beginning of carbonation the reaction started behind the hydrophobic layer for the surface impregnated concrete in this project. The coefficient of carbonation can be experientially described by a hyperbolic function of time. Concrete treated by 400 g/m2 silane gel showed highest efficiency on reducing carbonation, 400 g/m2 silane cream and 100 g/m2 silane gel are next. Coefficient of capillary suction of treated concrete with and without carbonation decreased greatly compared with non-treated concrete. It is still a feasible method to apply WRT on concrete surfaces under carbonation conditions. But the efficiency on reducing capillary absorption had been reduced by carbonation action.