Effect of Surface Water Proofing Admixture on Carbonation of Concrete

Abstract

Carbonation is the reaction of carbon dioxide in the environment with the calcium hydroxide in the cement paste. This reaction produces
calcium carbonate and lowers the pH to around 9. At this value the protective oxide layer surrounding the reinforcing steel breaks down and
corrosion becomes possible. The reaction of carbon dioxide and calcium hydroxide only occurs in solution and so in external or internal
isolated concrete carbonation will be slow. In this study, rapid carbonation test was performed on internal isolated concrete. In most structures
made with good quality concrete, carbonation will take several (or many) years to reach the level of the reinforcement. Concrete members
were produced in standard curing and they were coated with water proofing materials. They exposed to rapid carbonation for 1, 5 and 10 days
in carbonation test cabinet. After test, samples were splitted and solution was poured on the concrete surface. At the same time, electrical
resistivity of series was determined. Carbonation dept was measured on the concrete sample. It was found that carbonation dept decreased on
external isolated concrete. For concrete with standard curing, it was found that the electrical resistivity measurement was the most reliable
parameter in predicting the resistance of concretes to carbonation.