Investigation of the gas and vapour resistance of surface coatings on concrete and effects of weathering on their carbonation protective performance.

Carbonation of reinforced concrete has been recognised as a serious problem since the 1970's. Investigations of the performance of surface coatings have shown that various types provide different levels of protection. In this work accelerated carbonation testing was carried out with selected types of coatings aged artificially on a cementitious substrate. It was found that generally the permeability to carbon dioxide increased with ageing time. The causes of deterioration in carbonation protection varied according to the system type. The results indicated that permeability, and its increase with ageing, were related to thickness, compactness, porosity and regularity of the applied coating films. These characteristics were dependent on type and formulation. The durability of carbonation protection was judged from a combination of artificial weathering with testing of permeability and detailed examination of surface condition of the films. (A)