THE HISTORY AND REVIEW OF RESEARCH INTO SURFACE COATINGS FOR REINFORCED CONCRETE

(1) Surface coatings have been widely used on concrete for many years, both for weatherproofing and for aesthetic reasons (ref 1). However> over the last decade the scope of their use has changed to include the maintenance of protection against deterioration of the cover provided to steel-reinforced concrete (ref 2).This additional requirement has emerged due to the growing recognition of the problems associated with the progress of carbonation to the full depth of cover in many concrete components. The consequent loss of alkaline protection to the steel allows the possibility of corrosion (ref 3). The resulting deterioration of many existing structures has been largely due to poor site practice during construction (ref 4). Coatings have an essential complementary role in the completion of repairs by providing additional protection and improving the aesthetic appearance of the repair and must therefore perform a number of essential functions (ref 5). Most important of these are resistance to carbon dioxide transmission and retention of integrity and appearance for many years. The first requirement has necessitated the development of new techniques for investigation and evaluation of the permeability of coatings. The latter has entailed greater emphasis on the more durable types and characteristics of masonry coatings (ref 6). Considerable experience of performance is available as a basis for selection of particularly suitable coating types (ref 7). Resistance to water vapour (ref 0), alkalinity, salt and atmospheric ageing also continu to be^ important properties. Finally coatinq flexibility (where pigmentation plays an important role) and adhesion (both to the substrate concrete and between coating layers) are critical factors in good long-term performance (ref 9).