Guidelines for the selection of external protective wall finishes for smooth concrete surfaces in Hong Kong

Abstract

This paper is concerned with the specification and selection of external protective decorative coatings for direct application to smooth concrte surfaces on tall blocks in Hong Kong. It is based on research carried out during 1989. The research method consisted of visual surveys of existing public and private sector housing blocks, and a product survey. The surveys were supplemented by the examination of documentation, analysis of laboratory tests, and interviews with architects, site managers, maintenance surveyors, housing managers and technical representatives. Present practice relies on the use of cement renders and applied facings, usually glass mosaic tiles. This is now considered inadequate in the light of increased mechanization of concrete production, and the specification of high strength, high quality concretes. Both these trends result in smooth, dense concrete substrates with low porosity and suction, and no mechanical key. Performance data on specific protective coatings is however limited, although available results relating to anti-carbonation properties appear encouraging. The paper concludes that protective coatings may prove a viable alternative to traditional cement renders and tile facings if designers can overcome their natural resistance to these products, and if manufacturers can address the problems of life expectancy and maintenance.