Significance of property mismatch in the patch repair of structural concrete Part 1: Properties of repair systems

Abstract

Approximately £500 m is spent in the UK each year on the repair of concrete members. Despite the existence of this large and expanding market, little fundamental attention has been paid to the structural implications of property mismatch between patch repair materials and the substrate reinforced concrete. To pursue this question, it was necessary to identify the desirable characteristics of repair systems for satisfactory structural performance, and then to measure the relevant mechanical and physical properties of the various systems currently on the market. It was found that these repair systems could be conveniently categorized in nine generic types; a representative system from each was selected. Properties measured included strength, modulus, Poisson's ratio, coefficient of thermal expansion, tensile adhesion, early curing shrinkage, long-term creep and shrinkage. Where deemed appropriate, standard test methods have been utilized; otherwise techniques have been developed specifically for the purpose. These techniques, some of which now form the drafts of revisions to British Standards, are described. The range of property values determined are discussed in relation to patch repairs in typical reinforced concrete members and the desirable characteristics previously identified.