Strength and serviceability of repaired reinforced concrete beams undergoing reinforcement corrosion

The paper presents the results of an experimental study on 99 under-reinforced concrete beams which were subjected to corrosion before and after the cover zone was repaired with three different generic materials. The repairs represented a wide range of tensile strengths, elastic modulii, ductility and permeabilities. The beams were reinforced with two longitudinal bars, and shear reinforcement was provided externally by steel collars. Different degrees of reinforcement corrosion were induced before and after repair, ranging incrementally from 0% to 5% at a corrosion rate of 3 mA/cm². The results show that low ultimate flexural strengths and high deflections under service loading result in corroding beams which incorporate repairs made with materials having the following combination of properties: low strain capacity and low tensile strength; high stiffness, high flexural strength and very low permeability. A relatively ductile repair material with a high coarse aggregate content provides significantly superior structural performance. Time-performance functions for the corroding beams have also been derived by non-linear regression analysis of the experimental data. These can be used to assess (a) long-term ultimate flexural strength of repaired beams undergoing known rates of reinforcement corrosion, and (b) the limiting flexural load capacity required of corroding beams in order to prevent excessive deflections. Empirical coefficients representing the different repair materials have been derived for use in these time-performance relationships in order to assess the long-term strength and serviceability (deflection criteria) of repaired beams.