Contribution to the macro and microstructure analysis of repair mortars for corroded reinforced concrete structures

Abstract

This work aims to contribute to the durability of patch repair systems in corroded reinforced concrete structures. It is concerned with the macro and microstructure analysis of 13 mortars: six laboratory-formulated and seven industrialized repair mortars from Brazil. The experimental program is a study complementing the analysis of the mortars and the concrete used as a reference in two previos Master's theses. Some of the initial results from one of the theses are summarized in this paper. The main objective here is to compare and analyze the carbonation performance of the mortars under exposure first to inital conditions favorable to shrinkage, followed by exposure to conditions favorable to steel bar corrosion in Brazilian climates. Test specimens were initially exposed to a low relative humidity of around 50%, from three days up to two and half years. Then, nine alternating dry-wet cycles were performed in a ventilated heat chamber at a temperature of 40°C (14 days), followed by a moist chamber, with a relative humidity of around 95% and a temperature of 23°C (14 days). These experiments verified great heterogeneity in the evolution of the carbonation front for some of the mortars. Visual analyses with a stereomicroscope indicated that this behavior appears to be related to the amount and distribution of air content in the fresh mortars and with the fines content in the dry mixes. The study of durability prediction of patch repair systems with these mortars is being continued in additional research concerning macrocell corrosion.