On Durability of Reinforced Concrete Structures: A Design Methodology for RC Beams and Columns in Corrosive Environments

The work presents a design methodology for carrying out durability-based optimal design of reinforced concrete (RC) structures exposed to corrosive environments causing the problems of chloride-induced reinforcement corrosion. For the purpose, an extensive experimental investigation was carried out to generate the data required for obtaining empirical models for relating chloride-induced reinforcement corrosion rate with the key affecting factors. Concrete test specimens were prepared with cementitious material contents of 350, 375 and 400 kg/m(3), water-cementitious ratios of 0.4, 0.45 and 0.5, fine-to-total aggregate ratios of 0.35, 0.4 and 0.45 and cover thicknesses of 25, 37.5 and 50 mm. The specimens were then exposed to chloride solution of three different concentrations and were tested for determining corrosion rate using electrochemical and gravimetric weight loss methods. Reinforcement corrosion rates (determined electrochemically and gravimetrically) were first analyzed to determine statistical correlation between the corrosion rates obtained by the two methods. Then, the gravimetric reinforcement corrosion rate results were utilized for developing regression models for reinforcement corrosion rates in terms of concrete quality parameters, concrete cover thickness and chloride concentration. The regression models of reinforcement corrosion rates obtained through the present work and the models for strength and elastic modulus of concrete reported in the literature were adapted to develop an automated analysis and design methodology using Microsoft Excel solver for durability-based optimal design of RC beam and column under specified chloride exposure corrosive environments. Sample results obtained from the proposed optimal design methodology (for RC beams and columns in corrosive environments) are presented and discussed.