Integrating durability in concrete mix design for enhanced structural performance and remaining life estimation

Abstract

The effect of durability on reinforced concrete (RC) is often inferred indirectly, as variation of compressive strength between less durable concrete (LDC) and more durable concrete (MDC) conceals the true influence of durability. To isolate durability as the key parameter, this study presents a framework for capacity-based mix design of MDC, enabling direct comparison with a strength-matched (∼47 MPa) LDC. The framework establishes time-based durability assessments aimed at achieving low chloride diffusivity and high resistivity, ensuring that concrete performs its intended function over its service life. An assumption of uniform corrosion is considered throughout the length of the rebar in this study. A five-storey moment-resisting RC frame is modelled with material properties derived from experiments and codal specifications. Time-dependent degradation is captured through nonlinear static pushover analyses at different ages. The failure criteria are defined based on a significant loss in ductility leading to reduced energy dissipation capacity, with a damage index value reaching 1.0. Results indicate that LDC’s global ductility decreases at a much faster rate in comparison to MDC as age progresses. These results are further supported by a damage index-based analysis. The damage-index-based criterion also offers insights into the optimum content of supplementary cementitious material (SCM). Overall, this study integrates durability and strength in concrete mix design; uses experimental and code/literature-based data to simulate aging effects realistically; conducts a damage index-based analysis; and presents a simplified way to estimate the remaining life of a structure, highlighting the need for more durable and sustainable RC infrastructure.