Predicting corrosion in reinforced UHPC members through time-dependent multi-physics numerical simulation

Abstract

Ultra-high-performance concrete (UHPC) has superior durability characteristics over traditional concrete. Improved durability behavior of UHPC has been attributed to the dense material property, which effectively constrains harmful material ingress and oxygen supply. However, the corrosion performance of reinforced UHPC under sustained mechanical loading, which may induce cracking, in addition to environmental conditioning is still not well characterized. This study investigates the electrochemical-mechanical coupling effects on deterioration mechanisms of reinforced UHPC beams subjected to service loading conditions and chloride attack through multi-physics simulation techniques. Finite element models were simulated considering the cracking induced by service loads and deformations caused by rust expansion on the cementitious matrix. Material transport properties such as chloride and oxygen penetration parameters were updated in each step of the time-dependent process based on cracking conditions. The simulation results show that there is substantial steel cross section and yielding load capacity loss, initial stiffness reduction, and damage area increase in reinforced concrete members while UHPC members showed relatively small cross section loss, negligible increase in UHPC damage, no observable reduction in initial stiffness, and minimal loss in yield load capacity. The effect of oxygen supply level on the corrosion performance is also explored showing that the corrosion rate of reinforced UHPC specimens were limited due to depleted oxygen at the steel-UHPC surface. Numerical simulation results were verified against experimental trends on corrosion performance of reinforced UHPC specimens. Further, the numerical framework herein provides an alternative way in predicting deterioration processes and evaluating service life performance of ductile reinforced concrete infrastructures in a computationally efficient manner.