An Experimental Study of Time-Dependent Loss of Tension Stiffening in Corroded Reinforced Concrete Members Subjected to Tensile Forces

This paper studies the influence of steel reinforcement corrosion on the durability of reinforced concrete (RC) structures in chloride-rich environments. The research investigates three main bond characteristics on the time dependent degradation of tension stiffening: concrete strength, cover depth, and corrosion levels. The current study conducted two experimental works: pull-out tests and time-dependent tension stiffening tests. In the initial phase, 108 specimens, both corroded and uncorroded, underwent pull-out tests to obtain the relationship between concrete properties (cover depth, compressive strength) and corrosion levels. The second phase tested 72 tension stiffening specimens, classified into two sets based on concrete strength: normal strength concrete (NSC) and high strength concrete (HSC). These specimens had varying cross-sections (80×80, 100×100, and 120×120 mm) and subjected to sustained loading at 45, 55, and 60 kN to determine the combined effects of corrosion processes and sustained loading levels on tension stiffening degradation over time. Results from the pull-out tests showed that maximum bond strength is considerably affected by the number and width of corrosion-induced cracks. Especially, specimens with thicker concrete cover (45 mm) revealed higher bond strength across normal and high strength concrete, with a gradual decrease monitored as concrete cover thickness reduced to 15 mm. The tension stiffening tests under corrosive conditions illustrated that steel reinforcement corrosion had negligible influence on tension stiffening behavior in the early stages of testing. Although, as testing progressed, corroded specimens displayed a noticeable decrease in tension stiffening. Moreover, specimens with thicker cover showed enhanced corrosion resistance, resulting in delayed initiation and progression of reinforcement corrosion and less pronounced tension stiffening degradation in the prisms.