Effect of coarse or fine aggregate reactivity on bonding deterioration of reinforced concrete exposed to alkali–silica reaction

Composite performance in concrete structures requires steel–concrete bonding. Environmental conditions prone to alkali–silica reaction (ASR) steadily impact the mechanical properties of concrete, including its bond strength. This research aims to investigate the effect of reactive aggregate size on the bond strength of concrete in ASR environmental conditions. To this end, four mixtures were prepared with different combinations of reactive and non-reactive fine and coarse aggregates. Then, Reinforced Concrete (RC) blocks with 12 and 16 mm rebars were cast with these various mixtures. These specimens were immersed in NaOH solution at high temperature for 3 or 6 months to accelerate the ASR. Subsequently, the pull-out test (POT) was performed to evaluate the bond strength of the concrete blocks. The results showed that with the passage of time and intensification of the ASR, the ultimate bond stress decreased. Also, with the decrease in reactive aggregate size in the concrete mixture, the ultimate bond stress loss intensified. The ultimate bond stress of the 12 mm rebars embedded in the RC blocks where reactive gravel was solely used decreased by 5.8% and 8.2% compared to RC blocks where reactive sand was solely used, after 6 months of immersion. Moreover, the variation in the reactive aggregate size or immersion duration did not affect the failure mode of the specimens with the same diameter rebar. However, by changing the rebar diameter from 12 to 16 mm, the ASR caused a variation in the failure mode of the specimens. Finally, a proposed bond-slip model was employed for the pull-out specimens by adjusting the coefficients within the CEB-FIB model.