Behaviour of corroded RC beams with ground granulated blast-furnace slag under torsion

Corrosion of reinforcing steel significantly impairs the torsional performance of reinforced concrete (RC) beams. This study experimentally investigated the effect of reinforcement corrosion on the torsional behaviour of RC beams incorporating ground-granulated blast-furnace slag (GGBS). Beams with 0%, 20%, 40%, and 60% GGBS as cement replacement were subjected to accelerated corrosion levels of 0%, 10%, and 15%, followed by pure torsional loading. Increasing corrosion substantially reduced torsional strength, twist capacity, and energy dissipation. Among the investigated mixtures, 40% GGBS provided the best overall performance, increasing torsional capacity by 15.64%, 10.98%, and 7.74% at 0%, 10%, and 15% corrosion, respectively, compared with corresponding control beams. In contrast, 60% GGBS resulted in strength reductions of 28.41% and 43.16% at 10% and 15% corrosion, respectively. For 40% GGBS beams, twist capacity decreased by 28.16% and 56.33% at 10% and 15% corrosion, respectively, while energy dissipation capacity decreased by up to 82.24% as corrosion increased to 15%. Experimental results showed good agreement with empirical predictions and finite element analysis, with a maximum deviation of 10%. Overall, 40% GGBS improved corrosion resistance and torsional performance, while corrosion remained critical to strength and deformation capacity under severe torsional loading conditions.