Strengthening Strategy for RC T-Beams in Negative-Moment Region Using Steel-Reinforced Polymer Cement Mortar

This study investigated a strengthening strategy for reinforced concrete (RC) T-beams in the negative-moment region using polymer cement mortar (PCM) systems. Monotonic loading tests were conducted on beams retrofitted with PCM, incorporating steel reinforcements of either 13 mm or 16 mm in diameter. The flexural performance of the strengthened specimens was assessed under three-point bending, with a focus on load–deflection behavior, crack patterns, and failure modes. Key structural parameters governing the structural response were analyzed. The findings indicated that incorporating PCM markedly improved the flexural capacity of RC T-beams, with increases in the ultimate load of 55% and 99% for the two reinforcement configurations. Although the beam strengthened with 16 mm steel bars exhibited reduced ductility, its energy absorption was 29% higher compared to its 13 mm counterpart. A three-dimensional nonlinear finite element model was also developed in ABAQUS 6.14, and its predictions closely matched the experimental observations.