<p>Corrosion-induced deterioration in reinforced concrete (RC) structures significantly reduces the cross-sectional area of steel reinforcement, leading to severe loss in flexural capacity and structural performance. Although externally bonded FRP systems have been widely investigated for rehabilitation of deficient RC members, premature debonding and inadequate interfacial bonding remain major challenges limiting effective utilization of the strengthening material. The present study investigates the flexural restoration of deficient RC beams strengthened using Unidirectional Basalt Textile-Reinforced Polymer (UDBTRP) with optimized surface preparation techniques. Different surface preparation methods were experimentally evaluated to improve the bond interaction between concrete and UDBTRP. Among the investigated techniques, checked pattern grooving exhibited superior interfacial performance and achieved 74.84% higher flexural strength compared to the control prism specimens. The optimized surface preparation was subsequently adopted for strengthening deficient RC beams with varying UDBTRP configurations. The strengthened beams demonstrated flexural capacity enhancement ranging from 5.5% to 26.8% compared to the deficient control beam. Improved surface preparation and overlay anchorage promoted rupture-dominant behaviour and delayed premature debonding failures. Analytical predictions showed good agreement with experimental results, with a maximum deviation of 10.6%. The proposed strengthening methodology demonstrates practical applicability for the rehabilitation of deficient RC structural members. However, the present study is limited to uniformly deficient reinforcement conditions and does not account for actual corrosion-induced bond deterioration or non-uniform pitting effects. Future studies should focus on accelerated corrosion-damaged specimens, long-term durability behaviour, and bond degradation mechanisms in UDBTRP-strengthened systems.</p>