Evaluation Of Pull-Out Bond Effects of Reinforcing Steel Coated with Exudates

Corrosion of reinforcing steel greatly impacts the structural performance and service life of reinforced concrete structures. This study evaluated the influence of reinforcing steel corrosion and natural exudate coatings on pull-out bond strength through experimental testing. Plant exudates have potential as green, cost-effective corrosion inhibitors for reinforcing steel. A total of 36 reinforced concrete specimens containing 12mm reinforcing bars were fabricated. Specimens included uncoated control samples and bars coated to thicknesses of 150, 300, 450 and 600 μm using exudates extracted from Ficus platyphylla tree bark. All specimens were immersed in a 5% NaCl solution for up to 360 days to accelerate corrosion. Pull-out tests were conducted at intervals to measure failure load, bond strength, maximum slip, and weight loss. Rebar diameters and weights were directly measured before and after corrosion. Results showed bond strength and failure load decreased with increasing corrosion from 0% to 5%, while maximum slip increased proportionally. Uncoated bars experienced the highest cross-sectional area and weight reductions after corrosion exposure. Exudate coatings enhanced bond strength and corrosion resistance compared to uncoated bars. Coatings as thin as 150μm improved failure loads by up to 30% in some cases. Performance of exudate coatings was comparable or superior to previous studies using epoxy coatings and better than unprotected corroded bars. Quantitative data validated theoretical models linking corrosion level and bar diameter/area/weight changes to the consequent reductions in bond strength and increases in slip. Exudate coatings effectively mitigated corrosion impacts, highlighting potential as environmentally-friendly and inexpensive alternatives to synthetic coatings. Further optimization of exudate sources and coating properties, as well as long-term durability assessments, could establish practical guidelines for infrastructure applications. Keywords: Reinforcing Steel, Corrosion, Pull-Out Bond, Exudate Coatings, Ficus Platyphylla, Reinforced Concrete