Bond of Epoxy-Coated Reinforcement in Normal and High-Strength Concrete

Epoxy-coated reinforcement and high-performance concrete are commonly used materials in exposed structures located in cold regions and marine environments of the United States. Their popularity is due to their resistance to corrosion in areas where chlorides are used as deicers in roads and bridges. This paper summarizes an experimental investigation regarding the difference in bond behavior of epoxy-coated and uncoated reinforcement in normal and high-strength concrete. The objectives were to investigate the effect of bar surface (epoxy, uncoated,) bar size (No. 6, No. 8, and No. 11), concrete strength (6, 10, 12, 14 ksi) and the addition of micro-silica to concrete. Ninety-four inverted half-beam specimens were tested. All of the specimens were designed to fail in bond by splitting of the concrete. The reinforcement in four of the specimens (two uncoated and two epoxy-coated reinforcement) was instrumented with internally embedded strain gages to measure the distribution of strain along the embedment length. The tests showed clear differences in the strain distribution at service level between coated and uncoated reinforcement. A comprehensive review of the effect of epoxy-coating on bond strength was conducted using the results of this study and 151 tests results from seven other research studies in the USA. The experimental results were compared to values of design bond strength calculated using ACI 318-89(1) and ACI 318-95 (2) equations.