Effect of Epoxy Coating Thickness on Bond Strength of Reinforcing Bars

Abstract

The effect of epoxy coating thickness on bond strength is evaluated using No. 19 (No. 6) reinforcing bars with coating thicknesses ranging from 160 to 510 mm (6.4 to 19.9 mils). Three deformation patterns are evaluated using epoxy meeting the requirements of ASTM A 775. The reduction in bond strength caused by epoxy coatings between 160 and 420 mm (6.4 and 16.5 mils) is largely independent of coating thickness. The reduction, however, becomes significant for coatings thicker than 420 mm (16.5 mils). When combined with earlier research on bars ranging in size from No. 10 to No. 36 (No. 3 to No. 11), the results demonstrate that an increase in the maximum allowable coating thickness, from 300 mm to 420 mm (12 to 16.5 mils), is justified for No. 19 (No. 6) and larger reinforcing bars in the ASTM standard.