ffect of Epoxy Coating on Bond and Anchorage of Reinforcement in Concrete Structures

Bilal S. Hamad

         The objective of the research program was to assess the influence of epoxy coating on the bond characteristics of reinforcing bars and to devepol or revise the existing recommendations for the design of splices and anchorage of straight and hooked epoxy-coated reinforcement .

 In one phase of the study, eighty pullout specimens were tested to determine differences in stress transfer between normal mill scale uncoated and epoxy-coated bars using different bar sizes, coating thicknesses, bar deformation patterns, rib face angles, concrete strengths, and different levels of restraint to spliting . Results indicated that coating reduced the bond strength of reinforcing bars . However, the magnitude of the reduction in bond strength of coated bars relative to uncoated bars was independent of the level of the variables investigated .

 In the second phase of the program, twelve beams with splices in a constant moment region were tested in negative bending . All bars were cast in a top bar position with more than 12 in. of concrete below the bars . Variables included bar size, bar spacing, and amount of transverse reinforcement crossing the splitting plane in the splice region . Failure of all beams was governed 11 by splitting of the concrete cover . The presence of ties in the splice region increased the deflection capacity of the beams and improved the bond strength of coated bar splices relative to uncoated bar splices . The improvement was independent of bar size or bar spacing .

 In the third phase of the program, twenty-four specimens simulating typical beam-column joints in a structure were tested to compare the anchorage capacities of uncoated and epoxy-cated hooked bars . Variables included bar size, concrete strength, concrete cover, hook geometry, and the amount of transverse reinforcement through the beam-column joint . Epoxy-coated hooked bars consistently developed lower anchorge capacities and greater slips than uncoated hooked bars .

 Using the results of this study and results of other tests on coated bars in the literature, the most comprehensive review of the effect of epoxy coating on structural aspects of coated bars was performed . Design equations were recommended of coated straight and hooked bars .