Bond Strength of Reinforcing Bars with Deformation Spacings that Exceed Maximum Specified in ASTM A615

No. 5 and No. 10 bars are tested for bond strength in accordance with ASTM A944. For each bar size, the bond strength of bars with deformations that exceed the maximum spacing requirements in ASTM A615 is compared with the bond strength of bars that meet the spacing requirements. All bars exceed the requirements for minimum deformation height. Research related to the effect of deformation properties on bond strength, including the research used to establish the requirements for deformations in ASTM A615, is also reviewed. The test results match earlier research and demonstrate that (1) bond strength is not governed by the specific value of deformation height or spacing, but by the combination of the two as represented by the relative rib area of the bars, (2) the bond strength of the bars with deformation spacings that exceed those specified in ASTM A615 is similar to the bond strength of the bars that meet the specification, and (3) the differences in bond strength observed in the tests are not statistically significant. The bars tested in this study with deformation spacings that exceed those specified in ASTM A615 have relative rib areas that exceed the minimum values that result from the provisions of ASTM A615. They will provide satisfactory bond performance and can be used in all concrete construction