Pull‐Out Bond Tests of Epoxy‐Coated Prestressing Strand

Abstract

An investigation is conducted to determine the effects of a grit‐impregnated epoxy coating on the bond of prestressing strand. The coating is intended to inhibit corrosion, but in the process the bond characteristcs are changed. A simple test is needed for production control of the bonding capability. Fifty‐two direct tension pull‐out tests are performed on prismatic specimens made of concrete and 270‐ksi seven‐wire strand. These specimens are made with 3/8‐in. (9.5‐mm), 1/2‐in. (12.7‐mm), and 0.6‐in. (15.2‐mm) strand in an uncoated and coated condition. The 1/2‐in. (12.7‐mm) coated strand is tested with three grit densities and a coating without grit. Results indicate that the grit‐impregnated epoxy coating can provide bond strength similar to or greater than that of uncoated strand when the grit density is properly controlled. Although pull‐out specimen tests do not produce results identical to previously published values of bond stresses in the transfer length and flexural bond length of beams, they follow similar patterns. Therefore, it may be possible to develop a quality‐control test for coated strand production based on pull‐out tests.