Bond performance of alkaline solution pre-exposed FRP bars with concrete

Abstract

An experimental investigation is conducted on the influence of the degradation of fibre-reinforced-polymer (FRP) bars on their bond performance with concrete. A basalt fibre-reinforced vinyl ester (BV) bar, basalt fibre-reinforced epoxy (BE) bar, carbon fibre-reinforced epoxy (CE) bar and E-glass-fibre-reinforced vinyl ester (GV) bar are adopted. The bars are pre-exposed to 40°C alkaline solution for 0, 15, 30 and 45 d and then tested under a direct pull-out condition. The test parameters include the resin type, fibre type and conditioned age. The test results indicate that, for the unconditioned bars, the bond strength of CE bars is the largest, next are the GV bars and BE bars, whose strengths are very close to each other, and the BV bars have the least bond strength. For the conditioned FRP bars, the bond strength retention of BE bars with an epoxy matrix are generally greater than those of BV bars with a vinyl ester matrix. The bond strengths of the conditioned CE bars and BE bars with the epoxy matrix both increase, whereas the BV bars and GV bars show a decreasing trend. It is concluded that the order of bond durability is CE > BE > GV > BV for the bars used in this paper combining the test results with a mechanism analysis.