Bond study on CFRP rod panels externally adhered to concrete

Fiber-reinforced polymer (FRP) laminates used as externally bonded reinforcement (EBR) to strengthen or repair concrete structural members have proven to be an economical retrofit alternative. However, when strengthening long-span members with limited access (e.g., over waterways and freeways), labor and equipment demands may hinder the use of continuous EBR FRP. Recently, carbon FRP (CFRP) rod panels (CRPs) have been developed and used to overcome these limitations. Each CRP is made of several small-diameter CFRP rods placed at predefined spacing. Several CRPs are brought together and made continuous to achieve the strengthening length by means of an overlap (or finger joint). This study experimentally investigated the bond behavior between CRP and concrete. Eighteen double-lap shear specimens were tested under pull-off loading to evaluate the bond strength, development length, transfer mechanism, and bond-slip relation. The bond strength and development length were established for two CRPs, CRP 070 [generated from rods of 2.00 mm (0.08 in.) in diameter, spaced at 6.25 mm (0.25 in.)], and CRP 195 [generated from rods of 4.00 mm (0.16 in.) in diameter, spaced at 9.35 mm (0.38 in.)]. The development length measured 100 mm (4.00 in.) and 119 mm (4.75 in.) for CRP 070 and CRP 195, respectively. The bond strength per unit width of CRP was 563 kN/m (38.5 kip/ft) for CRP 070 and 712 kN/m (48.8 kip/ft) for CRP 195.