Bond-dependent coefficient and cracking behavior of lightweight self-consolidating concrete (LWSCC) beams reinforced with glass- and basalt-FRP bars

Abstract

Crack width is one of the issues that can often control the design of flexural elements reinforced with fiber-reinforced polymer (FRP) bars due to the relatively low modulus of elasticity. This paper aims at investigating the cracking behavior of lightweight self-consolidating concrete (LWSCC) beams reinforced with glass- and basalt-FRP (GFRP and BFRP) bars and evaluating the bond-dependent coefficient (kb) values. Fifteen reinforced concrete specimens 200 mm in width, 300 mm in height, and 3100 mm in length were prepared and tested up to failure. Twelve specimens were made using LWSCC, while the other three were made with normal-weight concrete (NWC) as reference specimens. The test variables were concrete density (LWSCC and NWC); reinforcement type (GFRP and BFRP bars) with various surface conditions (sand-coated and helically grooved); and longitudinal reinforcement ratio. The experimental results show that the FRP-reinforced LWSCC (FRP-LWSCC) beams exhibited cracking behavior similar to that of the counterpart FRP-reinforced NWC (FRP-NWC) beams. The FRP-LWSCC beams had a linear crack response up to failure by concrete crushing, regardless of the amount and surface condition of the FRP reinforcement. Moreover, the recorded crack widths of the FRP-LWSCC beams are presented and compared to those predicted according to FRP design provisions. The comparisons indicate that the crack widths of the FRP-LWSCC beams can be estimated with the FRP design provisions with a variable degree of conservativeness. Furthermore, the determination of the kb factor reveals that the sand-coated GFRP and BFRP bars yielded smaller kb values than the helically grooved GFRP and BFRP bars.