Bond strength of GFRP bars to high strength and ultra-high strength fiber reinforced seawater sea-sand concrete (SSC)

Abstract

Fiber reinforced polymer (FRP)-reinforced seawater sea-sand concrete (SSC) structures are prospective substitutions for traditional steel-reinforced concrete structures, especially in maritime environment. To demonstrate the feasibility of the FRP-reinforced SSC structures, an in-depth understanding on the bond strength of glass FRP (GFRP) bars to SSC under pull-out loading is essential. In this regard, pullout tests on 45 specimens with a 10 mm diameter GFRP bar embedded in ultra-high strength concrete (including normal concrete with river-sand and fresh water and SSC) are conducted in this study. Particularly, the experimental tests focus on some key factors that governing the GFRP bars in concrete, such as the bar embedment length, the polyethylene (PE) fiber volume fraction, and the concrete strength (i.e., 80 MPa and 120 MPa). Three major failure mechanisms and two types of average bond stress-slip curves are obtained from the tests. The results show that substitution of seawater and sea sand for normal concrete has no distinct effect on short-term change in bond strength (less than 9%). In addition, it indicates that the increase in concrete strength and PE fiber content could improve the bond strength, whereas increasing the embedment length (from 2.5 times to 10 times of bar diameter) could result in a decrease in bond strength (by 20–30%). Furthermore, it demonstrates that the CMR model has better performance than the mBPE model in capturing the experimentally observed ascending part of the bond-slip curve.