Shear Behavior of Fiber Reinforced Concrete Beams with Basalt FRP Reinforcing Bars and Glass FRP Stirrups

Abstract

The State of Qatar suffers from a harsh environment in the form of high temperature that prevails almost all year round in addition to severe humidity and coastal conditions. This exposure leads to the rapid deterioration and the reduction of the life span of reinforced concrete (RC) infrastructure. The full functionality and safe use of the infrastructure in such environments can only be maintained by holistic approaches including the use of advanced materials for new construction.With the developments in materials science, the advanced composites, especially fiber reinforced polymer (FRP) materials are becoming viable alternatives to the traditional construction materials. Having superior durability against corrosion, versatility for easy in-situ applications and enhanced weight-to-strength ratios compared to their counterpart conventional materials, FRPs are promising to be the future of construction materials. More recently, FRP composites made of basalt FRP (BFRP) have been introduced as an alternative to traditional steel reinforcement at a price comparable to glass fibers of about $2.5-5.0 per kg, which is significantly lower than carbon fibers. BFRP bars are characterized by their corrosion resistance, greater strain at failure than carbon fibers, and better chemical resistant than glass fibers, particularly in a strongly alkaline environment. Knowing that FRP bars are anisotropic materials with weaker strength in the transverse direction compared with the longitudinal direction, and having a relatively low modulus of elasticity compared with steel reinforcement, it is important to investigate the concrete contribution to shear strength for beams reinforced with BFRP bars. In addition, due to the elastic performance of the FRP reinforcing bars compared with steel bars, FRP bars fail in a brittle manner. Moreover, concrete itself is a brittle material. Previous investigations have shown that using discrete fibers in concrete increases its ductility due to the large compressive strains exhibited at failure. Therefore, basalt macro-fibers is proposed in this study. A total of 14 concrete beam specimens were tested under four point loading until failure. The parameters investigated included the reinforcement ratio (2rb, 3.1rb, and 4.53rb,where rb is the balanced reinforcement ratio), the span to depth ratio (a/d=2.5, and a/d=3.3), the spacing between stirrups (S1=170mm, and S2=250mm) and the basalt fiber volume fraction (0%, 0.75% and 1.5%). Test results clearly showed that both BFRP bars and basalt macro-fibers can be used as sustainable and eco-friendly alternative materials in Concrete Structures in Qatar.