Basalt FRP Bars

Fiber-reinforced polymer (FRP) bars are a non-corrosive and long-lasting alternative to traditional steel reinforcing bars used in RC structures. These composite bars are made of longitudinally aligned fibers embedded in a resin matrix using a manufacturing process called pultrusion. FRP bars have been used in civil engineering structures for over three decades. Glass fiber is the most-used fiber type because of its availability and low cost. Due to the physical properties of basalt fibers, which exceed those of glass, and the marginal cost difference between the two fiber types, more people are opting for this fiber type. With a growing supply of basalt fibers, BFRP) bars are becoming economically feasible.

BFRP bars provide a high tensile strength [over three times higher than Grade 60 steel (Fe 415)for equivalent bar diameters]. As with glass FRP (GFRP) bars, BFRP bars are lightweight (one-fourth the weight of steel), electrically nonconductive, and transparent to electromagnetic fields. The main advantage of these composites, however, is the high corrosion resistance, even when exposed to harsh environments like seawater.

Similar to other FRP composite, BFRP bars show linear elastic behaviour up to failure and do not exhibit a plastic plateau-like mild steel. Also, the elastic modulus of BFRP bars is about one-third of that of steel reinforcement. When compared to other FRP types, BFRP bars fall between glass and carbon for both strength and stiffness. In comparison to FRP bars made of E-CR glass, BFRP bars have a slightly higher elastic modulus and strength as well as greater chemical stability.

Use of FRP Bars

Historically, FRP bars have been most frequently used in transportation infrastructure rather than in buildings. The main reason behind this is the goal of departments of transportation (DOTs) to increase the service life and reduce maintenance costs of bridges and other highway structures. Since 2005, E-CR glass fiber has been produced in accordance with ASTM D578/D578M, “Standard Specification for Glass Fiber Strands.”

As per FDOT Standard Specifications, Section 932-3 and?FDOT Structures Manual, V. 4,“…The design of all concrete members containing GFRP reinforcing bars shall be in accordance with the AASHTO LRFD Bridge Design Guide Specifications for GFRPReinforced Concrete. For BFRP use the same design criteria as GFRP.”

This information has been extracted from the paper: Emparanza, A.R., McMahon, B. and Nanni, A.(2022) Basalt FRP Reinforcement in Concrete Topping Slabs in a Commercial Building A sustainable and durable solution, Concrete International, Dec. pp.28-33