BASALT FRP BARS: DURABILITY AND APPLICATIONS IN REINFORCED CONCRETE ELEMENTS

Abstract

This dissertation is designed to examine the durability characteristics of basalt fiber reinforced polymers (BFRP) bars under severe environmental conditions that are usually encountered in civil engineering structures. These exposures comprise continuous immersion to different environmental conditions such as seawater with an elevated temperature of 50 oC, alkaline solution, sulfuric acid solution, and exposure to freeze-thaw cycles. Under these conditions, the mechanical characteristics and the bonding efficiency of BFRP bars with the surrounding concrete were evaluated by conducting tensile and pull-out tests, respectively. Furthermore, the BFRP bars were implemented in different large-scale reinforced concrete elements such as beams and one-way slabs. The beams were immersed in a seawater environment to investigate their flexural durability. For the slabs, their shear capacity was studied, then the tested slabs were numerically simulated to perform a sensitivity analysis and propose an analytical model to calculate the shear capacity of one-way slabs reinforced with BFRP bars. The experimental findings showed that the 50 oC seawater environment had the most detrimental effect on the tensile and bond strengths, whereas the degradation was less significant under the rest of the exposures. Also, in comparison to the conditioned pull-out specimens with plain concrete, the loss in bond strength was mitigated in the conditioned specimens with basalt fibers, while the higher loss was recorded for pull-out specimens with polypropylene fibers. Moreover, the obtained findings revealed insignificant effect of the concrete compressive strength on the bond strength of the sand-coated bars. Furthermore, the bond strength in the ribbed bars was significantly higher than that in the sand-coated bars and the ribbed bars were less influenced by the surrounding environments. For large-scale testing of beams, all beams have satisfied the deflection and the crack widths requirements at the serviceability stage. For the tested slabs, the shear capacity, and the slabs' stiffness were significantly enhanced, and the shear crack width was delayed at a higher reinforcement ratio and with the addition of basalt fibers to the concrete mix. Finally, a design equation that can predict the shear capacity of one-way BFRC-BFRP slabs was proposed based on a genetic algorithm approach.