Compressive behavior of basalt FRP-confined circular and non-circular concrete specimens

Abstract

This paper presents an experimental study on the compressive behavior of concrete specimens confined by a new class of composite materials originated from basalt rock, Basalt Fiber Reinforced Polymer (BFRP). The main objective of this study is to observe the difference between compressive behavior of circular and non-circular concrete specimens jacketed with BFRP composite. For this purpose, a total of 56 small scale specimens without internal steel reinforcement were tested under monotonic axial compression to failure. The parameters considered were the cross-section shape (i.e., circular, square, and rectangular), corner radius in case for non-circular specimens (i.e., 0 mm defined for sharp corner, 13 mm, and 26 mm), and number of BFRP layers (i.e., 0 for unconfined specimens, 3, 6, and 9). The results of BFRP-confined concrete specimens of this study exhibited a similar bilinear stress-strain response with different confinement effectiveness depending on the considered parameters particularly in the inelastic range. The results also demonstrated an improvement of the ultimate condition of confined concrete with an increase in number of BFRP layers or corner radius. In contrast, the BFRP confinement effectiveness was decreased with an increase in sectional aspect ratio or when the cross-section was changed from circular to non-circular. Overall, the experimental results indicated the well-performing of basalt fiber in improving the concrete compressive behavior. Finally, ultimate condition of BFRP-confined specimens of present study is predicted by seven existing models developed for other FRPs. The comparison indicates that the ultimate strength of BFRP-confined specimens is predicted in a good way by some models; however, these models were unable to predict well their ultimate axial strain and need further improvement.