Experimental Study on Normal-Strength, High-Strength and Ultrahigh-Strength Concrete Confined by Carbon and Glass FRP Laminates

Abstract

Confinement of concrete columns with fiber-reinforced polymer (FRP) laminates has been extensively studied in recent decades due to their important applications for strengthening purposes or construction of hybrid elements. Significant differences were observed in confinement effects obtained for normal-, high-, and ultrahigh-strength concrete when wrapped by FRP laminates. There are few studies explaining these differences, especially when ultrahigh-strength concrete (UHSC) is taken into consideration. This paper reports on an analysis of confinement effects generated by carbon and glass fiber-reinforced polymer (CFRP and GFRP) wraps in normal-, high-, and ultrahigh-strength concrete (NSC, HSC and UHSC) cylinders. In total, 102 concrete cylinders confined with GFRP and CFRP wraps were tested, including 7 concrete mixes and different number of layers. The results showed that, different from NSC, both HSC and UHSC confined with FRP have a stress-strain behavior with a considerable strength enhancement in the first branch of the curve and a softening or hardening in the transitional zone depending on the confinement pressure.