Compressive stress-strain behavior of CFRP-confined lightweight aggregate concrete reinforced with hybrid fibers

Abstract

The axial compressive stress-strain behavior of CFRP-confined lightweight aggregate concrete (LWAC) with short carbon fiber and/or polypropylene fiber was investigated. Thirty cylinders with different concrete types (normal weight concrete and LWAC), fiber types (carbon fiber, polypropylene fiber, and mixture of these two fibers), volume faction of fibers (from 0% to 0.4% for each fiber type in single and hybrid form), and spacing between CFPR straps (0 mm, 30 mm, and 50 mm) were experimentally studied. The compressive strengths of CFRP-confined LWAC were improved to 1.01–1.51 times the unconfined strength, and LWAC showed less enhancement in compressive strength provided by confining pressure compared with normal weight concrete. The increase in spacing between CFRP straps declined the confining effect. Addition of carbon fiber in both single and hybrid form positively affected the toughness of CFRP-confined LWAC, while the polypropylene fiber showed few influences on properties of LWAC. Models for the peak stress and corresponding strain were established by collected and present test data. Then theoretical stress-strain model was developed by combining iterative calculation of ascending portion and close-form formula of descending branch. The proposed model showed good match to the test results.