Environmental Aging of Fiber-Reinforced Polymer-Wrapped Concrete Cylinders
Publication Name: ACI Materials Journal
An environmental aging test protocol for evaluation of environmental durability of concrete wrapped with fiber-reinforced polymer (FRP) composites is proposed. The wrap material was made ofE-glass and aramid woven fabric impregnated in an epoxy resin matrix. The effect of temperature, moisture, pH level, and freezingand-thawing cycles on the mechanical properties of FRP-wrapped concrete was investigated. Aged FRP concrete hybrid cylinders were tested in compression after 1000, 3000, and 8000 h of environmental exposure. FRP composite coupons were exposed to the same conditions and tested in tension to identify the degradation mechanisms. Hygrothennal swelling of the FRP wrap was observed for the different aging conditions and led to a reduction in concrete confinement. The main cause of environmental damage in the hybrid system was the combined effect of moisture and elevated temperature on the tensile strength of the E-glass fibers. Residual hygrolhermal strains in the FRP wrap and reduction in tensile strength of the E-glass fibers controlled the changes in the stress-strain response of the concrete-FRP hybrid system due to environmental aging. The following mechanical indicators were proposed to characterize environmental durability of FRPwrapped concrete: 1) critical stress (onset of unstable cracking propagation) of concrete FRP cylinders; 2) retained compressive strength of concrete FRP cylinders; and 3) retained tensile strength of FRP coupons. The rate at which the retained compressive strength varied with time under the influence of the various environmental conditions was studied.