Environmental aging of fiber-reinforced polymer-wrapped concrete cylinders

An environmental aging test protocol for evaluation of environmental durabi lity of concrete wrapped with fiber-reinforced polymer (FRP) composites is proposed. The wrap material was made off-glass and aramid woven fabric impr egnated in an epoxy resin matrix. The effect of temperature, moisture, pH l evel, and freezing-and-thawing cycles on the mechanical properties of FRP-w rapped concrete was investigated. Aged FRP concrete hybrid cylinders were t ested in compression after 1000, 3000, and 8000 h of environmental exposure . FRP composite coupons were exposed to the same conditions and tested in t ension to identify the degradation mechanisms. Hygrothermal swelling of the FRP wrap was observed for the different aging conditions and led to a redu ction 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 hygrothermal strai ns 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 hy brid system due to environmental aging. The following mechanical indicators were proposed to characterize environmental durability of FRP-wrapped conc rete: 1) critical stress onset of unstable cracking propagation) of concret e FRP cylinders; 2) retained compressive strength of concrete FRP cylinders ; and 3) retained tensile strength of FRP coupons. The rate at which the re tained compressive strength varied with time under the influence of the var ious environmental conditions was studied.