Experimental Research On Durability Of CFRP Confined Concrete Under Wet Hot Environment

Fiber reinforce polymer (FRP) has the advantages of light weight, high strength, corrosion resistance, and is gradually widely used in civil engineering. With FRP is widely used in reinforced concrete structures, durability of FRP reinforced concrete structure attracted people’s attention. Both results of the experimental research and engineering practice at home and abroad show that FRP reinforcing concrete structures have good mechanical properties. However, FRP used in structural reinforcement is not a long time, and in many practical engineering structures inevitably are subject to environmental corrosion, so to ensure the safety and effectiveness of FRP reinforcement techniques durability of FRP reinforced concrete structure must be research.This paper studies the effect of environmental corrosion to the mechanical properties of CFRP^epoxy resin and concrete cylinder confined with CFRP. There are two types of environments, namely saline wet-dry cycle and natural exposure. Salt solution wet and dry cycle test specimens were divided into four groups based on the number of cycles, namely60,120,240,360(times); Natural exposure test specimens are divided into10groups according to the exposure time, respectively6,12,18,30,48,72,96,120,144,180(months). Each group included12specimens cylinder,7CFRP tensile specimens and seven epoxy tensile specimens.By the tensile test, the mechanical properties of CFRP and epoxy has changed after salt solution dry and wet cycles and natural environment exposed. After360salt solution dry and wet cycles,tensile strength、ultimate strain and elastic modulus of CFRP specimen have decreased8.11%、7.73%and-1.40%, while tensile strength、ultimate strain and elastic modulus of epoxy resin specimen have decreased43.10%、-6.73%and45.97%. After18months natural environment exposed,tensile strength、ultimate strain and elastic modulus of CFRP specimen have decreased6.63%、4.12%and1.38%, while tensile strength、ultimate strain and elastic modulus of epoxy resin specimen have decreased39.63%、12.44%and46.77%.Through the cylinder axis pressure test, compressive strength of the cylinder specimen has changed after salt solution wet and dry cycles and natural environment exposed. After360salt solution dry and wet cycles, compressive strength of concrete cylinder has improved9.38%, ultimate axial strain has decreased9.42%, ultimate hoop strain has decreased9.54%, and compressive strength of CFRP confined cylinder has decreased12.10%(1layer)、10.81%(2layers)、13.88%(3layers),, ultimate axial strain has decreased11.41%(1layer)、2.22%(2layers)、4.10%(3layers), ultimate hoop strain has decreased16.78%(1layer)、5.22%(2layers)、15.61%(3layers) After18months natural environment exposed, compressive strength of concrete cylinder has improved12.55%, ultimate axial strain has decreased-0.55%, ultimate hoop strain has decreased23.12%, and compressive strength of CFRP confined cylinder has decreased9.11%(1layer),9.63%(2layers)、10.32%(3layers),, ultimate axial strain has decreased5.22%(1layer)、1.98%(2layers)、2.30%(3layers), ultimate hoop strain has decreased0.41%(1layer)、9.16%(2layers)、14.10%(3layers)The experimental data by linear regression analysis, obtained CFRP confined concrete strength model which considering the environmental effect. Verify CFRP confined concrete strength model presented with the test data to prove its accuracy in this paper.