THE EFFECT OF MATERIAL DEGRADATION ON BOND PROPERTIES OF FIBER-REINFORCED PLASTIC REINFORCING BARS IN CONCRETE

A research study on the effect of material degradation of fiber reinfo rced plastic (FRP) reinforcing bars on their bond strength and bond st iffness properties is reported in this paper: A convenient new embedde d-rod rest (ERT) specimen was developed and used in the study The ERT specimen is recommended for future environmental degradation studies o f FRP bars. The ERT specimen enables microscopic and mechanical tests to be performed on portions of the same FRP bar after it has been subj ected to environmental conditioning while it is embedded in concrete. Photographs and scanning electron micrographs were used to investigate the nature of the degradation in the polyester and vinylester resin m atrices and the E-glass fibers of smooth and deformed FRP bars. Pullou t rests were used to investigate the bond strength and bond stiffness characteristics of the FRP bars. A descriptive model of the mechanism of the deterioration of the FRP material is proposed to relate the dec reases in bond strengths and stiffnesses to the degradation of the mat erials in the FRP bars.