Durability of GFRP composites reinforcing rods in concrete environment

Extensive studies have been conducted on the durability of FRP composites for construction at the University of Sherbrooke. Some results from the study on fundamental material properties of GFRP rebars with respect to durability are presented in this paper. More than 400 accelerated ageing tests have been conducted on GFRP bars manufactured by FRP industrial partners. GFRP rebars are grouped into more than 20 types of specimens with different combination of resin matrix, glass fibres, manufacturing parameters, sizing chemistry, sizes and shapes, and surface coatings. The FRP bars have been subjected to different tensile sustained load (22-68% of ultimate strength) using three different loading systems, in various alkaline environments, such as NaOH, simulated alkaline pore water solution, and embedded in moist concrete samples. Time to rupture or residual strength, as applicable, has been determined. Additionally, various micro-structural analysis techniques and absorption measurements have been carried out to understand stress corrosion mechanism of the bars. The results showed clearly that alkaline ions and moisture could penetrate or diffuse through the resin (or through cracks and voids) to the inter-phases and the fibres and damage the FRP reinforcements through many mechanisms which change depending on the type of resin matrix, sizing, stress level, pH of the alkaline environment, and manufacturing process. Furthermore, most of the studied GFRP reinforcing rods in this research project are quite durable in alkaline environments under stress levels corresponding to 25% of the tensile ultimate stress.

• INTRODUCTION

• MATERIALS

• EXPERIMENTAL PROGRAM

• SELECTED RESULTS AND DISCUSSIONS

• CONCLUSIONS

• ACKNOWLEDGEMENTS

• REFERENCES