Effect of various rebar types and crushed glass coating onto BFRP rebar on the bond strength to concrete

Abstract

This study demonstrates the bond-slip behaviour of steel, BFRP, CFRP and GFRP rebars to concrete obtained from a series of pull-out tests. Results show that CFRP can achieve higher bond strength than steel, whereas BFRP attains half of the bond strength of steel. The bond strength was decreased by 23–28% in steel and BFRP due to an increase in bar diameter. However, the CFRP and GFRP showed a 73–78% reduction in bond strength due to the increase in bar diameter. Steel had the steepest slope in the bond-slip curve, followed by CFRP, BFRP and GFRP. Since BFRP attained optimum performance, the surface coating was applied onto BFRP using natural sand and recycled crushed glass to evaluate the roughness of FRP on the bond performance. Sand and glass coated BFRP demonstrated 37% and 75% higher bond strength compared to uncoated BFRP, while bond stiffness was increased by 14 and 11%, respectively. Compared to the sand coated BFRP, crushed glass coated BFRP exhibited approximately 20% and 10% more bond strength for the 6 mm and 10 mm diameter rebars, respectively. However, the glass coated BFRP exhibited more brittle behaviour compared to its sand coated counterparts. Based on the analytical results, surface roughness and embedment length are found to have a significant influence on the ultimate bond strength (p-value < 0.05) at a 5% level of significance. Additionally, the interaction effect of diameter*embedment and diameter*coating was found to have a significant effect on bond strength.

Keywords:

• Bond strength
• BFRP
• crushed glass coating
• FRP rebars
• sand coating
• Pull-out test

Acknowledgement

The authors would like to thank Mr. Keerthi Prakash, Ms. Kim Chung, Mr. Mihail Illijevski, Mr. Jingshen Liu, Mr. Joshua Kaiser, Mr. Rowan Pritchard, and Ms. Tanya Tanya and Mr. Mitch O’Dowd for their help and support in this project. Also, the authors would like to acknowledge Mr. Lube Veljanoski and Dr. Ikramul Kabir for their help in testing the samples.

Disclosure statement

No potential conflict of interest was reported by the author(s).