Experimental and analytical study of bond between basalt FRP bars and geopolymer concrete

This paper presents an experimental and analytical study of the bond behaviour of basalt fibre reinforced polymer (BFRP) bars in geopolymer concrete (GPC). Pull-out tests were conducted on ribbed BFRP bars embedded in GPC cubes considering different bar diameters (6, 8 and 10 mm) and embedment lengths (5db, 10db and 15db) to investigate their effects on bond behaviour in terms of bond-slip response, bond strength and failure mechanisms. Results indicate that the chemical adhesion is low, and the bond is mainly dependent on mechanical interlocking which stopped when pullout occurred by local crushing of the GPC with the BFRP ribs remaining undamaged, suggesting high rib shear strength. A theoretical bilinear model was used to describe the local bond-slip relationship and the bond interface properties. There exists nonlinear bond stress distribution, especially for longer embedment lengths and lower load levels with a bond stress concentration factor of 3.9. A parametric study was performed to estimate the influences of bar diameter, embedment length and elastic modulus on maximum pull-out load, based on which the load transfer mechanisms between BFRP bars and GPC were explored, and a formula for predicting the bond strength was proposed in comparison with experimental data.