Predicting the bond-slip relationship between concrete and CFRP using anchoring holes technique

This study investigated the influence of special anchoring holes on the bond-slip behavior between CFRP composites and concrete. For this purpose, one hundred and forty-four concrete prisms (200 × 200 × 200 mm) were casted with different concrete compressive strength (20 MPa, 30 MPa, 40 MPa), holes direction (N: None, V: Vertical (Parallel to the fibers), H: Horizontal (Perpendicular to the fibers)), number of holes (0: None, 1, 2, 3, 4), CFRP sheet bonded length (100 mm, 150 mm) and CFRP sheet bonded width (100 mm, 150 mm). The bonding surface of each concrete blocks was prepared and then anchoring holes were drilled using rotary drill before bonding of CFRP sheet. The experimental results showed that the pattern of the anchoring holes has a significant effect on the bond-slip behavior. In general, both the bond strength and ultimate slippage increase as the number of holes increases and as the CFRP sheet width or length increase. However, for an equivalent CFRP sheet area, the influence of the length (parallel to the direction of loading) is more significant in improving the bond strength than the influence of the width of CFRP sheet. For similar number of anchoring holes, the horizontal (Perpendicular to the fibers) pattern was the most effective followed by vertical (Parallel to the fibers) pattern, and one-hole pattern respectively. The special characteristic of the present study is that the new proposed bond–slip model is based on anchored hole CFRP composite and concrete; instead, the existing bond–slip models are based on CFRP composite without anchorage and ordinary concrete. This proposed model is then assessed using experimental test results on anchored holes concrete bonded blocks subjected to double-shear pull-off test, existing bond–slip models in the literature, and database of pull tests published by several researchers. Finally, the proposed bond–slip model is provided an accurate prediction of the large test database of bond strength and corresponding slippage.