Influence of interface roughness geometrical parameters on the shear behaviour of old and new concrete interface

Interface shear failure of composite concrete structures highlights the importance of shear performance research. Existing research results indicate that surface roughness plays a pivotal role on the shear behaviour of the old and new concrete interface. In several studies, interfaces with random roughness tooth geometries have been utilised, while, researches considering regular and defined tooth geometries are very rare. In this paper, an experimental and numerical investigation of the influence of roughness tooth geometrical parameters on the shear behaviour of an old and new concrete interface, considering a roughness tooth, was presented. This serves as a proof of concept in the use of quantitatively controlled roughness surface geometry for improved interface shear performance. Using the tooth angle, tooth depth, and the external normal pressure as test parameters, eighteen double-sided shear test specimens were prepared and tested till failure. In addition, numerical parametric studies on the roughness tooth angle and tooth depth for enhanced interface shear behaviour were conducted. Obtained results show the significant effect of roughness tooth angle and tooth depth on the shear capacity of the interface. Using a roughness tooth angle of about 20° approved to produce the highest interface shear capacity among all tested roughness angles. Also, increased roughness tooth depth enhanced interface shear capacity. A 10 mm increase in the tooth depth increased the ultimate shear load by a significant 47%. Furthermore, the external pressure significantly increases the shear capacity of the interface, with the positive influence of the initial external pressure more obvious at lower external pressure values. Increasing the initial external pressure from 1.0 to 1.5 MPa and from 1.5 to 2.0 MPa improved the interface ultimate shear capacity by 16.3% and 12.3%, respectively.