Effect of roughness and adhesive on the strength of concrete-to-concrete interfaces cast from 3D-printed prefabricated plastic formworks

Increasing interface roughness and using adhesives are two effective methods to improve the bond strength of the concrete-to-concrete interface. In this paper, the influences of interface roughness and adhesives on the splitting tensile strength, bi-surface shear strength, and slant shear strength of the concrete-to-concrete interface were quantitatively studied for 180 specimens. In order to accurately evaluate the bond strength of different adhesives, the repeatable interface roughness specimens were prepared by casting concrete. The roughness of the concrete interface was manufactured based on 3D printing technology and described by the concept of fractal dimension. Test results indicate that the splitting tensile strength and bi-surface shear strength have a good linear correlation with the concrete interfacial fractal dimension. Compared to the slant shear test, adhesives can obtain a better bond performance in the splitting tensile and bi-surface shear tests. Different types of adhesives have different bond effects, while epoxy resin presents the highest bond strength no matter in splitting tensile, bi-surface shear, or slant shear tests.