Numerical study on interface optimization of new-to-old concrete with the slant grooves

Abstract This paper aims to optimize the interfacial relationship by setting the reasonable groove. In order to achieve this objective, the meso-concrete model with cohesive crack model is established and proved based on the existing experimental result. The finite element model reveals the parameter influence on the performance of new-to-old concrete, where the parameters include aggregate location, strength ratio between ITZ and mortar, strength and fracture energy of ITZ, new concrete and old concrete. Further, the best interfacial dimension of the slant groove is proposed to control the failure mode and enhance the mechanical interlocking force between new concrete and old concrete. The main conclusions are that the strength of ITZ plays a pivotal role in improving the chemical adhesion force, whilst meso-concrete model is also sensitive to friction coefficient of modeling parameter. Compared to the specimen without groove (42.2 MPa), the optimal strength of concrete with single groove is 48.7 MPa under the static loading, where the best depth and width of the interfacial groove are 9 mm and 55 mm according to the theory calculation. The necessity of the interface optimization is demonstrated by the case analysis which can provide a guidance for the engineering application.