Aggregate interlock in fractured concrete mesoscale models: a novel finite element modelling approach

Abstract

Aggregate interlock is a stress transfer mechanism in cracked concrete. After concrete cracks under tensile loading, crack interfaces can experience significant slip deformation due to the applied crack kinematics. Upon rising slip along crack interfaces, aggregate interlock stresses are generated which transfer shear stress and normal stress. Many experimental programmes and analytical expressions have been developed for several decades. However, a finite element model considering realistic crack surfaces was still not developed. The complexity of developing a FE model lies due to the mesoscopic nature of the problem. In this study, concrete mesoscale models were employed to generate realistic cracked concrete surfaces. Uniaxial tensile fracture propagation in concrete mesoscale models were achieved using Zero-thickness cohesive elements approach. Once cracked concrete FE models are developed, validation of the proposed FE models was conducted against two experimental campaigns. The study comprises the evaluation of the surface roughness index of the cracked concrete surfaces. The FE model predicts secondary cracking under low initial crack widths and mixed mode angles. FE predictions were further compared with Walraven’s simplified formulae, Bažant’s rough crack model, Cavagnis’s aggregate interlock formulae and contact density model and consistence agreement was observed. Finally, strengths and weaknesses of the proposed FE modelling approach for aggregate interlock was discussed and further implementations were also highlighted.