3D cohesive fracture of heterogeneous CA-UHPC: A mesoscale investigation

• Published in: International journal of mechanical sciences Vol. 249; p. 108270
• Main Authors: Zhang, Hui, Huang, Yu-jie, Xu, Shi-lang, Hu, Xun-jian, Zheng, Zhi-shan
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.07.2023
• Subjects: 3D fracture and damage; Discrete cohesive crack; Fibre bridging; Mesoscale modelling; Ultra high performance concrete with coarse aggregates (CA-UHPC); Discrete cohesive crack; Ultra high performance concrete with coarse aggregates (CA-UHPC); Mesoscale modelling; 3D fracture and damage; Fibre bridging
• ISSN: 0020-7403; 1879-2162
• DOI: 10.1016/j.ijmecsci.2023.108270

•Simulate complex 3D cohesive fracture of CA-UHPC at mesoscale for the first time.•Efficiently model fibre-mortar interactions by orientation-based pullout force-slip relations.•Elucidate coupling effects of aggregate barrier, interfacial cracking and fibre bridging.•Provide quantitative bases to optimize the mechanical performance of CA-UHPC. Ultra high performance concrete with coarse aggregates (CA-UHPC) exhibits complicated damage and failure mechanisms due to intricate interactions of irregular mesoscale phases, including random aggregates, fibres, mortar, and interfaces. This work proposes a 3D numerical framework to investigate the complex cohesive fracture of CA-UHPC at mesoscale for the first time. Automatic algorithms are proposed to model realistic aggregates, mortar, aggregate-mortar interfaces and steel fibres in large quantities. Zero-thickness cohesive interface elements are automatically inserted in the mortar and on the aggregate surfaces to capture potential cracks, and an efficient non-conforming methodology is developed to model the fibre-mortar bond-slip behaviour using orientation-dependant pullout force-slip relations. The proposed models are validated using typical uniaxial tension tests, and elucidate that the progressive interactions of aggregate barrier, interfacial cracking and fibre bridging govern the early cracking, strain-hardening behaviour, fibre activation and final crack networks. Quantitative analyses are performed to optimize the mechanical properties of CA-UHPC: as the aggregate content increases, there are more torturous crack surfaces and fewer activated fibres with lower load-carrying capacities, but the downside of coarse aggregates can be alleviated by increasing fibre content, especially when needing aggregates to reduce carbon footprints and improve anti-shrinkage performance. [Display omitted]