Role of Material Fabric in Flexural Failure in Concrete

A recently developed discrete-element capability was used to study the effect of mesogeometry on flexural failure in concrete. Fabric anisotropy in angular specimens was found to retard flexural crack growth. The fabric also played a key role in determining the geometry of the fracture process zone. Greater dispersion in the local fabric resulted in more tortuous cracks. Specimens with angular particles exhibited more crack branching and tortuosity, and hence had higher macrofracture energy, than specimens with rounded aggregates. Aggregate shape affected the peak stress and postpeak response of notched specimens. The slowing of crack growth and nonmonotonic evolution of the fracture process zone, also observed in experiments, was investigated. Crack tip shielding was found to play a critical role in explaining this behavior.