Fracture Behavior of Concrete using Cohesive Crack and Size-Effect Models

Abstract

During crack propagation in concrete, it is commonly known that a macro-crack has a tendency to follow a tortuous crack path due to microcracking, crack bridging, aggregate interlocking, etc. The meandering of main crack depends on the concrete mix design and the properties of the aggregate particles such as size, texture, and angularity. This phenomenon results in the energy consumption and affects the apparent toughness of the material. Because of this reason, a concrete specimen shows strain softening and well-defined size effect. The complete fracture process such as crack initiation, stable crack propagation, unstable fracture, strain softening and post-cracking behavior, concepts of ductility, and size effect of concrete can be predicted and analyzed using cohesive crack method. This model has got more popularity and wide applications to pre-cracked (even uncracked) concrete specimen because of its simplicity and predicting capability of nonlinear fracture behavior. In this chapter, cohesive crack model is developed for three-point bending test and compact tension specimen and the numerical results obtained using numerical models are compared with some experimental results available in the literature. Further, a systematic and extensive study using various softening functions of concrete is carried out to observe the behavior of different fracture parameters using cohesive crack model. Finally, size-effect study using size-effect law is also carried out.