Simulation of the mesoscopic concrete behavior using the real geometry
Concrete is one of the most widely used structural materials all over the world. It has a complex microstructure, composed of cementitious matrix and aggregates with random shapes and sizes, presenting random features over a wide range of length scales. Thus, it becomes important to study the cracking behavior of the concrete, which is non-trivial due to its intrinsic heterogeneous nature. The heterogeneities, i.e. randomly sized aggregates, act as imperfections, influencing the crack nucleation and propagation. Therefore, accurate numerical models are needed, which can simulate the cracking behaviour of the concrete accounting for its heterogeneous nature.
The phase field method for fracture is a recent and attractive method that elegantly simulates complicated fracture processes including crack initiation, propagation, branching and merging. Here, a continuous crack field parameter varying smoothly between damaged and virgin material approximates the sharp crack. The main contribution of this work is to study the cracking behavior in concrete using the phase field framework taking into account its heterogeneous nature.
In the first phase of the project, a spatial variation of elastic and fracture properties based on a suitable statistical distribution will be obtained through an experimental campaign, to account for the heterogeneous nature of the cementitious matrix. The validity of the proposed approach will be demonstrated through the simulation of available experimental tests in the phase field framework and comparison of the results with the experimental evidence in terms of crack pattern and load-displacement curve.
Several phase field models have been proposed for brittle fracture, which include additional constitutive assumptions that allow for the evaluation of physically possible solutions, i.e., they introduce a constitutive split prohibiting crack propagation under compression. The second phase of the project will deal with the identification of suitable constitutive split for the phase field model, which effectively simulates concrete cracking behavior. To benchmark the constitutive splits, a series of experimental tests will be perfomed and then simulated using phase field framework.