Numerical modelling can be used to predict the response of concrete structures under impact loading. To properly predict this response the rate dependency of concrete should be included in the numerical material model. The dimensional scale at which the fracture and energy absorption takes place influences the level of detail at which the concrete should be modelled. Therefore, the failure mechanisms under impact loading and the dependency of the failure mechanisms on the loading rate should be known. A combined computational and experimental research programme is performed at the Delft University of Technology. To fully understand the failure mechanisms, the data on mechanical properties are combined with stress-displacement curves and microscopic research of the fracture patterns. The results of the microscopic research and the reconstructed failure mechanisms are addressed in this paper.