The complex crack nucleation and propagation behavior in concrete is largely influenced by its mesostructural arrangement, thus, it is important to account for it to obtain realistic predictions of concrete fracture. X-ray computed tomography (CT) can be adopted not only to obtain the real 3D mesoscopic geometries, but also to visualize the crack onset and the 3D complex crack propagation pattern during a mechanical test. This information can be obtained from in-situ testing, i.e. by carrying out a mechanical test inside the tomograph and taking several CT images of the sample at different stages of the test. Moreover, using Digital Volume Correlation (DVC) it is possible to measure the 3D displacement field. The aim of this work is to calibrate and validate a phase-field fracture model to reproduce the concrete cracking behavior at the mesoscale, namely, within a description in which aggregates and pores are explicitly resolved. First, experimental tests are performed to characterize the elastic and the fracture parameters of both mortar and aggregates. Then, a series of in-situ wedge splitting tests is performed on concrete specimens doped with baryte contrast enhancers to improve phases segmentation. The CT image of the specimen before loading delivers the real mesoscopic 3D geometry, while from DVC analysis on the time series of images we obtain the 3D full-field displacement data including realistic boundary conditions that can be adopted in the numerical simulations. Finally, we perform numerical simulations on the real geometry with the real boundary conditions and compare numerical and experimental results.