Fracture in quasi-brittle materials, such as refractories and reinforced concrete, involves complex mechanisms due to a progressive micro-cracking process within a fracture process zone (FPZ). This study employs Wu's phase field model (PFM) to simulate fracture behaviour in a magnesia spinel refractory. The PFM integrates fracture mechanics and damage mechanics, predicting tortuous crack patterns when heterogeneous strength distribution is considered. Numerical simulations, including wedge splitting tests typically applied for fracture testing of refractories, demonstrate PFM's effectiveness in capturing fracture behaviour, offering a robust tool for simulation of fracture of refractories with reduced brittleness. Comparative analysis with experimental data confirms the model's accuracy and applicability.