Static Fatigue and Lifetime Prediction of Rosa Porriño Granite: Role of Flaw Population and Slow Crack Growth

Rosa Porriño granite is a widely used dimension stone in architectural and structural applications, yet its long-term reliability under sustained loading remains insufficiently quantified. Here, we combine mechanical testing, fractography and a fracture-mechanics/statistical framework to assess time-dependent failure in this granite. The material shows a high stiffness (dynamic E ≈ 60 GPa) and four-point flexural strength in the 10–12 MPa range. Strength scatter is moderate, with Weibull moduli mU ≈ 10–13, consistent with a relatively homogeneous population of strength-limiting flaws. Fracture toughness is KIC ≈ 0.76 MPam, and dynamic fatigue analysis yields a high slow-crack-growth exponent (n ≈ 44), indicating limited—but non-negligible—susceptibility to static fatigue. Integration of the experimentally determined dynamic fatigue parameters with an analytical slow-crack-growth model enables an illustrative estimation of lifetime under sustained loading. For an assumed constant stress of 6 MPa, corresponding to about 50% of the mean flexural strength measured at the highest stress rate, the model predicts a time to failure of approximately 30 years. This estimate has not been validated by constant-load experiments and should therefore be interpreted within the assumptions and environmental conditions of the model. These results provide a physically grounded basis for durability assessment and lifetime prediction of granitic materials used in load-bearing applications.