Sulfate attack of concrete: Reliability analysis

To determine the expected long-term performance of concrete in a sulfate-ri ch environment, a reliability analysis is performed using a previously deve loped model and data collected over more than 40 years by the U.S. Bureau o f Reclamation (USBR). The reliability analysis contains three main phases: 1) an expected time to failure analysis; 2) a probability of failure analys is; and 3) a sensitivity analysis. This analysis demonstrates that the conc rete mixtures of the USER program subjected to a severe sulfate environment have expected times to failure of 19 to 89 years, depending on the concret e mixture proportions and the portland cement composition. Probability of f ailure increases with increasing exposure time, water-cement ratio (w/c), a nd C(3)A content although at different rates. Through the use of a probabil ity sensitivity analysis, it is found that uncertainty in the w/c is the mo st influential parameter in the reliability model; it is roughly twice as i mportant as exposure time. Also, the influence of w/c is roughly one order of magnitude larger than the influence of the C(3)A content for cements wit h a C(3)A content less than 8%.