Empirical models to predict concrete expansion caused by sulfate attack

The development of empirical models to predict concrete expansion produced by sulfate attack is described. Data collected by the U.S. Bureau of Reclamation over a 40+ year period of non-accelerated testing form the basis for the model. In the nonaccelerated test program, concrete cylinders -were continuously submerged at room temperature in 2.1% sodium sulfate solution, which corresponds to severe field exposure conditions. Expansion measurements were made periodically. Over 8000 expansion measurements were collected for 114 specimens cast from 51 different mixtures. Analysis of the data showed the significance of water-cement ratio (w/c) and C₃A content of the cement, with the data revealing distinct behavior for mixtures containing cements with low C₃A content (< 8%) and high C₃A content (> 10%). As a result, two models are proposed to predict expansion by sulfate attack as a function of\\/c, duration of exposure, and C₃A content. The random effects method was used to capture unobserved heterogeneity in the data set, and the results from a simple regression and a regression including the random effects method are compared.