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 Reclama tion over a 40+ year period of non-accelerated testing form the basis for t he model. In the nonaccelerated test program concrete cylinders were contin uouslly submerged at room temperature in 2.1% sodium sulfate solution which corresponds to severe field exposure conditions. Expansion measurements we re made periodically. Over 8000 expansion measurements were collected for 1 14 specimens cast from 51 different mixtures. Analysis of the data showed the significance of water-cement ratio (w/c) an d C(S)A content of the cement, with the data revealing distinct behavior fo r mixtures containing cements with low C(S)A content (<8%) and high C(S)A c ontent (>10%). As a result, two models are proposed to predict expansion by sulfate attack as a function of w/c, duration of exposure, and C(S)A conte nt. 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.