Correlation of Results from Freeze-Thaw and Vacuum Saturation Testing of Cement-Treated Base and Subgrade Materials

Abstract

The purpose of this research was to better establish a correlation between the results of freeze-thaw and vacuum saturation durability tests, with particular respect to mass loss in the freeze-thaw test, for cement-treated base and subgrade materials. Seven materials were used in the laboratory testing, including five aggregate base materials and two subgrade soils. Materials were stabilized with various cement contents and subjected to three different performance tests, including the standard freeze-thaw test, the standard 7-day unconfined compressive strength (UCS) test, and the vacuum saturation test. Correlations between the results of these tests were investigated, with the primary measure of durability being the rate of mass loss. The correlation between freeze-thaw mass loss rate and the baseline UCS had an R2 value of 0.87, and the correlation between freeze-thaw mass loss rate and the UCS after vacuum saturation had an R2 value of 0.89. In both cases, increasing UCS was associated with decreasing mass loss. Corresponding to the threshold of 14 percent mass loss in the freeze-thaw test, values for baseline UCS and UCS after vacuum saturation were determined at confidence levels of 70, 80, and 90 percent, and the resulting values are recommended for design purposes. The researchers recommend UCS testing after vacuum saturation as a viable alternative to the freeze-thaw test. The standard 7-day UCS test could also be used but may yield false positives for some materials, as shown in this study. The correlation between baseline UCS and UCS after vacuum saturation is strong, with an R2 value of 0.92; on average, the UCS after vacuum saturation was 90 percent of the standard UCS in this study. Other correlations with freeze-thaw mass loss rate were not as strong.