Database of Sulfate Stabilization Projects in Texas

Highways in Texas are now constructed much more rapidly than they were 20 years ago. During this same time period, there has also been an increase in the number of pavement failures in Texas attributed to a phenomenon called sulfate-induced heave. As part of Research Project 0-4240, a database of pavement failures due to sulfate-induced heave problems was developed. The researchers traveled across the state in search of pavement failures due to sulfate stabilization problems with calcium-based stabilizers. All of the projects discussed in this report were verified by the researchers as being caused by sulfate-induced heave. This report details eight case studies located in nine counties spread across the state of Texas. Many failures that had previously been attributed to improper stabilization of expansive sub grades can now be classified as sulfate heave problems. Comments from the Texas Department of Transportation (TxDOT) inspectors and construction engineers like "roller coaster roads" and "diamonds sparkling on the hillside" were commonly applied to these areas. Geologic maps, available in a Geographic Information Systems (GIS) format, indicated the presence of sulfates on 75% of the projects discussed in this report. Two alternatives to lime and cement were evaluated on three soils containing sulfates in excess of 20,000 ppm. An acid stabilizer showed improvement in strength but did not reduce swell over the long term. A mixture of ground granulated blast furnace slag and lime increased strength and reduced swell in all high sulfate soils tested.