Sulfate-Bearing Soils: Problems with Calcium-Based Stabilizers

Several roads, airfield pavements, and parking lots in Texas and other states in the western United States have suffered severe pavement damage due to expansive minerals formed from the reactions of calcium-based materials used to stabilize sulfate-bearing soils. Remediation costs for projects that suffer sulfate-induced heave damage are very high, because often the entire pavement may have to be removed and reconstructed. Observations from several projects are described to illustrate the phenomenon of sulfate-induced heave and the current methods to predict the problem. Two recent projects described include one using cement as a replacement for lime and a second using a double application of lime. The discussion also includes limitations of the present methods for determining the so-called soluble sulfate levels in soils. The practice of a double application of lime and several other alternative methods and their limitations are discussed. Although research has clearly identified the expansive minerals as being calcium bearing, no published investigations of non-calcium-based stabilizers that could effectively stabilize sulfate-bearing soils were found.