Experimental Studies and Modeling of High-Sulfate Soil Stabilization

An experimental study was conducted to assess the effectiveness of lime stabilization with precompaction mellowing in stabilizing six different high-sulfate soils. Three mellowing times, 0, 3, and 7 days were studied. A test suite comprising engineering and chemical tests was performed on untreated and lime-treated high-sulfate soils. Four of the six soils considered in the research study responded positively to the lime stabilization with a precompaction mellowing period. Two soils with soluble sulfate levels exceeding 30,000 ppm were not successfully stabilized with the precompaction mellowing, resulting in the chemical treatments, and higher swell strain magnitudes. Two swell prediction methodologies were developed, one based on sulfate content consumed other based on compaction void ratio of the treated soils. Both methods rely on stoichiometric principles with mass-volume relationships of chemical reactions. Swell strains predicted by both methods were analyzed and compared with measured swell strains of all soils at different mellowing periods. Results showed that the sulfate content-based method predictions were not in agreement with the measured data, whereas the void ratio-based method provided better swell strain predictions. Better prediction by this method was attributed to accounting for ettringite crystal growth inside the void space of the treated soils. Potential implementation of this method to screen chemical treatments of high-sulfate soils for effective stabilization was described.