Sulfate-bearing subgrade soils treated with calcium-based stabilizers often experience heaving problems (three-dimensional swell) caused by chemical reactions with the sulfate or sulfide minerals. Two research questions were addressed: ( a) what sulfate content results in deleterious chemical reactions using traditional (no mellowing) lime stabilization and ( b) how effective mellowing, double lime application and increased moisture content are at reducing swell in high-sulfate soils. To determine what concentrations of sulfate are too high for stabilization with lime in Texas, a soil from the Vertisol order was selected for three-dimensional swell measurements. This soil did not contain any detectable sulfates. Two different compounds were added to the soil: sodium sulfate (Na2SO4) and gypsum (CaSO4.2H2O). The sulfates were added to individual samples at concentrations of 0; 1,000; 2,000; 3,000; 5,000; 7,000; and 12,000 parts per million (ppm). The samples were then subjected to a three-dimensional swell test for a minimum of 45 days. Results of systematic swell experiments revealed that sulfate contents up to 3,000 ppm could safely be treated with traditional lime stabilization. Coarse-grained sulfates take longer to swell, but still swell and form deleterious reaction products. Mellowing is effective at treating sulfate concentrations up to at least 7,000 ppm, higher molding moisture contents (2% above optimum moisture) reduce swell better than optimum moisture, and single application of lime reduces swell better than double application. With systematic laboratory experiments, empirical field observations of sulfate limits presented by other investigators were confirmed.
Hydrated Lime Stabilization of Sulfate-Bearing Vertisols in Texas
Transportation Research Record
Transportation Research Record: Journal of the Transportation Research Board ; 1868 , 1 ; 31-39
2004-01-01
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
PART 1 - SOIL STABILIZATION - Hydrated Lime Stabilization of Sulfate-Bearing Vertisols in Texas
Online Contents | 2004
|Recommendations for Stabilization of High-Sulfate Soils in Texas
Transportation Research Record | 2006
|Experimental Cold In-Place Recycling with Hydrated Lime
Transportation Research Record | 1999
|Experimental Cold In-Place Recycling with Hydrated Lime
Online Contents | 1999
|