Abstract
Abstract Sulfate-induced heave has become an expensive problem in many states when expansive soils containing high levels of sulfate are stabilized with calcium based stabilizers such as lime or cement. Colorimetric assessment of soluble sulfate concentrations (SSC) is the most accepted indicator to predict the degree of risk associated with using chemical stabilization to treat expansive soils. Questions surrounding the effects of sulfate source, water to soil ratio, contact time, and separation methods were investigated. Samples of a soil from northeastern Ohio were spiked with ferrous sulfate heptahydrate (FeSO4·7H2O) to yield 300 and 3000mg sulfate/kg soil and with gypsum (CaSO4·2H2O) to yield 300, 3000, 6000, and 12 000mg sulfate/kg soil. Subsamples of the spiked soil were then mixed with water at a 1:20 ratio of soil:water, shaken, and allowed to rest from 12 to 24h. A sample of the soil solution from each mixture was obtained by four different methods and analyzed for sulfate by colorimetric method. There was no significant difference for the contact time used; however, a 24h contact time is recommended. Results of colorimetric testing indicated use of partial and full filtration provided the most accurate SSC readings.
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