Sulfate rich soils, when stabilized with lime or cement for subgrade improvements, are known to form a crystalline mineral, ettringite. This mineral exhibits significant swelling due to moisture hydration and crystal growth. This swell causes distress to highways, runways and other infrastructure built on lime or cement treated sulfate soils. Sulfate heave mechanisms in lime and cement treated soils are still in hypothetical stages since it is often difficult to explain exact causes of sulfate heaving mechanisms, i.e. due to crystal growth or ettringite hydration or both. Better understanding of these mechanisms can be explained by studying the soil chemistry variations of various constituents during early phases of stabilizer reactions. This paper presents these results from a research study, which was conducted to understand heaving mechanisms in lime and cement treated soils. Soluble sulfate, pH conditions, reactive alumina measurements in all treated soils were made before and after moisture soaking. These results were used to understand sulfate heave related ettringite mineral formation in both treated soils. Conditions that lead to excessive ettringite formation in the treated soils are explained, which were supported by the larger swell strain results measured at those conditions.