Gypsiferous soils are not widely used as construction materials due to the unreliable behavior when water exists. Previous studies in these soils showed that dissolution problems in embankments and slopes were associated with gypsum, which may cause a shear strength reduction. This paper aimed to determine the strength properties of gypsiferous soils and evaluate whether the improvement of soil strength occurs after stabilization with class C fly ash. In order to understand the strength properties of gypsiferous soils, a laboratory testing program was conducted on gypsiferous soil samples collected from two different locations along the existing highway US 62/180 near the Texas/New Mexico state line. The laboratory testing includes Proctor compaction test, unconfined compression test, moisture determination, percentage of hydration determination and mineral trace analysis. From this laboratory testing program, a relationship was obtained between strength and moisture conditions for gypsiferous soils before and after stabilization with class C fly ash. Results indicate that the strength of gypsiferous soils are significantly influenced by moisture conditions. Furthermore, the addition of class C fly ash can improve the strength of gypsiferous soils.
Abstract