Alternative Explanation of “Lime-Induced Heave”

Lime-induced heave is a process whereby calcium from lime chemically reacts with sulfates within the soil, producing expansive minerals which result in expansion of the limed layer causing surface heave. This paper presents a case study of subgrade heave and offers an alternative explanation of the mechanism causing heave other than development of expansive minerals. After final grading, the site was subject to heavy rainfall. Relatively uniformly-spaced ridges developed within the limed layer in less than 4 days. The study included physical inspection of the ridges, elevation surveys, field density and moisture content tests, Atterberg Limits, soluble sulfate tests, and x-ray diffraction. None of the characteristics generally attributed to development of heave-related minerals were observed. Approximately 4 months of dry weather preceded the heavy rainfall event. It is hypothesized that development of the observed ridges is associated with closing of shrinkage cracks in the native subgrade which resulted in lateral stress and shear failure within the stabilized layer.