Laboratory evaluation of sulfate heaving mechanisms in artificial illite and natural soils.

摘要

Chemical reactions between lime, sulfates, and free alumina in soils are known to form expansive minerals, ettringite and thaumasite, which in turn create heaving distress problems to the highway infrastructure. The theoretical heaving mechanisms have already been established. However, the influence of soil compositional and environmental factors on the heaving mechanisms still needs to be evaluated in laboratory conditions. Hence, laboratory research was designed and conducted on lime-treated artificial Illite and natural soils to understand the influence of soil and environmental factors on the heaving process.;Physical, engineering, chemical, and mineralogical tests were performed on thirty day cured soil samples. Mineralogical tests showed that ettringite and thaumasite were formed in soil. This formation was attributed to the reactions between soil, lime and sulfate levels. The lime treated sulfate rich Illite soil samples exhibited heave related movements. However, in the case of natural soils, the ettringite formation did not result in significant heaving. These differences are attributed to clay mineralogy, presence of amounts of free alumina and curing period. Overall, low temperature and high moisture content conditions resulted in more heaving in Illite soil than any other conditions. Further research directions are also discussed.