In Situ Monitoring of Lime-Stabilized Road Subgrade

Abstract

Two refined clay minerals, English China Clay (predominantly kaolinite) and Wyoming Bentonite (predominantly sodium montmorillonite), were used to develop a method for assessing the time-dependent physicochemical behavior of lime-treated clay subgrade. The two clays, representing the extremes of structural negative charge development, were treated with two lime contents. Changes in the physicochemistry of the samples were monitored after three curing periods by performing batch leaching tests and by monitoring changes in undrained shear strength and Atterberg limits. The effects of changing the batch test operating parameters and increasing the curing period were assessed by measuring changes in solution pH and conductivity and by analyzing eight elements in solution. The solidification mechanisms caused by lime addition were found to be different for the two minerals. Pozzolanic reactions involving English China Clay and Wyoming Bentonite occurred because of the dissolution of aluminum and silicon from the respective mineral. Development of the batch leaching test showed that changing the operational parameters had no effect on the observed trends associated with the time-dependent modification and solidification reactions. In addition, it was shown that successful solidification could be monitored using simple conductivity measurements without the need for extensive and complex elemental analysis.