Development of stabilisation and solidification in lime–clay mixes

Two refined clay minerals, English China Clay (predominantly kaolinite) and Wyoming Bentonite (predominantly sodium-montmorillonite), were used to assess the time-dependent effects of mineral structural chemistry on the lime–clay reaction. The two clays, representing the extremes of structural negative charge development, were treated with two lime contents. Changes in the physico-chemistry of the samples were monitored after three curing periods by performing batch leaching tests and 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 analysis of eight elements in solution. The solidification mechanisms due to lime addition were found to be different for the two minerals. Pozzolanic reactions involving English China Clay and Wyoming Bentonite were found to occur owing to the dissolution of aluminium 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. It was also shown that successful solidification could be monitored using simple conductivity measurements without the need for extensive and complex elemental analysis.