Experimental Investigation on the Strength and Deformation Aspects of Thixotropic Aging in Reconstituted Clays

Abstract

This study is aimed at comprehending the effect of thixotropic aging on strength and deformation response of natural clays reconstituted in the laboratory. Three clays have been collected and samples were prepared at a moisture content of corresponding liquid limits. Prepared soil specimens were subjected to a thixotropic aging (constant moisture, constant volume and constant temperature conditions) period of 7, 14, 21, 28, 35 and 42 days. Unconfined compressive strength and direct shear tests were performed to assess thixotropic strength recovery. Thereafter, one-dimensional consolidation tests were conducted on the thixotropically aged samples to assess the compressibility characteristics. Interpretation of the responses from unconfined compression test, direct shear test coupled with Scanning Electron Microscopy imaging analyses suggest that thixotropic strength recovery is dependent on activity, percentage of clay fraction, and initial grain structure. Thixotropic strength ratio obtained from unconfined compression test and direct shear test are noticed to be different, although the trend is similar. Interpretation of 1-D consolidation test data suggest that as the thixotropic aging period increased, samples tend to provide higher yield stress compared to the unaged samples. All the void ratio-effective vertical stress responses for the clays at different thixotropic aging periods tend to converge at a same void ratio at a consolidation stress of > 1000 kPa, indicating no effect of thixotropic structuration at high consolidation stresses. In addition, it was observed that thixotropically active clays swell more than the inactive clays during the thixotropic aging period. In addition, a proportional relationship between thixotropic strength ratio and plasticity index was also noticed.