Assessment of lime treatment of expansive clays with different mineralogy at low and high temperatures

Abstract

This paper examines the impacts of clay mineralogy on the effectiveness of lime stabilisation at different temperatures. A comprehensive experimental programme was conducted to track down the evolution of lime-clay reactions and their durations through monitoring the evolution of strength gain at predetermined times using the Unconfined Compressive Strength (UCS) test. The study examined clays with different mineralogy compositions comprising Na+ Bentonite and Ball (Kaolinite) clay. Four different clays were tested including 100% bentonite, 100% Ball clay and two clay mixtures with ratios of 1:1 and 1:3 by mass of bentonite to Ball clay. All clays were treated using a range of lime content up to 25% and cured for a period of time up to 672 h at two different temperatures of 20 and 40 °C. The results showed that the continuity of the fast phase (stage 1) of strength gain was dependent on the availability of lime in particular at the higher temperature. Whereas, for the same lime content, the duration of the fast phase and the kinetic of strength gain were significantly related to the clay mineralogy and curing temperature. Except for the initial strength gain at 0 h curing time, the lime-treated Ball clay specimens at 20 °C appeared to show no strength gain throughout the curing period that extended up to 672 h. However, when curing occurred at 40 °C, the no strength gain stage only lasted for 72 h after which a gradual increase in the strength was observed over the remaining curing period of time. The addition of Bentonite to Ball clay succeeded in kicking off the strength gain after a short period of curing time at both curing temperatures.