Effective stabilization of expansive soils requires chemical reactions, beginning with surface modification (SM) of clay particles, followed by proper pozzolanic reactions (PR). These reactions are achieved by adding appropriate lime content and further enhanced by the incorporation of amorphous silica-rich pozzolanic materials such as rice husk ash (RHA). Before field application, it is essential to evaluate and confirm the occurrence of these reactions and optimize the stabilizer contents to ensure reliable and durable performance. However, this remains a challenge due to the complex mineralogy of natural expansive soils, variability in pozzolanic material chemistry, and limitations of conventional evaluation methods. To address these challenges, the present study proposes a simple laboratory evaluation method using batch test with electrical conductivity (EC) measurement. This method enables determining the optimum lime content (OLC) by identifying the point at which lime becomes available for PR after initial SM. RHA is then incorporated at OLC to enhance pozzolanic activity. Lime consumption and the extent of chemical reactions were confirmed by EC measurement. The study considered four degrees of soil expansivity to represent mineralogical variability. Strength gains were assessed using unconfined compressive strength tests at 7 and 28 days of curing, while durability was evaluated by comparing soaked and unsoaked strengths. This laboratory-based evaluation method offers a technically reliable and versatile approach for optimizing lime stabilization of expansive soils, serving as an effective alternative to conventional measurement techniques for preliminary assessment before field application and mix design. Soil treated using this optimization approach exhibits enhanced stabilization performance and durability. Further, incorporating RHA at the OLC achieves strength gains comparable to those obtained with higher lime dosages. The applicability of lime stabilization supplemented with RHA has been demonstrated across different degrees of expansive soils, ensuring both effective stabilization and durability.
Chandru et al. (Thu,) studied this question.