Effect of Micronized Rubber Powder on High Plastic Clay Stabilized with Cement Kiln Dust

Author

Sanjan Bussu, Southern Illinois University CarbondaleFollow

Date of Award

8-1-2024

Degree Name

Master of Science

Department

Civil Engineering

First Advisor

Kolay, Prabir

Abstract

Cement Kiln Dust (CKD) and Micronized Rubber Powder (MRP) offer sustainable solutions for soil stabilization, addressing both environmental and engineering challenges. CKD, a byproduct of cement manufacturing, is rich in pozzolanic materials that can enhance clayey soil properties by reducing plasticity and increasing strength. This makes CKD a valuable additive for improving the load-bearing capacity and durability of clayey soils used in construction. MRP, derived from end-of-life tires, contributes to sustainability by recycling waste rubber and adding ductility to treated soils. The incorporation of rubber waste not only helps in reducing the environmental burden of tire disposal but also enhances the flexibility and resilience of the stabilized clayey soil. Utilizing these industrial by-products in soil stabilization not only mitigates waste disposal issues but also promotes the development of resilient and eco-friendly construction materials, making them highly beneficial for sustainable infrastructure projects.The present study investigates the effects of various mix proportions of CKD and MRP on Carbondale soil, a high plastic clay. The soil was stabilized with CKD in proportions of 7%, 14%, and 21%, and MRP in proportions of 0%, 2.5%, 5%, and 10% of the dry unit weight of clayey soil. Comprehensive laboratory tests were conducted, including particle size distribution, Atterberg limits, compaction characteristics using the miniature Proctor, unconfined compressive strength (UCS), ultrasonic pulse velocity (UPV), and resilient modulus (RM). The RM test assessed the soil's elasticity under repeated loading, simulating traffic conditions to evaluate the material's performance in pavement design. These tests aimed to determine the optimal mix proportions that would provide the best combination of strength, stiffness, and durability for use in various geotechnical applications. Results from different tests showed that the addition of MRP significantly altered the properties of the CKD-stabilized soil mix. The miniature Proctor test revealed that the addition of MRP reduced the maximum dry density (MDD) of the mix and slightly increased the optimum moisture content (OMC) of the soil mix, indicating a change in compaction characteristics. From the UCS test, it was observed that while the addition of 2.5% MRP to the CKD soil mix reduced the overall strength, it absorbed considerable amount of strain. Specifically, for soil mixed with 7% CKD, the inclusion of 2.5% MRP absorbed over 60% more strain, despite a 50% reduction in strength. Similarly, the mix with 21% CKD and 2.5% MRP showed a 30% increase in peak strain with a strength reduction of up to 40%. The resilient modulus values indicated that the addition of MRP to the soil mix resulted in strain softening, leading to decreased RM values. The soil mix with 7% CKD and 2.5% MRP showed almost no gain in RM values across all curing periods due to strain softening effects. However, the regression analysis between predicted and experimental RM values showed a positive correlation, with a coefficient of determination (R2) ranging from 0.7 to 0.96, indicating a reliable predictive model for RM based on the tested parameters. These findings highlight the trade-offs between strength and stiffness in CKD and MRP-stabilized soils, offering insights for optimizing soil stabilization techniques in sustainable construction practices