Author(s): Hiroshi Takemura, Ayaka Fujimoto and Kenji Morikawa

Abstract: Expansive soils, known for their high shrink-swell potential, pose significant geotechnical challenges that threaten the stability and longevity of civil structures. This study investigates the stabilization of expansive soils using nano-additives specifically nano-silica (NS), nano-alumina (NA), and nano-clay (NC) with a focus on assessing their influence on strength and durability characteristics. The experimental program involved varying nano-additive dosages (0.5%, 1.0%, and 2.0% by dry soil weight) and evaluating unconfined compressive strength (UCS), wetting-drying (W-D) and freeze-thaw (F-T) durability, and microstructural properties through SEM and XRD analyses. Statistical analysis (ANOVA) confirmed the significant improvement in UCS and durability indices with nano-additive inclusion, particularly for nano-silica, which resulted in up to a 95% improvement in strength compared with untreated soil. After 12 W-D cycles, nano-silica-treated samples retained approximately 80% of their initial strength, demonstrating superior resistance to moisture-induced degradation. Microstructural observations revealed denser matrices, reduced pore connectivity, and the formation of C-S-H and C-A-S-H gels responsible for enhanced interparticle bonding. These findings substantiate the hypothesis that low-dosage nano-additives can achieve substantial strength and durability enhancement, minimizing the environmental and economic drawbacks of traditional stabilizers. The study concludes that nano-silica, due to its high surface activity and pozzolanic reactivity, is the most effective nano-additive for expansive soil stabilization. Practical implementation recommendations include maintaining optimum moisture content during mixing, curing for at least 14-28 days to ensure complete reaction, and adopting dosage ranges between 1.0% and 1.5% for maximum efficiency. The integration of nanotechnology into soil stabilization practices represents a promising step toward sustainable, durable, and cost-effective geotechnical engineering solutions, paving the way for its inclusion in future design standards and large-scale infrastructural applications.

Pages: 31-35 | Views: 3 | Downloads: 2

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