Stabilization of Expansive Soil Using High-Calcium Fly Ash, Lime, and Basalt Fiber Blends
摘要
Expansive soils pose significant geotechnical challenges due to their tendency to undergo substantial swelling and shrinkage in response to variations in moisture, leading to ground movement, cracking, and structural instability. This study examines the effectiveness of a ternary stabilizing blend comprising high-calcium fly ash (HCFA), lime (L), and basalt fiber (BF) in enhancing the physical, mechanical, and volumetric properties of expansive soils. Laboratory tests, including plasticity, unconfined compressive strength (UCS), shrink-swell consolidation test, chemical and microstructural analysis, were performed on treated samples at various additive dosages and curing durations (7 and 28 days). The results show that the optimal mix of 25% HCFA, 5% lime, and 0.2% BF achieved an 80% reduction in plasticity index and significantly suppressed swelling behavior. UCS increased to 1085.35 kPa after 28 days, while peak strain energy reached 12.21 kJ/m3, indicating enhanced strength and ductility. Chemical analyses confirmed increased calcium ion availability and the formation of cementitious compounds such as calcium silicate hydrate (C–S–H) and calcium aluminate hydrate (C–A–H) via pozzolanic reactions. This transformation led to a reduction in the secondary compression index (Cα) from 0.1413 to 0.0582 and a 62.77% decrease in settlement (Sc), reflecting improved soil stiffness and load-bearing capacity. Secondary consolidation was also significantly reduced, attributed to void ratio reduction and stronger interparticle bonding. Microstructural observations confirmed the development of denser, more coherent matrices. Overall, the HCFA-L-BF treatment effectively mitigates expansive soil behavior and enhances long-term performance, offering a cost-effective and sustainable stabilization approach suitable for subgrades, foundations, and pavement systems in regions with problematic soils.