Enhancing shear behavior of class F fly ash using non-woven carry bags: a sustainable geotechnical solution

Fly ash, a byproduct of coal combustion in thermal power plants, is widely available globally, but its disposal poses significant environmental concerns. In recent years, there has been growing interest in identifying sustainable and cost-effective applications for fly ash (FA), particularly in geotechnical engineering. This research investigates the potential of using non-woven carry bags as a reinforcing material to improve the shear behavior of Class F fly ash. To explore this possibility as a sustainable geotechnical solution, this study examines the shear behavior of Class F FA reinforced with non-woven carry bags. Unconsolidated undrained tri-axial tests were conducted on specimens with varying confining pressures (100 kPa, 200 kPa, and 300 kPa) and dimensions of 100 mm diameter and 200 mm height. Unreinforced specimens were compared to those reinforced with 1, 2, and 3 layers of non-woven carry bags. The results indicate a remarkable 84% improvement in peak deviator stress for FA specimens incorporating non-woven carry bags compared to the unreinforced controls. Additionally, the successive addition of non-woven carry bag layers resulted in changes in cohesion (c) ranging from 44.9 kPa to 62.7 kPa and the angle of friction (φ) ranging from 27° to 37° compared to the unreinforced specimen. This study demonstrates the significant enhancement of shear performance in FA due to the incorporation of non-woven carry bags. Considering the abundance of fly ash as a waste product, this research offers valuable insights into sustainable practices in geotechnical engineering. Potential applications include stabilizing subgrades, countering lateral earth pressure in backfills, and ensuring slope stability in embankments.