Shear Strength and Excess Pore Water Pressure Response of Fiber-Reinforced Class F Fly Ash

This experimental study focuses on the shear strength and excess pore water pressure response of class F fly ash reinforced with four different types of fibers. The fly ash was mixed with commercially available synthetic fibers, such as Polypropylene straight fibers (PPF), Polypropylene mesh fibers (PPMF), Nylon straight fibers (NF), and Polyester straight fibers (PEF). A series of unconfined compression (UC) tests and consolidated undrained (CU) triaxial tests were performed to evaluate the shear strength of fiber-reinforced class F fly ash. Further, the effect of different fibers on effective stress ratio and maximum angle of obliquity was also evaluated. It was found that PEF reinforced fly ash showed the highest UC strength and maximum deviatoric stress in CU triaxial tests as compared to other fibers. Except for PPMF reinforced specimens, all the specimens exhibited higher post-peak strength than the unreinforced fly ash specimen. The fiber reinforced fly ash specimens exhibited failure at larger strain levels as compared to unreinforced fly ash. The excess pore water pressure response of fiber reinforced fly ash showed more dilative behavior and larger obliquity as compared to unreinforced specimens. PEF reinforced fly ash specimens showed higher obliquity as compared to unreinforced fly ash.