Effect of Fiber Reinforcement on Mechanical Behavior of Alkali-Activated Binder-Treated Expansive Soil: Reliability-Based Approach

Expansive black cotton soil (BCS) exhibits volumetric instability when exposed to moisture fluctuation, rendering loss of geomechanical strength. The present paper evaluates the effectiveness of stabilizing BCS with two different types of fibers, polypropylene (PF) and glass fiber (GF), in conjunction with envirosafe alkali-Activated binder (AAB) at different proportions of fly ash and slag in alkaline mixture. AAB is produced by blending an alkali-Activator solution of sodium silicate and sodium hydroxide with aluminosilicate precursors (Class-F fly ash/slag) at 0.4 water to solid (w/s) ratio. PF and GF are varied from 0% to 0.4% with 5% AAB in BCS. Unconfined compression strength (UCS), indirect tensile strength (ITS), and California bearing ratio (CBR) tests are carried out as performance indicators of geomechanical strength of both fiber-reinforced AAB treated BCS. The research also focuses on proposing an optimum dosage of fly ash-slag ratio and fiber reinforcement in AAB-BCS. Monte Carlo Simulation is used to determine the reliability index for each case. The influences of varying dosages of fibers and fly ash-slag proportions in BCS show a significant improvement in shear strength and tensile properties. The reliability analysis also shows that the amount of fibers and fly ash-slag proportions are essential factors in UCS, ITS, and CBR strength for both PF and GF reinforcement.