Laboratory Investigation on Fiber-Reinforced Expansive Subgrade Soil Stabilized with Alkali Activated Binder: A Reliability-Based Perspective

Expansive soil possesses inferior mechanical behavior with periodic variability in heave/shrink, causing distortion and premature failure to the pavement structures. In the present study, an attempt was made to strengthen the expansive subgrade soils by combining alkali-Activated binder (AAB) with naturally available hemp (HF) and banana fiber (BF). HF and BF were chemically treated (10M of KaOH) to improve their durability. The influences of varying dosages of fibers and slag in fiber-reinforced alkaline soil significantly improved California Bearing ratio (CBR) and flexural strength. Microstructural and morphological studies using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were also carried out to understand the behavior of HF and BF-AAB soil mixture at varying slag and fiber content. It was observed that HF-Alkaline soil achieved higher interfacial bonding with good interlocking density relative to BF-AAB soil. Furthermore, the uncertainties associated with subgrade strength in terms of CBR were expressed in the form of a reliability index (ß_CBR) using Monte Carlo simulation (MCS). The results showed that the optimum dosages of slag and fiber in the alkaline soil mixture were essential factors for regulating the linear shrinkage tensile crack and strengthening the stiffness of subgrade soil.