Sustainable Stabilization of Reinforced Polymerized Subgrade Under Cyclic Loading

The functionality of pavement structure is significantly influenced by the subgrade properties. The saturation and desaturation of in-situ expansive subgrade contributes to pavement deteriorate through desiccation crack. To reduce these cracks, an expansive subgrade was polymerized and reinforced with sisal fibre, due to its promising prospect in pavement construction. This study investigated the cyclic crack restriction of polymerized expansive subgrade reinforced with 0.25%, 0.5%, 0.75%, and 1% of 30 mm sisal fibre. A series of zero swelling tests and resilient modulus tests were performed to explore the interactive effects of the polymer binder and sisal fibre on the expansive subgrade. The result revealed that the swelling stress of the expansive subgrade linearly decreases as the fibre content increases. Additionally, the resilient modulus of the treated subgrade increased as the fibre contents increases from 0% to 0.75% beyond which resilient strength decreased. The linear relationship between the increasing fibre content and the geopolymer binder mobilized the crack restrictions even at high cyclic stress and strain energy as the resilient modulus of the fabricated specimens increased. The test results confirmed that the polymer and clay minerals in the subgrade have a linear proportionality due to a complete polymerization reaction, as observed within the matrix of the fabricated specimens. The investigation confirmed that the coupling effects of geopolymer binder and sisal fibre significantly restricted cyclic cracks with an 88.1% decrease and 71.2% increase in swelling stress and resilient modulus, respectively. Whereas unreinforced polymerized subgrade failed to restrict the cracks at high cyclic stress and strain energy.