Long-Term Elastoviscoplastic Behavior of Fly Ash–Blended Indian Montmorillonite Clay in Oedometer Conditions

Abstract

The time-dependent behavior of soft and problematic soils is a major concern as constructional fill geomaterial. Several researchers have been utilizing different admixture to stabilize soft soil. In this study, fly ash (FA) has been used as an admixture to investigate the time-dependent behavior of Indian montmorillonitic clay (BC) by considering its elastic-viscoplastic behavior. A series of oedometer tests have been carried out on the test specimens at different FA contents. Microstructural arrangement of the BC–FA matrix was investigated using scanning electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy. The results indicate that the addition of FA increases the compression stiffness of the matrix and that the unloading–reloading index decrease continuously. Time-dependent parameters, that is, creep coefficient, swelling coefficient, and strain limit, are significantly reduced by the addition of FA. Results show that hydrated FA contents, which encounters BC soil, produce calcium silicate hydrate (C-S-H) gel due to pozzolanic reaction and form a dense BC–FA matrix. Microscopic study exhibits the contribution of specific minerals toward its elastic, plastic, and viscous behaviors. The results show that the constitutive elastic-viscoplastic model considering swelling (EVPS model) works well in predicting the long-term compressibility behavior of FA-blended soft soils.