Stabilization of Expansive Soil Reinforced with Polypropylene and Glass Fiber in Cement and Alkali Activated Binder
Expansive black cotton soil (BCS) exhibits dual nature (swelling/shrinkage) predominantly when it is exposed to moisture fluctuation. This behavior renders the BCS unsuitable for use in geoengineering applications. The present study emphasizes the polypropylene and glass fiber based soil reinforcement with a traditional cement binder and envirosafe alkali-activated binders (AAB). Cement stabilization is one of the most popular methods for reducing swelling properties of BCS. However, the production of cement leads to the emission of greenhouse gases, which is a threat to modern society. Hence the present study aims to compare the geomechanical strength between AAB and cement binder with inclusions of various discrete fibers. AAB is generated by the reaction between an aluminosilicate precursor (Fly ash and/or GGBS) and an alkali activator solution of sodium hydroxide and sodium silicate. The water to solids ratio is maintained at 0.4 in the present study. Mineralogical and microstructural characterization are performed for both cement and AAB treated BCS as well as untreated BCS through stereomicroscope, X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), and energy dispersive x-ray spectroscopy (EDS). The unconfined compressive strength (UCS), indirect tensile strength (ITS), California Bearing Ratio (CBR) and consolidation characteristics of both untreated and binder treated BCS are carried out at different combinations of cement-fiber and AAB-fiber in the clay. It is observed that the proposed treatment method shows a significant improvement in geoengineering properties and aids in enhancing the shear strength and ductility properties. An addition of 5% AAB with 0.3% of polypropylene fiber reduces the plasticity and swelling pressure by 17–25%, while CBR and ITS values are increased by 28–33%. Recommendations on the practical implementation of this technique for stabilization of expansive soils are proposed based on findings of the present study.
KeywordsStabilization of expansive soil Alkali Activated Binder Geotechnical characterization Fiber Microstructural analysis
The authors would like to express their sincere gratitude to the Central Analytical Laboratory Facilities at BITS-Pilani, Hyderabad Campus for providing the setup for the XRD, FTIR, and SEM-EDS analyses.
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