Chemical Stabilization of Expansive Shale Using Natural Bagasse Fibers: A Case Study from Qena Area, Egypt

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HE geotechnical performance of natural sugarcane bagasse fibers mixtures was investigated during chemical stabilization process of Dakhla expansive shale. Compositionally, Dakhla expansive shale, exposed at El-Mahrowsa, Qena, consists mainly of smectite, kaolinite, quartz, calcite, and anhydrite. These mineral associations are reflected by 36.83 wt.% SiO2, 16.76 wt.% Al2O3, 28.59 wt.% CaO, and 6.99 wt.% SO3. Geotechnically, the natural compacted shale without bagasse fibers addition exhibited 88 Kpa compressive strength, 35 Kpa tensile strength, and 450 m/s ultrasonic velocity. The free swelling percent of natural expansive shale is 73 %. During the chemical stabilization process, mixtures of natural bagasse fibers (1 %) were thoroughly homogenized and compacted with expansive shale. These mixtures were cured at 7, 28, and 90 days under room temperature and 100 % humidity. The geotechnical performance of these mixtures was evaluated using measurement of unconfined compressive strength, tensile strength, longitudinal ultrasonic velocity, and free swelling percent. The overall results indicate that the application of natural bagasse fibers (1 %) is useful to improve the geotechnical behaviour of the expansive shale at 7 days curing time (e.g. compressive strength increased from 88 to 310 Kpa, tensile strength increased from 35 to 130 Kpa, and ultrasonic velocity increased from 450 to 541 m/s). Unfortunately, the geotechnical properties of the treated expansive shale using natural bagasse fibers including unconfined compressive strength, tension strength, and ultrasonic velocity do not improve with increasing curing time from 7 to 90 days. Free swelling percent reduces very slightly with increasing curing time from 7 to 90 days.