Expansive soils sensitivity to volumetric change is one of the well-known challenges in the field of geotechnical engineering. Various attempts have been made by researchers to solve this problem. Current research presents the effect of human hair fibers on the behavior of expensive soils. A reconstituted soil of 80% kaolin as raw material and 20% bentonite with different percentages of human hair (0%, 0.5%, 1%, 1.5% and 2%) was used. The microstructure of the formulations was characterized by studying the interactions between soil and human hair using scanning electron microscopy (SEM). The microstructure of the formulations was characterized by studying the interactions between soil and human hair using scanning electron microscopy (SEM). Atterberg limits, compaction characteristics, swelling parameters, compressibility and shear strength were also examined. The results of this study indicate that the inclusion of human hair fibers significantly improves the properties of the expansive soil mixture. These results open up new prospects for the stabilization of expansive soils.
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Biochar has been extensively studied in the aspect of amendment of compacted sandy/clayed soils, whereas its application as amendment in expansive soil is rare. Hydraulic and mechanical properties of biochar-amended expansive soil especially impacts of drying–wetting cycles have been rarely investigated. Aiming at construction of sponge city, straw biochar-amended expansive soil and the control soil (i.e., without biochar) are subjected to drying–wetting cycles in this study. During drying–wetting cycles, energy-dispersive spectrometer and Fourier transform infrared (FTIR) spectroscopy analyses were conducted to investigate microchemical composition including. Pore size distribution and microstructure were measured using nitrogen gas-adsorption technique and scanning electron microscope, respectively. Further, changes in soil water retention curve, void ratio, crack intensity factor (CIF, i.e., ratio of cracked section area to the total soil area) and shear strength were also determined. It is found that there is no diference in water retention capacity between various soils for near-saturated samples. Under high suction, however, more water could be retained within mesopores of biochar-amended soil. FTIR analysis indicates that biochar-amended expansive soil shows stronger chemical bonding, irrespective of them being subjected to drying–wetting cycles. The weak alkalinity of straw biochar results from its main chemical composition (i.e., calcium carbonate). It is noteworthy that straw biochar improves soil water retention capacity, which further restrains desiccation cracks. Cohesion of biochar–soil composite is also improved due to chemical bonding. Aiming at green roofs, straw biochar could be promising option for expansive soil amendment technically and economically.
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