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Expansive soil is a source of risk to the foundations or subgrade engineering. Stabilization of expansive soil is imperative for practical engineering. A series of laboratory experiments were performed to analyze the physical-mechanical properties and microstructures of stabilized soil. Three stabilizers used in this study are fly ash, sand, and basalt fiber. Different percentages of fly ash (0, 5, 10, 15, and 20%), sand (0, 8, 16, and 24%), and basalt fiber (0 and 0.4%) were added by weight into natural soil. Experimental results indicate that the optimum moisture content of stabilized soil increases with the increase of fly ash content for a given sand content, whereas the maximum dry density shows a decreasing trend. The variation trend of optimum moisture content and maximum dry density turns reverse with the increase of sand content for a given fly ash content. Plasticity index is decreased by both increasing fly ash content and sand content. It is found that the maximum unconfined compressive strength and optimum growth rate of strength are obtained by selected mixtures of 10% fly ash, 8% sand, and 0.4% basalt fiber contents. As the analysis of complementary effect suggests, most of the mixt treatments applied in this study have produced good results associated with the strength enhancement of expansive soil. In line with the results of SEM tests, the connection among clay particles has been enhanced through the generation of hydration products (C-S-H and AFt) of fly ash. The filling effect of sand has increased the integrality and compactness of stabilized soil. Moreover, the gripping effect between fibers and soil particles notably improves the strength of stabilized soil. The effect of sand on reinforced soil with 0.4% basalt fiber increases the interfacial force between fibers and soil particles.

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Solid hydrogen storage and supply systems with high density in a hydrogen refueling station are the critical factor to realize large-scale application of hydrogen energy, and one of the biggest challenges is how to ameliorate the extremely large pressure hysteresis of Ce-rich rare-earth-based metal hydrides. In this work, two series of La–Ce–Ca–Ni–Co alloys with single CaCu5-type structure and uniformly distributed elements were prepared via induction levitation melting. With increasing Co content in La0.3Ce0.5Ca0.2Ni5–x Co x (x = 0, 0.5, 1.0, 1.5) alloys, a staged phase transformation occurs, contributing to a significant improvement in the pressure hysteresis without the monotonical sacrifice of dehydrogenation equilibrium pressure. An equilibrium-state thermal analysis method (ETA) is proposed and well verifies the thermodynamical phase transformation processes. Further first-principles calculations indicate that the enhanced charge synergy and increased charge transfer drive the conversion of staged phase transformation from dynamic to thermodynamically stable pathways. Thus, “dynamically staged phase transformation”, nominated as the dynamic realization of thermodynamic staged phase transformation, is more constructive for practical use. Consequently, the optimal composition of La0.25Ce0.55Ca0.2Ni4.5Co0.5 was developed with a saturated hydrogen storage capacity of 1.52 wt %, dehydrogenation equilibrium pressure of 10.68 MPa at 90 °C, and satisfactory cycling durability. The ETA method and composition design concept proposed in this work pave a convenient avenue for wider exploration of high-pressure hydrogen storage alloys.