水泥-碱渣改良膨胀土干湿循环耐久性及其劣化机制试验研究

通过系统的室内试验对水泥-碱渣改良膨胀土的工程性质及其干湿循环耐久性进行评价，并通过微观测试技术分析了改良机理以及干湿循环劣化机制。结果表明，经水泥-碱渣改良后，膨胀土的液限、塑性指数和自由膨胀率明显减小，无侧限抗压强度显著增大；降低水泥-碱渣质量比引起的工程性质劣化可归因于复合型化合物CaO·SiO₂·CaCO₃·nH₂O的胶凝性能比典型水化胶凝产物弱。干湿循环初期，试样宏观形貌及无侧限抗压强度无明显变化；随着干湿循环次数的增加，试样强度明显减小，其宏观破坏特征表现为剥落。干湿循环作用下，改良土的微观劣化作用机制在于水化胶凝产物对土颗粒或团聚体的胶结作用遭到破坏，以及微裂缝的发育及扩张。

Durability and deterioration mechanisms of the cement-soda residue treated expansive soils subjected to drying-wetting cycles

An evaluation on the engineering properties and cyclic drying-wetting durability of the cement-soda residue treated expansive soils was carried out depending on the systematic laboratory tests in this paper. Some microscopic technologies were applied to reveal the modification mechanisms associated with the treated soils, as well as the deterioration mechanisms subjected to drying-wetting cycles. Results show that liquid limit, plasticity index and free swelling index of the expansive soil decrease obviously with addition of cement-soda residue, while the unconfined compressive strength increases significantly. Decreasing the mass ratio of cement to soda residue causes some deterioration of engineering properties due to the formation of a complex (CaO?SiO2?CaCO3?nH2O) with a low bonding capacity. During the initial period of drying-wetting cycles, there is no obvious changes in the macro-morphology and strength of the treated samples. With the cycles of drying-wetting increasing, the soil strength decreases significantly, and the macro-morphology is characterized as spalling. Under cyclic drying-wetting conditions, the deterioration mechanisms of the treated soil can be attributed to the damage of bonding structures formed by hydrated cementitious products and the generation of micro-cracks and further expansion.