水泥改性强膨胀土理化试验研究

膨胀土是一种特殊的黏性土,具有遇水膨胀、崩解、软化,失水收缩、干裂、硬化等工程特性,膨胀土掺入水泥后其工程特性会发生改良.选取南水北调工程中河北邯郸地区的强膨胀土,在较长的养护龄期内,进行了水泥改性的试验研究.主要进行了基本物理性质试验、自由膨胀率试验、矿物分析试验、XRD和SEM显微结构试验和阳离子交换量试验,从不同角度说明了不同龄期下水泥改性强膨胀土的物理化学特性、矿物组成和微观结构的变化,分析了水泥改性膨胀土的机理.发现阳离子交换量不能作为判断水泥改性后膨胀土膨胀性能的有效指标,为膨胀土现场水泥改性的设计施工提供了科学的、有价值的依据.

Physical-chemical experimental investigation on cement-treated highly expansive soil

The expansive soil is a special type of clay with the engineering properties of swelling, disintegrating and softening when absorbing water and shrinkaging, desiccating and hardening when losing water. The engineering properties of expansive soil can be improved when treated with cement. The highly expansive soil in South-to-North Water Diversion Project was selected from Handan region, Hebei Province. A series of tests on the cement-treated Handan clay were carried out, mainly including the basic physical-chemical properties test, free swelling ratio test, mineralogy analysis and microstructure test by XRD, SEM test and cation exchange capacity test at different curing time over a long curing time. From different aspects, the variations of physical-chemical properties, mineralogy composite and microstructure were analyzed, and the mechanisms of cement treatment on highly expansive soil were discussed. Experimental results show that it is not reasonable to use cation exchange capacity to evaluate the swelling potential of cement-treated expansive soil. These results provide a scientific and valuable basis for design and construction of cement treatment on highly expansive soil.