EFFECT OF SULFATE CONTENT ON CLAY CHARACTERISTICS OF LOESS

Clay is the main component of loess particle group, and also the most active part of loess activity. The addition of salt makes the agglomeration and physical and mechanical properties of clay in loess obviously different, which also means that salt content plays a dominant role in many factors affecting aggregation. Loess was taken as the research object. The influence and mechanism of salt on the aggregation of clay particles in loess was studied. The loess salted soil was taken as the research object to study the influence and mechanism of salt on the aggregation of clay particles in loess. In this paper, the artificial sulfate saline soils with different mass ratios(0, 0.3%, 0.5%, 3%, 5.0%, 8.0%) were prepared on the basis of salt washing. Based on the grain size analysis and Atterberg limits tests, the macroscopic token of sulfate on the aggregation of clay particles was studied. Based on the compaction test, the microstructure and physicochemical mechanisms of the aggregation of clay particles were studied by combining XRD, SEM, EDS and BET. The results show that with the increase of salt content, the content of clay decreases, the liquid limit and plasticity index decrease, and the plasticity limit remains unchanged. When the salt content is more than 0.3%(saline soil stage), with the increase of salt content, too much sodium sulfate can not be dissolved and precipitated in the form of crystal. The precipitated crystal further absorbs water molecules and finally forms mirabilite crystal, the volume can increase sharply, resulting in the decrease of the maximum dry density, and the strong hydration can increase the optimum water content. Due to the agglomeration of sulfate on clay, when the salt content increases, the diffraction peak of sodium sulfate crystal is enhanced, the content of aggregate increases, and the specific surface area decreases, and compressing and thinning the diffusion layer, which leads to a decrease in the liquid limit and plasticity index.