可溶盐对水泥土强度影响的微观分析

Microstructural Analysis of Influence of Soluble Ions on Strength of Cemented Soil

为深入认识连云港地区软土中的易溶盐对水泥土搅拌桩桩身质量的影响,通过无侧限强度试验和扫描电子显微镜(SEM)及X-射线衍射试验研究方法,研究高含盐量特征对水泥土强度影响的内在原因。结果表明:Mg2+、Cl-、SO42-都对水泥土强度起了不同程度的负面作用,其中Cl-对早期和长期强度都有影响;Mg2+从中期开始发挥作用;SO42-则对水泥土长期强度影响较大。滨海地区软土及地下水中较多的Cl-,会与水泥成分和水化产物Ca(OH)2反应,一种强度较低的生成物会包裹在粘土颗粒表面,阻碍了水泥土的强度增长。当软土中含有较多SO42-时,大量钙矾石晶体的生成会使水泥土膨胀而变得疏松,从而使水泥土的长期强度变低。

For deeply understanding the influence of the soluble saline contained in the soft soil on the quality of cement treated soil piles in Lianyungang area, the unconfined compression test, scanning electron microscope （SEM） and X-ray diffraction （XRD） method were applied to explore the inherent reasons of the influences exerted by high salt content of soft soil on the strength of cement treated soil.The results indicate that, the ions Mg^2＋ , Cl^- and SO4^2- all have negative influence on the strength of cement treated soil; of these three ions, Cl^- affects the strength of cemented soils either at early date and long period of curing; Mg^2＋ mainly affects the 28d strength and SO4^2- impacts the long term strength of cement treated soils; rich Cl^- content in the soft soils and groundwater in the littoral area can react with some cement ingredient and hydration product, an outcome with low strength is formed and encapsulates the clay particles to hinder the strength increase of cement treated soil; while rich SO4^2- is contained in soft soil, large amount of ettringite crystal generated can cause cement treated soil to expand, the cement soil structure becomes loose, so the long term strength of cement treated soil becomes lower.