混凝土外加剂改性软土及其机理研究

发布时间：2018-02-24 00:20

本文关键词： 软土混凝土外加剂力学性能变形水稳定性　出处：《重庆大学》2015年硕士论文　论文类型：学位论文

【摘要】：软土作为一种特殊土,在我国分布十分广泛,它具有低强度、较差的透水性、较大的压缩量等不良的工程性质。因此,在软土地区修筑道路时,对软土进行处理是一项必须解决的技术难题。利用土壤固化剂对软土进行改性是一种常见的处理方法,而目前应用最广泛的仍是石灰、水泥这类固化剂,其取得一定成效的同时也出现一些弊端。混凝土外加剂大多为离子型表面活性剂且具有很好的分散性,在混凝土的施工过程中得到广泛应用,但利用混凝土外加剂的特性将其用到土壤固化中的研究还十分欠缺。为了探究混凝土外加剂对软土改良的效果和机理,本文选取了三种混凝土外加剂并研究了其对性软土力学性能、变形以及水稳定性的影响,同时也初步探索了对石灰土、水泥土再次改性的影响。最后,文章借鉴已有的固化剂的固化机理、外加剂的作用原理以及粘土颗粒的特性并结合微观试验来分析外加剂改性软土的机理。试验结果表明:缓凝高效减水剂、萘系高效减水剂和引气剂在适宜的掺量下能有效的提高软土的无侧限抗压强度和抗剪强度、减小软土的变形以及改善软土的水稳定性;缓凝高效减水剂和萘系高效减水剂分别与石灰一起改性软土要比石灰单独改性软土的无侧限抗压强度要高,且对水稳定性稍有改善效果;萘系高效减水剂作为水泥土添加剂时,其与水泥添加的顺序会对改性效果产生很大的影响,当先添加水泥拌合均匀闷料一段时间后再加入萘系高效减水剂时,软土的无侧限抗压强度会进一步提高。通过微观试验分析,外加剂能改变软土的结构排列,使其更密实,采用缓凝高效减水剂和萘系高效减水剂改性时,能在土粒表面生成胶结物;引气剂改性后土粒呈互相交错的较为密实的空间结构,其间可见细小的封闭孔隙;外加剂利于石灰改性土和水泥改性土中水化产物的生成,且使其分布更均匀,从而进一步提高改性效果;从CT扫描结果分析,外加剂能一定程度上优化土体内孔隙结构和分布,进而改善土体的性能。
[Abstract]:As a special soil, soft soil is widely distributed in our country. It has poor engineering properties such as low strength, poor permeability and large compression. The treatment of soft soil is a technical problem that must be solved. It is a common treatment method to use soil curing agent to modify soft soil, but at present, the most widely used curing agent is lime and cement. The concrete admixtures are mostly ionic surfactants and have good dispersity, so they are widely used in the construction of concrete. However, the study on the application of concrete admixture to soil solidification is still lacking. In order to explore the effect and mechanism of concrete admixture on soft soil improvement, In this paper, three kinds of concrete admixtures are selected and their effects on mechanical properties, deformation and water stability of soft soil are studied. In this paper, the mechanism of modified soft soil is analyzed by reference to the curing mechanism of the existing curing agent, the action principle of admixture and the characteristics of clay particles. The experimental results show that the retarding and high efficiency water reducing agent can be used to modify the soft soil. Naphthalene superplasticizer and air-entraining agent can effectively improve the unconfined compressive strength and shear strength of soft soil, reduce the deformation of soft soil and improve the water stability of soft soil. The retarding superplasticizer and naphthalene superplasticizer modified soft soil together with lime have higher unconfined compressive strength than that of lime alone modified soft soil, and have a slight effect on improving water stability, and when naphthalene superplasticizer is used as cement soil additive, The order in which the cement and the cement are added will have a great influence on the modification effect. When the cement is added to the cement for a period of time and then the naphthalene superplasticizer is added, The unconfined compressive strength of soft soil will be further improved. Through microscopic test and analysis, it is found that the admixture can change the structure of soft soil and make it more dense. When modified with retarding and high efficiency water reducer and naphthalene series superplasticizer, Cement can be formed on the surface of soil particles; the particles of air-entrainer modified soil are interlaced with each other with relatively dense space structure, in which small closed pores are observed; admixtures are conducive to the formation of hydration products in lime modified soil and cement modified soil, and the formation of hydration products in lime modified soil and cement modified soil is beneficial to the formation of hydration products. The results of CT scan show that the admixture can optimize the pore structure and distribution of soil to a certain extent and then improve the properties of soil.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U416

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