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类型 基础研究 预答辩日期 2018-03-27
开始(开题)日期 2014-12-18 论文结束日期 2017-08-31
地点 东南大学 榴园宾馆会议室 论文选题来源 国家自然科学基金项目     论文字数 9.1 (万字)
题目 水泥-乳化沥青交互作用及其机理研究
主题词 水泥,乳化沥青,水化,破乳,流变
摘要 作为高速铁路无砟轨道的关键工程材料,水泥-乳化沥青砂浆主要是灌注在无砟轨道的混凝土底座和轨道板之间的狭长结构内,起到减振的作用效果,从而保证了高速列车(时速大于250km)的安全平稳运行。作为一种灌注材料,水泥-乳化沥青砂浆的施工性能与其早期的流变性能有密切的关系,在工程实践中也 发现:水泥-乳化沥青砂浆早期的流变损失较大,直接影响了施工过程。 水泥-乳化沥青浆体是由水泥、乳化沥青、水和外加剂等组成的一种有机-无机复合材料,是水泥-乳化沥青砂浆的重要组成部分,对水泥-乳化沥青砂浆的流变性能有直接的影响。论文研究了水泥-乳化沥青浆体各组分的交互作用,探明了水泥-乳化沥青浆体早期流变损失的主要因素,建立了基于浆体微结构演变的流变模型,并提出了调控浆体流变行为的技术措施。论文的主要研究成果如下: 1、乳化沥青延缓了水泥的水化过程 在水泥-乳化沥青浆体中,阴离子乳化沥青影响水泥的水化过程,凝结时间、水化热、浆体电阻率、原位XRD、MIP、X-CT和SEM等研究结果表明了阴离子乳化沥青对水泥水化过程具有缓凝效应。 揭示了阴离子乳化沥青对水泥水化的缓凝作用机理为:(1)阴离子乳化沥青通过表面的阴离子乳化剂而选择性地吸附到水泥颗粒表面,占据了水泥矿物表面的“活性位点”,影响了水泥颗粒的离子溶出,从而延缓了水泥的水化进程;(2)水泥水化产生的Ca2+进入阴离子乳化沥青表面双电层而导致阴离子乳化沥青破乳团聚,形成沥青膜而覆盖在水泥颗粒表面,阻碍了水分向未水化的水泥颗粒表面的迁移和离子的溶出;(3)阴离子乳化沥青周围的不同水分子之间形成更多的氢键,降低了水分子与水泥矿物之间的化学反应活性,从而延缓水泥的水化过程。 2、水泥水化促进了阴离子乳化沥青的破乳 在阴离子乳化沥青中加入模拟CaCl2电解质溶液,结果表明:阴离子乳化沥青的平均粒径显著增大,光学显微镜观察到阴离子乳化沥青发生明显的破乳团聚现象;阴离子乳化沥青表面zeta电位下降,说明表面双电层被压缩。在水泥浆体滤液的作用下,阴离子乳化沥青的平均粒径随着时间的延长而逐渐增大,其变化趋势与阴离子乳化沥青在CaCl2模拟溶液中的结果比较类似,说明水泥水化会导致阴离子乳化沥青破乳。 水泥水化导致阴离子乳化沥青破乳的主要原因在于:(1)水泥水化产生的钙离子屏蔽了阴离子乳化沥青表面的部分负电荷,压缩了表面双电层,降低了阴离子乳化沥青颗粒之间的排斥力;(2)随着水化产物的生成和水分的逐渐消耗,吸附在水泥颗粒表面的阴离子乳化沥青颗粒相互聚集,并在水泥颗粒表面破乳而形成连续的沥青膜。 3、阴离子乳化沥青和减水剂对水泥颗粒存在竞争吸附关系 向水泥-乳化沥青浆体中掺入减水剂,随着减水剂向浆体内扩散,水泥颗粒表面吸附的阴离子乳化沥青含量逐渐减少,表明减水剂导致了已经吸附在水泥颗粒表面的阴离子乳化沥青逐渐发生脱附,上述结果证明了减水剂与阴离子乳化沥青对水泥颗粒表面的竞争吸附关系。 减水剂和阴离子乳化沥青在水泥颗粒表面的竞争吸附机理为:(1)与阴离子乳化沥青相比,减水剂分子由于粒径较小而迁移速度更快,使得减水剂优先吸附到水泥颗粒表面;(2)减水剂分子的电荷密度高于阴离子乳化沥青的电荷密度,使得减水剂分子与水泥颗粒表面之间的静电吸附作用力更强。 4、水泥-乳化沥青体系的早期流变损失原因、模型及调控措施 阴离子乳化沥青延缓了水泥的水化,抑制了早期水化产物的形成,表明水泥水化并不是导致水泥-乳化沥青浆体早期流变损失的主要原因。 阴离子乳化沥青中加入CaCl2溶液,会直接导致阴离子乳化沥青的破乳团聚,并导致水泥-乳化沥青浆体的剪切应力和塑性粘度都显著增加,浆体的流动性下降;但在纯水泥浆体中加入CaCl2溶液,水泥浆体的流变性能没有明显变化,证明水泥-乳化沥青浆体流变损失主要是由于乳化沥青的破乳而引起的。 此外,阴离子乳化沥青引入的水中存在大量的氢键,粘度显著增加,这可能也是导致水泥-乳化沥青浆体流变损失的原因之一。 建立了基于浆体微结构演变的水泥-乳化沥青浆体早期流变模型;加入减水剂可以对浆体的早期水化和流变行为进行调控。
英文题目 Investigation of the Interaction Between Cement and Asphalt Emulsion and Its Mechanism
英文主题词 cement,asphalt emulsion, hydration,demulsification, rheology
英文摘要 As a kind of key engineering material used in the system of ballastless track in High-Speed Railway (HSR), cement-asphalt mortar is mainly grouted in the long and narrow structure between the concrete base and track slab, which can play the role of damping adsorption, and thus ensure the high speed train safety and smooth running at the speed of more than 250km/h. As a kind of grouted material, the workability of cement-asphalt mortar is closely related to the rheological property during the early period, however, the workability loss was often happened in the engineering practice, which affected the process of construction directly. The cement-asphalt paste is composed of cement, asphalt emulsion, water and superplasticizer, which is an important part of cement-asphalt mortar and also would exert significant influence on the rheological property of cement-asphalt mortar directly. The thesis investigated the interactions between different compositions of cement-asphalt paste, and the main influencing factors of the rheological loss of cement-asphalt paste was proved, the rheological modeling of cement-asphalt paste based on the evolution of microstructure was established, and also the technical measures for controlling the rheological loss of cement-asphalt paste during early period was put forward. The main achievements of the thesis can be listed as follows. 1.Asphalt emulsion delayed the process of cement hydration In the cement-asphalt paste, the process of cement hydration would be affected by anionic asphalt emulsion, and the retardation effect of anionic asphalt emulsion on cement hydration was illustrated by the following experimental results of setting time, hydration heat, electrical resistivity, in-site XRD, MIP, X-CT and SEM. The retardation mechanism of anionic asphalt emulsion on cement hydration was discovered as below: (1) The surface of cement particles was adsorbed by anionic asphalt emulsion via anionic emulsifier, which resulted in the ion dissolution being hindered due to the activity sites of cement particles were occupied by anionic asphalt emulsion, and thus delayed the process of cement hydration. (2) The Ca2+ generated from cement hydration entered into the double electrode layers of anionic asphalt emulsion, which resulted in the demulsification of anionic asphalt emulsion and caused the formation of asphalt membrane. Therefore, the ion dissolution and hydration process were hindered due to the coverage of asphalt membrane onto the surface of cement particles being covered by the asphalt membrane. (3) Much more hydrogen bonds formed between different water molecules around anionic asphalt emulsion, which decreased the chemical reactivity of water molecules with cement particles, and thus hindered the cement hydration process. 2. Cement hydration promoted the demulsification of anionic asphalt emulsion Added the CaCl2 electrolyte solution into anionic asphalt emulsion, the results indicated that: the average particle size of the anionic asphalt emulsion became larger obviously, the anionic asphalt emulsion demulsified and resulted in the aggregation of asphalt particles observed by the optical microscope; and also the zeta potential of anionic asphalt emulsion decreased, which implied that the electric double layers was compressed. Under the action of cement slurry filtrate, the average particle size of the anionic asphalt emulsion became larger gradually over time, and the variation trend of which was similar to the action of the CaCl2 electrolyte solution. That is to say, the cement hydration would cause the demulsification of anionic asphalt emulsion. The main reason for the demulsification of anionic asphalt emulsion caused by cement hydration can be attributed to the following: (1) Partial negative charge of the surface of anionic asphalt emulsion was shielded by the Ca2+ generated from cement hydration, which compressed the electric double layers, and thus decreased the repulsion between asphalt emulsion particles; (2) With the formation of hydration products and the consumption of water, the anionic asphalt emulsion being adsorbed on the surface of cement particles would aggregate with each other, and finally formed a coverage of continuous asphalt membrane onto the surface of cement particles. 3. The competitive adsorption relationship between superplasticizer and anionic asphalt emulsion on cement particles While incorporating the superplasticizer into the cement-asphalt paste, the asphalt emulsion which has been adsorbed onto the surface of cement particles decreased gradually with the diffusion of superplasticizer into the cement-asphalt paste, indicating that the desorption of asphalt emulsion from the surface of cement particles caused by the addition of superplasticizer. In other words, the competitive adsorption relationship between anionic asphalt emulsion and superplasticizer on the surface of cement particles was further proved by the aforementioned results. The competitive adsorption mechanism of superplasticizer and anionic asphalt emulsion on the surface of cement particles can be supposed as below: (1) In comparison to anionic asphalt emulsion, the migration speed of superplasticizer was much quicker due to the smaller particle size, which resulted in the priority adsorption of superplasticizer on the surface of cement particles. (2) The charge density of superplasticizer was higher than that of the anionic asphalt emulsion, which caused the adsorption driving force between superplasticizer and the surface of cement particles much stronger. 4. The early period rheological, modeling and controlling measures of CA paste Anionic asphalt emulsion delayed the cement hydration process and hindered the formation of hydration products, which indicated that cement hydration was not the main reason for the early rheological loss of cement-asphalt paste. Adding CaCl2 solution into anionic asphalt emulsion would cause the demulsification of anionic asphalt emulsion, and also would result in the obvious increase of yield stress and viscosity of cement-asphalt paste, namely the workability loss of cement-asphalt paste. However, the rheological property of pure cement paste did not present obvious variation while adding CaCl2 solution, which could infer that the rheological loss of cement-asphalt paste was mainly caused by the demulsification of anionic asphalt emulsion. In addition, much more hydrogen bonds would be formed between water molecules around anionic asphalt emulsion, which resulted in the increase of viscosity of water in cement-asphalt paste, and this may also be one of the reasons for the rheological loss of cement-asphalt paste. The early period rheological modeling was established according to the evolution of the microstructure of cement-asphalt paste in the thesis; Superplasticizer could be utilized to controlling the cement hydration process and rheological behavior of cement-asphalt paste during early period.
学术讨论
主办单位时间地点报告人报告主题
东南大学材料学院 2015.04.01 材料学院会议室 Yun Bai 微波养护混凝土
东南大学材料学院 2014.11.20 材料学院B楼432 李炜 The investigation of retardation effect of emulsifier on cement hydration
东南大学材料学院 2015.12.03 材料学院A楼601 李炜 The action mechanism of anionic asphalt emulsion on cement hydration and its effect on rheological property
University College London(UK) 2016.05.04 Thompson Room, Chadwick Building, UCL,London 李炜 Introduction of doctoral thesis---The interaction mechanism between cement and asphalt emulsion and its influence on rheological property of CA paste
全国高等学校建筑材料学科研究会 2015.07.25-26 青岛理工大学 李炜 第六届全国建筑材料研究生论坛
江苏苏博特新材料有限公司 2015.11.30 苏博特研发中心会议室 李炜 乳化沥青对水泥水化过程的作用机理及对流变性能的影响
University College London(UK) 2016.01.11 Classroom 102, Chadwick Building,UCL Shishi Multi-stage Microwave Curing for Manufacturing Alkali-activated Fly Ash
University College London(UK) 2016.02.10 Classroom 102, Chadwick Building,UCL Zhicheng Liu Development of Novel Cushion Materials for High-speed Railway Tracks
     
学术会议
会议名称时间地点本人报告本人报告题目
Conmat 15 2015.08.19-21 加拿大 温哥华 Research on workability control indexs of cement asphalt mortar based on the rheological properties
Innovation in Construction Materials 2016.04.12 英国 伦敦 Effect of asphalt emulsion on the hydration of Portland cement
     
代表作
论文名称
Retardation mechanism of anionic asphalt emulsion on the hydration of Portland cement
 
答辩委员会组成信息
姓名职称导师类别工作单位是否主席备注
陆采荣 正高 教授 博导 南京水利科学研究院
高建明 正高 教授 博导 东南大学
钱春香 正高 教授 博导 东南大学
白云 正高 教授 博导 伦敦大学学院(UCL)
肖鹏 正高 教授 博导 扬州大学
      
答辩秘书信息
姓名职称工作单位备注
冯攀 其他 讲师 东南大学