无砟轨道充填层砂浆流变性的时温效应及其机制

Filling layer mortar( Cement asphalt Mortar,CA mortar) is the key component of ballastless slab track structure, the desirable workability of which is the prerequisite for CA mortar to achieve the performances designed. However, its large and quick lose of fluidity, high sensitiveness to humidity, and shortly working time severely affect the progress and quality on the construction of high speed railway. The current study, based on rheological theory, will focus on revealing the time-dependent changing law of plastic viscosity and yield stress of the four-element compound system (CA mortar)-water， cement, emulsified asphalt and superplasticizer-at different environmental temperatures. From both the levels of macroscopic phenomena and micro structure, the early cement hydration, emulsified asphalt breaking, the adsorption-and-separation behavior, and its variation law of CA mortar with time and temperature will be investigated under the interaction of cement, asphalt and superplasticizer. Additionally, the interactive mechanisms of those three components will be demonstrated, which will be the foundation for the further study on the interactive effect and their internal relation of the cement hydration, emulsified asphalt breaking and adsorption of water reducer. Critical factors influencing CA mortar's time-temperature effect will be determined, and the mechanisms on the time-temperature effect of CA mortar will finally be revealed essentially. Results of this study can provide theoretical basis for the solution of the short-working-time problem of CA mortar and can help promote its technical innovation in our Country.

充填层砂浆（简称CA砂浆）是板式无砟轨道的关键组成部分，良好的工作性是CA砂浆达到设计性能的前提。但CA砂浆流动性损失大、对温度敏感、可工作时间短的问题严重影响了高速铁路的施工进度和质量。项目以水-水泥-乳化沥青-减水剂四元复合体系（CA浆体）为研究对象，基于流变学原理，在不同温度环境下，考察复合体系的塑性粘度和屈服应力的经时变化规律。从宏观现象和微细观结构两个层面，在水泥-乳化沥青-减水剂交互作用下，研究CA浆体早期水泥水化、乳化沥青破乳和减水剂吸附分散行为及其随时间和温度的变化规律，阐明水泥-乳化沥青-减水剂的交互作用机理，分析并探寻水泥水化、乳化沥青破乳、减水剂吸附及三者交互作用与流变性变化的内在联系，明确影响CA砂浆时温效应的关键因素，并最终从本质上揭示CA砂浆时温效应的作用机制。研究成果为解决CA砂浆可工作时间短的问题提供理论依据，有利于推动我国CA砂浆的技术创新。

研究了水泥-乳化沥青浆体各组分的交互作用，探明了水泥-乳化沥青体系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。.通过凝结时间、水化热、浆体电阻率和原位XRD等手段阐明了阴离子乳化沥青对水泥水化过程的缓凝效应；揭示了阴离子乳化沥青通过静电作用选择性的吸附到水泥颗粒表面，影响了水泥颗粒的离子溶出，从而延缓了水泥的水化的缓凝作用机理。.揭示了水泥水化促进乳化沥青破乳机制：水泥水化产生的高价阳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斥力位能，打破了阴离子乳化沥青颗粒之间的相互吸引与排斥的平衡状态，从而导致阴离子乳化沥青之间发生破乳团聚。.通过改变减水剂与阴离子乳化沥青的加入顺序，首次发现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，即减水剂优先于阴离子乳化沥青而吸附到水泥颗粒表面；并阐明了减水剂与阴离子乳化沥青对水泥的竞争吸附机理：减水剂分子粒径较小，迁移速度更快，优先于阴离子乳化沥青而迁移到水泥颗粒表面；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。.水泥-乳化沥青浆体流变损失的影响因素：乳化沥青延缓了水泥的早期水化过程，说明水泥水化并不是导致浆体流变损失的直接因素；阴离子乳化沥青的破乳，在浆体内形成团聚体，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，是造成水泥-乳化沥青浆体流变损失的重要原因之一；阴离子乳化沥青周围的水分子由于受到乳化剂的作用而形成了大量的氢键，导致粘度较大，也是造成水泥-乳化沥青浆体流变损失的因素。.建立了基于浆体微结构演变的浆体流变模型；从微观角度揭示了CA砂浆流变性损失机制。.揭示和阐明CA砂浆中各组分的交互作用和影响规律有助于丰富CA砂浆工作性能的调控的理论依据，对于拓展CA砂浆的应用也有积极的意义。