自密实混凝土填充性能及堆石混凝土界面微观特性研究

发布时间：2018-03-14 00:02

本文选题：自密实混凝土　切入点：堆石混凝土　出处：《清华大学》2014年博士论文　论文类型：学位论文

【摘要】：堆石混凝土是一种基于自密实混凝土的新型大体积混凝土施工技术，具有施工速度快、节能减排等诸多优势，已经在全国40多个工程中得到应用。然而，在堆石混凝土研究与应用中仍存在两个核心问题：自密实混凝土能否有效填充堆石体内部孔隙；堆石混凝土独特的施工工艺和大粒径块石的应用是否会影响块石/浆体的界面特性。目前有关这两个问题的研究还局限于工程经验和宏观试验，缺乏机理性的研究。本文旨在通过一系列基础试验，探索这两大问题的作用机理，分析相关因素的影响，为堆石混凝土工程中方案设计、参数选取及工程安全评价提供理论与试验依据。本文采用了多尺度方法来研究自密实混凝土的填充性能。利用自主设计的试验装置，本文首先研究了自密实净浆、自密实砂浆在堆石体中的流动和填充过程。利用流体阻塞模型和颗粒阻塞模型对自密实净浆和自密实砂浆在堆石体中的填充性能和阻塞机理进行了分析和讨论，得出了两种阻塞模型各自的适用范围，并研究了石子尺寸、浆体流动性等相关因素对填充性能的影响。在此基础上，结合Roussel提出的颗粒阻塞概率模型，利用改进的试验装置，本文对自密实混凝土的通过性能进行了试验研究，根据试验结果对Roussel的模型进行了补充，使其更适用于堆石混凝土工程。本文提出了一种研究自密实混凝土在堆石体中填充性能的新方法——多孔介质填充法，通过理论分析建立了浆体屈服应力与填充结果的关系，并通过自密实砂浆填充多孔介质模型试验验证了方法的可行性。最后，，对自密实混凝土充隙能力及相关影响因素进行了初步的试验研究。另一方面，为了研究堆石混凝土的界面微观特性，论文首先对当前有关水泥基材料界面微观特性的研究方法进行了整理和比较，选出最有效的两种微观试验方法：背散射电子图像分析和纳米压痕。本文以模型堆石混凝土试件为样本，选取多个试样在相同位置进行背散射电子图像分析和纳米压痕试验，对试验结果进行拟合，建立了孔隙率与弹性模量的量化关系。在此基础上，本文利用自密实净浆和自密实砂浆填充堆石体形成的模型堆石混凝土试件，分别对净浆/石子界面和砂浆/石子界面进行了背散射电子图像分析，得到了两种模型堆石混凝土的的孔隙率和微观弹性模量。利用界面孔隙率结果，本文分析了各试验参数对界面微观结构的影响，并通过与传统混凝土的界面特性研究成果进行比较，得出了堆石混凝土界面的新特点。
[Abstract]:Rockfill concrete is a new mass concrete construction technology based on self-compacting concrete. It has many advantages such as fast construction speed, energy saving and emission reduction, and has been applied in more than 40 projects in China. There are still two core problems in the research and application of rockfill concrete: whether self-compacting concrete can effectively fill the internal pores of rockfill; Whether the unique construction technology of rockfill concrete and the application of large-size block stone will affect the interfacial characteristics of mass stone / slurry, the current research on these two problems is limited to engineering experience and macroscopic test. The purpose of this paper is to explore the action mechanism of these two problems through a series of basic tests, to analyze the influence of related factors, and to design the scheme for the rockfill concrete engineering. Parameter selection and engineering safety evaluation provide theoretical and experimental basis. In this paper, a multi-scale method is used to study the filling performance of self-compacting concrete. Flow and filling process of self-compacting mortar in rockfill. The filling performance and blocking mechanism of self-compacting mortar and self-compacting mortar in rockfill are analyzed and discussed by using fluid blocking model and particle blocking model. The respective applicable ranges of the two blocking models are obtained, and the effects of stone size, slurry fluidity and other related factors on the filling performance are studied. On this basis, combining with the particle blocking probability model proposed by Roussel, the improved test device is used. In this paper, the passing performance of self-compacting concrete is studied experimentally, and the model of Roussel is supplemented by the experimental results. In this paper, a new method to study the filling performance of self-compacting concrete in rockfill is presented. The relationship between the yield stress of slurry and the filling result is established by theoretical analysis. The feasibility of the method is verified by the model test of self-compacting mortar filled with porous media. Finally, the filling capacity of self-compacting concrete and related influencing factors are preliminarily studied. On the other hand, in order to study the microcosmic characteristics of the interface of rockfill concrete, the present research methods of the interface micro-characteristics of cement-based materials are sorted out and compared in this paper. Two most effective microcosmic test methods were selected: back scattering electron image analysis and nano indentation. In this paper, several samples were selected for back scattering electron image analysis and nano indentation test in the same position. The quantitative relationship between porosity and elastic modulus is established by fitting the test results. On this basis, the model rockfill concrete specimens formed by self-compacting mortar and self-compacting mortar filled with rockfill are used in this paper. The porosity and elastic modulus of the two kinds of model rockfill concrete were obtained by using the back scattering electronic image analysis of the clean slurry / stone interface and the mortar / stone interface, respectively. The results of the interfacial porosity were used. In this paper, the influence of test parameters on the microstructure of the interface is analyzed, and the new characteristics of the interface of rockfill concrete are obtained by comparing with the research results of the interface characteristics of traditional concrete.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TV431

【参考文献】