【作者】 杨婷婷；

【导师】 胡曙光； 王发洲；

【作者基本信息】 武汉理工大学 ， 建筑材料与工程， 2010， 博士

【摘要】 混凝土是一种多相多层次结构复合材料,混凝土各相间性能的匹配性和相间弱界面过渡区的存在是影响结构与性能的最主要问题。相与相之间的界面,尤其是水泥石-集料之间的界面结合情况,对混凝土力学性能和耐久性有着十分重要的影响。以往对改善界面过渡区的研究大多数集中在对水化产物性能提高、外加辅料增强作用以及集料的简单处理等方面,尚不能形成从材料组成与结构整体优化的层面实现突破。本文针对该问题,提出了通过采用功能集料的技术方法,改善与优化水泥石与集料的界面过渡区,从本质上解决影响混凝土结构与性能的关键问题,大幅度提高混凝土的性能特别是耐久性。丰富和完善混凝土设计理论,为高技术混凝土的设计、开发和应用提供理论基础。论文进行的主要工作和取得的重要成果有：在深入分析界面过渡区特性和形成机理的基础上,提出功能集料的设计理念。在混凝土中,功能集料既具有增强与优化ITZ的作用,又具备调整和控制水泥石形成的功能。依据材料设计原理与技术方法,研究提出了功能集料的理想结构模型。功能集料的理想结构由多孔的高强基体和具有表面水化活性反应层两部分组成。在这种混凝土中,功能集料的表面通过良好的水化反应,增强与水泥石的粘接；功能集料内部的多孔结构能提供储水和释水的转换空间,能对水泥石及界面起到内养护的作用,可从根本上增强和改善界面过渡区,提高混凝土的整体性能,为高技术混凝土的研究与开发提供了新的途径。根据所研究提出的功能集料的理想结构模型,研究提出了功能集料的设计与制备方法。功能集料由高强的多孔基体和表面水化活性层组成。系统研究了基体的材料组分、矿物组成、以及工艺参数对其微观结构与性能的影响规律,确定原材料的合理组成以及制备的关键技术。研究结果表明具有良好热稳定性作用的堇青石的引入可减少集料在急冷过程中形成微裂缝,从而提高集料的强度,降低吸水率。通过选择不同的表面活性层材料体系,研究了添加剂对表面物质组成的影响,结合基体材料与表面活性层材料比例的合理设计,制备出表面以p-C2S,内部以莫来石和堇青石为主要组成的功能集料,其筒压强度达到13.5MPa,真空饱和吸水率低于8%,具有良好的力学性能和设计功能。采用SEM、EDXA、显微硬度等测试方法,研究功能集料的表层活性矿物的水化反应特征。由于β-C2S的早期水化活性低,且高温生成时可能会被一些玻璃相包裹,集料表层在28d以后逐渐表现出水化活性,集料表面的Ca逐渐向水泥石迁移,Ca/Si降低,生成的水化产物可修复早期水化产生的裂缝并填充界面过渡区的孔隙,界面显微硬度得以提高。通过研究水灰比、矿物掺合料与掺量、养护环境对集料界面过渡区性能和结构的影响规律,结合直接观察法和显微硬度方法,系统研究了功能集料对水泥石的内养护效应,探明集料与水泥浆体界面过渡区结构形成规律与性能调控机制。系统研究了功能集料制备混凝土的力学性能、体积稳定性以及抗渗性性能,建立了混凝土的内部相对湿度和自收缩的线性规律：AS=κRH+b。随着混凝土内部相对湿度RH的降低,其自收缩值AS增加,可通过预湿功能集料的内养护有效降低混凝土的自收缩。功能集料的界面增强与内养护调控水泥石结构的双重作用使界面过渡区结构和性能得到优化,混凝土结构密实,是功能集料制备混凝土具有优良力学性能和抗渗性的主要原因。从材料科学设计原理出发,提出混凝土的精细设计方法与理念,围绕水泥石与集料的强度和弹性模量相匹配的原则,优化胶凝材料体系,再通过精细设计的级配形成集料骨架的最大密实化和最小的集料间隙率,根据混凝土性能要求优化集料表面水泥膜厚度,实现混凝土的整体优化设计。更多还原

【Abstract】 Concrete is a multi-phase and multi-scale composite material and its structure and performance is predominantly influenced by the compatibility between each phase and the presence of the weak interfacial transition zone (ITZ). The interface between phases, especially between cement paste and aggregate is of paramount importance to the mechanical properties and durability of concrete. Previous research on the improvement of ITZ was focused on the amelioration of hydration products, the enhancing effect of supplementary cementitious materials and some treatment on aggregates, which failed to make a breakthrough in the overall optimization of composition and structure of concrete. In this thesis, the concept of function aggregate is put forward to improve the ITZ between cement paste and aggregate so that the performance, especially the durability, of concrete can be substantially improved and hopefully it will provide a theoretical basis for the design, development and application of high technology concrete.The main results obtained in this study are as follows:This study examines the characteristics of ITZ and its the formation mechanism, develops the concept of function aggregate. In concrete, function aggregate can enhance and optimize ITZ, and also has the ability to adjust and control the formation of cement paste. The ideal structure of functional aggregate is envisioned as composed of by a porous matrix of high strength and a reactive layer of hydration activity. In concrete proportioned with functional aggregate, the adhesion between cement paste and aggregate is enhanced by the highly reactive surface of function aggregates and its the porous structure can be a moisture reservoir for internal curing, both of which can essentially improve ITZ and provide a new direction on the research and development of high technology concrete.The study proposes the design and processing method of functional aggregate, explores the influence of the material and mineralogical composition of the matrix and processing parameters on the microstructure and properties of concrete. Results indicate that the incorporation of cordierite with excellent thermal stability can reduce the micro-cracks formed during the rapid cooling of aggregates, so as to increase its strength and decrease the water absorption. The effect of additives on the material composition of the aggregate surface is analyzed by using different surface active layer materials. A function aggregate is obtained with an outer layer ofβ-C2S and mullite and cordierite inside; its crushing strength is up to 13.5 MPa and vacuum absorption is less than 8%.By employing the test method of SEM, EDXA and microhardness, the hydration characteristics of the outlayer active minerals is studies. Sinceβ-C2S has a lower hydration activity at early age and a glassy phase is likely to be formed on the outerlayer when produced under high temperature, little hydration activity is exhibited until 28d. Ca2+ on the surface of aggregate immigrates gradually to cement paste, leading to a decreased Ca/Si; the hydration products can heal the cracks generated at early age and compact the porous ITZ. By studying the effect of w/c, supplementary cementitious materials and curing conditions on the property and performance of ITZ, the internal curing effect of functional aggregate is researched and the formation law and property adjustment mechanism are elucidated.This study examines the mechanical properties, volume stability and impermeability of concrete proportioned with functional aggregates and establish the linear relation between internal relative humidity and autogenous shrinkage: AS=κRH+b. The autogenous shrinkage is increased with a decreased internal relative humidity, which can be improved by the internal effect of pre-wetted functional aggregate. The interfacial enhancement and internal curing of functional aggregates can improve the structure and performance of ITZ, which is the main reason for the better mechanical property and impermeability of concrete.Based on the design principle of material science, the fine design method and idea of concrete is proposed. The cementitious system is optimized based on the compatibility of strength and elastic modulus between cement paste and aggregate. By fine-tuning the grading of aggregate, the compactness of aggregate is maximized and the porosity is minimized; the thickness of cement layer on the aggregate surface is optimized based on the specific performance of concrete.更多还原