混凝土中钙矾石的时空分布-演变及影响因素研究

The ettringite in the hardened concrete exists in diversified forms, changes with the variation of time、space and environment, and its formation is controlled by many factors. The ettringite affects the properties of concrete through its whole life-cycle, and obtaining the information of the spatial – temporal distribution and evolution of the ettringite in concrete can provide invaluable reference to regulate the behavior of ettringite. In view of the fact that the formation region and temporal evolution of ettringite in concrete is difficult to know, this study plans to employ Raman spectroscopic technique associates with Scanning Electron Microscope and X-ray Diffraction analyses, in conjunction with macro-performance test, to investigate the factors affecting the spatial – temporal distribution and evolution of ettringite in concrete. The influence of aggregate、cracking and sulfur-source will be emphasized, and the effect of temperature、humidity、supplementary cementitious materials and admixtures is also studied. This project aims at understanding the spatial – temporal distribution and evolution of ettringite in concrete、digging out the key factors affecting this and relevant mechanisms、determining the potential causal relationship between the formation and evolution of ettringite and the cracking and aggregate interface defect、as well as revealing preliminarily the extent of the influence of the heterogeneous distribution and evolution of ettringite on the strength and volume stability of concrete. The outcomes of this study have great significance both in theory sense and engineering practice on the quality control and durability improvement of concrete, in particular on the theoretical understanding and control of the cracking formation and expansion failure associated with ettringite.

硬化混凝土中的钙矾石形式多样、形成受控于诸多因素，且随时空和环境改变而发生变化，对混凝土性能影响贯穿整个生命周期，获得钙矾石在混凝土中的时空分布与演变信息可为调控其行为提供依据。项目针对混凝土中钙矾石生成空间和随时间变化难以确定的实际情况，利用拉曼检测技术并辅助扫描电镜和X射线衍射等测试手段，与宏观性能测试相联系，研究影响混凝土中钙矾石时空分布与演变的因素，重点研究集料、裂缝和硫源的影响，同时研究温度、湿度及掺合料、外加剂的影响，掌握钙矾石在混凝土中随时间和空间变化的分布情况和演变规律，明确影响钙矾石时空分布的主要因素与机制，确定混凝土中钙矾石形成发展与已有裂缝以及集料界面缺陷可能存在的因果关系，初步探明钙矾石不均匀分布与演变对混凝土强度与体积稳定性的影响程度。研究结果对混凝土质量控制和耐久性改善，特别是涉及与钙矾石有关的裂缝形成与膨胀破坏的机理认识与控制具有重要的理论意义和实际应用价值。

钙矾石是硅酸盐水泥的重要水化产物，在水泥水化早期具有调凝、补偿收缩的作用，其对水泥石早期强度的发展有很大贡献。然而，硬化后混凝土中的钙矾石却表现出极大的复杂性与多样性，是引起混凝土耐久性问题的重要因素之一。已有的检测手段难以从宏观尺度确定钙矾石的形成区域，也难以确定钙矾石的生成量随时间的变化，含骨料的样品也难以被检测。本项目基于拉曼光谱检测手段，再辅助扫描电子显微镜、X射线衍射测试技术，研究钙矾石在不同温度、湿度与硫源情况下的时空分布与演变；混凝土中的孔隙和界面薄弱区特别是骨料周围界面区域中钙矾石的形成、分布与演变；同时建立了养护温湿度、硫源、骨料、裂缝等多种因素对钙矾石的影响规律及机制，并研究了钙矾石的分布对水泥石抗压强度和体积变化的影响规律。发现硫铝比为2或3时钙矾石可稳定存在，随着水化进行钙矾石生成量不断提高；骨料对钙矾石的生成有一定的促进作用，特别是界面过渡区及裂缝处；高硫铝比下钙矾石生成量高，水泥石体积膨胀明显，对强度有不利影响。项目研究将拉曼光谱技术用于检测甚至监测混凝土中钙矾石，能有效掌握钙矾石在混凝土中的分布情况，可为控制混凝土中钙矾石在裂缝形成与膨胀破坏方面的不利影响提供有价值的信息，以避免钙矾石的不利影响，发挥钙矾石的积极作用。