Development of Accelerated Test Methods for Ettringite Related Damage

该研究将评估膨胀率测量作为延迟钙矾石形成（DEF）的一种可能的快速测试方法。通过浇铸不同钾含量的混凝土试件，在高水分条件下加速DEF，利用基于不完全Gamma函数的非线性曲线拟合算法对实测膨胀率数据进行分析，提取膨胀特征参数。然后，这些参数将与形成的钙矾石数量的时间分辨测量相关联，这将通过扫描电子显微镜、定量x射线衍射、同步辐射能量色散衍射和其他手段的组合来确定。此外，计算机断层扫描将用于裂纹扩展的三维成像。体重增加作为湿度循环的函数也将作为一种可能的替代快速测试方法进行探索。钙矾石或ASR凝胶的形成涉及到水的吸收，这导致样品的永久重量或质量增加。由于测量质量比测量长度变化更灵敏、更方便，这表明用与DEF更直接相关的重量变化测量代替膨胀测量是可能的。本研究将有助于了解DEF损伤机理的原因，并有助于开发DEF的快速测试方法。

Development Of Accelerated Test Methods for Ettringite Related DamageNSF Proposal No. 9988725 (UM No. 990928-8477)ABSTRACT The study will evaluate expansion rate measurement as a possible rapid test method for delayed ettringite formation (DEF). Concrete specimens with different amount of potassium will be cast and stored under high moisture conditions to accelerate DEF. The measured expansion rate data will be analyzed using nonlinear curve fitting algorithms based on the Incomplete Gamma function in order to extract characteristic expansion parameters. These parameters will then be correlated with time-resolved measurements of the amount of ettringite formed, which will be determined through a combination of scanning electron microscopy, quantitative X-ray diffraction, synchrotron radiation energy dispersive diffraction, and other means. In addition, computer tomography will be used for 3D imaging of crack propagation. Weight gain as a function of humidity cycling will also be explored as a possible alternative rapid test method. The formation of ettringite or ASR gel involves the uptake of water, which results in a permanent weight, or mass, gain of the sample. Since mass can be measured more sensitively and conveniently than length change, this suggests the possibility of replacing the expansion measurement with a weight change measurement that is more directly related to DEF. The study will contribute to the understanding of the cause for the distress mechanism in DEF, and will contribute to the development of a rapid test method for DEF.