Microscopic Study of Ice Formation and Propagation in Concrete

尽管在减轻冰层形成和扩散对波特兰水泥混凝土的损害方面取得了重大进展，但霜冻作用继续对暴露在气候条件下的结构造成严重破坏。P.I.S计划使用一种新的微观技术--定向冷却，对混凝土及其组件中的冰的形成和传播进行全面的研究。这项研究将表征不同混凝土孔隙溶液中的冰的形态和速度，它将确定过冷水的局部浓度，并将确定冰在混凝土中传播的动力学随不同数量的夹带空气的空隙和除冰剂的函数。冰晶与混凝土微观结构的相互作用将使用新一代场发射低温扫描显微镜在高倍率下进行表征，这使得研究小空隙中的冰形成成为可能。利用最近开发的声发射装置，将建立混凝土中的冰形成和微裂缝发展之间的关系。测试结果将在微观结构和微裂纹之间建立联系，这与冷却速度、除冰剂的存在和基质中的空气夹带量有关。这一综合研究计划的结果将有助于开发下一代高性能混凝土，用于修复暴露在寒冷气候下的老化钢筋混凝土基础设施。

Despite the significant progress research has made in mitigating the damage to portland cement concrete from ice formation and propagation, frost action continues to cause serious damage to structures exposed to the elements. P.I.s plan to use a new microscopic technique using `directional cooling` to undertake a comprehensive research program on ice formation and propagation in concrete and its components. This study will characterize the ice morphology and velocity in various concrete pore solutions, it will establish local concentrations of super-cooled water and it will determine the dynamics of ice propagation in concrete as a function of different amounts of air-entrained voids and deicers. The interaction of ice crystals with the concrete microstructure will be characterized at high magnifications using a new-generation field emission low-temperature scanning microscope, which allows the study of ice formation in small voids. The relationship between the ice formation in concrete and the development of microcracks will be established using a recently developed acoustic emission set-up. The test results will create a link between microstructure and microcracking as affected by cooling rate, presence of deicers, and amount of air entrainment in the matrix. The results of this integrated research program will help the development of the next generation of high-performance concretes to be used in the repair of the aging reinforced concrete infrastructure exposed to cold climate.