X-Ray Microtomography of Mortars Exposed to Freezing-Thawing Action
X-Ray Microtomography of Mortars Exposed to Freezing-Thawing Action
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DOI：
10.3151/jact.8.97
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发表时间：
2010-06
影响因子：
2
通讯作者：
M. Promentilla;T. Sugiyama
中科院分区：
文献类型：
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作者：
M. Promentilla;T. Sugiyama
本文介绍了我们在应用x射线显微断层扫描来表征暴露于冻融作用的砂浆的内部结构方面的发现。采用微焦x射线CT （micro-CT）扫描仪对内部空隙或裂缝进行空间分辨率为10微米的无损三维成像。在不同次数的冻融循环后，对四种不同类型的砂浆试件（即不掺气和不掺气的波特兰水泥砂浆，不掺气和不掺气的粉煤灰砂浆）进行扫描。结合图像分析，对微ct获得的孔隙空间进行三维表征，包括孔隙率、气孔尺寸分布、连通裂缝网络的裂缝宽度和弯曲度。结果表明，无论砂浆类型如何，初始孔隙均服从对数正态分布，模态尺寸在30 ~ 50 μm附近分布最多；由于不掺气砂浆的分布气孔数量较少，特别是粉煤灰砂浆的抗冻损性能最差，表现为在较弱的膏体-骨料界面周围形成内部裂缝。迹象还表明，这些裂缝在三维中连接良好且各向异性。
This paper presents our findings on the application of X-ray microtomography to characterize the internal structure of mortars that were exposed to freezing-thawing action. A microfocus X-ray CT (micro-CT) scanner was used for the nondestructive 3D imaging of internal air voids or cracks at a spatial resolution of the order of 10 microns. Four different types of mortar specimens (i.e., non-air-entrained and air-entrained Portland cement mortar, and non-air-entrained and air-entrained fly ash mortar) were scanned after being subjected to different numbers of freeze-thaw cycles. Coupled with image analysis, the void space obtained from micro-CT was characterized in three dimensions (3D) in terms of void fraction and air void size distribution, as well as, the crack width and tortuosity of the connected crack network. Results suggest that the initial air voids follow a lognormal distribution with the highest population of modal size around 30-50 μm, irrespective of the type of mortar. As the distributed air voids of non-air entrained mortars were relatively few in numbers, the fly ash mortar in particular was the least resistant against frost damage as shown by the formation of internal cracks that meander around the weaker paste-aggregate interface. Indications also suggest that these cracks are well connected and anisotropic in 3D.