THREE-DIMENSIONAL IMAGING OF CEMENT-BASED MATERIALS WITH X-RAY TOMOGRAPHIC MICROSCOPY: VISUALIZATION AND QUANTIFICATION

X-ray computed microtomography is now becoming a popular non-destructive method to study the microstructure of materials. As this technique operates on the same basic principle of medical computed tomography (CT) scanners, it provides the three-dimensional (3D) reconstruction of images from finite radiological images; but with much higher spatial resolution. For example, microfocus X-ray CT systems are now being designed to study the internal microstructure of specimen at spatial resolution of order of several microns. Furthermore, since the development of synchrotron as an X-ray source, advanced X-ray CT system is continually improving to approach spatial resolutions to submicron level. Such high-resolution technique is referred in this paper as X-ray tomographic microscopy (XTM) to highlight the distinction of this 3D imaging technique from the relatively well-established method of 2D microscopic imaging obtained from optical or electron microscope. This paper, therefore, demonstrates the use of XTM technique to investigate the microstructure of cement-based materials. The potentials for high resolution microtomographic images to understand the 3D microstructure of cement-based materials in relation to the durability performance of these materials are given. For instance, the application of synchrotron microtomography to examine the pore connectivity and tortuosity of the 3D pore space in hardened cement paste is presented. In addition, application of microfocus X-ray CT to characterize the air void system of air-entrained mortar is also described in this paper.