Concrete: 2
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Development of a Non-destructive CT-XRD Coupling Method and Its Application
Visualization of the microstructure of hardened cement
To develop innovative cement-hardening materials, we are devising a non-destructive integrated CT-XRD method, a novel measurement method combining the CT method to obtain geometric and spatial information on microstructures inside concrete with an accuracy of several microns, and a diffraction method to investigate hydrates and alterations in the region of interest.
Research
Concrete is structurally hardened by binding rock (aggregate) through a hydration reaction between cement and water. As a structural material, concrete is intended to withstand loading and certain weather/environmental conditions, but these may cause cracking of the concrete, which may progressively deteriorate due to strong acids and other chemical reactions caused by erosion and materials from the atmosphere, seawater and groundwater that come in contact with it. To stably use the social infrastructure for a long period of time, it is important to be able to see inside the internal structure of concrete with “bug eyes” and find any abnormalities that have occurred.
With the pioneering “non-destructive integrated CT-XRD method,” the sample is irradiated with high-intensity X-rays from synchrotron radiation to selectively visualize 3D structures from transmitted monochromatic X-rays at 25 keV. Energy-dispersive X-ray diffraction is also performed in specific regions of interest through multiple slit operations to identify hydrates (portlandite, calcite, etc.), their alteration and aggregate minerals.Takafumi Sugiyama Professor -
Prediction Model for Transport properties in Hardened Cement
Prediction of transport properties of cement-based materials
Concrete is widely used for infrastructure, and its longevity is essential for the construction of a sustainable society. To realize this, appropriate performance prediction technology is indispensable. In this study, we predicted the transport properties of hardened cement paste (HCP), which is a main component of concrete.
Research
The transport properties of porous materials such as concrete does not only depend on the porosity, but also on the spatial distribution of each phase. Therefore, the transport properties of HCP, which is a main component of concrete, was predicted. Figure 1 shows a cross section of HCP observed using a backscattered electron image, showing the distribution of each phase. We extracted each phase, calculated the autocorrelation function, and based on the results, distributed each phase in three-dimensional space to construct the three-dimensional spatial image model shown in Fig. 2. Figure 3 shows a comparison of the results of the diffusion coefficient calculated by the finite difference method and the measured values. The estimated and measured values agreed well with each other, even for different samples, indicating that the diffusion coefficients of hardened cement can be predicted using this model.
Kiyofumi Kurumisawa Associate Professor
