The characterization of the processing-induced defects is an essential step for developing defect-free processing, which is important to the assurance of structural reliability of brittle ceramics. The multiscale X-ray computed tomography, consisting of micro-CT as a wide-field and low-resolution system and nano-CT as a narrow-field and high-resolution system, is suitable for observing crack-like defects with small length and with very small crack opening displacement. Here we applied this powerful imaging tool in order to reveal the complicated three-dimensional morphology of defects evolved during sintering of alumina. The hierarchical packing structure of granules was the origin of several types of strength-limiting defects, which could not be eliminated due to the differential sintering of heterogeneous microstructures. This imaging technique of internal defects provides a link between the processing and the fracture strength for the development of structural materials.
This paper presents a theoretical analysis of the hydration and hydrated layers of blast furnace slag grains in high-volume blast furnace slag cement. Hydrated high-volume blast furnace slag cement paste contains a large number of unreacted slag grains, and hydrated layers are observed surrounding the unreacted slag grains. To analyze the hydration reaction of the blast furnace slag components, an extended effective coefficient is adopted instead of the conventionally used Tomosawa's equation. This makes it possible to explain the rate of heat liberation of blast furnace slag in comparison to that of ordinary Portland cement. The simulation results for the thickness of the hydrated layer around the slag particles in terms of its conversion radius dependence are in good agreement with the measured values.
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