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Abstract:
This paper investigates the gas transport behaviors of a special type of concrete—shielding concrete—designed for use in nuclear structures, where mitigating radiation and ensuring long-term durability in harsh environments are critical. Cracking is identified as a key factor influencing gas transport in nuclear environments, where it plays a critical role in determining material performance. In the current phase of the research, cracks and gaps, caused by significant variations in the interfacial transition zone (ITZ) and influenced by thermal treatment of concrete, depending on the type of aggregate and cement, were analyzed. Three types of concrete mixtures incorporating magnetite, serpentinite, and a combination of both aggregates are studied, alongside two types of cement: CEM I and CEM III. The transport properties of these concrete mixes, crucial for assessing their performance in nuclear shielding applications, were evaluated using three complementary methods: the Cembureau method for gas permeability, the Torrent method for measuring surface permeability, and the Air Permeability Index (API) using the Autoclam method. Additionally, microstructural analysis was conducted using scanning electron microscopy (SEM) to gain deeper insights into the material's behavior. The impact of microcracks on permeability was examined, as such cracks often behave differently under gas transport conditions. In the next phase of the research, supplementary cracking will be intentionally induced, both mechanically and thermally, to simulate the conditions expected in typical nuclear operations.

Keywords:
Shielding Concrete, Gas Permeability, Microstructure, Interfacial Transition Zone, Cracking