Influence of High Ambient Temperature on Chloride Penetration into Nuclear Reactor Containment Buildings

Abstract

In this thesis, the effects of thermal diffusion, water-to-cement (w/c) ratio, and supplementary materials like silica fume (SF) and ground granulated blast furnace slag (GGBS) on chloride ion penetration and corrosion initiation in concrete under various conditions was investigated. First, we examined the influence of thermal diffusion on chloride diffusion in concrete exposed to high ambient temperatures. Concrete samples were tested under both isothermal and temperature gradient conditions. The results showed that chloride concentration in samples subjected to temperature gradients was significantly higher compared to those under isothermal conditions at the same temperature (50 °C). An analytical model was used to predict chloride diffusion under temperature gradient conditions, effectively combining mass and thermos-diffusion coefficients. This model correlated well with experimental data, providing insights into the impact of thermal diffusion on chloride diffusion. Next, we investigated the combined impacts of the w/c ratio and thermal diffusion on chloride ion penetration in concrete located in arid climates. Concrete samples with varying w/c ratios were subjected to chloride diffusion tests. Results indicated that higher w/c ratios led to increased chloride ion penetration. Under temperature gradient conditions, the chloride concentration was significantly higher compared to isothermal conditions at 50 °C. The thermo-diffusion coefficient increased with higher w/c ratios, showcasing the influence of the w/c ratio on chloride transport. Furthermore, the effects of SF and GGBS on chloride ion penetration in concrete structures exposed to high ambient temperatures was explored. Concrete samples containing SF and GGBS exhibited lower chloride contents compared to control samples, regardless of exposure conditions. The inclusion of SF and GGBS improved the chloride binding capacity of concrete, reducing additional chloride content induced by thermo-diffusion. Finally, the effects of thermos-diffusion, w/c ratio, SF, and GGBS on the corrosion initiation time of nuclear reactor containment buildings (RCBs) exposed to specific environmental conditions of the UAE was estimated. Thermo-diffusion, w/c ratio, and additives were found to influence corrosion initiation time values. Thermo-diffusion could reduce corrosion initiation time by up to 40%. Changes in w/c ratio and the inclusion of SF and GGBS affected corrosion initiation time values, with additives effectively enhancing corrosion initiation time under temperature gradients.

Date of Award	11 Dec 2023
Original language	American English
Supervisor	Tae Yeon Kim (Supervisor)