低放射性最終處置設施之主體為混凝土，但不同於一般混凝土結構物之用途，低放射性最終處置設施的服務年限可能長達數百年之久。另外由於台灣環境氣候潮溼，四面環海，場址的選擇可能位於臨海區域且採用地表處置或隧道處置，此環境利於腐蝕反應之發生，使得最終處置設施長期在此環境下可能產生劣化，進而影響混凝土長期耐久性。 本研究乃針對添加不同含量飛灰之混凝土進行氯離子浸泡試驗(ponding test)，以實驗室模擬混凝土工程障壁受海水入侵作用下，不同飛灰使用量之混凝土對改善混凝土抵抗氯離子入侵的成效。實驗證實添加不同含量之飛灰對混凝土抵抗氯離子入侵有顯著的效果，且使擴散係數隨時間而降低；並利用試驗結果依據費克第二定律(Fick’s second law)評估氯離子擴散係數與時間的效應及飛灰添加量之影響，同時以迴歸方法求取擴散係數隨時間變化之影響參數。另外，運用Life-365及4SIGHT等二個程式，預測氯離子入侵剖面與實驗所得氯離子入侵剖面的關連性，期未來可進一步發展，應用於低放射性廢棄物最終處置場混凝土障壁服務年限之推估。 Salt ponding test was conducted on mature concrete specimens dry-stored in laboratory condition and on concretes immediately exposed to chloride after 28 days of moist curing. Analysis on the various properties of concretes with fly ash addition and their implication to chloride ingress were done. Experimental result indicates that fly ash addition increases the maximum surface chloride value of concrete while reducing the chloride diffusivity with time. These concrete properties proved to have an important effect to the prediction of chloride ingress using error function solution to Fick’s second law. The prolonged dry-storage does not seem to have a significant impact on the change in chloride diffusion properties of the concrete specimens. General agreement between experimental data with Life-365 & 4SIGHT predicted values of concrete properties indicate the applicability of both concrete performance prediction software in considering the influence of fly ash addition and the reduction of diffusion coefficient with time.
