低放射性廢棄物處置設施之工程障壁主要是由混凝土組成，但不同於一般混凝土結構物之用途，其服務年限需長達數百年之久。由於台灣處於四面環海環境，使得低射性廢棄物處置場之場址位於濱海區域，處置場障壁混凝土長期處於此環境下，對混凝土造成劣化以及耐久性的影響非常巨大。本研究主要探討混凝土材料受氯離子入侵之劣化情形，並使用氯離子濃度門檻值與擴散係數，用於經驗公式中，來預估鋼筋開始腐蝕之時間。以可能使用於高完整性容器之HIC 配比、傳統配合設計方法ACI 配比與緻密配比，進行相關試驗與分析。試驗結果顯示，低水膠比以及添加較多卜作嵐礦物摻料之混凝土內部結構較緻密，導致氯離子擴散係數較小，但氯離子會在混凝土表層持續累積，造成表層氯離子濃度較高。主要以擴散係數判定混凝土抵抗氯離子入侵之能力，HIC-C 配比和HIC-M配比明顯優於ACI 配比，緻密配比則依據水膠比的不同，抵抗能力也不同。為推估氯離子入侵，造成鋼筋保護層破裂，造成腐蝕時間，以亂數理論配合經驗公式推估預測，推估出鋼筋開始腐蝕之時間。The barriers of facilities which dispose wastes with low radioactivity are mainly composed of concrete, but unlike the normal purpose of concrete, it should be used for more than several hundred years. However, due to Taiwan’s geographic feature- island, the sites of such facilities are mostly placed in marine environment, which will cause immense influences on the degradation and durability of concrete over a long period of time.This research aims on studying the degradation level of concrete while percolated by chloride ions, through using diffusion coefficient and threshold chloride concentration in empirical formulas, along with doing relative tests and analyses with HIC, ACI, to predict the time when reinforcing steel starts to be corroded. According to the test result, the internal structure of concrete which has low W/B or is blended with pozzolanic materials is comparatively denser, leading to the low diffusion coefficient of chloride ions. But chloride ions may constantly accumulate on the surface of concrete, setting up a high concentration chloride profile.By using diffusion coefficient to determine the ability of concrete to resist chloride penetration, research consequence reveals that HIC-C and HIC-M result is preeminent compared with ACI in an obvious way. On the other hand, owing to the fact that concrete’s changes with W/B, the resistant ability of concrete changes too. Random. number and empirical formulas are used to predict the time to corrosion initiation while chloride ions percolate and start to destroy the reinforcing steel’s barrier function.
