低放射性廢棄物處置場障壁主體由混凝土構成，然而台灣地區多雨且四面臨海，因此處置場易因海水、地下水、酸雨以及乾濕循環的作用而造成障壁混凝土材料遭受硫酸鹽侵蝕劣化，若處置場在此種服務環境下，可能對障壁混凝土造成損害或劣化而影響其耐久性。 本研究針對低放射性廢棄物處置場工程障壁所使用之混凝土材料，以實驗室模擬混凝土材料長期受硫酸鹽侵蝕作用下，探討障壁混凝土材料長期在此環境下的行為，分析其可能劣化機制及對耐久性之影響。試驗結果得知: (1)混凝土受硫酸鹽侵蝕時，其入侵之深度及濃度皆隨著歷時時間增加而增加；(2)以卜作嵐材料取代部分水泥及降低水膠比，可提升混凝土緻密性進而改善抗硫酸鹽侵蝕能力；(3)將試驗結果依據費克第二定律(Fick’s second law)加以擬合可推估硫酸根離子擴散係數及邊界濃度，藉以評估卜作嵐材料取代水泥之影響；(4)最後再以擴散係數以及現地硫酸根離子濃度來推估混凝土劣化情形。The proposed engineered barrier for low-level radioactive wastes disposal site is made of concrete. Since Taiwan is surrounded by the sea, the low-level radioactive wastes disposal site is very possible to suffer from the attack of different elements of the environment, such as sea water, ground water, acid rain, wet-dry cycle, and sulfate attack. The attack by sulfate on concrete material used at the low-level radioactive wastes disposal site was simulated in the laboratory to determine the long-term durability of concrete material. The possible degradation mechanism of concrete under sulfate attack and the influence on its durability are carefully examined in this study. The results of the laboratory works show that: (1) the depth of sulfate penetration increases with elapsed time of sulfate attack; (2) the replacement of a portion of Portland cement with pozzolanic materials and use of low w/b were found to help the concrete to resist the sulfate attack; (3) the diffusion coefficient can be determined from the sulfate profile experimental result according to Fick’s second law, such that the effect of replacement of a portion of Portland cement with pozzlanic materials can be assessed; (4) Finally, estimate the diffusion coefficient of concrete deterioration.
