水中自充填混凝土耐久性之研究

Abstract

台灣位於環太平洋地震帶，地震發生的次數非常頻繁。自921地震後地震力之提升，工程界開始注重耐震設計，結構物鋼筋用量增加，多數設計間隙更密集，在進行水中澆置時，傳統水中混凝土與高流動性水中混凝土的工作度與水中性能已不符合需求。若是採用同時擁有自充填特性以及水中不分散能力的高性能水中自充填混凝土，便能避免混凝土因施工不良所造成的缺陷。 本研究以自充填特性與水中不析離，以及抗沖離的能力為目標，比較不同的水中混凝土配比。測試新拌混凝土：工作度、水中L型流度、濁度值、pH值、抗沖離試驗。為了模擬現地施工，在水中澆置時使用特密管工法製作試體，在混凝土硬固後，嘗試放置於不同環境，如空氣、淡水、海水、淡水乾溼循環、以及海水乾溼循環，結果顯示水中自充填混凝土在各種環境下水中澆置與空氣澆置的強度比皆大於0.9並優於其它水中混凝土。進行RCPT時水中自充填混凝土於水中澆置之總電荷量大致上為其它水中混凝土的1/2。而氯離子擴散深度試驗水中自充填混凝土水中澆置與空氣澆置的氯離子含量差異最小，而其它水中混凝土水中澆置與空氣澆置的氯離子含量差異甚大，顯示水中自充填混凝土於水中澆置時完整性高。經由一系列試驗發現水中自充填混凝土品質優良，可大量應用於地下與水下結構物中。

Underground and underwater structures are important members to resist both gravity and horizontal forces, such as earthquake forces. However, it is very difficult to guarantee the quality of the construction, since no vibration is possible and underground water around the members. This is especially true after the 921 earthquake, because the design peak ground acceleration was increased. Various types of concrete were employed to compare the fresh and hardened properties. The fresh properties include flow distance in L test, turbidity, pH, self-compacting and anti-washout abilities. The hardened properties included the strength development and durability test under sea water environment. It is found that the underwater SCC has the best performance compared to conventional underwater concrete and anti-washout concrete and shall be used for underground and underwater strucutes.