水中自充填混凝土之研究

Abstract

構造物因配置鋼筋量的增加，間隙越來越密集導致混凝土澆置不易，自充填混凝土的發明對這些問題已找到解決之方法。自充填混凝土藉著本身之重量，不需要搗實、振動即可通過鋼筋間隙，並充填至模板各個角落，目前已在國內各項工程廣泛使用。目前工程界進行之水中結構物，尤其是連續壁或深基礎樁，仍然使用傳統混凝土或者高流動性混凝土，其澆置品質並不容易控制。如果水中混凝土擁有自充填混凝土的特性，必能避免發生混凝土的施工品質不良之缺陷。 本試驗以自充填特性和水中不析離，以及抗沖蝕能力為試驗目標，使用不同種類與劑量之抗沖蝕劑，並經過工作性能測試、凝結時間、pH值與懸浮物對新拌混凝土測試相關性質，並符合自充填混凝土之規定標準。在混凝土硬固後，測試力學性質、耐久性與體積穩定性之試驗以確保混凝土之品質。水中自充填混凝土搭配特密管施工，能夠有效提升混凝土之施工品質。

Taiwan is in the seismic region and the design ground acceleration was increased substantially after the 921 earthquake. This leads to the increase of steel ratio and thus the congestion of reinforcements. This causes a problem in compacting and some times even impossible to vibrate the concrete. Self-compacting concrete (SCC) is a concrete which can fill into every corner of the form by its own weight without vibration and no segregation. SCC is gaining popularity all around the world. The underwater RC structures still use traditional underwater concrete. This concrete has good anti-washout capability but the workability is not as good as SCC. In order to guarantee the integrity and quality of underwater RC members, a new type of underwater SCC is thus needed for piers, harbors, slurry walls, and deep foundations. This research develops this underwater SCC which will not segregate in water and have excellent workability and is anti-washout in water. Various agents were tested to determine the suitability. The indices for the performance include pH values, suspended material, anti-washout ability, and workability. It is found that several agents can satisfy the criteria and this new type of concrete is thus developed. The mechanical properties, durability, and volume stability are also tested and all satisfy the criteria in code. The quality of underwater construction is guaranteed.