反覆載重下高性能混凝土樑抗蝕效能之研究

The Anti-Corrosion Effect of High Performance Concrete Beam Under Cyclic Loading

本研究採用符合最新美國ACI 318-95規範，採用耐蝕性具低水膠比且高流動性之高性能混凝土為材料，探討一般鋼筋混凝土與預力混凝土，添加不同摻料在人工海水環境下，經歷反覆載重後，內部鋼材腐蝕行為，更佐以SEM晶相分析瞭解材料內部構造之改變，期能瞭解高性能混凝土中鋼材腐蝕之機理及比較與傳統鋼筋混凝土之差異點。研究結果顯示，添加卜作嵐材料之高性能混凝土比一般傳統混凝土具有高達數倍之電阻係數，且顯示出混凝土用水量與電阻係數有反比關連性。預力鋼纖維高性能混凝土在反覆載重下較一般鋼筋混凝土有較小之變位及裂縫寬度，其鋼材電位變化較小。依田口式分析其S/N比較小得知鋼纖維高性能混凝土具有較佳的抗蝕效應。本研究發現HPC應用卜作嵐材料對受壓構件是有絕對功能的，然而對張力構材，無論何種混凝土，只要裂縫一發生腐蝕均無可倖免，而此現象更顯示用電位量測方法太過保守，而且ACI之設計觀念對張力構件不恰當必須修正。

The high performance concrete (HPC) with corrosion resistance, low W/B ratio, high flowability and made according to the newest ACI Code 318-95 was used to study the corrosion behavior of the embedded steel in ordinary reinforced concrete (RC) beams and prestressed concrete beams under cyclic loading in artificial sea water environment. With the aid of SEM micrograph, the corrosion mechanism of steel embedded in high performance concrete was also studied to compare the difference between HPC and conventional concrete under the same circumstances. The results show that HPC with the addition of pozzolans has higher resistivity than that of ordinary concrete. It leads to the conclusion that there is an inverse-proportional relationship between the water content and resistivity. High performance prestressed fiber concrete (HPFC) under cyclic loading possesses smaller deflection, crack width and steel potential than those of ordinary reinforced concrete beam. According to the smaller S/N ratio analyzed by Taguchi method, high performance steel fiber concrete has better corrosion resistance. It is discovered in this research that the application of pozzolanic materials in HPC is useful for the compressive concrete member. The corrosion will always accompanies with the cracks existing in any tensile concrete member. The results indicated that it will be improper to have this phenomenon measured by steel potential and to use the ACI Building code for tensile concrete member.