不同配比混凝土內置鋼筋之腐蝕行為及防蝕策略

A Strategy of Steel Corrosion Behaviors and Anti-Corrosion within Different Mixture Concrete

本研究係針對分別使用ACI配比設計之傳統混凝土及緻密配比設計之高性能混凝土（HPC）製作鋼筋混凝土樑，在人工海水環境中分析腐蝕行為，探討此兩種混凝土配比設計對保護鋼筋腐蝕之效益。結果顯示，混凝土未開裂前，ACI配比設計及緻密配比設計之兩種高性能混凝土，均具有良好保護鋼筋之效果，而使用緻密配比之高性能混凝土，電阻係數比ACI配比之混凝土高出三倍強，且鋼筋電位及腐蝕速率均明顯較低。但是一旦混凝土樑開裂後，此時無論使用何種配比設計，鋼筋電位隨即下降至－267 mV ~－413 mV間，已達腐蝕電位範圍，腐蝕速率也大幅提升。為了防止腐蝕物擴散，本研究亦推論透過緻密配比提高電阻值而降低腐蝕速率似乎是可行的。

This study focus on the corrosion of single RC beam under artificial brine condition. Two single reinforcing bar concrete beams designed by ACI mixture design algorithm and high DMDA (densified mixture design algorithm) were cast. The results show that before the cracks of concrete both ACI mixture design and HPC showed well-protective effect of steel as ACI specification mention, while under the same strength condition the electrical resistance value of HPC is higher than that design by ACI. However, after cracking whatever concrete will shows potential drop in the rang between －267 mV and －413 mV. A tentative strategy is proposed as to design the concrete with higher resistivity is beneficial to protect corrosion of steel, even after cracking due to the lower diffusion rate of sound concrete than the low resistivity concrete.