本研究內容主要區分為三個項目：第一、探討鋰離子與水泥水化作用、水化產物及鹼矽膠體反應情形；第二、利用電化學方法抑制混凝土AAR，探討鋼筋通電對鋼筋混凝土抗壓強度、鋼筋握裹力及鋼筋抗拉強度等性質之影響；第三、設計不同通電模式之縮小尺寸RC試體，分析不同電場作用下離子傳輸行為。 研究發現鋰離子會參與水化作用，也會與水化產物及鹼矽膠體反應，甚至取代出鹼矽膠體中部分Na+、K+離子。為了減短維修時間及加速鋰離子進混凝土，利用電化學技術抑制混凝土AAR時，採用較高的電流密度，若以鋼筋作為陰極，施加9 A/m2以上電流密度對水泥砂漿抗壓強度影響較小，但是會造成握裹力下降、增加鋼筋周圍AAR發生機率及鋼筋氫脆現象及等不利的影響，而且電流密度愈大影響愈嚴重；此外，試體內部會有電化學作用「無效區」存在，此時可在試體內部鑽孔作為輔助陽極，增加Li+離子進入及Na+離子移出試體的路徑。實務上建議使用單維電場通電模式，在混凝土兩側外加輔助陰、陽極，對於抑制AAR的效果較佳。 The scope of this research are: (1) study the effects of lithium on hydration of cement, reactions with hydration product, and ASR gel; (2) investigate the influence of electrochemical technique on the properties of rebar and the bond strength between rebar and concrete; (3) study of the migration of Li+, Na+, and Ca2+ ions under electrical fields resulted from different designs of cathode and anode. Test results showed that lithium ions involve with the hydration of pure cement, react with the hydration product, and even replace the sodium ions of ASR gel. The sufficient amount of lithium ions driving into concrete should be noticed. In order to reduce treatment time and increase the amount of lithium penetration, high current density was adopted. However, a current density higher than 9 A/m2 will induce the hydrogen embrittlement of rebar and reduction of the bond strength between rebar and concrete. If the rebar was used as cathode and an auxiliary anode was applied on the concrete surface, Na+ ion will concentrate near the rebar to increase the possibility of AAR. Improper design of electrodes resulted in ineffective areas to remove Na+ ion out of concrete and migrate Li+ ion into concrete. The better choice is to establish 1-dimensional electrical field by applying auxiliary cathode and anode on each sides of the concrete. Keywords: AAR, lithium, electrochemical technique
