| Summary: | 碩士 === 國立海洋大學 === 河海工程學系 === 91 === Abstract
In this study, whether or not the cathodic current will accelerate the alkali-silica aggregate reaction is investigated. It is expected that sodium and potassium ions willbe attracted to the rebar-concrete interface due to the cathodic current such that thealkali-silica aggregate reaction will be initiated and accelerated. Using NaOHsolution to adjust the initial alkali content and pyrex glass, the specimens having highpotential of alkali-silica aggregate reaction were made. Variables considered were w/cratio, initial alkali contents and cathodic current density. Crack initiation time, crackmouth opening history, microhardness and tensile strength of rebar were adopted toinvestigate the effects of cathodic current. In addition, chemical titration to determineamount of accumulated sodium and potassium ions was performed to support ourviewpoints.
Results showed that the crack initiation time shortened as increasing the initialalkali content, w/c ratio and/or cathodic current density. Crack opening rate alsoincreased in the same manner. In addition, microhardness test indicated thatrebar-concrete interface significantly softened when potassium and sodium ionsincreased. It was found as the influence parameter, (defined as the product ofcathodic current density and polarization time, i.e., ic×tp), increased the yield strength,the ultimate strength and elongation percentage all decreased. The decrement inelongation percentage was most apparent. This result indicated that hydrogenembrittlement of rebar existed. Our research pointed out that application of thecathodic current required careful consideration.
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