A Study of Using One Dimension Electrochemical Cation Migration Technique to Inhibit Concrete ASR

• Main Authors: Wei-Chien Wang, 王韡蒨
• Other Authors: Chau Lee
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/15762044750189802762

博士 === 國立中央大學 === 土木工程研究所 === 98 === The Accelerated Migration Technique (ALMT) uses the driving force of electrical field to remove Na+ and K+ from concrete, and simultaneously drive Li+ into concrete to inhibit alkali-silica reaction (ASR). This study discusses the behavior of cations under ALMT influencing by the electrical field conditions, the proportion of concrete mixtures, and the ASR deterioration degree, firstly, to seek the evaluated index of the migration parameters of cations, propose the required items of the parameter and the analysis method, then establish the relationship between the migration parameters and the index. The result shows that the curves between the cation concentrations in catholyte and time, can be divided into two types according to the ASR deterioration degree of concrete. The two types both contain the Na+ and K+ stable migration and the completed migration stages, and the Li+ non-steady state, transition, and steady state. For concrete with higher ASR deterioration degree, the needed time to reach the Li+ steady state is shorter. From the curve between the cation concentrations in catholyte and time, the required migration parameters can be obtained, including the removal time, removal amount and unit time removal amount of the Na+ and K+, and the passing time, the non-steady state migration coefficient, the steady state flux and migration coefficient of the Li+. Though the test condition may change, the above parameters can still establish suitable relationship with the applied current density. Increasing the electrical field, a/c ratio, w/c ratio and the ASR deterioration degree, and reducing the length of sample and alkali amount of cement, can increase the unit time removal amount and reduce the removal time of the Na+ and K+, reduce passing time and increase the steady flux and migration coefficient of the Li+. The relationship between the cations accumulated charge migrating into the catholyte and the applied charge shows that the curve include the alkalis removed and the Li+ impregnated linear regions (TA and TLi). The accumulated charge until Na+ is removed completely is found just in the boundary between the two regions. The linear slope of the alkalis removed region is greater. While increasing the applied voltage, a/c ratio, w/c ratio, and the ASR deterioration degree, and decreasing the length of sample, can increase the proportion of the applied charge being used for cation migration. But increasing the system alkali amount can increase TA and reduce TLi. Finally, this research proposes the standardized procedure to obtained the migration parameters of the Li+, Na+, and K+, including the needed testing steps, the observing items, may applied theory, and the relationship between the migration parameters and the current density.