Migration of cations in mortar under an electrical field controlled by a constant current density

In this study, an Accelerated Lithium Migration Technique (ALMT) was applied to simultaneously drive alkali out and lithium into concrete as a remedy for alkali-silica reaction (ASR) problem. The mortar specimens used in the experiments contained 2.0% Na₂O_eq. Constant current denities were applied during the ALMT testing process. The anolyte and catholyte solutions consisted of LiOH·H₂O and Ca(OH)₂, respectively. The results show that there are a well correlated linear relationship between the applied current density and the steady flux and migration coefficient of the Li⁺. During the process of ionic migration, K⁺ was first removed completely from the specimen, followed by Na⁺, after which the Li⁺ flux remained steady. The system resistance initially decreased, and then increased gradually. The time corresponding to when the Li⁺ concentration in the cathode/Li⁺ in the source cell was equal to 0.1% indicates the time-span needed for Li⁺ to penetrate throughout the specimen. Furthermore, the accumulated charge carried by the cations and the accumulated charge applied during testing showed a similar in all test cases.