Discuss the effective electrode distance of accelerated Lithium Migration Technique from the viewpoint of ion migration

The development of Accelerated Lithium Migration Technique (ALMT) is used to inhibit the alkali-silica reaction (ASR) problem of concrete. When apply constant voltage, the migration rate of ions is affected by the structure of concrete and the electrode distance of ALMT. This research uses the constant voltage of 60 V on three kinds of wlc ratio concrete. Using different specimen lengths adjust the distance between electrodes of ALMT to be 8, 16, 24, 32 and 38 cm. Monitor the concentrations of the lithium, sodium and potassium ions in catholyte during the ALMT processing. The ALMT test stop when the removed alkalis from concrete no more increase apparently or the applied current density of ALMT lower than 1 A/m². Evaluate the migration efficiency by establishing relations between ion concentration and the cumulative amount of charge to analyze the effect of the electrode distance on the migration behavior of ions. Results show that the higher wlc ratio of concrete is beneficial to the migration of ions. The initial current decreases with the electrode distance increases, and the migration efficiency of ions will reduce. For concrete with the wlc ratios of 0.48, 0.58 and 0.68, the electrode distance lower than 16, 24 and 32 cm, respectively, have the better migration efficiency of ions, remove alkalis from concrete more than 80% and drive enough lithium ion into concrete. Therefore, for concrete with different wlc ratio, the above electrode distances can be the upper limit of applied electrical field under the practical ALMT application.