The use of lithium compounds to treat hardened concrete suffering damage due to alkali-silica reactivity

The purpose of this study was to examine the effectiveness of using lithium to treat hardened concrete experiencing distress due to alkali-silica reaction (ASR). A number of concrete structures in the U.S. have been treated with lithium to mitigate ASR but little is known about the effectiveness of the treatment. In this study, the effectiveness of the treatment was evaluated by measuring the depth of penetration of lithium into both laboratory concrete and ASR-affected structures in the field and by determining the effect of the treatment on the subsequent expansion of the concrete. The treatments performed were simultaneous electrochemical lithium impregnation and chloride extraction, electro-osmotic pulse, vacuum impregnation and surface ponding (topical treatment). Control specimens that did not receive treatment were also prepared. A second phase of treatment involved casting and treating smaller blocks to investigate the effects of treatments on expansion at the surface and at depth. It was also of interest to determine what effect exposure to sodium chloride de-icing salts and to potassium acetate, a non-chloride anti-icing salt, has on concrete that is being treated with lithium salts. Several samples of concretes that have been topically treated with lithium in the field were collected and the effectiveness of these treatments was assessed. Field treatments in this study did not deliver a sufficient concentration to a sufficient penetration depth to constitute an effective treatment as judged by the guidelines published in FHWA-HRT-06-073. Laboratory topical treatments performed similarly. Electro-Chemical treatments did not consistently deliver sufficient concentrations but warrant further study. Electro Osmotic treatments did not outperform ECE type treatments.