USE OF A LITHIUM-BEARING ADMIXTURE TO SUPPRESS EXPANSION IN CONCRETE DUE TO ALKALI-SILICA REACTION

The findings of a laboratory study on the effects of a lithium-based admixture on alkali-silica reaction are presented. The admixture essentially represents an intermediate stage in the lithium extraction process of the ore spodumene. Spodumene ore is normally crushed and fired in a kiln to "untie" the lithium prior to its extraction. The material at this stage is known as decrepitated spodumene (DS). DS is basically an amorphous alumino-silicate that contains significant quantities of "available" lithium. As such, DS has the potential to act both as a pozzolanic mineral admixture as well as a chemical suppressant of alkali-silica reactivity. Laboratory testing included pore solution studies of pastes and mortars containing DS and expansion studies of mortar bars containing Pyrex glass (ASTM C311) and concrete prisms containing reactive aggregates from three different sources in North America. The results show that significant quantities of lithium are released by the DS into the pore solution of pastes a...