The Alkaline Reactivity of Opal in Mortars Modified with Lithium Nitrate

Preventing the destructive reaction between reactive aggregate and sodium and potassium ions in concrete pore solution is vital for the maintenance of concrete durability. There are several methods of preventing this adverse reaction, such as the application of cement with pozzolanic additives. Several papers also indicate the high efficiency of lithium compounds in mitigating the alkali-aggregate reaction.The aim of this study was to determine the effect of lithium nitrate on the reaction between opal and alkali in mortar bars. The mortar samples contained alkalis of two different concentration levels.Lithium nitrate was applied at a fixed molar ratio of lithium to sodium and potassium ions. Expansion studies were conducted in accordance with the methodology included in the ASTM C1260 standard. The modification of samples with lithium nitrate contributes to the decrease of expansion both for the low alkali cement and high alkali cement. The microstructure of mortar samples, both modified and non-modified with lithium nitrate, was examined and X- ray microanalysis was performed.