This section will define lithium compounds, particularly lithium carbonate and lithium nitrate, which are used in cement and concrete applications. The chemical mechanisms by which lithium interacts with cement components will be detailed, focusing on its role in mitigating alkali-silica reaction (ASR), a deleterious chemical reaction that causes expansive cracking in concrete. The process by which lithium ions inhibit the gel expansion by interacting with reactive silica found in aggregates will be explained.