Ettringite is a hydrous calcium aluminum sulfate mineral that forms during the early stages of cement hydration as part of the normal hardening process. It can also form later in the life of concrete under certain conditions, known as delayed ettringite formation (DEF), which can be detrimental. Ettringite formation is primarily influenced by the sulfate content in the cement and the reaction of these sulfates with calcium and alumina compounds present in the cement. In its beneficial role, ettringite contributes to the initial strength gain of concrete. However, in its delayed form, it can cause significant expansion and cracking due to its larger volume.