Cement Anti-shrinkage Additive

Cements suffer short and long-term drying autogenous shrinkage and are subject to volume reductions due to thermal changes. These phenomena may cause concrete cracking and net shrinkage of building blocks, compromising the durability of the structure. Certain applications, such as dams, suspension bridges and foundation works, are sensitive to these effects and require extra measures, such as the addition of expansion or anti-shrinkage additives in concrete formulations. Magnesium oxide can act as such an additive due to its volumetric expansion upon hydration. The reactivity of the MgO must be carefully adjusted to avoid premature or late hydration, depending on the application. Calcined magnesium oxides provide early expansion while deadburned MgOs provide delayed expansion effects. See also Drilling Cements.