Magnesia as an expansive additive

MgO has been employed to compensate for the thermal shrinkage in mass concrete in China. More recently, the application of MgO expansive additive is gradually extended to various concrete structures for the shrinkage compensation of concrete at all the ages, owing to the designable hydration and expansion properties of MgO. This chapter mainly introduces the history, microstructure and properties of MgO expansive cement/additive as well as the performance of concrete added with the MgO expansive additive. Moreover, the state-of-the-art manufacture technology and application of MgO expansive additive in real concrete structures are comprehensively reviewed.