Concrete expansion agent is used to prepare expansive concrete (including compensating shrinkage concrete and self stressing concrete). Compensating shrinkage concrete has the functions of compensating for concrete shrinkage and compacting concrete, and improving concrete impermeability. It is mainly used for waterproofing and crack resistance in civil engineering. It is commonly used in the preparation of high-grade waterproof concrete and appropriately extending the spacing between expansion joints or post pouring strips.