Concrete expansion agent is a calcium sulphoaluminate concrete expansion agent, does not contain sodium salt, it should not cause concrete alkali aggregate reaction. The durability is good, the expansion performance is stable, and the strength continues to increase. Ordinary concrete cracks due to shrinkage, leakage often occurs, reducing its use of function and durability. In the cement, 8%-12% of the expansion agent can be mixed into the compensation shrinkage concrete, which greatly improves the crack resistance and waterproof ability of the concrete structure. External waterproofing work can be eliminated, and the length of the rear splice gap can be extended to prevent the occurrence of temperature difference cracks in mass concrete and high-strength concrete.