Concrete expansion agent and application thereof for compensating concrete dry shrinkage

The invention relates to a concrete expansion agent and the application thereof for compensating concrete dry shrinkage. The concrete expansion agent has low wet curing requirement after slurry is formed, has proper expansion in an early period, continuous micro expansion in a later period and stable hydration products after expansion and has a better compensation function for the concrete dry shrinkage. The concrete expansion agent is light-burned MgO with a hydrated activity value of 40-90s. The concrete expansion agent has the MgO content which is larger than or equal to 85 percent and burnloss which is less than or equal to 5 percent, a concrete analysis sieve of 80 micron is used for detecting, and the residue on sieve of the concrete expansion agent is ranged from 3 percent to 10 percent. Compared with the prior product, the hydration product has low water requirement, low wet curing requirement after the slurry is formed, higher hydrated activity, quicker expansion in the earlyperiod and continuous micro expansion in the later period, and the expanded hydration product has stable performance, can not generate a retraction phenomenon and has a better compensation function for the dry shrinkage of the concrete slurry.