Alunite concrete expanding agent

The invention discloses an alunite concrete expanding agent, and belongs to the technical field of concrete admixtures. The invention aims to provide the alunite concrete expanding agent capable of fully utilizing local resources and meeting the standard requirements of conventional Chinese expanding agents. The alunite concrete expanding agent comprises the following components in percentage by weight: 8 to 15 percent of ammonium alum, 10 to 15 percent of natural alunite, and 75 to 79 percent of natural anhydrous gypsum or gypsum dihydrate; and the alunite concrete expanding agent is prepared by pulverizing the natural alunite and the natural gypsum uniformly and mixing the powder and ammonium alum powder uniformly. The alkali content of the alunite concrete expanding agent is reduced, the limited expanding rate is produced in advance, the expanding performance is enhanced, the compressive strength is improved, the physical and chemical properties of the alunite concrete expanding agent reach and exceed the