本发明提供了一种混凝土外加剂,由下列重量份的原料制成:硫酸亚铁10~20份、硅藻土2~4份、硝酸钡2~4份、乙烯基树脂2~5份、2-甲氧基苯基硼酸3~5份等,本申请的外加剂可以使减水率达到45%以上,最高可以达到56%;同时,该外加剂对于 The concrete admixture comprises the following raw materials in parts by weight: 10 to 20 portions of ferrous sulfate, 2 to 4 portions of diatomaceous earth, 2 to 4 portions of barium nitrate, 2 to 5 portions of vinyl resin, 3 to 5 parts of 2-methoxyphenylboronic acid, etc. The admixture of the present application can achieve a water reduction rate of over 45% and a maximum of 56%; meanwhile,