Preparation method of concrete admixture based on C70 high-strength concrete broken pebble and gravel

The invention discloses a preparation method of a concrete admixture based on C70 high-strength concrete broken pebble and gravel, and the method comprises the following steps: adding unsaturated polyoxyethylene ether macromonomer and water in a mass ratio of 1: 3 into a reaction kettle at 25-30 DEG C, and performing stirring; after uniformly stirring, dropwise adding the material A and the material B at the same time, wherein the material A is a mixed aqueous solution of unsaturated anhydride or carboxylic acid, a reducing agent and a chain transfer agent, and the dropwise adding time is 3-3.5 h, the material B is an oxidizing agent aqueous solution, and dropwise adding for 2-2.5 hours; after dropwise adding, performing curing for 1 hour, adding a sodium hydroxide solution, adjusting the pH value to 5-7, and obtaining the concrete polycarboxylic acid admixture with the solid content of 40-45%. The concrete admixture based on the C70 high-strength concrete broken pebble and gravel does not need to be heated i