High-magnesium waste stone dust-based composite mineral admixture, and applications thereof in medium-strength concrete

The invention discloses a high-magnesium waste stone dust-based composite mineral admixture, and applications thereof in medium-strength concrete. The high-magnesium waste stone dust-based composite mineral admixture is prepared via following steps: (1) high-magnesium waste stone, wet discharged fly ash, and manganese residue are dried until water content is lower than 1.0%; and (2) by weight, 70 to 85 parts of the dried high-magnesium waste stone, 10 to 20 parts of the dried wet discharged fly ash, and 0 to 10 parts of the dried manganese residue, 0 to 10 parts of mineral waste residue, and 0 to 10 parts of a clinker are smashed into powder respectively and then are mixed, or are mixed and then are smashed into powder with a specific surface area ranging from 601 to 900m2/kg so as to obtain the high-magnesium waste stone dust-based composite mineral admixture. According to the high-magnesium waste stone dust-based composite mineral admixture, morphology effects and filling effects of high-magnesium waste stone powder are used so as to increase compactness of concrete mixtures, and increase fluidity of concrete; slump loss is less; less additives such as polycarboxylic acid are absorbed; concrete early-stage strength development is accelerated, and later-stage development is stabilized. And in addition, the high-magnesium waste stone dust-based composite mineral admixture can be applied to concrete together with high-magnesium waste stone coarse and fine aggregates so as to increase utilization ratio of high-magnesium waste stone greatly.