Abstract: First,add red mud to the slag cementing materials as modifier which is consist of slag, gypsum and cement clinker, then study the compression strength influence of red mud dosage, and analyze the microstructure of the gelled material by SEM.The test result shows that with the increase of red mud dosage, compression strength first increased, then decreased, and got a optimum at the red mud dosage of 6%（the ratio of the other elements was slag 74%, gypsum 10%, cement clinker 10%, while PC 0.3% of the total amount of the raw materials）, and in this situation, the gelled material can get compression strength of 61.93, 70.53, 81.02 MPa each on 3, 7 and 28 d.Hydration products of the gelled material mainly include C-S-H gel and ettringite; and with the increase of reaction time, the cover areas of C-S-H gel add continually, and ettringite interlace with each other closely, which show hydration processes tend to be completely.

Key words: Red mud, Modifier, Slag cementing materials, Compression strength