Study on the development of inorganic polymers from red mud and slag system: Application in mortar and lightweight materials

The conversion of red mud into valuable products remains an important issue to be addressed. Inorganic polymers from red mud and slag system were investigated. Slag was substituted at 25, 50 and 75% by red mud in the system. Sodium silicate solutions of modulus ranging from 1.6 to 2.2 were used and the samples were cured at 25, 40 and 60 °C. Slag was amorphous phase while red mud contained some crystalline phases, mainly hematite, crancrinite and katoite. A better reactivity, faster setting and lower shrinkage were obtained for higher contents of slag, with a modulus of sodium silicate solution of 2.0. The composition made of 50% red mud and 50% slag achieved a 7 days compressive strength of 54 MPa at 25 °C. The use of standard sand and hydrogen peroxide allowed the formation of mortar and lightweight materials with reduced mechanical properties, but still of interest to address both issues of sustainable use of resources and CO2 reduction in construction.