Synergistic mechanism of electrolytic manganese residue and red mud in ground granulated blast furnace slag -based cementitious materials system: Multiscale analysis based on hydration characteristics and mechanical properties

This paper investigates the synergistic effects and hydration mechanisms of ground granulated blast furnace slag-based cementitious materials under different types of solid waste composites. Innovatively proposes the use of sulfate from electrolytic manganese residue and alkali from red mud to synergistically activate blast furnace slag for the preparation of geopolymers. Additionally, three composite cementitious systems were constructed: electrolytic manganese residue-ground granulated blast furnace slag (E-G), electrolytic manganese residue-red mud-ground granulated blast furnace slag (E-R-G), and red mud-ground granulated blast furnace slag (R-G). The strength of synergistic effects between different solid wastes is evaluated based on the results of compressive/flexural strength tests. The hydration products of composite cementitious materials are analyzed using XRD, FTIR, TG-DTG, and SEM-EDS, and the setting time, flowability, and free bleeding rate of different cementitious material systems are analyzed. The experimental results indicate that there is a synergistic effect between electrolytic manganese residue, red mud, and blast furnace slag during the hydration process of composite cementitious materials. The ternary composite cementitious system of E-R-G exhibits the best composite synergistic effect, producing the most hydration products and the densest structure. A large amount of Ettringite(AFt) and C-S-H gel substances intertwine, reducing pores and defects and improving mechanical properties. Its compressive strength and flexural strength after 28 days reached 26.4 MPa and 6.6 MPa, respectively, and the addition of electrolytic manganese residue reduced the free bleeding rate and flowability of the system, while the addition of red mud increased the flowability and bleeding rate. This study reveals the composite activation effect of electrolytic manganese residue and red mud, as well as the hydration mechanism of composite cementitious materials, providing a theoretical foundation for the future synergistic utilization of various solid wastes.