Alkaline activation for production of slag-based binders from the manufacture of manganese ferroalloys

Abstract

The growing demand for sustainable development across different sectors is creating opportunities for research and development of products that incorporate waste materials in their production processes. One of the technologies that has gained prominence in this regard is the alkaline activation process, known for its low energy consumption and environmentally sustainable characteristics. In this sense, this work presents an evaluation of the application of slag generated in a manganese ferroalloy manufacturing plant as a precursor to alkali-activated binders. Grounded silico-manganese slag and NaOH at different molarities were used to prepare samples, which were then cured at room temperature (25 ± 2 °C). The rheological properties of the pastes and the technological properties of compressive strength and water absorption were analyzed. In addition, microstructural analysis was performed using XRD, TG/DTA, SEM/EDS, and FTIR. The results showed that the shear stress increases with NaOH molarity, and viscosities are higher for the paste with the lowest molarity. The maximum 91-day compressive strength of 14.4 MPa was achieved with a 6 M solution, and for this condition, the mass loss was 0.2%. Integrating SEM micrographs with TG/DTA, XRD, and FTIR analysis supports the hypothesis of gel phase precipitation during the synthesis of the alkali-activated binder. Thus, incorporating this slag into the production of an alkali-activated binder demonstrates the potential to revitalize this manufacturing process, which could lead to the adoption of clean and environmentally sustainable technologies in industrial processes.