Electrolytic manganese residue based autoclaved bricks with Ca(OH)₂ and thermal-mechanical activated K-feldspar additions

Electrolytic manganese residue (EMR) is a type of solid wastes generated along with the production of electrolytic manganese. Currently, treatment and utilization of the EMRs are essentially insufficient, leading to lots of cultivated land being occupied, together with serious environmental pollution. In this study, we prepared EMR based autoclaved bricks (EMR-ABs) with the addition of Ca(OH)₂ and thermal-mechanical activated K-feldspar. The orthogonal and single factor tests were performed to determine the influences of preparation conditions and associated mechanism. Results indicate that EMR-ABs could be obtained with 1-day compressive strength of 23.5 MPa and the Mn leaching concentration of <0.02 mg·L⁻¹, which not only meet the requirements in Autoclaved Lime-Sand Brick Standard (GB 11945-1999) for MU 20 autoclaved bricks, but also immobilize Mn from EMR. XRD and SEM analyses showed that the main hydration products in the bricks are calcium silicate hydrate gel and tobermorite, contributing to high compressive strength of the EMR-ABs. This research provides a new way to comprehensively utilize EMR to make value-added building materials with high compressive strength and simultaneously reduce EMR's harm to the environment.