Strength optimization and characterization of one-part geopolymer prepared from alkaline thermo-mechanical activated electrolytic manganese residue and vanadium-bearing shale leaching residue

Large amounts of solid wastes, such as electrolytic manganese residue (EMR) and vanadium-bearing shale leaching residue (VSLR), are generated in industry, causing severe environmental pollution. Although they can be utilized to prepare geopolymers, the viscous and corrosive alkali-activator solution limits practical application. Here, EMR and VSLR were activated via alkali-thermo-mechanical activation, producing one-part geopolymer binders similar to Portland cement. In addition, blast furnace slag (BFS) served as a calcium source to accelerate setting and improve geopolymer microstructure. Using response surface methodology, geopolymers with an A-EMR/R-VSLR mass ratio of 7:3 and 20 % BFS addition achieved a 14-day compressive strength of 23.8 MPa. After 14 days of autoclave-dry curing, the strength further increased to 35.1 MPa. XRD, FTIR, XPS, and SEM analyses revealed that C–S–H and N(C)–A–S–H gels synergistically improved mechanical properties. These innovative geopolymers demonstrate excellent strength without strong alkali activators, enabling green production and efficient recycling of EMR and VSLR. • One-part “just add water” geopolymer binders were developed from two solid waste residues. • Geopolymers with autoclave-dry curing achieved a maximum compressive strength of 35.1 MPa. • C–S–H and N(C)–A–S–H gels synergistically enhanced the compressive strength of geopolymer.