This study explores the potential of utilising aluminosilicate industrial wastes, electric arc furnace slag (EAFS), fly ash (FA), and ground brick (GB), as sustainable alternatives to ordinary Portland cement (OPC) in alkali-activated paste mixes. The binders were activated using a combination of sodium hydroxide and sodium silicate, with a concentration of 12% Na2O/binder and a SiO2/Na2O ratio of 1.0. The water-to-binder ratio was fixed at 0.3 for all mixes. Unary, binary, and trinary mixes of EAFS, FA, and GB were investigated to assess their performance under accelerated carbonation conditions (20% CO2 concentration). The impact of carbonation was evaluated by comparing the fresh and hardened state properties of carbonated and uncarbonated samples with pastes made with OPC. Fresh-state properties, including workability and density, were measured using the grout spread method and fresh-state density tests. Hardened-state performance was assessed through compressive and flexural strength tests. The results indicated that the optimum flexural and compressive strengths were found in mixes containing 50% EAFS (S) and 50% FA (F) (i.e. F50/S50) for both uncarbonated and carbonated specimens. The carbonation depth of pastes was evaluated using a phenolphthalein-based pH indicator. After 7 days of exposure to 20% CO2, minimal carbonation depth was observed, indicating the formation of highly compacted matrices. Additionally, microstructural and phase characterisation of selected paste samples were performed using X-ray diffraction (XRD), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). These tests were employed to analyse the microstructural development of alkali-activated materials, with a particular focus on identifying silanol groups (silica gels) and aluminol groups linked with OH− groups (e.g., N–A–S–H, N–S–H phases).