Synthesis and evaluation of alkali-activated blast-furnace slag materials with high compressive strength and CO2 capture properties

Abstract

This study investigated the synthesis and evaluation of alkali-activated materials (AAMs) derived from industrial by-products, targeting their dual function as sustainable alternatives to Portland cement and as CO₂ adsorbents. AAMs were prepared using iron blast furnace slag and calcined alumina. Response surface methodology was employed to optimize the formulation, focusing on the SiO₂/Na₂O and Si/Al molar ratios and the liquid/solid ratio to enhance mechanical and adsorption performance. The synthesized AAMs were characterized via compressive strength testing, nitrogen physisorption, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). CO₂ capture performance was assessed using thermogravimetric analysis. The optimal formulation (SiO₂/Na₂O = 0.5, Si/Al = 2.0) exhibited a compressive strength of 35.6 MPa after 7 days, a specific surface area of 49.3 m² g⁻¹, and a CO₂ adsorption capacity of 0.80 mmol g⁻¹ at 35 °C and P_CO2 = 0.2. SEM analysis revealed a homogeneous porous structure with micropores (1–3 nm) and mesopores. FTIR spectra showed characteristic bands at 1410 and 1470 cm⁻¹, associated with O–C–O stretching, confirming CO₂ adsorption. The findings demonstrate a simple and effective approach for developing multifunctional AAMs with promising mechanical properties and carbon capture capabilities.