Investigation into the alkali-activation of lithium slag: A sustainable alternative to conventional cement with optimized mechanical properties

Abstract

Utilizing lithium slag as a precursor for alkali-activated cementitious materials offers a sustainable alternative to conventional cement, addressing both environmental pollution and land-use challenges posed by lithium slag waste. Additionally, this practice reduces energy consumption and CO2 emissions associated with cement production. This study presents a novel methodology involving high-temperature calcination and mechanical grinding to enhance the reactivity of lithium slag. Analytical techniques, such as X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), were employed to elucidate the mechanisms behind lithium slag's increased reactivity. Subsequently, these activated materials were used to formulate alkali-activated lithium slag cement composites (ALC). Various factors, including the calcination temperature, water-to-cement ratio, NaOH concentration, and lithium slag content, were investigated for their effects on the fluidity and mechanical properties of the mortar. Analytical techniques including XRD, scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS), FTIR, and thermogravimetric analysis (TGA)/derivative thermogravimetry (DTG), were used to explore the hydration mechanisms. Results indicate that the optimal calcination temperature for lithium slag was 700 °C, while the optimal NaOH concentration was 1 mol/L. ALC exhibited robust mechanical properties, with compressive, flexural, and fluidity measures reaching 37.66 MPa, 10.13 MPa, and 200 mm, respectively. Predominant hydration products were found to be N-A-S-H and C-A-S-H. The production cost of 1 ton of ALC is $49.8, which is roughly 70% of the cost of producing 1 ton of OPC. Additionally, the total CO2 emissions and energy consumption of producing ALC amount to 60.56% and 64.95% respectively, compared to the total CO2 emissions and energy consumption of producing 1 ton of OPC.