Triethanolamine-enhanced carbonation efficiency of carbide slag in low-carbon cement composites

Abstract

Carbide slag (CS), a calcium and alkali-rich industrial byproduct, shows potential for CO₂ capture but is limited by the low dissolution rate of calcium ions during carbonation. This study proposes a triethanolamine (TEA)-modified carbonation approach to enhance CO₂ uptake efficiency and application of CS in cement-based materials. Results show that the addition of 10 g/L TEA significantly enhances the CO₂ uptake of CS from 12.58 % (without TEA) to 21.35 % by accelerating calcium ion dissolution during the carbonation process. Besides, TEA-modified carbonation also promotes the formation of needle-like calcite with a high aspect ratio, which could be attributed to the site-selective adsorption of TEA molecules on the planes of CaCO₃ crystals based on the molecular modeling analysis. Considering the incorporation of TEA-modified carbonated CS (TCCS) into cement-based materials, the compressive strengths are significantly increased by 10–25 % and 5.2–12.6 % at 1 d and 28 d, respectively. Further analysis indicates that the adsorbed TEA–CO₂ complexes on the surface of TCCS facilitate the formation of nano-CaCO₃ particles and enhance the dissolution of aluminate phases, which can enhance cement hydration and increase the formation of hydration products. This work provides new insights into alkanolamine-regulated carbonation mechanisms and offers a sustainable strategy for CO₂ capture and solid waste utilization in low-carbon cementitious materials.