Preparation of aragonite whisker-rich materials by wet carbonation of magnesium slag: A sustainable approach for CO2 sequestration and reinforced cement

In this study, aragonite whisker was prepared from magnesium slag (MS) by a wet carbonation method, aiming to effectively capture CO2 and be added to cement as microfiber. Firstly, various parameters governed the formation of aragonite, including temperature and MgCl2 concentration, are systemically investigated. Needle-like Aragonite with single crystal length of 10 - 12 µm and length-diameter ratio of 25 - 40 with amorphous silica gel could be prepared by wet carbonation of MS with the MgCl2 concentration of 1 mol/L at 80 °C. MS could absorb approximately 0.397 g CO2 in aragonite whisker-rich materials (AWM) by 1 g of MS during this carbonation process. Furthermore, AWM showed a smaller particle size distribution and higher surface area (74.52 m2/g) in comparison to cement (1.73 m2/g). Then the influence of added AWM on the performance of the cement was investigated. The hydration heat is increased with the increased AWM dosage. Aragonite whisker and amorphous silica gel both could work as nucleation sites for hydration products. Moreover, aragonite whisker could work as a micro-fiber in cement and amorphous silica gel has a high pozzolanic reactivity in cement hydration. Therefore, the addition of AWM resulted in a refined pore structure and a significant enhancement in compressive strength and flexural strength of cement mortar at both early and late age. These findings provide a sustainable approach for reinforced cement preparation using solid waste MS and CO2 sequestration.