Effects of Liquid Solid Ratio,Molding Pressure and Carbonization Time on Carbonization Properties of Magnesium Slag

Magnesium slag is an industrial solid waste with high mechanical properties and a capacity for CO₂ storage following carbonization.To date,there has been a paucity of research conducted on the carbonization of magnesium slag.The effects of the liquid-solid ratio,carbonization time and molding pressure on the carbonization properties of magnesium slag were examined,and the carbonization degree and carbon fixation efficiency of magnesium slag samples under three conditions were discussed.The mechanical properties,carbonation products,mineral composition and microstructure of the carbonation specimens were characterised by a series of analytical techniques,including pressure testing,thermogravimetric analysis,x-ray diffraction,infrared spectroscopy,scanning electron microscopy and mercury intrusion analysis.The findings demonstrate that:(1) In a humid environment with a high concentration of CO₂,the mineral main phase γ-C₂S of magnesium slag can react rapidly to form calcium carbonate crystals and silica gel with a high degree of polymerisation,resulting in a gel structure comparable to calcium silicate hydrate and an enhancement in the mechanical properties of the magnesium carbide slag test block.(2) The mechanical properties and carbon fixation efficiency of the magnesium carbide slag sample demonstrated an increase with the elevation of the liquid-solid ratio,molding pressure,and carbonization time.(3) When the liquid-solid ratio is 1/4,the molding pressure is 30MPa,and the carbonization time is 12h,the compressive strength of the magnesium slag carbonization test specimens reaches 69.7MPa,and the carbon sequestration efficiency is 10.9%.It is evident that the carbonization process can transform magnesium slag into a novel type of carbon storage material with enhanced mechanical properties.This offers a promising avenue for the recycling and mineralisation of magnesium slag as a means of storing CO₂.