Steel slag and phosphogypsum are two typical types of solid waste which were used to prepare composite cementitious ma-terial.The influence of carbonation activity of steel slag and the relative ratio of steel slag to phosphogypsum on the mechanical proper-ties of composite cementitious material was studied,and the solidification mechanism of carbonated steel slag on phosphogypsum was explored.The results indicate that steel slag possesses extremely high carbonation activity,and with the increase of steel slag content,the mechanical properties of composite cementitious material gradually improve.When the steel slag content is more than 40％,the compres-sive strength of composite cementitious material is more than 70 MPa,the softening coefficient of composite cementitious material is higher than 0.87.For the isolation effect of phosphogypsum powder the carbonation reaction of single particle of steel slag powder in-creases.Moreover,the neutralization of alkaline substances in steel slag and acidic substances in phosphogypsum reduces the alkalinity of the system.The calcium ions leached from steel slag combine with fluorine ions and phosphate ions in phosphogypsum,playing a chemi-cal solidification role in harmful ions.
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