Beneficial use of stainless steel EAF slag as composite cement admixture and its heavy metals leaching risk analysis

摘要

This study analyzes the feasibility of using stainless steel electric arc furnace(EAF)slag as composite cement admixture and the risk of leaching-out of heavy metals.The results show that the stainless steel EAF slag,mainly made up of Ca2SiO4,Ca3Mg(SiO4)2,some Cr-containing minerals and in small particle size,is easily ground and has cementitious activity.EAF slag,when used as cement admixture,can be added with a maximum percentage of 32%.It can meet the strength requirements of the standard P·C 32.5 cement.When the mixing percentage is decreased to 25%,the strength of the cement can be increased to that of P·C 42.5 cement.Other main quality indexes of composite cement,such as the setting time and stability,also satisfy standard requirements.The results also show that most of the heavy metals in the stainless steel EAF slag exist in a stable speciation.The concentration of heavy metals that leach out from the stainless steel EAF slag and the composite cement products is far lower than the standard limit of hazardous wastes.The main heavy metal,chromium,exists as less hazardous trivalent chromium.Therefore,the risk of heavy metals leaching out from the stainless steel EAF slag is low.The internal exposure index(IRa)and the external exposure index(Iγ)of the stainless steel EAF slag are both lower than 1.0,satisfying the standard requirements of the state for the radionuclides of building materials.Therefore,stainless steel EAF slag can be safely used as admixture to produce composite cement.