Property Analysis Of Steel Slag And Application Research On Preparation Of Building Materials By Carbonated Slag

Each year, a large number of steel slag is produced by steelmaking industry. Steel slag is difficult to exploit and a large number of outdoor stacking, as the characteristics of great composition fluctuation, poor stability. Meanwhile, CO2 emissions is continuous rising by industrial development, which causes global warming and the greenhouse effect. In addition, heavy metals in thev accumulative steel slag, washed by raining, continuous leach and pollute the ecological environment. At present, research related to sequestrating CO2 and heavy metals by steel slag carbonation has made some progress, but research on mechanism model of steel slag direct carbonation in alkali system, the use of direct carbonated slag and the impact of steel slag stacking on environment are relatively few. To the above problems, in this article, the physical properties, mechanism of steel slag direct carbonation in alkali system, application path of steel slag and leaching behavior of heavy metals on Huaian two kinds of steel slag, multiphase medium leached slag in pilot field and laboratory, and direct carbonated slag in the laboratory is analyzed. It has certain guidance and reference value for further understanding on properties of steel slag, broadening the way of application on steel slag and evaluating the impacts on environment of steel slag stacking. The main research contents and progress of this article are as follows:(1) Two kinds of Huaian steel slag, marked as No.1 and No.2 steel slag is respectively selected. The physical properties of them are analyzed, the results of research show that composition of 2 kinds of steel slag are quite different. Physical properties of No.1 is similar to the traditional steel slag, and belongs to the representative steel slag; Calcium content of No.2 steel slag is very high, at 60.25%, f-CaO content of it is relatively high, at 4.34%, and it is suitable for applied in research related to content changing of calcium component in steel slag.(2) In the system of different alkalies, pH changes of direct carbonation process, content changes of carbon sequestration and mechanism of carbonation process are analyzed, the results of research show that the amount of alkalies (NaOH, Na2CO3) can affect the efficiency of steel slag carbonation. With the condition of 8%(alkali-slag ratio) NaOH and 7.95% Na2CO3, the maximum content of carbon sequestration on steel slag can be achieved.(3) No.1 direct carbonation slag is used for the preparation of building materials, and its indexes and properties are detected. All indexes of No.1 direct carbonated slag can meet the technical requirements of the national standard GB/T 20491-20491; The rupture strength of No.1 direct carbonated slag baking-free brick achieves level Cf6.0, the compressive strength achieves level Cc50, which can meet the requirement of the standard GB 28635-28635.(4) 5 kinds of steel slag in Huaian and baking-free brick of No.1 direct carbonated slag are respectively selected to analyze the leaching behavior of heavy metals. The results of research show that in No.1 leached slag, concentration of Mn element is 6.318 mg/L, and V element is 4.447 mg/L, concentration of Ba element in No.2 original slag is 48.60 mg/L, and concentration of Ba element in No.2 leached slag is 52.10 mg/L, which are higher than the standard of heavy metal wastewater discharge. Concentrations of Mn, Ba, and Pb elements in 5 kinds of steel slag, Zn element in No.1 original slag, Ni element in No.2 original slag and leached steel slag, and Mn, Pb elements in baking-free brick of No.1 direct carbonated slag are higher than the hygiene standard of domestic and drinking water. The preparation of building materials by No.1 direct carbonated slag has an effect on sequestrating heavy metals and preventing them leaching into the surrounding environment in a certain extent.