Steel slag is a byproduct produced in the process of iron making. The purpose of steelmaking is decarburization, dephosphorization and desulfurization. It is a process of enrichment of products from oxygen blowing, slag making and element removal to slag. According to the smelting method, treatment process, shape and alkalinity of steel slag, steel slag can be divided into different types.
In order to improve the added value of steel slag, a very effective way is to use steel slag after ultrafine grinding as a mixture of cement to produce steel slag cement, or as an active admixture of concrete to prepare high performance concrete.
Steel slag (water slag for short) is a kind of molten material which is mainly composed of calcium silicate and calcium aluminosilicate discharged during ironmaking. The granular active material prepared by water quenching is brownish yellow, gray white and dark brown; porous and dispersed; particle size is generally less than 10 mm; bulk density is 400-800 kg / m3; natural moisture content is 5% - 18%; its chemical composition is Cao, SiO2, Al2O3, FeO, MnO, etc.
Although both slag and blast furnace steel slag are waste slag produced in the process of iron and steel smelting, there are significant differences in chemical composition and mineral composition. In terms of cementitious property, the differences between steel slag and water slag are as follows:
The content of Cao in steel slag is generally about 40%, and its main mineral composition is dicalcium silicate, tricalcium silicate and hermannite, blast furnace slag is less than 45%, and its main mineral composition is yellow feldspar and other minerals.
The content of alumina in steel slag is low, generally less than 5%, which exists in solid solution minerals; while the content of alumina in slag is more than 8%, which mainly exists in yellow feldspar minerals.
The content of silicon oxide in steel slag is low, generally less than 20%; the content of silicon oxide in slag is often more than 30%.
Iron oxides in steel slag are in the form of FeO and Fe2O3, with the total content below 30%, of which divalent iron (FeO) is the main component; the slag contains only less than 5% of ferric oxide (Fe2O3)
There is phosphorus pentoxide in steel slag, but there is no phosphorus pentoxide in slag. Moreover, when there is too much phosphorus pentoxide in the steel slag, it will adversely affect the formation of tricalcium silicate and reduce the activity of steel slag.
In conclusion, steel slag vertical mill has found a way of sustainable development for the reuse of steel slag. The grinding efficiency of steel slag vertical mill is high, the power consumption of the system does not exceed 50kWh/t, and the specific surface area of the ground steel slag powder can reach 4500 ~ 5000 cm2 / g.
