Slag is the glass-like by-product left over after a desired metal has been separated (i.e., smelted) from its raw ore. Slag is usually a mixture of metal oxides and silicon dioxide. However, slags can contain metal sulfides and elemental metals. While slags are generally used to remove waste in metal smelting, they can also serve other purposes, such as assisting in the temperature control of the smelting, and minimizing any re-oxidation of the final liquid metal product before the molten metal is removed from the furnace and used to make solid metal.

Slag is a strong and durable material which is highly versatile and ideally suited for use as an aggregate in many applications.

The steelmaker benefits from slag recycling by avoiding the cost of landfill. The community benefits, too. Slag is a man-made mineral, therefore its use as an aggregate in place of a natural aggregate product avoids the environmental footprint from quarrying.

The advanced technology of great wall slag vertical roller mill can be removed the iron effectively from the slag, and no less than 1% iron content can not only protect the machine, but also can increase additional income.