<P> Basic slag is a co-product of steelmaking, and is typically produced either through the blast furnace--oxygen converter route or the electric arc furnace--ladle furnace route . To flux the silica produced during steelmaking, limestone and / or dolomite are added, as well as other types of slag conditioners such as calcium aluminate or fluorspar . The major components of these slags therefore include the oxides of calcium, magnesium, silicon, iron, and aluminum, with lesser amounts of manganese, phosphorus, and others depending on the specifics of the raw materials used . </P> <P> Because of the slowly released phosphate content in phosphorus - containing slag, and because of its liming effect, it is valued as fertilizer in gardens and farms in steel making areas . However, the most important application is construction . </P>

Chemical composition of slag during smelting process in the extraction of iron