Editing Slag (section)

=== Ferrous slag ===
Ferrous slags are produced in different stages of the iron and steelmaking processes resulting in varying physiochemical properties. Additionally, the rate of cooling of the slag material affects its degree of [[crystallinity]] further diversifying its range of properties.  For example, slow cooled blast furnace slags (or air-cooled slags) tend to have more crystalline phases than quenched blast furnace slags ([[ground granulated blast furnace slag]]s) making it denser and better suited as an aggregate. It may also have higher free [[calcium oxide]] and magnesium oxide content, which are often converted to its hydrated forms if excessive volume expansions are not desired. On the other hand, water quenched blast furnace slags have greater [[Amorphous solid|amorphous]] phases giving it latent hydraulic properties (as discovered by Emil Langen in 1862) similar to [[Portland cement]].<ref>{{Citation|last=Cwirzen|first=Andrzej|title=10 – Properties of SCC with industrial by-products as aggregates|date=2020-01-01|url=https://www.sciencedirect.com/science/article/pii/B9780128173695000106|work=Self-Compacting Concrete: Materials, Properties and Applications|pages=249–281|editor-last=Siddique|editor-first=Rafat|series=Woodhead Publishing Series in Civil and Structural Engineering|publisher=Woodhead Publishing|language=en|isbn=978-0-12-817369-5|access-date=2021-11-26}}</ref>

During the process of smelting iron, ferrous slag is created, but dominated by calcium and silicon compositions. Through this process, ferrous slag can be broken down into blast furnace slag (produced from iron oxides of molten iron), then steel slag (forms when steel scrap and molten iron combined). The major phases of ferrous slag contain calcium-rich [[olivine]]-group silicates and [[melilite]]-group silicates.

Slag from [[steel mill]]s in ferrous smelting is designed to minimize iron loss, which gives out the significant amount of iron, following by oxides of [[calcium]], [[silicon]], [[magnesium]], and aluminium. As the slag is cooled down by water, several chemical reactions from a temperature of around {{convert|2600|F|abbr=on}} (such as [[Redox|oxidization]]) take place within the slag.<ref name=":0" />[[File:Slag2.jpg|thumb|upright|A path through a slag heap in [[Clarkdale, Arizona|Clarkdale]], Arizona, showing the striations from the rusting corrugated sheets retaining it.]]

Based on a case study at the Hopewell National Historical Site in [[Berks County, Pennsylvania|Berks]] and [[Chester County, Pennsylvania|Chester]] counties, [[Pennsylvania]], US, ferrous slag usually contains lower concentration of various types of [[trace element]]s than [[non-ferrous slag]]. However, some of them, such as [[arsenic]] (As), iron, and [[manganese]], can accumulate in [[groundwater]] and [[surface water]] to levels that can exceed environmental guidelines.<ref name=":0" />