Use and Treatment of Blast Furnace Slag
Slag is a by-product generated during the production of iron from iron ore. When hot iron is extracted from the furnace, an extremely hot, liquid compound referred to as slag is produced. The slag generated from iron manufacturing, specifically from the blast furnace process, has economic and environmental advantages, with potential significant applications in many industries.
1.Properties of Blast Furnace Slag
The blast furnace slag (BFS) generated from iron ore is composed of crystalline silica particles that grow when the liquid slag cools. It is a fairly lightweight material with a low specific gravity of 2.9 to 3.2 and contains a great proportion of calcium (CaO), aluminum (Al2O3), and silicate (SiO2). Apart from that, it also consists of sulfur (Sa) and phosphorus (P) in low proportions. Each of these elements has strong properties that can be advantageous in a wide range of applications.
2.Use of Blast Furnace Slag
In most cases, the slag produced is not an economically attractive product, and so most of it is discarded in landfills. However, slag can be put to good use in many applications—especially in construction and cement manufacturing.
a. As Aggregate
In construction, blast furnace slag can be used as an aggregate for concrete or asphalt pavements. It can improve the workability and strength of the concrete or asphalt, reducing cracking, shrinkage, and temperature variations.
b. As Cement Substitute
When used as a cement substitute, it can improve the physical and mechanical properties of concrete or mortar, as well as reduce water permeability, shrinkage, and temperature variation. It can also enhance durability, reduce drying shrinkage, and increase the freeze–thaw resistance of concrete.
c. As Building Material
Slag can be used as a building material in a wide range of applications, such as filler material and drainage appli-cations, due to its thermal insulation properties. The cellular structure of slag also offers a higher strength, giving it potential for use in building panels, precast walls, and even cement boards.
3.Treatment of Blast Furnace Slag
The available treatments for blast furnace slag depend on the desired end-use of the slag, such as aggregate and cement substitute. The process of converting slag into usable products involves cooling, crushing, classification, and aging.
For instance, the slag is cooled by air or water, then crushed and screened to separate the fine particles from the course ones, before being sorted into different particle sizes for various applications. This is followed by aging, where the slag is placed in an aggregate pile and monitored for maturity over time.
4.Conclusion
In conclusion, blast furnace slag is a by-product generated in the production of iron from iron ore that can be used for a variety of applications, including aggregate for construction and cement substitute for concrete and mortar. Through cooling, crushing, and sorting, this waste material can be converted into usable products with a variety of beneficial properties that can offer economic and environmental benefits.
