What is Slag?
Slag is a non-metallic product consisting essentially of glass containing silicates, alumino-silicates of lime and other bases and is obtained as a by-product in the manufacture of pig iron in a blast furnace or electric furnace. Granulated slag is used in the manufacture of Portland Slag Cement (PSC).
Slag is a byproduct of metal smelting, and hundreds of tons of it are produced every year all over the world in the process of refining metals and making alloys. Like other industrial byproducts, slag actually has many uses, and rarely goes to waste. Slag appears in concrete, aggregate road materials, as ballast, and is sometimes used as a component of phosphate fertilizer. In appearance, slag looks like a loose collection of aggregate, with lumps of varying sizes. Slag is also sometimes referred to as cinder, in a reference to its sometimes dark and crumbly appearance. Slag is produced during the smelting process in several ways. Firstly, slag represents undesired impurities in the metals being smelted, which float to the top during the smelting process. Secondly, metals start to oxidize as they are smelted, and slag forms a protective crust of oxides on the top of the metal being smelted, protecting the liquid metal underneath. When the metal is smelted to satisfaction, the slag is s
A.S.T.M. (the American Society for the Testing of Materials) defines blast furnace slag as the non-metallic product, consisting of essentially of silicates and alumino-silicates of lime and other bases, which is developed in a molten condition simultaneously with iron in a blast furnace. In other words, iron and steel makers produce slag by using limestone to purify their iron-based products. After the molten slag is separated from the iron or steel, it cools and hardens with its own unique set of properties. Because of the high temperatures of a blast furnace, approximately 2700 degrees F, the impurities have been chemically bound. What results is an extremely hard and resilient rock. In addition, because gases escape from the slag as it cools, it has a porous (or vesicular) structure that makes it lighter in weight, yet extremely strong and durable. A further benefit is that the carbon dioxide was driven out of the rock when it was calcined in the furnace, which is a strategic benefi
