LD Slag is one of the by-products generated in steel making process during separation of impurities from molten steel in steel melting shops. It is then tapped into slag pot which solidifies on cooling and is the separated. The solid form of the Steel slag has both metallic & non-metallic ingredients and has various undesirable characteristics which limits its usage in as is form. Hence the Steel Slag undergoes various value-adding processes such as Crushing, Screening, Weathering & testing to transform it into the usable product.
Processing of Steel Slag involves following steps:
1. Crushing & Screening: The free metallic are magnetically separated and the non-metallic slag left after the Slag is passed through a Jaw crusher and series of screens which segregates it into different size fractions ranging from 0-65mm with sub-fractions of 0-6mm, 6-20mm, 20-40mm and 40-65mm for usage in various combination for different layers of road.
2. Weathering: Steel Slag is prone to volume expansion – the CaO and MgO contained in the flux remain partly inactive and reside in the slag or crystallize while the slag is solidified and cooled. These inactive materials, referred to as free-CaO and free-MgO, react with water, and in the process their volume nearly doubles through hydration. To eliminate this property, the Steel Slag is subjected to weathering through the process of Dry and Wet Cycle ageing or it is subjected to an advanced Open Steam Ageing Process.
3. Testing: To ensure the readiness of the product and consistent quality, the processed Slag is taken through an exhaustive testing procedure of ten tests such as Volume Expansion, Iron Unsoundness, Free Lime, Water Absorption, Abrasion Value, Crushing Value etc. in an NABL accredited lab.