What are Iron making and Steelmaking Slag? These slags are byproducts of the manufacture of iron and steel. They are a renewable resources with many practical applications. Through a variety of processing methods, slag can be used as the main raw material in the manufacture of fire resistant rockwool insulation, when ground to cement fineness, is used as a Portland cement replacement in concrete, and principally as an aggregate for topping driveways, parking lots and industrial work yards. Why form an Association? Our members provide a variety of products and services and are dedicated to the promotion of proper uses of these products. Processors & Distributors The following products and services are available from various locations in Canada: Blast furnance slag aggregates Steel slag aggregates Pelletized blast furnace slag Granulated blast furance slag Raw material handling & processing Material crushing, screening & blending Explore our website to learn more.