No. 381: Move to utilize steel slag is growing fast (December 15, 2011)

Steelmakers are busily occupied with the development of technology to apply steel slag to the reconstruction of disaster-stricken areas in the Tohoku region. JEF Steel developed the material called “SmartGrout” to fill in the hollow space created by liquefaction of ground. Made of three major elements of steel slag, blast furnace cement, and bentonite, it is a mortar-like material that combines reasonably water and air bubbles created by a surface active agent. Thanks to the high flowability, it easily flows in every corner of a hollow space. At the same time, it does not hurt pipes in the ground like water pipe because it has only one tenth of the strength of concrete when it is solidified. Nippon Steel proposes a technology to adulterate the sludge brought to land by tunami in alliance with Nippon Steel Engineering. The technology puts a steel slag-based reforming material into sludge mixed with wreckage, and hydrates and solidifies silica component in the sludge and calcium in slag while eliminating wreckage from the sludge. It adulterates the sludge to be usable as a material for embankment and reconstruction of the devastated region.   

In the steelmaking process, 40 kg of slag is generated for every one ton of raw steel. The domestic slag production increased 16.5% over the previous year to about 40 million tons in 2010. Slag is mostly mixed with standard cement to create furnace cement and used a base course material. Japanese steelmakers are increasing slag exports because of the dwindling public investment and the growing competition with other kinds of recycled products in the domestic market. In the export business, the competition with Chinese and Korean steelmakers is expected to intensify. Nippon SlagAssociation is intensifying its efforts to spread slag as an environmental material in alliance with the Japan Iron and Steel Federation.