Disposing of slag is a millennia-old problem , but the "waste material" is highly sought in construction. Recycled slag performed 8 percent better in concrete than "raw" slag. Australian scientists are trying to close the loop on steel waste and sewage wastewater. When they made new concrete using these waste materials, the results were 17 percent stronger than concrete made with traditional materials. Let’s talk about slag. Steel is first made in extremely high-temperature blast furnaces, where natural iron ore or recycled scrap is purified by fire, and then combined with the right elements to make different kinds of alloys. There are strict definitions for these types, and each has narrow windows for which elements are allowed (and in which quantities). During this process, impurities are sloughed off continuously. These leftovers are called slag. Slag is both plentiful and potentially valuable. For some alloys, even the so-called byproduct of the furnace process is just a second saleable product. And regular slag is highly prized as a strong, durable aggregate material for concrete. “The global steel making industry produces over 130 million tons of steel slag every year," water engineer Biplob Pramanik, of Melbourne’s RMIT University, said in a statement. […]
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