Steel production generates some hundred million tons of steel slag worldwide each year. This giant mountain of leftovers is largely dumped. TU/e professor of building materials, Jos Brouwers, will be working with industrial partners to investigate whether he can make cement out of it. If he succeeds, more CO2 emissions can be cut than is produced yearly by all the traffic in the Netherlands.Steel slag is produced by the conversion of raw iron into steel – around 125 million tons of it per year. Much of that is dumped and only a small portion used, in embankments. That’s a shame, professor Jos Brouwers says, because the mineralogical composition very closely resembles that of cement. It contains the same components, but in different ratios. And it is public knowledge that the cement industry emits a very high amount of CO2: five percent of the global total. A cement substitute with no extra CO2 emissions would, therefore, be most welcome.