"The #cement industry alone accounts for nearly eight percent of human-caused CO2 #emissions.
The Cambridge researchers approached the problem by looking at an industry that was already well established—steel recycling, which uses electric-powered furnaces to produce the alloy.
Instead of waste being produced, the end result was recycled cement ready for use in #concrete, bypassing the emissions-heavy process of superheating limestone in kilns."
" An electric arc furnace needs a "flux" material, usually lime, to purify the steel. At the end of the process, the used flux is discarded as a waste material. So for the Cambridge method, the lime flux was swapped out for the recycled #cement paste. And sure enough, not only was it able to purify the steel just fine, but if the leftover slag is cooled quickly in air, it becomes new Portland cement. "
"A research group at RMIT University in Melbourne, Australia, found a way to replace 80% of the #cement in #concrete with a waste product from coal-fired power plants.
#FlyAsh is mainly comprised of silicon, oxygen, aluminum, iron, and calcium. By adding nano silica and hydrated lime to their fly ash, the RMIT team have successfully produced concrete with 65% and 80% replacement of cement."
Sure, they can feed the electric furnace with recycled concrete to avoid heating pure limestone, but the energy for the electric kiln comes from somewhere.
There is much more concrete being created than destroyed, and you still have to carry the recyclable concrete to the plant.
So no, you can't make zero emission concrete. And you aren't going to make much of a dent in the 7.5% emissions.