Good question. I know for a fact that the type of sand is important, specifically that the shape and grain of the sand required for concrete makes a lot of readily available sand unusable for concrete.
As for iron dust, I have to agree. The only way I could see iron dust being practical is if this tech was able to repurpose industrial waste (rusted up sheet metal, old rebar, etc).
> It’s actually created from waste steel dust which is normally discarded from industrial processes and silica from ground up glass. The iron within the steel dust reacts with C02 and rusts to form iron carbonate. It’s this that is fused into the matrix of Ferrock and, like concrete, after it’s dried, it cannot be melted back into a liquid form but retains its hard, rock-like qualities.
> ... But there’s skepticism from the cement industry that while Ferrock could be great for niche projects, it isn’t practical for large-scale industrial use, like highways for example. If steel dust suddenly goes from being a “waste” material to a highly-prized building resource, it’s price will increase exponentially and the costs of producing Ferrock may limit its application.
I read that the Sahara is useless, for example, because desert sand is rolled rounded. The only sand that concrete can use is the dug up, sharp cornered kind.
I wonder if it's possible to "roughen up" smooth sand for this purpose. Shoot it against itself in a special machine, thus breaking it to smaller, sharp-edged pieces... or something.
"Large Saharan Collider – not what you think it is!"
You're forgetting that it's easier to create rock dust from scratch than it is to create iron dust from scratch. That's important when you're comparing the two, since you can't simply scoop up iron dust off beaches and river banks anyway. Given the choice between manufacturing rock dust and manufacturing iron dust, the choice is obvious.
To manufacture rock dust you:
1. Quarry rock.
2. Pulverize it.
To manufacture iron dust you:
1. Quarry ore.
2. Pulverize it.
3. Smelt it (which requires coke, a basket of worms in itself.)
4. Cast it.
5. Grind it.