I thought the secret of Roman concrete was the Tufa, a pyroclastic sand, which was used, for instance, in the construction of the Port of Ostia. This civic work has 2000 year old concrete that's intact and in direct content with the sea water.
I thought it was the use of pozzolana--glassy aluminosilicate volcanic ash--along with lime. The Roman marine concrete may also have an advantage from being mixed with seawater. It gets stronger in saltwater. Portland cement concrete with iron rebar gets weaker in seawater, because the rebar swells and makes the concrete spall off.
Although it is true that sand from different geologic deposits can show vastly different results when used in the same building product. Superior binder plus superior aggregate could make superior concrete.
I think there is a fair amount of interest in pozzolana type cements because it's becoming apparent that portland cement + rebar has a finite life.
> sand from different geologic deposits can show vastly different results
That's the other bugaboo about portland cement, Aggregate expansion/alkali-silica reaction/concrete cancer. They used the wrong type of aggregate and dune sand in the old foundation of my house (rental not my problem unless I'm in it during the next earthquake). So now it's crumbling.
Granted if you keep reinforced portland cement dry, it's fine. Otherwise eventually it'll fail.
The highly inovative thing about this glow in the dark cement isn't that it glows in the dark - it's the fact that it's UV condusive, similar to translucent concrete:
Like many fields of science, material science seems to have become absolutely crazy in the last two decades with a huge swath of research, so much of it that nobody actually manages/bothers to combine all the disparat and different discoveries into one huge gigantic leap. Instead you get special materials A to Z, each with their own special flavor. It seems highly likely that ~7±2 years from now, someone will come along and do so, synthesizing the majority of these discoveries into one bigass leap in material science. If it hasn't happened already in someone's head and we'll find their paper on arxiv later this year. I'd speculate this will likely come out of either India or China, as western patent laws would make any such leaps-and-bounds innovations absurdly expensive with gigantic patent wars happening. Whereas if China or India suddendly start using concrete of this kind inside their own countries only, what you gonna do about it to stop them? Sue them? Watch either of them give negative shits. (I could see this becoming problematic with China and their massive road construction in Africa tho.)
To provide some additional future speculation:
It seems likely to me that this will then lead a pseudo-revival of Brutalist architecture, but modified by knowledge we have today, with structures appearing, paradoxically, as both more organically rounded (hence the pseudo-, since that won't match the Brutalist style) AND more synthetically jagged.
I say this because:
1. It seems almost certain to me that any such 'new concrete' would end up a lot less grey than Portland cement, if you look at Roman concrete as an example, both normal Roman concrete and Roman marine concrete have a color significantly less grey than normal Portland concrete. Adding Titanium dioxide and other materials innovations to that would likely shift this further into a more white-ish hue.
2. It seems highly likely to me that they'll modify the Trichoderma reesei from the parent article to include bioluminescence. Likely for the purpose of making it easily tracable in the concrete as part of research. And then someone in the lab will go "wow that looks pretty". Combine this with what I've already pointed out and you'll get very crazy looking buildings.
3. We know a lot more about the geometry of architecture than we did in the last century. For examples, see here:
A lot of Roman concrete has lasted to this day. The aqueducts are still impressive, the colosseum is only 2/3 standing because of an earthquake hundreds of years ago (and is otherwise a fine museum), and the pantheon is as shockingly gorgeous today as when it was built 2000 years ago.
Totally agree, but just wanted to expand on the colosseum for a moment. While traveling there, I spent a full day at the Roman Colosseum. Its outer travertine stones were all without mortar and originally held together with numerous iron clamps. Since the fall of Rome, the clamps were slowly harvested, leaving the surface of nearly every outer stone with huge holes. In the opinion of those I spoke with, had the structure been left intact with it's clamps, it would have endured in much better shape.
It's not survivorship bias because no one claimed that all Roman concrete was better than all modern concrete.
The point is that the vast majority of modern concrete, especially using rebar, will last decades compared to some Roman concrete, which has lasted millenia.
The wikipedia article above indicates that the durability of aquatic roman concrete is the result of a reaction between the lime and tufa
>The seawater instantly triggered an exothermic chemical reaction. The lime was hydrated – incorporating water molecules into its structure – and reacted with the ash to cement the whole mixture together.
