As the title suggests. If roman concrete supposedly has the capabilities to mend tiny cracks via chemical reaction, why isn’t it used with modern reinforcements to seal the pathways to the steel beams to protect it from oxygen and elements and prevent corrosion? Are there any major downsides to hot-mixed concrete, is it not as good as the studies make it out to be, or is it simply not viable due to cost and manufacturing process/storage requirements?
In: Engineering
We are still finding out new things about concrete and new ways to make it better. The concrete we have now are a lot better then the Roman concrete. What you are talking about is quicklime chunks in the concrete, likely due to poor mixing quality of the concrete. These chunks does make the concrete weaker and more likely to crack. But the self-healing capability is that when you mix this quicklime with water it fills the crack making it water tight again. However this lime crack is even more brittle then the original concrete. So the chances of it cracking again is very high.
So for example if there is a hole eroded under your concrete driveway and you drive over it cracking the driveway. Then yes, the crack may “heal” itself after a few weeks. But if you drive over it again then it will crack again. And it will not heal the second time.
Because the exact formulation used was lost for about 2000 years. Only recently have chemists be able to replicate the formula used by the Romans. One of the big items was volcanic ash.
[https://www.labroots.com/trending/chemistry-and-physics/24482/chemists-recreated-long-lasting-roman-concrete](https://www.labroots.com/trending/chemistry-and-physics/24482/chemists-recreated-long-lasting-roman-concrete)
Just because it has the ability to self-heal in some situations doesn’t mean it’s better.
We have the added advantage of 2000 years of development and advances in material sciences.
A weaker concrete that self-heals is much less useful than stronger concrete that doesn’t get damaged in the first place.
It’s mostly not very good concrete. It’s fun to hype it up as some sort of mythical lost technology. But it’s not really supernatural. It lasted a long time, but mostly by just lumping up huge amounts until it held.
Very simply, because Roman concrete’s magical properties are somewhat overstated by urban legend.
There are a few factors here. For one thing, the only examples of Roman construction still standing today are those which were wildly overbuilt and which happened to have particularly strong materials, because everything else has long since crumbled due to errosion and earthquakes and scavanging. This in turn means that we are *only* seeing the absolute strongest examples of Roman concrete ever poured; not every batch was this good, and not every building was built this strong (in fact, only a small number of each were). This is related to the old maxim that any engineer can build a bridge that stands, but it takes a really good engineer to build a bridge that *barely* stands. Modern mathematics and technology has made us much, much better engineers than the Romans, which ironically means we tend to build things that are much less durable (but also vastly cheaper).
Another important factor here is that Roman concrete isn’t really *that* mysterious in terms of chemical properties. We’re well aware of how to make similar concrete, and we’ve been aware for a long time (though we only recently got confirmation of what exactly the Romans were doing), but we actively choose not to. The main reason we choose not to is modern construction has other techniques available to it, most notably steel reinforcement, which makes it better to mix concrete with a different set of tradeoffs than what the Romans had to do. Modern concrete sets a lot faster and is a lot stronger than Roman concrete under compressive forces (which are the only forces modern concrete has to withstand, specifically because of reinforcement).
There’s more that goes into all of this, but the tldr is that we *could* make Roman concrete if we wanted to, and we’ve been able to do it for a long time (even though we didn’t know for certain that it’s what the Romans were doing), but we choose not to because the concrete mixtures we’re using today are much better than what the Romans were using *within the context of modern construction*. Additionally, we *could* build things to stand for thousands of years, the way the Romans built a few of their works, but doing so is wildly expensive and probably completely unnecessary: after all, it’s not like the *Romans* are benefitting from the fact that the Pantheon is still standing. So we don’t tend to overbuild anything to that extent because no one wants to pay for it.
I suspect that we tend to get overexcited over click bait titles that make claims about how “Romans had better concrete that last thousands of years. Modern concrete is lousy and we’re too cheap/dumb/lazy to figure things out.”
The truth is much more prosaic. Modern concrete is better, more consistent and stronger than ancient concrete. Modern construction methods use far less materials to achieve results. We make things out of concrete today in areas and situations that civil engineers just a few hundred years ago (not to mention Romans) could only dream about.
The Roman concrete structures that survived are all arches and similar.
They figured out a way to make their stone structures last longer, not how to make string concrete.
We know how to make Roman concrete. There’s simply no reason to do so.
1. Until recently we didn’t quite know how Roman concrete stood the test of time.
2. Modern concrete is, even without reinforcement, stronger and more specialized the Roman concrete. So is still a better alternative.
There are probably engineers and scientists out there trying to blend the two together right now to make a modern concrete that self heals. But unless it is economically competitive against modern concrete it won’t take off.
Well for one, we lost its technology, only recently did we draw some connections to the mineral composition amd inclusion of certain materials. But by the time we figured it out we had developed alternative processes.
1) Roman concrete was really, really good for its time, but the formula was lost until we figured it out in modern day. If you could go back 1,000 years or even 300 years ago, it might have been a game-changer. But we’ve surpassed Roman concrete.
2) I wouldn’t call the materials that make up Roman concrete “rare” exactly, but seawater and volcanic ash in close proximity is a lot easier to find in Italy than most places, which is a big reason why nobody else rediscovered Roman concrete.
3) The chemical makeup of Portland cement is actually very similar in concept to Roman concrete. Portland cement had a very different discovery history but ultimately Roman concrete is basically just a low tech version of Portland.
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