Branden Simon
Senior Member
February 14
Hamilton The Design District 41 | ?m | 31s | Emblem Developments | Arcadis
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Chronamut
Active Member
Is that concrete damage on that one pillar?
Branden Simon
Senior Member
Yes there’s is a concrete pillar on one of pillar and they need to inspect and repair it with a fresh concrete
Chronamut
Active Member
mm.. well.. at least there's rebar inside.. but that's always an unsettling feeling..
Chris R.
Senior Member
Concrete is strong compressively so even cracks are fine often. Rebar is what holds concrete under tension. In this case they'll likely Jackhammer out the poorly poured concrete and reform it and fill it again.
Chronamut
Active Member
Unfortunately we do not make concrete the way the ancients did - the exact recipe was lost to time for the longest time - but one of the key ingredients was volcanic ash from Mt. Vesuvius which works as a perfect cement and cures eternally. They also didn't use rebar. Over 2000 years later, their structures still stand - and our bridges deteriorate after 20-50 years, often because the metal expands and rusts and cracks the outer surface. It's one reason so much damage was done to the Parthenon when earlier restorations used iron uncoated with lead to hold the pieces together - metal expanded and rusted and cracked the blocks - lead was used as a rustproofing in ancient times and they were I shaped to hold the marble blocks together - now they use titanium, because titanium won't rust - same reason it's used to hold bones together inside people.
Our concrete will never be as good because we make it cheaper. If we were smart, we'd use titanium rods with roman concrete, but that's expensive to make things that last an eternity, because we live in an ikea disposable world where buildings will just be demolished in 50-100 years time to make way for new ones - cue the city center.
Yes they can remold it, but the fact is if it's that easy to be defective, there is no guarantee it won't just happen again down the line.
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TheHonestMaple
Active Member
This is completely wrong lol. Modern concrete is leaps and bounds ahead of ancient stuff.
This type of mispour is very common and will be easily fixed...
This type of mispour is very common and will be easily fixed...
Chronamut
Active Member
You are incorrect. Even concrete people have admitted that the inclusion of volcanic material in ancient cement makes it much superior because it never stops curing and thus has more versatility, among other things. Concrete was part of my education as part of my architectural schooling background.
Read more about it here - roman concrete is much more durable: https://riskfrontiers.com/insights/why-is-roman-concrete-more-durable-than-modern-concrete/#:~:text=Why is Roman concrete more,result in cracks and spalls.
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Chris R.
Senior Member
I think from my understanding that concrete is a complex material with more than one type. There will be different aggregate used, different ratios, and different chemicals to get different properties.
From that same understanding, modern concrete is capable of being much stronger than Roman concrete, however older concrete was able to self-repair. Some newer concrete is weaker, but cheaper to make, but is more than strong enough for our needs. Our ability to create a weather seal also removes the necessity for self-repairing concrete.
Prior to modern engineering they just built stuff much thicker and stronger than needed. My house for example has joists for the first floor that are 3 full inches thick, and 12 full inches tall, and are less than 12 inches apart. That is super overkill.
Same with the foundation, it's a stone laid foundation and is almost 2 feet thick. There's no need for it to be that thick, but it will outlive me certainly.
We've been able to engineer the exact material properties of construction items to fully meet the needs of what we're building without spending extra money to overbuild.
Chronamut
Active Member
The problem with modern cement is its inert properties and inability to deal with moisture getting into it and thus splitting, dissolving it and cracking it- roman cement could bend/flex and also, as you said, self-repair. So yes you are correct, we use different properties in different ratios, some are finer, sometimes we use things like vibrating rods to get a slump test to properly settle if not enough water is used, or a superplasticizer agent in replace of water, we have different options. The ancients relied a lot on volcanic ash because they did a lot of stuff by the sea and it pretty much solidifies on contact with the seawater and only gets stronger with exposure to it. With our concrete being inert generally in places inside where the weather and temperature is controlled and not super moist we can generally get away with it and its most likely cheaper the way we do it, but that doesn't make it "better".
Ancient cement will far outlive our modern cement, and not just because they made it thicker, but simply due to the different properties of their cement. They are actually looking into research to combine the modern and ancient cement recipes together to create an overall superior one that has resilience and also can self-repair and flex. In the life after after humans series it was stated the coliseum would be one of the very last things to collapse several thousand years later while our buildings would last 50-100 years. We just don't build things for durability anymore because it's much easier to just tear them down and build something else after their modern life cycle of 50-100 years.
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TheHonestMaple
Active Member
You actually think ancient Roman engineers created more sophisticated materials than modern engineers? Cutting edge research at countless universities know less than ancient peoples? Sure, some roman cement was good. But we are far far more capable of producing better today. No question.
Chronamut
Active Member
If you're going to imply we know more than all the ancients in the world just look no further than many of the wonders of the ancient world we still cannot replicate today because the technology has been lost. Giant foundations and stones weighing so many tons our best equipment cannot replicate moving it, yet they somehow could back then - all the fine arts that created the parthenon that to this day they are still rediscovering, with all the slight adjustments to level out optical illusions of sagging, ancient buildings built with such precision you cannot fit a razor blade between their joints, the pyramids build with giant blocks angled with such precision it is within a difference of millimeters. I believe it is hubris to believe that all we are now is greater than all we were then.
A lot of what we have accomplished now is through reverse engineering what existed in the past. We wouldn't even HAVE modern civilization without greece/rome, and probably not concrete without them either.
And yes, I do, because their buildings, unlike ours, are still standing 2000 years later. One only has to look at the pantheon, one of the most incredible feats of engineering that has a circular oculus that is freestanding without any rebar, and is still standing. Now do you honestly think our concrete, with its rebar will still be standing in 2000 years, or could replicate the below oculus and survive 2000 years? I personally don't think so, but of course only time will tell, but if our bridge overpasses are any indication, those start to crack and fall away from the rebar in a short 20 years time..
You make it sound like what we use nowadays is so groundbreaking - in reality what we use are still common materials, just in different ratios - sand, stones, pebbles, portland cement etc. It ALL comes from the ground. They relied on physics and geometry to keep things stable, and golden ratios, harmony of form etc. We're not using space-age technology for concrete - its still mainly sand rocks and binding agent, roughly mixed together by contractors, and poured into formwork and molds. Look at any sidewalk - over time you can see the stones bonded to the sand on the surface.
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TheHonestMaple
Active Member
You're literally describing survivorship bias.
Chronamut
Active Member
Considering an awful lot of the roman world survived in some form into the present day that wasn't "deliberately" destroyed, I wouldn't call that survivorship bias - it's not a small demographic of small surviving instances but lots of them.
But I digress, as usual this has veered off course lol - either way, hope they can repair that pillar.
Undead
Senior Member
It's not an apples to apples comparison. You're referencing what were mega projects at the time, consuming vast resources over generations. If we were to go all out today, surely we'd produce something unreal.