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2,050-year-old Roman tomb offers insights on ancient concrete resilience
- httpz 5y agoBefore we start comparing Roman concrete structures to modern ones, we have to consider that there's a heavy survival bias here. We're only looking at Roman concrete structures that happened to survive for 2000 years while most Roman concrete structures probably didn't survive.
- peter_retief 5y agoWhat I found interesting about Roman cement is that it was ironically softer than modern cement and had an almost self repairing property, think of ancient docks that had constant waves wearing it down yet lasted hundreds of years.
- sk2020 5y agoIt seems like someone makes a “novel” discovery about Roman concrete every few months. I’m curious what the real reason for that is.
- shiftpgdn 5y agoAlso they didn’t fill it with rusty metal.
- sillyquiet 5y agoThe civil engineering-oriented channel Practical Engineering has a pretty good video on Roman concrete vs. modern. https://www.youtube.com/watch?v=qL0BB2PRY7k https://www.youtube.com/watch?v=qL0BB2PRY7k The primary tldw; is the fact modern concrete uses steel rebar for tensile strength, whereas the Romans relied on architectural techniques to minimize tensile forces on their structures. Steel rebar is the primary route through which concrete deteriorates.
- leoc 5y agoThere's also a YT channel about concrete run by a concrete-engineering academic, Tyler Ley: https://www.youtube.com/channel/UCrvfiHNDS_QI-FgKQSmTITQ https://www.youtube.com/channel/UCrvfiHNDS_QI-FgKQSmTITQ .
- anitil 5y agoHe is so compelling!
- grp000 5y agoI did a quick check, and it looks like rebar concrete has a lifespan of about 50 years, and I had to check the lifespan of post-tensioned concrete because I suspected it has a shorter lifespan. Most sources are saying 15-20 years for post-tensioned. Any structural engineers able to report in? If that is the case, it's a bit surprising, given how expensive buildings are, although technically I believe post-tensioning can be replaced, but I also imagine that replacement cost would also be high. Edit: Thanks, civeng, this is a good warning to be aware of validation bias when googling. Here is a paper that cites comparisons of post-tensioned concrete bridges. From the paper: "As an example, two optimal post-tensioned concrete box-girder road bridges located in an eastern coastal region of Spain were assessed... In addition, maintenance was optimized to ensure that the bridge complied with all the performance requirements during its life-span of 150 years." https://www.researchgate.net/publication/320444421_Life-Cycle_Assessment_A_Comparison_between_Two_Optimal_Post-Tensioned_Concrete_Box-Girder_Road_Bridges https://www.researchgate.net/publication/320444421_Life-Cycl...
- civeng 5y agoPost tension should not decrease the lifespan, if anything in some applications it could increase the lifespan since there can be smaller or less cracks, which is easier to maintain. Maintenance is the main requirement to get 100+ years in a normal environment.
- tingletech 5y agoIf that is true; how could I refinance my 30 year loan on a 20 year old post tension pedistal slab condo? And why isn’t replacing the slab in our reserves budget?
- tingletech 5y agoAlso, the first rebar structure, in golden gate park, is still extant https://99percentinvisible.org/episode/episode-81-rebar-and-the-alvord-lake-bridge/ https://99percentinvisible.org/episode/episode-81-rebar-and-...
- escape_goat 5y ago
- nojokes 5y agoIt is also possible to use carbon fiber reinforced polymer rebar.
- robbedpeter 5y agoAnd now graphene nanoflakes in the concrete, https://www.specifyconcrete.org/blog/graphene-reinforced-concrete-the-possibilities https://www.specifyconcrete.org/blog/graphene-reinforced-con... If you can get an economical, efficient route from co2 to graphene, using graphene flakes in composite materials might be an excellent method of carbon sequestration.
- Eric_WVGG 5y agoArchitectural design isn’t everything, it appears that their concrete “recipe” was in fact different: “University of Utah geologist Marie Jackson… and her colleagues have found that seawater filtering through the concrete leads to the growth of interlocking minerals that lend the concrete added cohesion.” http://unews.utah.edu/roman-concrete/ http://unews.utah.edu/roman-concrete/ includes some tasty microscopic photography
- mrtnmcc 5y agoWe couldn't use seawater for concrete today, again because of the rebar.
- drran 5y agoWe should replace iron rebar with corrosion resistant fiberglass rebar.
- bluGill 5y agoSteel and concrete have similar thermo coefficient of expansion factors, while fiberglass does not. Thus fiberglass rebar works in temperature stable environments, but if the temperature changes a lot it is prone to failure. The above is a generalization. See a proper engineer if you are actually building something to get the correct details for your application.
- picsao 5y agoEh rebar can be almost eternal if protected by solar and a https://en.m.wikipedia.org/wiki/Galvanic_anode https://en.m.wikipedia.org/wiki/Galvanic_anode in the ground?
- rootsudo 5y agoVolcano ash. There you go.
- lyrachord 5y agoThere must be a missing of zero, 20,500
- stephc_int13 5y agoRoman concrete and general architectural prowess should be a hint that technology is not always improving over time. It baffles me that people studying the longevity of Roman concrete tends to attribute it merely to luck… Since when astonishing technology performance is found by luck? I think it is was more likely found with a lot of experiments and progressive improvements over centuries.
- XorNot 5y agoKeep in mind though that the well-built structures are also going to be the ones which survive the best. We have a degree of material quality control (at an affordable price) that the Roman empire could really only dream of.
- stephc_int13 5y agoObviously, not everything the Romans built is still there. But still, I don’t think they merely stumbled upon a super durable concrete formula by accident. Trial and errors and elbow grease can go a long way.
- tsimionescu 5y ago> Keep in mind though that the well-built structures are also going to be the ones which survive the best. This is of course true, but the amount of buildings still standing is large, not small. And there are plenty more that were purposefully destroyed, or that collapsed during huge earthquakes. It's not like we're fawning over one temple or palace. There are aqueducts, temples, houses, bridges, fortifications - so many. Not to mention things like the Hagia Sophia, the largest church in the world for about 1500 years, built in 5 years.
- ClumsyPilot 5y ago"Hagia Sophia, the largest church in the world for about 1500 years, built in 5 years." Today it would take 25 and be 250% overbudget, and then require repairs because subcontractor of a subcontractor of a subcontractor fucked up somewhere. And then the IT system in charge of doors wouldn't work.
- egberts1 5y agoThe Roman Concrete Research Department had 200 years of trial-and-error to get the strongest concrete. I’m quite sure they poured hectares worth of varied concrete mixture ratios and different material. Probably had a guy with a sledgehammer have had given it a daily whack on each of the thousand of test plots.
- philipswood 5y agoI love the quotes in "'Roman Wisdom'". Yeah, they had a few centuries of practice in the art of building. Yeah, they had materials and techniques effectively unavailable to us (think slavery and enough volcanic ash). Yup, we're studying structures they build millennia ago that are still standing and learning from it... But we're pretty much convinced that they were just lucky and we are so much better at it. 'Interesting'.
- white-flame 5y agoThe actual ultra-tough material formed in Roman concrete seems to be Tobermorite: https://en.wikipedia.org/wiki/Tobermorite https://en.wikipedia.org/wiki/Tobermorite
- johnohara 5y agoIt's unlikely the Romans fully understood the chemistry behind the concrete they created and instead relied upon centuries of trial and error to perfect their mixes. Beginning with their insistence on using pozzolanas found near and around Mt. Vesuvius. Those pozzolans were so important they were transported by ship from Naples to Caesarea and preferred over local materials to make the concrete studied there today. Marie Jackson's research over the past twenty-thirty years has been stunning and quite simply, is a gift to the world. I was pleased to see her mentioned, quoted, and continuing to perform her understated yet very valuable research into Roman Concrete. Well done Marie, again.
- ClumsyPilot 5y ago"It's unlikely the Romans fully understood the chemistry behind the concrete they created and instead relied upon centuries of trial and error to perfect their mixes." We don't fully unserstand quantum mechsnics, but have working CPUs. We dont fully understand even fucking sand. https://www.nytimes.com/2020/11/09/science/what-makes-sand-soft.html https://www.nytimes.com/2020/11/09/science/what-makes-sand-s... https://en.m.wikipedia.org/wiki/List_of_unsolved_problems_in_physics https://en.m.wikipedia.org/wiki/List_of_unsolved_problems_in...
- DeathArrow 5y ago>It's unlikely the Romans fully understood the chemistry behind the concrete they created and instead relied upon centuries of trial and error to perfect their mixes. Some of the greatest achievements were perfected by trial and error. It is a valid way to build things.
- EVa5I7bHFq9mnYK 5y agoActually, this is how we were made.
- johnohara 5y agoAgree completely. But her research continues to answer the question "why", not "how." Millenia after the fact.
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- DeathArrow 5y agoPart of the bridge Apollodorus of Damascus constructed over Danube for emperor Trajan is still standing. It took 1600 years for the modern people to construct another one.
- ncmncm 5y agoI see that we have known for more than a decade how the Egyptians could have used a form of concrete to make the blocks the pyramids were made out of, to mold them at the point of use. (It involves crushed limestone and clay.) But no one talks about that. Presumably, the (precursors to the) Incas could have done the same, explaining how they fit their odd-shaped stone blocks together so tightly. Is there any reason not to use the same method for modern concrete, instead of the enormously polluting method used today?
- hoseja 5y agoHuh? I've never seen anyone seriously saying pyramids aren't made from natural stone. Seems like it would be very easy to check.
- Luc 5y agohttps://en.wikipedia.org/wiki/Joseph_Davidovits https://en.wikipedia.org/wiki/Joseph_Davidovits It's amusing to look into. Checking is not so easy - the concrete looks just like natural material. Finding an object embedded in the stone would prove it.
- ClumsyPilot 5y agoCouod we X-ray large sections of the pyramid?
- ncmncm 5y agoX rays do not penetrate bone. Limestone, of whatever provenance, is denser than bone. Examining a chip off a block under an electron microscope revealed differences from native stone.
- habi 5y agoX-rays do penetrate bone, just not very good. Otherwise one would not be able to make an X-ray of a human body.
- fartingflamingo 5y agoKnowledge of "Roman cement" roughly speaking was never really lost. How do you think the quay walls in medieval Dutch and Flemish harbours were built? The mortar was made with Trass [0], a natural puzzolanic from the Eifel, transported along the Rhine. "Roman cement", also known as hydraulic lime [1] mortar, was in widespread active mainstream use in many places in Europe until the 1920's, and in some the 1930's. In Latvia for example, large scale Roman cement production only came to an end with the second world war flooding specific quarries. The main problem with these hydraulic cements is they cure/set much more slowly. That's very much guaranteed to limit their use in speed focused modern construction. There's still a market for hydraulic lime mortars. There's even a euro norm for it, EN-459. These products have excellent breathability and moisture resistance properties. The entire field is seeing a revival in monument restauration and ecological construction. Most straw bale construction in Europe for example is plastered using hydraulic lime plasters. Some interesting products: - natural hydraulic limes (NHL), like Saint-Astier from France - formulated/artifical hydraulic limes (HL), often using blast furnace fly ash - natural puzzolanic additives, like trass from the volcanic Eifel, has been used continuously since the Roman era! [0] https://en.wikipedia.org/wiki/Trass https://en.wikipedia.org/wiki/Trass [1] https://en.wikipedia.org/wiki/Hydraulic_lime https://en.wikipedia.org/wiki/Hydraulic_lime
- diordiderot 5y agoI've been looking into straw bale construction just out of curiosity recently, do you have some good resources to learn more about construction and regulation?
- sk2020 5y agoRegulation is going to be particular to your municipal or county government. Unless you’re in a major city, the permits desk will probably be approachable and will take the time to explain what you can and can’t do. They will probably entertain a variance unless you seem like you’re really out of your depth. They may be able to tell you about other bale construction in your area.
- fartingflamingo 5y ago
- DeathArrow 5y agoMaybe it's a dumb question, but I wonder if material science experts are studying geological processes and try to replicate what nature did.
- rob74 5y agoOne building that always gets mentioned when it comes to Roman concrete (not in this article though, so I felt compelled to add it) is the Pantheon (https://en.wikipedia.org/wiki/Pantheon,_Rome https://en.wikipedia.org/wiki/Pantheon,_Rome), which is only ~100 years younger than the tomb of Caecilia Metella and features the world's largest unreinforced concrete dome (43 m / 142 ft diameter).