5 ms·
Chemistry might be important, but we don't necessarily need that deep of an analysis. Romans didn't mind over-engineering with massive, inefficient structures.
by legitster 4y ago
Chemistry might be important, but we don't necessarily need that deep of an analysis.
Romans didn't mind over-engineering with massive, inefficient structures. They didn't worry about complex/thin shapes, or any tensile elements. No rebar, no "piping" cement, etc. And they could put up with extremely long cure times.
The end result is very, very dense concrete.
We could probably recreate the durability of their concrete if we were actually willing to put up with the compromises they represent.
https://practical.engineering/blog/2019/3/9/was-roman-concrete-better https://practical.engineering/blog/2019/3/9/was-roman-concre...
- titzer 4y ago[flagged]
- DenisM 4y agoPlease don’t do this, it’s against the rules: https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html Please don't comment on whether someone read an article. "Did you even read the article? It mentions that" can be shortened to "The article mentions that".
- starfallg 4y agoIn this case, the original poster went on a complete tangent without addressing the topic of the article at all. So my vote is for the person who pointed this out as he's most likely right in his deduction.
- ghshephard 4y agoI don't think there is any requirement to read an article - that's implicit in the guideline that you don't comment on whether a poster read the original article. I would say 75-80% of the time I read the comments first, and probably close to 25% of the time I never read the posted article. Also - I found that comment regarding modern concrete, and the pointer to PracticalEngineering to be, by far, the most interesting comment so far - significant contribution. (And yes, I did read both in their entirety) Perhaps a better response might have been, "The PracticalEngineering article is missing the key detail regarding the exothermic hot baking associated with using quicklime instead of, or in addition to, the slaked lime, and the self-healing properties associated with that. Though the lack of corrosive iron, long curing times, and large structures might be more important - and its unfortunate the original article doesn't mention those as an important detail to at least demonstrate the authors were aware of this."
- starfallg 4y agoThat link is 'old news'. What the poster of that link effectively said is that I know all there is about this topic, then post an 'interesting' link as his source, without realising that the current topic is new development not covered by it.
- bob29 4y agoPlease don’t do this it’s also against the rules: Don't feed egregious comments by replying; flag them instead. Live by the sword die by the sword
- Zircom 4y ago[flagged]
- samstave 4y ago100% disagree with flagging. Have the knowledge balls to respectfully disagree. flagging just looks like throwing rocks as opposed knowingly refuting something. its also why I am very conservative upvoting anything, anywhere, any site.
- maximus-decimus 4y agoBut... you also just did it
- mortehu 4y agoI think we can make an exception when someone essentially says "we don't need this article" without addressing its contents.
- samstave 4y agoI dont know if in a minority ; I always read the comments on a post before I read the article... I do this here and on reddit as well... I still read the articles, but I like to grab the gist from comments first, it allows me to be able to read the article faster as I can skim and search at the same time.
- teilo 4y agoWe do need a deep analysis. Roman concrete is self-healing, and this article explains why. And the reason is exactly the opposite of the one you postulate.
- NegativeLatency 4y agoSounds like the chemistry is important > Previously disregarded as merely evidence of sloppy mixing practices, or poor-quality raw materials, the new study suggests that these tiny lime clasts gave the concrete a previously unrecognized self-healing capability. > As soon as tiny cracks start to form within the concrete, they can preferentially travel through the high-surface-area lime clasts. This material can then react with water, creating a calcium-saturated solution, which can recrystallize as calcium carbonate and quickly fill the crack, or react with pozzolanic materials to further strengthen the composite material.
- deleted 4y ago[deleted]
- trynewideas 4y agohttps://www.science.org/doi/10.1126/sciadv.add1602 https://www.science.org/doi/10.1126/sciadv.add1602 > ... evidence that the Romans employed hot mixing, using quicklime in conjunction with, or instead of, slaked lime, to create an environment where high surface area aggregate-scale lime clasts are retained within the mortar matrix. Inspired by these findings, we propose that these macroscopic inclusions might serve as critical sources of reactive calcium for long-term pore and crack-filling or post-pozzolanic reactivity within the cementitious constructs. The subsequent development and testing of modern lime clast–containing cementitious mixtures demonstrate their self-healing potential ... Or, this study finds that Roman concrete regenerated using water-reactive calcium carbonate introduced through hot mixing–transformed lime clasts. This included observations of Roman concrete used in structures that weren't characteristically massive or inefficient, and reproducible in reformulated modern concrete. > In the present study, we demonstrate the calcium enrichment of matrix phases adjacent to the lime clasts, supporting the hypothesis that the lime clasts are a source of calcium for leaching and recrystallization within the pore space of the mortars. Microcrack filling by calcite has been recently observed in ancient Roman mortars from the tomb of Caecilia Metella (29), and the self-healing tests carried out on our modern samples described in the present study further support this hypothesis.
- marcosdumay 4y agoInterestingly, the article founds out that their concrete cured quickly. Anyway, no, our usual concrete completely breaks down in a few centuries. No matter how it's structured, it does not match the durability of that concrete without ongoing maintenance.
- samstave 4y ago>>A few centuries Sounds good to me? Although, many centuries old sound structures also sounds better to me...
- User23 4y agoLike the Pantheon[1]? It's still got the world's largest unreinforced concrete dome and it's in active use as a church not to mention major tourist attraction. [1] https://en.wikipedia.org/wiki/Pantheon,_Rome https://en.wikipedia.org/wiki/Pantheon,_Rome
- deleted 4y ago[deleted]
- gerdesj 4y ago"Chemistry might be important" Conc is nearly all about chemistry. You mention curing rather than drying so you surely have some idea about what is going on. The Romans did not have electron microscopes so could not watch the way the matrix develops around the aggregate etc etc from the get go. To be fair, I fried my first sample in the beam at college by over focussing. They didn't use rebar because they generally built in compression - arches etc. Rebar and pre-stressing enables members to cope much better under tension. A PS beam or slab is a modern marvel and even protects the steel from fire - bonus. Cure times: weather/environment. In hot climes you need to stop the water buggering off the surface and leaving cracked and spalling surfaces before it even cures. It may also over heat (exothermic reaction). Cold - slower curing, too cold - no cure and frozen water (total disaster). Underwater - watch your fines wandering off and going for a smoke behind a reef and your structure collapsing, unless you keep them in place. Concrete curing is not like smoking a joint of meat! A quick or slow cure may be indicated depending on conditions. We have admixtures and all sorts to fiddle with parameters. Then you have things like grading and composing your agg. and other exciting stuff. I could go on at some length - it is really, really complicated. Roman engineers managed to invent an ancient wonder of chemistry and physics that was concrete. Their approach to its use and improvements was obviously rather better than what passed for science and medicine at the time! They do seem to have experimented and gone with what worked best but it was never deliberately developed from first principles. The self healing thing was probably a happy accident. A Roman engineer had some rather different design constraints than a modern Civil. For starters, failure could quite legitimately be blamed on the god's displeasure. "When that bridge was commissioned, we made all the correct sacrifices and anyway, you are holding it wrong, I mean walking on it incorrectly". (sp)
- UncleEntity 4y ago> Roman engineers managed to invent an ancient wonder of chemistry and physics that was concrete. Technically, the ancient Egyptians used concrete in construction long before the Roman engineers were a thing. The difference is they used it for mundane things like wine cellars while the Romans integrated it into their whole architecture system. Once in a while that art history degree comes in handy…
- 4y ago
- knodi123 4y ago"Anyone can create a bridge that will hold up under a maximum load. It takes a real engineer to create a bridge that barely holds up under a maximum load."
- sph 4y agoIt takes an accountant with a tight budget, you mean. Engineers will tend to make the most durable thing ever, if given enough time and money.
- User23 4y agoYeah, I can't imagine a municipality letting their concrete roads cure for a couple years before letting cars on them.
- interfixus 4y ago> massive, inefficient structures How does a building, an aqueduct, or a bridge still in use after 2000 years manage to be inefficient?