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Earlier quoted context omitted.
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Please don’t do this, it’s against the rules: 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".
Earlier quoted context omitted.
Please don’t do this, it’s against the rules: 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".
In 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.
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."
Now onward to replacing the roads and bridges on freeways and highways with these new concrete.
Also, people vastly underestimate how cheap road surfaces need to be. Try and calculate the volume of material making up the US road system.
Now onward to replacing the roads and bridges on freeways and highways with these new concrete.
what we don't do today is follow through on the maintenance and replacement schedules, in an attempt to save money. we try to repeat our tradeoff after the infrastructure is built, again trading away longevity in favor of money. well, infrastructure decays if you don't maintain it or build it to last longer.
skimping on maintenance after you skimped on longevity is trying to eat the cake, and still have it after you've eaten it. it doesn't work that way.
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 concr…
> ... 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.
very exciting! and I imagine there will be follow-on work delivering even greater results. There's also an interesting finance project here, to integrate the impact of this material into projects budgets, so that designers and investors can justify this material over cheaper alternatives. In particular, different construction projects have very different expected lifespans.
Now onward to replacing the roads and bridges on freeways and highways with these new concrete.
Here is an excellent read on this subject from 2013: https://cedar.wwu.edu/geology_facpubs/75/