Morning Ed: World {2017.08.17.Th}
[Wo1] Despite all the negative hype, the world is getting better! Or is it?
[Wo2] A view of the fall of Venezuela.
[Wo3] A look at the origins of the ancient Greeks.
[Wo4] Cuba declares war on the auditory senses of diplomats.
[Wo5] An interesting hypothetical: If five historical great empires existed concurrently, what might that look like?
[Wo6] Since he’s not associated with any of the longstanding political parties, Macron’s popularity level may end up being quite volatile. On the other hand, Hollande became so unpopular that even his party hated him, so Macron may not even see his predecessor’s floor.
[Wo7] Is Britain done with capitalism?
[Wo8] X-Rays and minor chords, a look at music, censorship, and the Soviet Union.
[Wo9] Behold, the power of Roman concrete.
[Wo9] I’ve seen a few historical shows on Roman concrete and hydro crete, but few got into the chemistry very much. Nice article.Report
And here’s the rebuttal to that Roman concrete article (h/t SSC). Basically, it’s about tradeoffs. You can’t use rebar in the Roman formulation and the cure times are ridiculously long (like, two years).Report
Killjoy!Report
Interesting. IIRC, the shows I watched the roman concrete mentioned the long curing time. Not sure about the tension/compression argument. Still cool.Report
Very interesting link. It also points out that the technology of Roman concrete is in fact well known, but rarely used today except in special circumstances where the trade offs make sense.Report
Good find Bert!
Steel is not the only pretensioning option, it’s just the most cost effective in most construction projects. One of my tech posts had a link to a concrete that was worked with a polymer (I think?) that demonstrated good tradeoffs between strength, flexibility, and durability.
As I mentioned before in a different tech post, the Roman formulation is useful to know specifically for Marine applications, and I think that, should sea levels rise as predicted, we will want a formulation that can not only survive, but thrive in seawater.Report
The range of new concretes is kind of amazing, given how long the basic stuff has been around. The replacement carport pad they poured at my mom’s old house was fiber-reinforced rather than the wire mesh that was used in the old one. The concrete guy told me that his crews loved it because they didn’t have to mess with wire mesh and the customers loved it because it was much more resistant to cracking.Report
Berts link is pretty accurate in describing tension/compression parameters. There are a few problems in concrete seldom if ever shatters like glass unless it is impacted by something. The failure observation looks like a crumble, giving away to the stresses of the load.
Modern concrete has a pretty fast cure rate. It does make most of its strength in 28 days, as the article mentions, but even modern concrete will continue building strength for several years if properly hydrated.
The problems with internal steel corrosion has many environment/material parameters. Rebar that is closer to iron than steel will have different corrosion rates. If the concrete is in a environment that is low humidity, and dry, the cement will eventually dry all the way through its section. Construction crews that have demode reinforced concrete in desert like conditions can testify to reinforcements looking nearly as good as the day it was encased 50 years before.
The Romans did some work with types of flyash that we don’t fully understand. Also I would wager the sources they derived cement had different elements than our own.Report
Re: Hoover DamReport
Yeah, they had some issues with heat on that one. I apologize that my comment was supposed to be a reply to Damon above about the tension compression issue.Report
Is it strange that I don’t even think to talk about the whole compression issue with concrete? It’s so embedded in my understanding of concrete that I kind of assume it’s something every moderately educated person knows, like how to use ‘there’, ‘their’, and ‘they’re’ properly.
(Wait, I’ve been on social media, maybe that example is a bad one…)Report
I guess I have worked with a spectrum of materials, that i just look for the neutral axis, then what happens in both dynamic and static loading of the compression axis and tension axis.
Much of the time we end up putting reinforcement in the compression axis in case there is a dynamic ‘bounce’ in the structure and the axis switch for brief amounts of time. Mostly assuming concrete has zero tensile strength, even though it has some.
I’ve had a few engineers ignore advice about reinforcing the compression axis because of dynamics. It’s a sad and expensive thing to see several cracks form in the compression axis of a brand new structure.Report
How do you reinforce the compression axis? Bushings?Report
Just rebar, like you would do in the tensile, as thats what can occur in the bounce. A small duration tensile that occurs in the compression axis, due to dynamics.Report
If I’m reading the article correctly, Roman concrete requires extended exposure to sea water in order to acquire its durability properties. Sort of limits the opportunities for use…Report
It’s time to dust off the concrete boat ideas again….Report
Something the Civil Engineers at my Alma Mater do every year.Report
[Wo6] Yeah, Macron would be popular until he tried to govern.
There’s a constituency for not-Le Pen, but not a governing coalition… a lot like the US, in reverse.Report
The French like the work-life balance created by the French welfare state. Any attempt to temper with it will be met with hostility.Report
Right… but once you get past the not-Le Pen… what exactly did he promise to do?
Those are a lot of bœufs in line for a good goring by a political neophyte. Gore me once, shame on you; Gore me twice and I get to stone you. {or something like that}Report
[Wo7] I would say it’s less that Britain is done with capitalism than that they beginning to understand Cain’s Law™: Any situation in which it is easier to become wealthy by manipulating financial instruments than by producing the underlying goods and services will end badly.Report
A while back, Lion of the Blogosphere used to write quite a bit about “Value Transference” in contrast to value creation. I didn’t agree with all of his characterizations, but a lot of what he said made sense.Report
It’s like an electrical transmission network. Sure, you can probably just keep the electricity flowing through the network, but at some point it has to leave the network and do actual work, or the system losses will eat it up.Report
Michael, if you’re interested, you may enjoy reading “Institutions, Institutional Change, and Economic Performance” by economic historian Douglass North. It’s the fleshed-out version of your law.Report
That looks like it plugs into state capitalism a little too easy, also Wills comes out of the Marx class based analysis.
Cain’s Law appears to work over a broader range of analysis, since his starting parameters are less dependent on frameworks.
(Now I’m curious as to the history)Report
Wo5: That map looks like a game of “18Civs” in Civilization IV. Rome wisely picked off other European powers early, and is grinding away at research. But China has emerged to dominate Asia, and just took Russia. Rome will be down to a few cities in the next 50 turns.Report
Saudi Arabia has said that Qatari pilgrims can cross the border for the Hajj.
Exhale a little bit.Report
Wo5 – the war elephant in the room that he doesn’t talk about is that Britain was a significant part of the Roman empire at its height.Report