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Why was Roman concrete so durable?

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Re: Why was Roman concrete so durable?

#61

Post by kibwen »

JanSolo wrote: post #42
Retric wrote: post #23

Earlier quoted context omitted.

Modern roads are designed to take serious abuse. 50 years of load cycling 20 ton semi at highway speeds causes mechanical damage which Roman concrete wouldn’t be effective in preventing. In ancient sites you can sometimes see the walls in high traffic areas have gotten smoothed and indented from hundreds of years worth of people gently dragging their fingertips across the surface as they walk by, tires are less genti…

I live in Montreal; many of the concrete structures in my city are crumbling and decaying due to the constant freeze/thaw temperature cycling that they're exposed to. I wonder if the self-healing property of this new advanced concrete would help to avoid some of the cracking & flaking we're seeing in constructions from the 60s & 70s.

Only if you take out the rebar. Concrete is porous, water penetrates to the rebar inside, the rebar rusts and expands, cracking the concrete. But if you remove the rebar, you remove much of the tensile strength of the structure, which means you need to use way more concrete to compensate (via the sheer compressive force of its own weight).

Re: Why was Roman concrete so durable?

#62

Post by betaby »

JanSolo wrote: post #42
Retric wrote: post #23

Earlier quoted context omitted.

Modern roads are designed to take serious abuse. 50 years of load cycling 20 ton semi at highway speeds causes mechanical damage which Roman concrete wouldn’t be effective in preventing. In ancient sites you can sometimes see the walls in high traffic areas have gotten smoothed and indented from hundreds of years worth of people gently dragging their fingertips across the surface as they walk by, tires are less genti…

I live in Montreal; many of the concrete structures in my city are crumbling and decaying due to the constant freeze/thaw temperature cycling that they're exposed to. I wonder if the self-healing property of this new advanced concrete would help to avoid some of the cracking & flaking we're seeing in constructions from the 60s & 70s.

I live in Montreal too, and while all what you say is true ... the same is not true for the xUSSR cold cities I lived before immigration. So quality makes difference. Also planing and designing for less maintenance. Concrete structures from the same era across xUSSR are in way better shape.

Re: Why was Roman concrete so durable?

#63

Post by nemo44x »

magicpin wrote: post #36
Retric wrote: post #23

Earlier quoted context omitted.

Modern roads are designed to take serious abuse. 50 years of load cycling 20 ton semi at highway speeds causes mechanical damage which Roman concrete wouldn’t be effective in preventing. In ancient sites you can sometimes see the walls in high traffic areas have gotten smoothed and indented from hundreds of years worth of people gently dragging their fingertips across the surface as they walk by, tires are less genti…

A fun exercise is to calcualte the cost of some road in a neighboorhood, and compare that to the total collected property tax of all the homes along that road.

Then multiple that by 20 (the lifetime of the road surface) and factor in that the resurfacing is significantly cheaper than the initial build and you quickly find roads are easily subsidized by property taxes.

Re: Why was Roman concrete so durable?

#64

Post by twelve40 »

> following all of the detailed recipes that had been optimized over the course of many centuries

i wonder how all those detailed recipes were passed around for many centuries and now all is gone. Was it all passed down verbally?

Re: Why was Roman concrete so durable?

#65

Post by dwater »

nemo44x wrote: post #63
magicpin wrote: post #36

Earlier quoted context omitted.

A fun exercise is to calcualte the cost of some road in a neighboorhood, and compare that to the total collected property tax of all the homes along that road.

Then multiple that by 20 (the lifetime of the road surface) and factor in that the resurfacing is significantly cheaper than the initial build and you quickly find roads are easily subsidized by property taxes.

Even in rural areas? Even if we add in the cost of maintaining infrastructure that runs under the road surface (water, sewer, and gas)?

Re: Why was Roman concrete so durable?

#66

Post by jonnycomputer »

dang wrote: post #54

Related: Why Ancient Roman Concrete Outlasts Our Own (2017) - https://news.ycombinator.com/item?id=29366911 - Nov 2021 (67 comments) 2,050-year-old Roman tomb offers insights on ancient concrete resilience - https://news.ycombinator.com/item?id=28833525 - Oct 2021 (101 comments) Why Roman concrete is stronger than it ever was, while modern concrete decays - https://news.ycombinator.com/item?id=25690803 - Jan 2021 (7…

our obsession with Roman concrete.

Re: Why was Roman concrete so durable?

#67

Post by samstave »

HPsquared wrote: post #45
sarchertech wrote: post #17

Earlier quoted context omitted.

That depends on the what you mean by smarter. At least some component of what we consider intelligence is cultural. Just one example is that the ability to write/draw allows you to solve problems that are impossible without it.

Being literate definitely means some faculties get less practice. Practically nobody today can recite epic poetry like the Odyssey, for example. That lack of rote memorization skill may have unexpected side-effects. https://daily.jstor.org/how-do-we-know-that-epic-poems-were-...

Thats a really good, succinct, statement that triggers thought - where ironically - being literate is required to reply to via the most advanced machine I have ever used...

But there are so many skills lost due to the privilege of technologically enabled sedentary life-styles...

can you imagine attemting to found a town/village/city in flat/cold/resource-constrained climates without electricity/supply-lines?

Those people before us had balls and conviction of steel - and even more-so for the women. You would not exist without a woman (mother) and women are stronger than men.

Re: Why was Roman concrete so durable?

#68

Post by hinkley »

nimbius wrote: post #47

on the other end of the spectrum, did you know concrete can be used to demolish concrete? dexpan is a special demolition concrete mix that, when poured into holes, expands at 18kpsi. it gets used when jackhammers and explosives cant be used, for example, in refineries and explosive atmospheres.

Presumably dexpan has lower tensile strength so it can be disposed of easily? Or is the piece excavated and hauled away intact?

Re: Why was Roman concrete so durable?

#69

Post by Toutouxc »

This is from the article:

> Masic wondered: “Was it possible that the Romans might have actually directly used lime in its more reactive form, known as quicklime?”

And this is from Wikipedia, with the source dated 2011:

> Gypsum and quicklime were used as binders. Volcanic dusts, called pozzolana or "pit sand", were favored where they could be obtained

Is it just me or are popular science articles really so simplified that they often completely misrepresent the point of the research?

Re: Why was Roman concrete so durable?

#70

Post by barathr »

nimbius wrote: post #47

on the other end of the spectrum, did you know concrete can be used to demolish concrete? dexpan is a special demolition concrete mix that, when poured into holes, expands at 18kpsi. it gets used when jackhammers and explosives cant be used, for example, in refineries and explosive atmospheres.

It's also useful if you want to do concrete demolition yourself using only hand tools. You drill holes, pour, wait for cracks, and then use a pick and hammer to remove the remaining chunks. Often sold as "expansive grout".
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