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Why was Roman concrete so durable?

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Re: Why was Roman concrete so durable?

#141

Post by I_complete_me »

jesuspiece wrote: post #102

It is a testament to the ingenuity and expertise of the ancient Roman engineers. It will be interesting to see what other insights this research may lead to and how it could potentially be applied to modern construction techniques.

The subject is complicated. For example see this paper[0]. The setting of concrete goes on for a long time and the Romans were probably not aware of how long their concrete(s) was/were going to last. There is a type of 'survivorship bias' going on here. But still, I guess, they knew something important. Adding reinforcement to concrete may well be a source of shortevity - or what ever the complement to longevity is.

[0] https://www.sciencedirect.com/science/article/abs/pii/S00225...

Re: Why was Roman concrete so durable?

#142

Post by jhallenworld »

ogogmad wrote: post #81

For people who don't know the difference between cement, mortar and concrete: Cement is a substance used for producing mortar and concrete. It's never used on its own. It is a "binding agent". Note that the term "cement" is often not used correctly in everyday speech, with people talking about gluing bricks together with cement, when bricks are actually glued together with mortar. Mortar is the glue between bricks. Y…

There are different types of cement: Portland and CSA (Calcium Sulfoaluminate).

https://caltra.com/wp/wp-content/uploads/2016/11/What-is-CSA...

Portand is the cheap stuff- like the $6 Quikrete bag at Home Depot. CSA is more expensive, but also available at Home Depot- look for the "Rapid Set" brand (Rapid Set Cement All is like $28 a bag).

It's kind of awesome, it's so fast you can sculpt vertically with it. You use more water with it than Portland, it starts out more mud-like. It tends to be preferred for repairs.

https://www.youtube.com/watch?v=XO8wyQfjpt4

https://www.youtube.com/watch?v=kaB22ceIrqk

Re: Why was Roman concrete so durable?

#143

Post by hbarka »

ogogmad wrote: post #81

For people who don't know the difference between cement, mortar and concrete: Cement is a substance used for producing mortar and concrete. It's never used on its own. It is a "binding agent". Note that the term "cement" is often not used correctly in everyday speech, with people talking about gluing bricks together with cement, when bricks are actually glued together with mortar. Mortar is the glue between bricks. Y…

Breaking down cement further, the raw materials are limestone, clay, and touch of iron ore (“red earth”).

Re: Why was Roman concrete so durable?

#144

Post by moloch-hai »

masklinn wrote: post #134
oakwhiz wrote: post #132

Earlier quoted context omitted.

The rusting and getting wet is cyclical in nature and part of what accelerates that is the formation of cracks in the first place. Part of the maintenance of concrete is to fill any cracks that you can find to prevent it from getting worse. The cracks typically start small, and they might form in places that are hard to get to as well as being too small to see, so if the concrete is self-healing it will prevent some…

> as well as expanding rust. Ideally they’d seal before the rebar is exposed and can rust. As long as the rebar is encased, unless you fucked up dramatically it should be safe.

The rust is essential to bind it to the cement. Without, it adds little strength.

Modern concrete isn't expected or designed to last more than a century. It could have been made to last longer, if they wanted, but that would cost a little more. Making no provision for when it will predictably fall apart is a modern failing. That major construction with concrete is about a century old should worry everyone.

We have a very great deal of infrastructure that will fail on a predictable schedule, with nothing budgeted to replace it all.

Re: Why was Roman concrete so durable?

#145

Post by mitthrowaway2 »

dreen wrote: post #123
twelve40 wrote: post #64

> 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?

I don't think the knowledge is gone, we could make that or maybe even better. The point is nobody wants it, most things we build need to be torn down after at most a few decades anyway.

So why didn't the researchers just ask one of the people who knows how it's made, instead of wasting all this time conducting tests and doing spectroscopy?

Re: Why was Roman concrete so durable?

#146

Post by moloch-hai »

mitthrowaway2 wrote: post #135
adolph wrote: post #90

Earlier quoted context omitted.

One method to reduce cement’s carbon footprint (which accounts for up to 8% of total global greenhouse gas emissions), is to improve the longevity of concrete through the incorporation of self-healing functionalities. The resulting extended use life, combined with a reduction in the need for extensive repair, could thus reduce the environmental impact and improve the economic life cycle of modern cementitious constru…

Survivor bias comes up every time this topic is mentioned, but it really has less explanatory power than most people think. If you meet a man born in 1932 who is still running marathons and doesn't need glasses, it's probably luck, although he might have some valuable diet tips to share. If you meet a man born in 1732 running the same marathon, it's time to rule out luck, and start collecting blood samples because he…

Right. Romans experimented with the formula for concrete for centuries, and learned a lot about how centuries-old concrete structures deteriorated. They didn't have modern chemistry, but they had observational skills and were serious about their work.

It would not be surprising to find that most structures weren't built to last any longer than ours, but that some were meant for the ages. An important difference today is we don't build the latter sort, excepting maybe the Sydney Opera House. Many people act personally offended that it doesn't have steel inside.

Re: Why was Roman concrete so durable?

#147

Post by oakwhiz »

moloch-hai wrote: post #144
masklinn wrote: post #134

Earlier quoted context omitted.

> as well as expanding rust. Ideally they’d seal before the rebar is exposed and can rust. As long as the rebar is encased, unless you fucked up dramatically it should be safe.

The rust is essential to bind it to the cement. Without, it adds little strength. Modern concrete isn't expected or designed to last more than a century. It could have been made to last longer, if they wanted, but that would cost a little more. Making no provision for when it will predictably fall apart is a modern failing. That major construction with concrete is about a century old should worry everyone. We have a…

Yes although it is true what the grandparent comment said about sealing - that keeping things dry, using coatings or topper materials, dewatering, etc. will all help extend the longevity and reduce maintenance requirements a bit.

Re: Why was Roman concrete so durable?

#148

Post by saalweachter »

moloch-hai wrote: post #144
masklinn wrote: post #134

Earlier quoted context omitted.

> as well as expanding rust. Ideally they’d seal before the rebar is exposed and can rust. As long as the rebar is encased, unless you fucked up dramatically it should be safe.

The rust is essential to bind it to the cement. Without, it adds little strength. Modern concrete isn't expected or designed to last more than a century. It could have been made to last longer, if they wanted, but that would cost a little more. Making no provision for when it will predictably fall apart is a modern failing. That major construction with concrete is about a century old should worry everyone. We have a…

On the plus side it makes for some wicked post-apocalyptic ruins. Remove maintenance, add 20 years, and you get the most photogenic wasteland you could ask for.

Re: Why was Roman concrete so durable?

#149

Post by aidenn0 »

jhallenworld wrote: post #142
ogogmad wrote: post #81

For people who don't know the difference between cement, mortar and concrete: Cement is a substance used for producing mortar and concrete. It's never used on its own. It is a "binding agent". Note that the term "cement" is often not used correctly in everyday speech, with people talking about gluing bricks together with cement, when bricks are actually glued together with mortar. Mortar is the glue between bricks. Y…

There are different types of cement: Portland and CSA (Calcium Sulfoaluminate). https://caltra.com/wp/wp-content/uploads/2016/11/What-is-CSA... Portand is the cheap stuff- like the $6 Quikrete bag at Home Depot. CSA is more expensive, but also available at Home Depot- look for the "Rapid Set" brand (Rapid Set Cement All is like $28 a bag). It's kind of awesome, it's so fast you can sculpt vertically with it. You use…

There are many, many, types of cement. Another common type of cement that people are probably familiar with is asphalt (a.k.a bitumen).

Re: Why was Roman concrete so durable?

#150

Post by anonuser123456 »

masklinn wrote: post #134
oakwhiz wrote: post #132

Earlier quoted context omitted.

The rusting and getting wet is cyclical in nature and part of what accelerates that is the formation of cracks in the first place. Part of the maintenance of concrete is to fill any cracks that you can find to prevent it from getting worse. The cracks typically start small, and they might form in places that are hard to get to as well as being too small to see, so if the concrete is self-healing it will prevent some…

> as well as expanding rust. Ideally they’d seal before the rebar is exposed and can rust. As long as the rebar is encased, unless you fucked up dramatically it should be safe.

Steel gives concrete tensile strength. Unfortunately, defects in the epoxy coating become a focal point of oxidation, often pitting that single point more than otherwise uncoated steel. The result is, the pitted area fails quickly and the integrity of the entire member is compromised.
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