Super Strong Concrete

[billfish678]

@Irishman

Looks largely compressive. There may be some tension on the inner surfaces. Hmm.

As a quick WAG, for any finite sized sample, if it has a load on it, there are going to be some( though possibly minor) areas under tension along/around its perimeter.

[Snarky_Kong]

Domes, arches, etc. are shaped that way specifically to decrease the need to resist tensile forces and put all the stress into compression. I’d imagine any real world shape ends up having some tensile stress, but not much.

[gaffa]

Any idea why this concrete dome has lasted so long?

The building across the street from the Sears Tower (Willis can suck it) is reportedly the tallest concrete building in the world. I remember reading that the concrete didn’t use water, but silicone. Anyone familiar with that?

[Irishman]

gaffa, each of the following likely contributed:

1. The original was built in 31 BCE, but was eventually torn down, then rebuilt after 110 CE.

2. It has been in constant use since then. Originally built as a mass temple (temple to all gods), later given to the Pope in 609 CE.

3. Once in the hands of the RC Church, nobody wanted to tear it down.

4. Physical construction methods, it’s not actually a full dome: the top has an opening, or oculus, to let in light. That means less weight to support.

5. It was built with layers, and each layer used less dense aggregate.

The stresses in the dome were found to be substantially reduced by the use of successively less dense aggregate stones in higher layers of the dome. Mark and Hutchison estimated that, if normal weight concrete had been used throughout, the stresses in the arch would have been some 80% higher.

6. The inner surface has arched pockets that lighten the load.

The top of the rotunda wall features a series of brick relieving arches, visible on the outside and built into the mass of the brickwork. The Pantheon is full of such devices — for example, there are relieving arches over the recesses inside — but all these arches were hidden by marble facing on the interior and possibly by stone revetment or stucco on the exterior.

So lots of innovative design, and being well protected and highly desired to keep intact.

I don’t know about construction of concrete without water. Portland cement requires water to activate the chemical reaction and form the bonds. However, the article by GameHat talks about polymer concrete, using resins instead of portland cement as the bonding agent. That might be what you mean.

[paperbackwriter]

@gaffa

The building across the street from the Sears Tower (Willis can suck it) is reportedly the tallest concrete building in the world.

If it every was, the Burj Khalifa (known through most of construction as the Burj Dubai) has definitively eclipsed it.

[Snarky_Kong]

@paperbackwriter

@gaffa

The building across the street from the Sears Tower (Willis can suck it) is reportedly the tallest concrete building in the world.

If it every was, the Burj Khalifa (known through most of construction as the Burj Dubai) has definitively eclipsed it.

I think the upper parts of the Khalifa are steel, so depending on how they determine that sort of thing, it might be the building in Chicago.

[paperbackwriter]

I doubt it. The Burj has 156 floors of reinforced concrete before the steel spire begins. That’s almost 2,000 feet up. I don’t know enough of Chicago to know for sure which building gaffa means, but this page says that the Trump Tower makes that claim. It is 98 floors tall, or 1,131 feet to the roof.

[Snarky_Kong]

@paperbackwriter

I doubt it. The Burj has 156 floors of reinforced concrete before the steel spire begins. That’s almost 2,000 feet up. I don’t know enough of Chicago to know for sure which building gaffa means, but this page says that the Trump Tower makes that claim. It is 98 floors tall, or 1,131 feet to the roof.

Right, but if the claim was “completely concrete structure” or something along those lines, it wouldn’t matter if the Burj was 10,000 ft tall, with 9,000 of that structure being concrete.

[paperbackwriter]

Ah, well, granted.

[billfish678]

@Snarky_Kong

@paperbackwriter

I doubt it. The Burj has 156 floors of reinforced concrete before the steel spire begins. That’s almost 2,000 feet up. I don’t know enough of Chicago to know for sure which building gaffa means, but this page says that the Trump Tower makes that claim. It is 98 floors tall, or 1,131 feet to the roof.

Right, but if the claim was “completely concrete structure” or something along those lines, it wouldn’t matter if the Burj was 10,000 ft tall, with 9,000 of that structure being concrete.

Bahhh.

What if its a concrete structure that has a metal roof? Is that no longer in the running just because it has a metal roof?

[gaffa]

This was a long time ago when the building in question made the claim. I sure it has been eclipsed. I was mostly curious about the silicone concrete. From what I remember reading, it made the building far more flexible. Again, this is from memory, but the concrete had no, or little, water in the mix so when it cured, there would be no micro-fissures left where the water had evaporated as the concrete cured.

Again, I know nothing about the field and am repeating something I read in the Chicago Tribune many years ago.

[billfish678]

@gaffa

Again, I know nothing about the field and am repeating something I read in the Chicago Tribune many years ago.

THAT RAG?!

The one spreading ignorance since ???

[Snarky_Kong]

@billfish678

@Snarky_Kong

@paperbackwriter

I doubt it. The Burj has 156 floors of reinforced concrete before the steel spire begins. That’s almost 2,000 feet up. I don’t know enough of Chicago to know for sure which building gaffa means, but this page says that the Trump Tower makes that claim. It is 98 floors tall, or 1,131 feet to the roof.

Right, but if the claim was “completely concrete structure” or something along those lines, it wouldn’t matter if the Burj was 10,000 ft tall, with 9,000 of that structure being concrete.

Bahhh.

What if its a concrete structure that has a metal roof? Is that no longer in the running just because it has a metal roof?

Load bearing… whatever.

Did you know there are roughly 12,000 different ways to decide what building is the tallest?

[billfish678]

@Snarky_Kong

Load bearing… whatever.

Did you know there are roughly 12,000 different ways to decide what building is the tallest?

Yes.

I was just pointing out yours made little sense, though a lawyer would probably love it.

[Snarky_Kong]

@billfish678

@Snarky_Kong

Load bearing… whatever.

Did you know there are roughly 12,000 different ways to decide what building is the tallest?

Yes.

I was just pointing out yours made little sense, though a lawyer would probably love it.

Really? It makes no sense to distinguish between a completely reinforced concrete and a composite structure when determining what the tallest structure is?

Would a building that had the top floor as concrete and the bottom 150 as steel count as the tallest concrete structure? What percentage, in your estimation, would be required to be concrete?