Destroying a Big Hunk of Concrete

[Paul in Qatar]

I am reading on the reconstruction of Germany after WWII. The Nazis loved concrete and left a basketload of Big Concrete Hunks in all the major cities. They are impossible to remove by explosives (being in a city and all) and are generally a pest.

Perhaps the worst examples are a number of large high-rise bomb shelters used to mount AA guns. They are useless for almost any other purpose, and destined to be with us for a very long time.

Underground bunkers are less of a problem, since they are mostly underground we can just plant ivy and let nature do its work over the next couple of centuries. (How long would nature take to break up concrete to pebbles?)

Can anyone think of a good way to remove Big Hunks of Concrete from the middle of a major European City?

It is an interesting puzzle, isn't it?

[Der Trihs]

The government during economic downturns could hire the unemployed, give them tools and have them break it up and cart away the chunks. I'm not sure how much training that would take to do safely though. But if it could be done practically, you'd eliminate an eyesore and give people who need them jobs.

[gotpasswords]

Is there something unique about these lumps of concrete? Explosives are commonly used to demolish buildings inside of cities. Generally, the rubble lands inside of the structure's original footprint, and it's all very well controlled to prevent damage to neighboring buildings.

[mac_bolan00]

barring explosives and manual breaking with sledge hammers, the only other methods would be pneumatic hammers and sawing. if it's a really big hunk, it'll just be like quarrying. you cut slots and sections.

[TriPolar]

One way to break rocks is to drill holes in and fill them with a cement that expands as it cures. Now concrete can be incredibly strong, much stronger than most rocks, so maybe that wouldn't do the job. But repeatedly heating and cooling the concrete should cause it to crack. Heat it enough and it will just break down. And explosives should do the job for the underground ones.

If they haven't been maintained for the past 70 years, they should be showing a lot of cracking and crumbling on the exposed surfaces already.

[Dewey Finn]

Use a hydraulic breaker.

[Boyo Jim]

Prison labor and sledge hammers.

[andyleonard]

This is done all the time. The rock or block is bored and a low pressure explosive will break it into chunks and leave them in a pile. They blew a boulder the size of a small house that landed in the middle of Topanga Canyon Boulevard a few years ago and the road was clear by sundown.

[Kolak of Twilo]

Out of curiosity, could the OP post a link to an article or a picture so we have a better idea what these structures are? I admit I'm very curious since I've never heard anything about things like this littering German cities.

[mac_bolan00]

Originally Posted by Kolak of Twilo

Out of curiosity, could the OP post a link to an article or a picture so we have a better idea what these structures are? I admit I'm very curious since I've never heard anything about things like this littering German cities.

yeah, the only notable structure i can remember from the cornelius ryan book (the last battle) are the fuhrer bunker and the zoo bunker. but the city had other fortifications as fort experts were called in for the final defense.

[flodnak]

The Nazis had plans to use the harbor in Trondheim, Norway, as a submarine base, and built two large concrete submarine bunkers there, called Dora-1 and Dora-2. The walls are three meters thick and well reinforced. No one has yet come up with a plan to destroy them, at a reasonable cost, without damaging surrounding buildings. The solution has been to re-use them, and in the years since the war they have served as everything from military offices to warehouses to bowling alleys and racketball courts to practice rooms for amateur rock bands (insert your own joke here).

So if anyone figures this out, please contact the Trondheim city council, who would probably be delighted to clear that prime real estate for sale to a developer....

[Paul in Qatar]

Originally Posted by Kolak of Twilo

Out of curiosity, could the OP post a link to an article or a picture so we have a better idea what these structures are? I admit I'm very curious since I've never heard anything about things like this littering German cities.

My pleasure;

Flak Tower

Submarine pens

Even low-brustilnce explosives would be a pain the butt, as these constructions are right in major cities.

[Paul in Qatar]

OK, so how about we use very hard drills to put holes a couple of centimeters across all over the thing? This will let water in to do the work over a couple of decades. The things are huge, but the work must be shoddy, so the rebar would rust easily for example.

The things would turn into a pile of ruble over time and eventually will be easier to cart away.

===In the post above of course I got it backwards===
I mean even explosives with low shattering power would be a pain in the butt, no low pushing power. The editor regrets the mistake.

[lisiate]

According to the wikipedia page you linked to a lot of the flak towers were demolished after the war. So it can certainly be done.

[Der Trihs]

Originally Posted by Paul in Qatar

Even low-brustilnce explosives would be a pain the butt, as these constructions are right in major cities.

Originally Posted by Paul in Qatar

===In the post above of course I got it backwards===
I mean even explosives with low shattering power would be a pain in the butt, no low pushing power. The editor regrets the mistake.

The word you were looking for is "brisance", I believe.

Originally Posted by lisiate

According to the wikipedia page you linked to a lot of the flak towers were demolished after the war. So it can certainly be done.

It also said that demolishing many others was impractical.

[Paul in Qatar]

There are other Big Hunks of Concrete that need destroying. I understand that in South Korea a number of the old road blocks are now surrounded by towns and need to be removed.

(A road block in this sense is a concrete wall at some choke point. A Big Hunk of Concrete is balanced on wide side or the other of the only opening. In an emergency, the BHoC can be tilted into the space blocking the road.)

[Dewey Finn]

Originally Posted by Paul in Qatar

My pleasure;

Flak Tower

Submarine pens

Even low-brustilnce explosives would be a pain the butt, as these constructions are right in major cities.

There's also the Schwerbelastungskörper, basically just an 18m high concrete cylinder. It's not really a fortification, but instead just a big heavy thing designed to see how stable the ground is.

[Cheesesteak]

Originally Posted by Paul in Qatar

OK, so how about we use very hard drills to put holes a couple of centimeters across all over the thing? This will let water in to do the work over a couple of decades. The things are huge, but the work must be shoddy, so the rebar would rust easily for example.

If these are in the middle of major cities, I imagine a 100 foot tall tower with chunks of concrete falling off of it is not going to go over terribly well with residents. Better to wall off the area as best you can, and go to town with explosives and heavy machinery. They use explosives in the middle of NYC, it just takes time, care, and money, lots and lots of money.

[Ludovic]

Originally Posted by Paul in Qatar

The things would turn into a pile of ruble over time and eventually will be easier to cart away.

In Russia, piles of rubles cart away YOU!

[Leo Bloom]

From my standpoint, I would go the opposite way entirely. They appear (at least by the reduced size jpgs) to be quite attractive. They're no-longer-used forts, and that's what they look like. The enhance the architecture of New York, as well as all the major cities in Italy. Even the Schwerbelastungskörper have their own bizarre attraction (although perhaps one is enough).

Needless to say, as in any culture, esthetic/socio-historic factors change over time, and Germany has its own set.

[Argent Towers]

I agree. Instead of destroying them, they should be fixed up as best as can be and then repurposed as practical structures. They are obviously well built. With some decoration, they could be made to look very good. Some should also be left unaltered, as historical landmarks.

[ZenBeam]

Originally Posted by Dewey Finn

There's also the Schwerbelastungskörper, basically just an 18m high concrete cylinder. It's not really a fortification, but instead just a big heavy thing designed to see how stable the ground is.

"Because of nearby apartment buildings the structure could not be demolished with explosives at the end of World War II, and since 1995 it has been protected as a historic monument." so you better not go destroy it.

[Dewey Finn]

I know. I was replying to Kolak of Twilo, who was unfamiliar with WWII-era things still present in German cities.

[jz78817]

Originally Posted by Dewey Finn

I know. I was replying to Kolak of Twilo, who was unfamiliar with WWII-era things still present in German cities.

he was busy putting walnuts in people's hats.

[Der Trihs]

Originally Posted by jz78817

he was busy putting walnuts in people's hats.

And stealing thumbs.