Secret Tunnel/Garage Update #4

Secret Tunnel/Garage Update #4

WELL I’M SHOCKED……….And very Pleased.
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37 Responses

  1. 2 Much ColinFurze says:

    Well i’m Surprised, Pleased and comforted by that discovery. What do you think, is it what you expected?

    • Goat Goaterson says:

      Definitely not but I was pleasantly surprised, I’m no expert but I think if you continue the concrete on steel without anything in between it’ll work the best

    • noseeye says:

      I guessing that the polythene is trapping any moisture that is getting in. And the bare concrete would be more porous just a guess I’m no expert

    • Squirreland says:

      Colin, you should put a window in the wall somewhere that looks out into the rockface.

    • Cash says:

      Something to note could be that the moisture levels are different in the areas you drilled out compared to the roof, so is that a safe thing to use as a generalization? Also the top hole may have rusted more than the lower one simply because it got more moisture than the lower one.

    • southern 207 hobbies says:

      You could use truck bed liner as a water sealer

  2. luke greenway says:

    Nothing better than a Colin furze tunnel video ❤

  3. DarthGator says:

    Hello Colin, fellow engineer here. I would pour the concrete right on top of the steel. Rebar reinforcements are also poured into concrete without any protection, it is the concrete that seals the metal from oxygen and stops further corrosion. There will be some water content present in the concrete for some time, but it will dry and harden over time (even submerged in water!) In big civil engineering structures they usually inspect the concrete for cracks, as these can lead to water ingress. So I would be more worried about the concrete cracking over time then the steel corroding from the inside.

    • Bruce Le Smith says:

      Rebar in concrete is a helpful analogy, thanks!

    • Matt Taylor says:

      Also if u r worried of water going through the concrete, you can add a product like Xypex to fill the voids in the cement lattice structure. We use it for water retaining structures. Although looking at the second hole with no poly, I would just do that, 8 years, no rust, just go with it and if it fails in 100 years, it’s someone else’s problem

    • Tony Blanco says:

      I totally agree here. I’m an engineer working for an electric utility. We create foundations for structures using concrete reinforced with rebar or we bury the steel poles directly. For corrosion you need moisture, steel, AND oxygen. Even when we direct-bury a steel structure we only cover the steel in preservative coatings deep enough to get past the oxygen layer. Beyond that: bare steel. We have structures in service over 100 years old and still going strong. Your roof is probably the only area at risk of significant rust (the rest is too deep) and you’re encasing it anyway. The plastic outside the concrete as a moisture barrier is probably better than no plastic at all, but I’d argue not worth the effort as it can puncture/tear and then loses its effectiveness.

      If you’re really concerned, cathodic protection is absolutely an option. This can be a passive system that requires no electricity (that is a different type of cathodic protection used on pipelines). Dams and other steel things in sea water use blocks of zinc bolted to the steel. If you start to see rust in the future you can look to add it at that point.

      Short version: don’t worry about the plastic and do it exactly how you did the rest of the tunnel and you should be fine.

      Love the vids as always!

    • Mars Revol says:

      To add onto your comment, rebar that’s been epoxy coated for corrosion resistance has failed at a greater rate than uncoated rebar due to moisture entrapment and debonding. I’m not an engineer, I just watch a lot of youtube.

    • Braydon Fisher says:

      Agreed, the concrete should be enough. If anything, a waterproof layer over the concrete would be perfect.

  4. David K says:

    The polyethylene sheet is definitely holding moisture against the steel. Here in Florida, we don’t use moisture barriers in our walls like the rest of the country does, because it will trap moisture and cause mold.

    If you want a consult, Grady at Practical Engineering would probably be happy to lend some Civvie Knowledge about rust. He even already has a video on it.

  5. Unlimited Space says:

    In 10 years time I half expect Colin to be digging a tunnel straight down.

  6. 💘TAP BELOW👇 says:

    I suspect the plastic sheet is acting as a kind of humidity trap for moisture, particularly when you consider the heat differential between the cool metal and the dirt/earth. The concrete likely does a better job of sealing against the metal, preventing moisture from entering underground. I’m all for this.

  7. 💘TAP BELOW👇 says:

    Colin, don’t worry, we‘ll be here watching you patching the steel in 40 years!

  8. Luke Martin says:

    I’m a bridge engineer. We use uncoated structural steel all the time for weathering steel superstructures and driven steel piles. Depending on the environment (coastal areas, corrosive soils, etc.), you can count on a certain thickness of section loss. However, as long as the steel isn’t disturbed, the outer layer of rust will protect the material beneath. Because you’ve encased all your steel in concrete, you’ve got nothing to worry about.

    • hydorah says:

      You’re not an engineer! How does concrete cancer work then?

    • Luke B says:

      Embedded rebar rusting thus compromising the integrity of the concreate is not the same thing as here. @hydorah

    • James Clark says:

      @hydorah how about a half bar (about 5oz) of tallow wash per m3 of concrete… i dont know how old this technique is but i know its pre-skillset-lack of ww2… really interested please reply

    • Simon B says:

      Weathering steel is a specific type of steel designed to rust and form a protective patina. Its not being used in this tunnel.

    • Dennis Cliff says:

      I believe that you are referring to “Cor-Ten” steel in which the surface rust protects the steel underneath just like aluminum oxide protects the aluminum from further corrosion. Regular steel will continue to rust until it becomes 100% iron oxide. The US-Mexico wall is Cor-Ten steel. In the case of Colin’s project, I would put as much epoxy primer and catalyzed urethane on the back of the panels as possible, knowing that the heat of welding would affect small areas. There would still be some paint residue to slow down corrosion.

  9. medium sized cal says:

    Colin, if you were ever in any doubt as to whether people cared or loved your work, you hit a million views in under 7 hours in your second channel. Your audience is as dedicated as they come and you deserve it.

  10. Fidd88 says:

    My thoughts are to let it age gracefully. Peeling paint and efflorescence are the usual problems with wartime deep bunkers, unless very very well built and deep. Condensation may become a problem over many winters. Thermal and draught insulation on the underside of your steel access hatches may help to keep heat in and reduce condensation. I think painting it would be a VERY bad idea, as it’ll show any blemish, and out-gassing from any volatile paint – such as might be suitable for mild-steel – might render the spaces unpleasant for a very long time indeed. Red-lead is likely out of the question for obvious reasons. My advice – do nothing. If rust becomes a problem down the line, concealment might be a better strategy than prevention in your lifetime anyway! Sacrificial anodes are an interesting thought, but as they usually require submersion, you may have other problems than rust if ever you proceed down that route!

    • Alexis Lemieux says:

      plus, sacrificial anodes need to be replaced after sometime and in this case, it would be very impractical and extremely difficult to replace without being less trouble than just replacing the whole thing since they would be wedge between the steel and the concrete

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