Secret Tunnel/Garage Update #4

WELL I'M SHOCKED..........And very Pleased.
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[@2MuchColinFurze]

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

[@GOAT_GOATERSON]

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]

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]

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

[@cash69696]

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.

[@southern207hobbies]

You could use truck bed liner as a water sealer

[@MrDrakkus]

I'm a structural steel detailer, I make the drawings that steel fabricators use. We always make sure to note the areas that are in contact with concrete to not be painted. The reason is that when the paint gets scratched water will get through the crack and stay trapped there, causing it to rust faster. Plastic traps water as well, which will lead to more rust over time. With no coating the water will run right off the steel and through the concrete. That and the chemical reaction you mentioned protects the steel surprisingly well.

[@BinaryBunyip]

Well, please explain how we see examples of halftrack tanks from ww2, being pulled out of water, even with the original PAINT on it, looking brand new?

[@Justfinnishguy]

@@BinaryBunyip It is affected by the oxygen content and PH value of the water, In perfect conditions, rusting almost doesn't happen.

[@Biomaterials_Science]

If the water is deep enough it does not contain oxygen. The iron in steel is not reactive enough to rust in deoxygenated water (unlike zinc or aluminium) so if there are enough bacteria in the water to use up incoming oxygen steel artefacts are surprisingly stable. @@BinaryBunyip

[@Lemonaitor]

See also for this the sunken ships of the great lakes that are basically unchanged. Being submerged in fresh water is a lot less harmful to steel than saltwater.

[@David-uu3wq]

Less oxygen, less rust.

[@Poor.Sausage]

As the wet concrete cured, it created heat. From that heat, condensation built up underneath the plastic sheeting. The concrete fully cured, trapping the condensation indefinitely. The trapped moisture is accelerating the rusting process. Which is why you have less rust in the lower test hole, as it is not covered by plastic sheeting. Great job Mr Colin, great work ;))

[@willfrye4736]

I was literally thinking the same thing. Better off without it from my experience. You want that concrete in direct contact with the steel.

[@DrTheRich]

It only trapped that condensation until it all reacted up with the steel. So it's not going to be trapped forever. And there likely hadn't been enough to react with all the steel.

[@aspzx]

How does heat produce condensation?

[@Eatongee]

@@aspzx Steam?

[@phunkydroid]

@@aspzx Until the concrete is cured, it's wet. Add heat and you get water vapor. Cool steel gives it a place to condense. Any behind plastic isn't in contact with the concrete to cure into it.

[@ianharman2568]

I've been working in concrete technology for the past 18 years. I have always been a fan of keeping things simple. Don't bother with the plastic sheeting, just order a concrete with a cement content at or above 400kgs per M3. Make certain you order one of the following cement types. CIIB-V+SR PFA blend or a CIIIA a ggbs blend. This will help control the temperature that is generated by the curing concrete. The high cement/cement replacement content will stop water even getting to the steel. If your still concerned about rusting you can always go with a waterproof concrete, this is more expensive but it's easy. Things to be aware of. Try and get proper compaction, avoid cold joints in the concrete where possible and don't be tempted to wet the concrete up on site. If you want it to flow just order an S4 so you don't change the water cement ratio by adding water on site. Good luck

[@thenorsemen1959]

This comment is 100% on point, I would let you pour all my foundations.

[@ds-1111]

What about cracks that naturally form over time. You're going to want a barrier.

[@thenorsemen1959]

@@ds-1111 my understanding is that Colin is in a place where it isn’t very geologically active “earthquakes” so that risk should be minimal

[@Questionabledecisionmaking]

That’s all good in theory but concrete won’t flow out the shoot if it’s to dry an ya don’t have a choice ya have to wet it down or it’s guna set in the bowel even though it slumped up perfect before it left the yard when it gets to site it’s completely different couple times we were aiming for a slump of 100 + or - 10 an it showed up at 80 put 10L of water an it brings it back to 100 we were only doing mass pour so it was the weight of the concrete that was more important not so much the strength you would loose

[@adamthompson1597]

Civil Engineer here. I second the above. The poly sheeting is actually preventing the formation of the passivating layer. If left bare the passivating layer will protect the steel for years to come. Poly can also act as a bond breaker allowing any water that does make it into the soil to travel between poly and steel causing a larger area of surface rust. Use a concrete vibrator when pouring the concrete to eliminate honeycombing and voids. Water will cause some corrosion but the real harm is chlorides within that water. In Canada we have problems with the road salts used to melt ice and snow on the roads accelerating the deterioration of our reinforced concrete structures. Not sure if you have enough snow to merit use of salt but you will want to avoid salting your driveway to prevent accelerated corrosion.

[@johnlee3619]

Fellow engineer here and newcomer to this 2nd channel - This is fantastic! On the front of rust control, put the steel directly in contact with the concrete and have the moisture barrier agsinst the dirt. Your conclusion about alkilinity and rust corrosion is 100% correct!

[@bryanlu93]

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.

[@kailashbtw9103]

Yep, this. Put poly between concrete and soil. Let soil sit against metal, the concrete is porous and will wick away moisture (from hot/cold differences)

[@PatrickOReilly]

Like those cheap but really waterproof coats, where you end up soaked from sweat instead of rain. Concrete is more "breathable". Not an engineer, but if I was to augment the concrete it'd be just a single layer of plastic between the concrete and topsoil to act as a roof and divert excess water to the sides where it can soak into the earth.

[@paulmichaelfreedman8334]

the boundary between steel and plastic works as a capillary, it literally draws in water. Ion diffusion takes care of transporting the salt, but it goes extremely slowly

[@Stevo_1985]

Does make a lot of sense! Nice explanation 🙂

[@Rodney_Trotter_Dave]

Yes your right 100%

[@thomaspase9536]

Hey Colin, I'm in a non-profit association, which restores old Fortresses and bunkers from before WW1. Some of them are rearmed in WW1 and/or WW2 with corrugated iron sheeting. We were facing a similar problem, because parts of the sheeting was directly exposed to dirt. Thus the restauration requires as minimal change as possible because of it's historical protection, we decided to cover the entire sheeting with bitumen. Now, 10 years later there is still no rust on the outer side. Also we discovered a bunker from the early WW2 which was covered in bitumen initially. There where only two or three spots of rust, after the farmer who found the bunker hits it with his plow.

[@BarryBollox.]

That is a great idea but would it outweigh the effort it would take to get the sheeting removed, covered and then replaced. I don't think he has to worry about it for another 300 years. Its 5mm mild steel not 0'9 mm corrugated. The concrete and rebar will hold. Consider the the steel collateral and expendable in the grand scheme of things. Just leave it Colin!

[@MrFreesearcher]

Yes bitumem is a good idea, and I do like it. Only drawback is when the steel sheeting is welded, it would gas off or possibly set alight, but if applied after the welding work is done, before the concrete is added, then yes it would work well.

[@titmusspaultpaul5]

Wow, great info.

[@pf824]

Conc. direct on steel is good as the alkalinity stops rust. Embedded steel rebar is nearly always rusty by the time concrete is poured and it doesn't rust. The rebar/steel will rust if the concrete is porous and allows water with chlorine/salt to penetrate or Sulpur pollution (sulphuric acid). A membrane (plastic/ bitumen) will protect the concrete and hence the steel from these. The other risk is the build up of moisture in the bunker that will rust the inside. Think of a saw left hung up in an unheated out house or shed open to the atmosphere and moisture. Ventilation whilst occupying is a must, but care needs to be taken when bringing air into the bunker that is high in moisture content. A problem with the British climate.

[@ntsmullen3096]

Good one 😂

[@darthgator639]

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]

Rebar in concrete is a helpful analogy, thanks!

[@matttaylor8390]

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

[@tonyblanco305]

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!

[@marsrevolutionary]

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.

[@braydonfisher9273]

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

[@robbzelf]

I'm a NDT engineer (non destructive testing) and you can get a ultrasonic wall thickness measurement set for not to much money with which you can always check for corrosion on your backwall. The wall thickness itself is a give away as well. Asume you measure around 4.1 for new steel (factory over thickness). But you can also see if a backwall is corroded on your echoes (asuming you pick a ultrasonic wall thickness set that shows you echo's and not just a number. Love the channel!!!

[@jean-philippefortin1307]

I work in NDT as a technician using Ultrasonic testing and everyday, I look for corrosion between isolation and steel or concrete and steel. This is a realy good way of knowing for sure if you have and where you have corrosion issue.

[@lukemartin9209]

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]

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

[@LukeBrewMoreBeer]

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

[@jamesclark3938]

@@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

[@xaze21]

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

[@denniscliff2071]

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.

[@mygardenofthings]

Hi mate, if you speak to your local concrete supplier ask them about concrete additives they can add to your batch. You can get a totally waterproof concrete mix that they use in construction on projects that are affected by water like bridges, foundations to protect the reinforcement. This may solve the problem at a much lower cost. They should have brochures with typical ranges of different mixes to help you choose the right one👍

[@behrhub7052]

Couldn't agree more. It's called corrosion resistant concrete.

[@edm514]

That is a phenomenal suggestion.

[@RicJG7]

I'm sure that will have a similar effect as the polythene sheets, trapped moisture. The moisture will get in there against the concrete eventually in a short time. And might not dry out well in summer

[@mikebradley4096]

Such waterproof concrete is great for things like swimming pools, or pits that are dug below the water table, to stop permeation in or out. But it's clear that Colin's excavations are above the water table - the limestone is full of gaps which are all totally dry. So it's not really necessary here. The chemistry of the concrete against the rebar will give all the protection that is needed for any structure above the water table.

[@jakewebb9071]

Im surprised he wasn't putting microfiber in the mix. That would make it so much stronger

[@HMB106]

Hi Colin, I’m a civil engineer. If you are going to use plastic it’s better to put it between the concrete and the soil than between the concrete and the steel. If you put the plastic between the steel and concrete it will essentially trap moisture between the two which will marginally accelerate rusting. If it’s between the concrete and the soil it will prevent water from getting to the concrete and seeping in through any cracks that you won’t be able to see. In other words the ideal solution would be to line the hole with the plastic before pouring the concrete in but it should be fine if you didn’t Alternatively you could use the more expensive option and use hydrophobic concrete

[@shino346]

this dude smart smart

[@TheKoisto]

What about rubber bitumen on the outside of the concrete? I don't know how he could apply it to the sides if he's pouring to fill the hole but you could put some on the top when it's open.

[@HMB106]

@@TheKoisto could work. Depends how much you care about costs tho as that is more expensive than plastic

[@calholli]

Exactly.. Just look at how they do basements with concrete walls. They put the plastic on the outside of the concrete and lay the dirt up against that. Worst case scenario, you can always pull the steel completely out later (if it rusts through and looks terrible, etc.) and just have a concrete bunker with no exposed steel. You may have to patch some ugly "bubbles" in the concrete that didn't fill in perfectly. I personally would paint the interior steel, at least with a clear coat-- so it doesn't ever rust on the inside. Eventually the entire interior will rust over just like the sheet you showed in this video-- due to humidity; unless you keep a layer of oil on it, like WD40 or something else that will block the moisture. But even paint will fall off and look terrible in 50 years.. Just look at old creepy bunkers that are 50 years old with lead paint peeling off.. :)

[@tb-nz]

Yep the polythene should be on the outside of the concrete and I would have primed the steel too (a bit late now).

[@sebastianlarsen6923]

I'm a constructions expert and I've been working with steel for about 6000 years. When building the pyramids we ran into some weathering issues when it started raining frogs, but if you stay clear of god's wrath you should be in the clear. Hope that helps.

[@1nvisible1]

*Sacrificial zincs every 20 feet like steel boats use would work.*

[@Rulez29]

Structural engineer here, its recommended to use the vapor barrier sheets on the dirt side, so you would put up the sheets against the earth , the concrete goes in between it and the tunnel steel. Great project!

[@damiendeecee]

Mechanical engineer here. I have zero idea about protecting structures, so I loudly insist you listen to expert structural engineers. Like this guy.

[@haakman123]

I am a computer engineer, don't listen to me.

[@andydavies8232]

Agree, for anyone interested look up A + C water proofing. A stops water getting into the concrete and C collects any water that sneaks past A. - architectural technician.

[@wapted]

Software engineer here. Just test in production.

[@lukeponsonby7926]

I’m a paper aeroplane pilot here and desperately need a shit as I’m typing this so I wouldn’t listen to me neither. I would strongly not listen to the mechanical engineer here and listen to the structural engineer way up the top here.

[@neilyboyuk]

I worked offshore for 15 years in the salty North Sea and I can honestly say painting Blue Steel Rust Convertor is the best thing ever for putting on bare steel. Looks like milk and so easy to put on using a roller brush and wont change the colour of the steel much. The steel will outlast you I promise you!

[@pontiusthepilot]

i'm not an offshore guy but this sounds like the best option tbh. the rust converter probably makes a small film that does what you were hoping the plastic would initially.

[@SEEvans1236]

Definately but make sure you got over the top with ventilation, that stuff is nasty

[@Guvnor100]

I think you need some rust on the steel first? Could be wrong?

[@ArrowStudios]

@@Guvnor100 I think the idea is that the solution forms a film over the steel so the sooner the better, it is probably designed to be used on something that you want to stop from rusting further but it probably works just fine on new steel for the same reason. Don;t quote me on this though I don't know anything about it that's just my "intuition".

[@jwalster9412]

​@@Guvnor100if you have it there before, and the steel rusts it will instantly stop the rust.

[@MrFlamel]

Structural engineer here, if you use a moisture barrier, it is best to attach it to the earth side of the concrete so that the water is never going to interact with the concert. If you want to use a sacrificial anode, it is pretty easy to install. You basically just attach it to the steel wall and power. Cost a couple of bucks a year to operate, but not much. But in general you can say that 1mm of Steal can hold about 10 years of normal rust activity, so in your case potentially more. The garage interior however is a different story as it will be exposed to way more water and salt. There you should probably put a coating of some sort on.

[@CitroF]

i was suggesting the sacrificial anode too :) another idea could de using an electrical anode (like how it's done in boats arbors) or using a concrete addtive to made it whaterproof (like penetron)

[@nd7368]

what is a cutting?

[@rodgersrcaviation2785]

@@nd7368I’m going to assume it’s another term for coating

[@ChrisTheSparky]

Which concert is that?

[@MrFlamel]

@@nd7368 meant coating, thanks.

[@glynnepritchard2526]

Hi Colin, dam and tunnel engineer here - As others have said (so I wont go into too much detail) and you stated, the concrete will protect the steel due to passivation. Providing the concrete doesnt crack you will not have an problems. Looking at the ground conditions, you are basing your structure on rock and so teh chance of deformation is low, reducing the possibilities of cracking plus you seem to have compacted the concrete properly during construction. However, you may still encounter shrinkage cracks over time. I do not know your mix ratios supplied by the batching plant, so can not comment on the longevity of the concrete. Dont use the plastic sheet, you want steel to concrete connection for a number of reasons but this is a difficult format in which to explain why. For the interior, if you want to keep it mill scale just spray oil and wipe down. I presume that you are using a humidifier in the tunnels?

[@starofgracebbq]

I would put the poly on the out side of the concrete to separate that and the ground soil. That is what you do when digging out and pouring concrete for a garage floor or basement. You lay poly down over the dirt then pour your concrete over it. In your case you want the reverse. You pour your concrete and then lay the poly then backfill. That should give you the best protection, and the least amount of moisture to seep into the concrete.

[@reesehuntiii3070]

That's exactly how we do it in South Texas on the coast.

[@dpuamuishu]

Exactly what I was going to suggest. Concrete against steel then waterproof the outside of the concrete to reduce moisture ingress.

[@ShawtysJ]

yep needs more upvotes

[@thomasthemtman]

Pouring the concrete then covering with plastic would require a lot of concrete forms down in the hole ... and space to remove the forms

[@andyarchitect]

I was also going to suggest this but then it occurred to me that as concrete is full of water, that water will need a way to escape to avoid trapping it between the polythene and steel. Perhaps its best to simply cap the top of the concrete with polythene like a flat roof with a bit of an overhang beyond the bunker walls, and leave the concrete to the sides free to wick moisture away into the surrounding ground.

[@philippointon3692]

Greetings from Phoenix, Arizona! I have over 30 years experience in the construction trades. The plastic sheet is a vapor barrier, and it should be placed against the moisture trying to get in, i.e. the dirt. If it was my bunker/garage, I would be putting the vapor barrier against the dirt, then pouring the concrete in. You could easily accomplish that beforehand, with a very slim chance of actually getting it so hot that it melts from welding. The fact that you have no surface rust on your previously built sections, really tells the tale. I can’t wait to see when the garage is finished! :-)

[@eskoelmwood5936]

That makes sense. Im a professional youtube watcher and i aprove this message. But seriously you may need to drill more test holes to confirm

[@wesleychapman8842]

Best yes

[@zeoblow]

9 years in construction and 100% agree with this. Or you could get galvanized steel but that expensive.

[@waynerick5755]

I'm a brain surgeon lmfao 😅😅

[@JBengaIII]

I once listen to 7 minutes of a podcast on digging and I too approve this message

[@kobl1168]

I think you've actually chosen quite a good steel for this project, especially combined with it all being buried in thick concrete. You may want to look into more aggressive rust prevention for the garage interior though as that's going to be exposed to far more outside air, salt, and moisture than your other entrances

[@chrisblake4198]

I agree with this. Definitely treat (paint) the interior surfaces in the garage, and if it's not already part of the design, consider an air-lock doorway between the garage and the rest of the complex. I'd also suggest visiting some other local underground complex, like the sewer system or even a historical castle. It won't show what concrete backed steel looks like, but it will give an idea of that humidity cycles in that part of England can do. Obviously a storm drain is a lot wetter than Colin's nice cozy Fullmetal Hobbit Hole, but he'd be able to get a look at the metal pipes and fittings and see a sort of worst case scenario for painted metals vs exposed.

[@hunterfreeman8662]

This needs to get seen great idea 🎉

[@sytherslicer3524]

@@hunterfreeman8662 its an obvious idea 😂

[@Malmstrom92]

On top of that such a large room with dark steel will be very dark. If he paints the room a lighter color like grey or white it will feel even larger as well as making the room brighter.

[@davidedwards267]

Deicing salts will be a big issue I would think. However seeing as it’s a deloren he is putting in there it’s a question of if the car rusts first.

[@TheContainerGuyTV]

Thanks! 2lb closed cell spray foam will water seal it and insulate it.

[@luukroelofs3672]

I'd love to see a window out onto the limestone rocks with a light in it in one of the walls! I think it would be a nice funny addition! :D

[@aquatus1]

It would be pretty cool, but it would have to be a sealed window, considering the amount of humidity it would let into the bunker.

[@Loberless]

I think you're forgetting something, you can't see through concrete.

[@bdog1995113]

@@Loberless sounds like someone doesn’t have X-ray vision

[@retneprac]

A little nautical window and a mini cave on the other side with real-sized model dwarves with pickaxes and classic beer steins perched on a rock.

[@mattdixon8750]

​@@retnepracnow that would be great!

[@TimeBucks]

The electrode thing is a good idea.

[@djazt.8053]

Or the electricity thing that Colin also mentioned. I think it's called catalytic protection. An underground environment is basically perfect for it, as it needs a permanent earth connection to work.

[@Zahra_974]

@TimeBucks

[@goneshhalder6859]

👍

[@Aseal223]

Good

[@danieladewumiodewenwa5575]

Thumbs up

[@TommyWadsworth]

Hi Colin, as a structural engineer with a background in advanced concrete applications (all be it in blast applications & not underground tunnels!) I can provide some advice here: - Ditch the plastic sheet, all this will do is trap moisture between the steel & concrete (especially during curing) which will go on to promote rust. - Concrete is great at protecting steel from rusting, and time should be spent to perfect the mix design to yield the best protection results for your steel. Things to consider: 1) Cement quantity - more cement typically results in a denser concrete matrix & one with a higher pH (more calcium hydroxide aka CH). Moisture ingress will thus be more difficult & ions that would otherwise react with the iron in your steel (i.e. rust) are more likely to be neutralised by the CH (passivating layer of the concrete). 2) Cement additives - certain additions will bolster the passivating layer (produce more CH to protect your steel from rust) while others will subtract from it so choose wisely (e.g. choose a cement with a higher pH). 3) Proportion of fines & aggregate size - a finer matrix will typically be more dense and again prevent moisture and harmful ion ingress. 4) Water content/use of plastericisers - these can be added to the mix to greatly improve workability while reducing need for water (lower water/cement ratios will again yield a denser matrix). - With regards to the science of it all that you touched on, concrete is natually alkaline due to the presence of calcium hydroxide (CH) in the concrete matrix which is a cement hydration product. This is what we refer to as the passivating layer which is depleted over the lifetime of the concrete due to actions such as carbonation and acid attack (both promoted by water ingress). Once harmful ions deplete this protection barrier, rust will begin to occur - rust is primarily a worry in reinforced structures as steel expands when it rusts at a much greater rate than the surrounding concrete and thus the concrete cracks. Hope the above points help.

[@lewisgiles8855]

You are so thorough I'd almost say robot-like! Great advice here, wow

[@michaelattle1815]

As a bridge engineer, this answer is so thorough and correctly explained It could be recorded as CPD 😂 well done mate.

[@krasky]

This guy concretes!

[@aaronprice1497]

Rust at a much greater rate than the concrete? Concrete rusts? Edit: I'm an idiot it doesn't rust it expands 🥴🙄 great explanation I just didn't read it properly.

[@devonwilliams2423]

This is a dope response, not building a tunnel but super cool info. Your name makes me think your some anonymous engineer hah

[@HaSte1]

Hey Colin, i think the best way to deal with this situation is, to "cover" the soil walls itself with the polythene and create some kind of "pool" for the concrete. The steel gets covered directly in concrete, but the concrete itself is also protected from the moisture inside the soil and can´t soak in the water. In germany the baseplate (groundplate) of most houses without basements are build that way. Sorry, english is not my native language.

[@jerome2362]

Hi Colin, structural engineer here. Ditch the polythene. Because the joints are not waterproof it will trap moisture between the concrete and the steel. You have the proof of this as the bottom hole show no signs of rust. If you want better protection, you could decide to use a better concrete mix, a formula that resist better to salts and/or admixtures designed to reduce cracking. Or, if the frost depth in winter is a couple a feet (5-6 feet here in Montreal), you could use air-entrained concrete (the micro bubbles leaves space for the water to froze, thus reducing cracking). I love to see that you are thinking about the longevity of your tunnel!! Congrats!

[@nooooheyyy]

So much fake engineers today LOL

[@Medabee8]

​@@nooooheyyyand yet you have nothing to add

[@CheatcodeGamingOfficial]

@@nooooheyyyJudging by the fact you can’t use proper grammar and say “so many fake engineers” I’d doubt you have any more credibility than anyone else.

[@crimewatchuk999]

lol@@CheatcodeGamingOfficial

[@thomaswburkhart]

@@nooooheyyymany* stay in school😮‍💨😮‍💨

[@ortusdux]

Definitely get an ultrasonic thickness gauge. You can non-destructively test the thickness anywhere you want. I use one daily at work. You could even get in a local UT NDT inspector to come by. I'm sure they'd love it!

[@charliem9925]

Jumped on here to say this as well. Get a UT scope!

[@djstoplichtofficial]

that's brilliant

[@hydorah]

Only sensible comment here! Lots of 'engineers' who think rust sleeps. You're suggestion is great. Actually test. Actually know what is happening

[@PITTBULL0]

The only issue i might see is the fact that the steel he bought will most likely have variations across the surface do to stress relieving and inaccuracy in whatever machine rolled it (assuming it is rolled steel) im not a construction worker or engineer by anymeans but was just wondering if those variations could amount to inconsistency in the data

[@danwhiffen9235]

You find any issues with UT scans at 4mm thickness?

[@RallyX26]

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.

[@blackkissi]

now that is a collaboration video I'd like to watch. "Colin and Grady tunnel research institution"

[@kickoutthehookers]

Oh man, a Grady/Colin combo? That feels almost as fun to say as 'Toblorone Rolo combo' in a geordie accent

[@nfcopier1]

This would be the most amazing collab ever!

[@warrensteel9954]

I'd love to see this collab!

[@aquatus1]

Absolutely. These two knuckleheads getting together? "Well, we were in two different continents, so we figured a bridge would be the best way to connect--"

[@andrewfulton1456]

G’day Colin, I’m a builder in Australia. We use a product called xypex which is an additive for concrete that makes it pretty much water tight. As I understand it, it’s a salt of some sort that expands when in contact with moisture and seals any micro cracks in the concrete… might be a bit of extra insurance…

[@Valkyrixa]

Keep in mind that the garage is going to have exposure to the elements through the car lift and having a potentially very wet car inside of it. Might need to have extra strong moisture extraction methods!

[@SP4CEBAR]

He needs an airlock!

[@manic2002]

@@SP4CEBAR or a decontamination unit! jet powered hair dryers? lol - more funny because I can imagine Colin actually doing that.

[@Sammonoske]

I'm wondering just how water tight the doors will be. I'm worried heavy rain could flood the whole thing.

[@simonjz05]

Ship builder here (cruise ships!) Floating dry docks use a hard coating as they are designed to be in water for 50+ years, but overkill for this, as is any sort of plating such as nickel or zinc. The polythene barrier used on the bunker may accelerate the corrosion by preventing moisture from escaping. Long and short is that concrete is porous, therefore moisture will get through! An impressed current cathodic protection system will help, but you will need multiple grounding rods around the tunnel and some aluminium or zinc anodes on the outer shell (which you can get to to replace) and a system to control to the current balance (again, overkill). Cheap and easy is an oil based coating with some minor oxidation ("flash rust") before applying. This will slow to a near stop any further oxidation, but will eventually disappear through the porous concrete. Other ways is to use an additive to the concrete to reduce its porosity. Either way, you will be dead before you have any issues.

[@Blackout13425]

Has it already been 8 years since I followed this bunker build? Man time flies...

[@кяуртіс]

I was shook when he said that.

[@fredericoespinoza]

i almost died when he said that

[@PsyCho-zi5ou]

My jaw dropped

[@papafigo2253]

I was like "already"?

[@nickcapps85]

Above the under ground garage, when it is finished, where will rain water go? Normally rain water settles through your grass/dirt. If you are getting rid of the dirt below, and you put plastic and concrete where water would normally settle… your front driveway area (above ground) might turn into a “bog” (very wet area) until water can drain off. So you may want to put a slight slope to the roof of your under ground garage but do it in the direction you want the water to drain to (i.e. you don’t want the water to drain toward your house). You might want to consider making concrete drain tunnels that allow the water to go from ground level to below your metal floor. That way the water can still settle into the earth and off your under ground garage roof. Your bunker didn’t have this problem because your lawn is slightly sloped away from the house. Water naturally drains behind your fence or just into the surrounding dirt/earth. That’s my thoughts. Great work, keep it up! From Florida, USA

[@KTannerPaisleyKK]

Mickey Mouse is gay

[@spackerinternational6131]

Structural engineer here! Commonly used in the baltics is bitumen on the outside of the steel before concrete or dirt. Recently oversaw excavated underground transformer housing for military installation from the 60s to extend it again for water pump. It was dug, metal struts installed, steel panneling boxed, bottom 10% concreted and the rest just soil and mud compacted down. The oustide and inside of the steel painted with bitumen. The only parts that rusted out were the parts that were later extended in the 80s and it was just concreted around shoddily. Sections of the metal were sent off for spectral analysis from both eras and they were exactly the same Soviet composition yet massively different outcomes. I had a younger engineer working along side us for his phd and that data will be available in 2024. The exact methods of original construction werent documented but would recommend laying your steel out on a hot day, blowtourching the steel to open its pours and apply a thinned layer of bitumen primer (steel should be colder than the flash point of the bitumen primer 😂)

[@thJune]

That is wildly interesting. I’d be excited to see that data when it’s published

[@DavidKnowles0]

bitumen is water proof isn't, so it kind make sense. An tough than any paint.

[@thikim8562]

ok

[@RobinTheBot]

Isn't bitumen pretty dangerous to work with?

[@DavidKnowles0]

@@RobinTheBot It use all the time in highway construction, so it doable.

[@squirreland]

Colin, you should put a window in the wall somewhere that looks out into the rockface. the rock fae looks so cool and it's all covered up!

[@wrylnd]

Probably not great for structural integrity

[@aweiner8667]

The required concrete will just cover it unfortnately

[@joolofw]

Ooohhhh I definitly like *that* idea! :D

[@jamessever8936]

This is such a cool idea!!!!

[@alfinpogform4774]

How about a window that has a view into a small cavity that has the skeleton of a Morlock in it....

[@CompactFlesh]

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

[@sebastianmuller1210]

He will have a hard time getting anything up than.

[@theoledicktwist6247]

No, robot limbs

[@randywl8925]

No, he'll just build a slightly smaller stainless steel tunnel inside the first one. 😂

[@nitehawk86]

@@randywl8925 Yo dawg, I heard you like tunnels...

[@nitehawk86]

I duno, from the samples, it looks like theres not going to be much need for repairs even in 40 years :)

[@teeslunk]

8 years ago u done the bunker. Time flys ❤❤🎉🎉

[@mikebradley4096]

Hi Colin. I'm an engineer specialising in silos, including reinforced concrete ones. Simple answer - LEAVE OUT THE PLASTIC FOR BEST PROTECTION! The key, as you said at the outset, is in the chemistry. Steel does not go rusty in an alkaline environment. So as long as the concrete is touching the steel, no rusting will occur. Even when the concrete is buried in the ground below the water table (not in dry rock like you are) the presence of the cement against the steel will protect it. In especially severe environments, like submerged in seawater, you would have to ensure you had a sufficient thickness of concrete to step chlorides permeating through to the steel (a few inches). Without it you can get "concrete cancer" due to the rebar rusting and blowing out the concrete - old bridges, silos etc often need repair if there was not enough coverage of the rebar. The other reason for concrete cancer is the concrete cracking and letting excessive water through to the rebar. This occurs when the concrete flexes and cracks, which is a natural thing for reinforced concrete under tension (eg the bottom of beams). Nowadays we used post-tensioned reinforcements to make sure the concrete is always in compression. However, flexing is unlikely in your case because the concrete is under absolutely minimal load. In addition, your environment is very friendly towards steel - the limestone itself is alkaline, so even any water seeping through the normally dry limestone will also be alkaline, so there is very little danger of rust. The really important thing is to have the cement touching the steel. DO NOT put plastic in as it can seal in moisture between plastic and steel and actually prevent the alkalinity of the concrete doing its anti-corrosion job. Rebar is never coated! Always provided with a rusty finish and as long as there is enough coverage of concrete and no cracking, rusting is not a problem. NO PLASIC PLEASE! Mike

[@rainrainwebdesign]

Wow succinct and informative - always wondering

[@greenerz]

Nothing better than a Colin furze tunnel video ❤

[@leevividgren2623]

True

[@theeggman6056]

Yes

[@Grinderluke]

I agree 👍

[@kyleowen3371]

Winning the lotto?😂

[@TheMadJoker87]

how about TWO Colin furze tunnel videos? :D

[@thecyclingarchitectUK]

Architect here. Who lives above a WW2 bomb shelter. So 80 something years old. The steel beams in the structure arenow completely rusted though but the 400-500mm thick concrete is still holding the house above it up. I'm sure your structure will see you out ! Love your work #keeptunnelling

[@glenmorrison8080]

We need more information on why and how you live in a WWII bomb shelter.

[@catchagoogoo1]

That’s what I was going to say! Just like it’s an everyday thing lol! 😂 Do you have a KZbin channel good sir?

[@chshrkt]

@@glenmorrison8080 He lives *Above* a WWII bunker, not *in*.

[@gmailisaretard]

@@chshrkt If I could tell you I lived "above" a WWII bunker you better bet your butt I'd spend as much time as I could in the sucker XD

[@boejoss]

I thought an Andersen shelter owner might pop up with some useful advice!

[@beliasphyre3497]

That is so awesome to know! Thank you for digging a secret tunnel and updating us on it!

[@rogueshadowunit4964]

I think a lot of us love the tunnel videos because there’s that almost childlike obsession of building pillow forts or camping in your yard. And for be I’ve thought it’d be really cool to have a bunker or secret rooms behind bookcases. That’s the Maine thing I always loved.

[@corentinoger]

He really should make one of those bookcase secret entrances. Or possibly a swiveling fireplace.

[@fredrikjohansson]

I remember as a kid there was a rumor of a guy in the town that had a tunnel and bunker underneath his yard. Was of course only a rumor, but I’m glad to know that in Colin’s town that rumor is true.

[@rogueshadowunit4964]

@@corentinoger yeah, he could have a bookcase in his tunnel even and behind it would be a secret room or something.

[@rogueshadowunit4964]

@@fredrikjohansson oh yeah that’s awesome. I mean who knows if Colin has a bunker and a tunnel it’s fully possible that those rumors were true. I know there was some bunkers being built during the wars in certain areas.

[@devonwilliams2423]

Im in texas so its rare but every now and then we get a tornado and the thought of being able to go undeground literally sounds like a potential blessing lol

[@tombickmore]

This video and some comments reminded me of another concern for underground bunkers: Radon Gas! The UK Radon map shows your area as having high concentrations, so you will probably want to consider Radon ventilation in the new larger areas. A few simple steps can make a big difference!

[@howlingwolven]

The bunker is pretty well sealed, so I’m not concerned about radon ingress. Definitely a consideration.

[@JStoppie]

If the steel lining is air tight, which I think it is because it’s completely welded. The radon is not likely to seep in…

[@hellomark1]

He does have ventilation in the bunker at least, but he should definitely get a radon detector or two down there.

[@apveening]

The radon won't be able to penetrate the steel bottom (and the concrete underneath), so there probably is less radon in the bunker and the tunnel system than in the house.

[@autotalon]

I thought he tested this on the bunker build already?

[@dumflex5895]

I could feel that Ryobi crying! Interesting regarding the rust. I worked on a concrete and cathodic rust prevention system on a Marina arm many years ago. They ran low level electricity through a titanium mesh and cathodes inserted into the concrete to prevent the steel inside the concrete corroding further. The marina arm is still standing so im guessing it works! Saying that it was fairly costly enterprise! Good luck with it all, what a project!

[@damianmckenna9899]

I've been a welder for over 20 years and made various things but when I used to make silos or storage tanks which went underground of forecourts and petrol stations we used to coat the cradles they sat on with red oxide paint,when they were dug up to be replaced or serviced 15-20 years later the cradles were rust free...In short I think painting the side the concrete is being poured onto with red oxide paint 1st would be a great protective barrier...great content as usual 👍

[@CptToeNail]

Red Oxide paint is good, had a car painted with it and it resisted rust quite well. They use it all over Saldanha in the western cape on the Iron Ore export machines.

[@sindrome303]

red oxide is good stuff BUT when the put steel in the ocean they wrap it in Tar and Grease (Denzo Tape)

[@ProDMiner]

I was thinking this as well, worked as a fitter helper at a place for a short time, and they sprayed that same stuff, nothing bypassed it., They would acid etch, then spray that on to the vessel.

[@mikebradley4096]

Red oxide is good to protect steel, but having the alkaline concrete in direct contact with the steel is more effective!

[@JessePenedos]

Pppp

[@ChaosCraiven]

"Asking questions to us, thinking about it, comes up with his own solution." We are glad to be of assistance, Mr Furze. Always a pleasure to work with you :D

[@Shoop83]

Sometimes it's just really nice to have someone to talk it through with.

[@Soken50]

We're just rubber ducks he can talk at to think things through

[@JensRoland]

We’ll of course still mail him an invoice for building engineering consulting services.

[@cody_powell]

Came to say the same thing - I love the internet@@Soken50

[@Nevir202]

Basically me with my sister whenever I lose something. "Hey, have you seen my... Oh, I remember now!" So effective I even called her a few times after she'd moved out of state to ask about something she couldn't possibly know lol.

[@STUCASHX]

Red oxide paint before concreting would probably be the most helpful... I put up a hand made chimney cover 15 years ago for my next door neighbour which was just welded sheet steel painted with red oxide. I can see it from my hallway window and it's not rusted even though the paint seems to be wearing off from the weather. ... and it's slow and heavy for cutting steel Colin! not "hyper speed" you'll melt everything. lol

[@DrTheRich]

I think it's just a waste of money and effort to add that, especially after having seen that sample that was straight against concrete.

[@verrueckteriwan]

Exactly what I had in mind, I hope collin sees this :)

[@STUCASHX]

​@@DrTheRich To be fair, I wrote that while still watching the vid though there could still be wetter areas once its all done that would benefit. Besides, you can't put a price on peace of mind.😉

[@DrTheRich]

@@STUCASHX "Besides, you can't put a price on peace of mind." I mean, if you're a super anxious person who doesn't test and try out, research and asks experts, then sure. If you know what you're doing than you can have piece of mind without wasting money.

[@trevorsaniga]

Sacrificial anodes are easy to install. Connect one wire to whatever and leave the anode in moist soil. I used to build cell tower foundations with bare steel I-beams encased in concrete for the guy anchors. These anchors were often in swampy soil. Sacrificial anodes kept the rust away. They are also used on earthworks equipment here in Canada and work great.

[@daxmakes]

Holesaw trick: After drilling the centre hole (and JUST marking out the main hole), drill another hole at the edge of the main hole. This will improve the cutting efficiency tenfold as the chips have a way to leave the groove of the main hole.

[@charmio]

Good tip! It's also worth checking you've got the right holesaw for the material. Carbide tipped, carbide grit, diamond and bimetal are the options you'll find at a hardware store and each is best for some metals and horrible on others. There's also the tooth geometry to be aware of. Annoyingly there's a bit to it but it's worth reading as choosing the right one saves you time, money and gives a better hole.

[@drakessupersecretchannel6086]

That’s a really good tip actually. Thanks

[@oldtimefarmboy617]

@@drakessupersecretchannel6086 Most metal saws have small teeth on them. Saws with larger teeth are designed for wood and wood like material. Steel reinforced concrete with larger aggregate usually require carbide or diamond impregnated saws to get through all the different materials easier. Wood saw will work on metal, but you could see that using the wood saw on the sheet metal resulted in him smoking the drill motor.

[@pabrennan6877]

Great tip - thanks for sharing this

[@maxwelllucas896]

This! It helps in wood, metal, or especially fiberboard that loves to clog the teeth

[@brianmaietta]

I make below grade waterproofing products. Try to avoid the plastic liner if it isn’t adhered (without gaps) to the steel as it will trap moisture in once it finds its way in. Paint is always great for steel. Consider a solvent based coating to prevent rust and mineral degradation. You can also prime the metal, put a polymer modified cement on it, add a water based acrylic membrane, and then the concrete. That would be bullet proof. Feel free to reach out if you have any technical questions. Family has been doing this sort of thing for over 40 years. CHEERS!

[@panzer8as]

welding steel plates would burn off everything arround weld

[@MonkeyJedi99]

Sacrificial anodes of zinc on the concrete side? edit: Ah, he mentioned those. They don't need electricity run to them. The galvanic reaction takes care of that.

[@jakobhansen1396]

​@@MonkeyJedi99great solution, only problem is they have to be inspected and exchanged regularly. Not impossible though

[@brianmaietta]

Right, you would have to prime and coat post weld, which is typically the standard in below grade practices. @@panzer8as

[@davidbranly7919]

For me, it's not all just the projects you do. People watch because of you Colin. Your personality and how you explain everything is what attracts all of us to you

[@shudaen]

your spot on!

[@scoobidywoobidy7214]

That's exactly true. Colin's energy radiates through the screen, and his projects match the energy that he puts out.

[@ThinkLiveLife]

I have a degree in building construction technology. The reason having a moisture barrier like a sheet over the metal is worse is that you are trapping any moisture between 2 impervious surfaces leaving water contact with your metal. If you were going to go that road you would want to use some sort of spray liner or closed cell foam around your metal so that it bonds to the metal and there is no room for moisture to contact the metal. Unfortunately I can not speak intelligently about the PH interaction by contact of concrete but I feel like the PH of the moisture itself that gets into contact with the metal is what matters more. Keep in mind that concrete (unless its specially engineered to be) is not impervious and water does move through it at a very slow rate. To the point though, With the rate of rust you are seeing over 8 years in your climate zone I wouldn't even bother addressing it.

[@adamwilliams5426]

I worked at a submarine base in the middle east, during its construction we did lots of tests on steel/concrete combinations to see which would last the longest as we were dealing with saltwater. We found the best method for support beams was concrete filled steel tubes that we left in direct contact with the salt water. We didn't paint the steel just left it as is. The concrete inside the steel reacted with the saltwater on the outside and created a sort of barrier that prevented any rust at all. For the 10 years I worked there we saw little to no surface rust form on the steel and no loss to the structure.

[@gOnzoLT]

I live on the coastline in Norway and often see something being build in the sea. People building peers, ferry stations, etc. utilize this method aswell. They pile drive large diameter steel pipes in tho the bottom, fill them with concrete and continue building upon them.

[@TherapyGel]

I wonder how that works chemically, sounds like magic tbh. Very clever idea if it's that effective!

[@acinonyx6333]

The concrete inside the pile did not protect the exterior of the pile, there is no mechanism by which it could do so. When you say you did not see surface rust, I assume you are not referring to the sub-surface steel which would presumably be covered in marine growth anyway. Steel directly exposed to seawater with no protection system applied to the sea-facing side will absolutely be actively corroding. It's nevertheless not uncommon to do this anyway, and simply add a greater mass of steel to achieve your desired design life.

[@adamwilliams5426]

@@acinonyx6333 There was no rust at all, the steel sort of blackened over time. We measured the outer diameter twice a year and it never lost any mass in my 10 years there. Also there was no "marine growth".. this was a military installation not SeaWorld.

[@mm2pitsnipe72]

Sea world... lol.@@adamwilliams5426

[@mediumsizedcal]

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.

[@Nougification]

1.25 mil at 10. Hours. That's more than most people get on their channel in the channels lifetime.

[@potatojz38]

This channel wasn't created today

[@nfcopier1]

@@potatojz38 They're talking about just the video's views. Which is more than most people's whole channels get. Nearly 1.5 mil now at 13 hrs.

[@d8l835]

​@@potatojz38 don't pretend you didn't know what he was talking about lol

[@cals4887]

Its also #9 on trending.

[@Nomadic2b34u-bt4zs]

Owatrol. I've worked with boats for years and this stuff has never let me down. It's like an oil that sets like a paint. Once its applied it penetrates the steel and then you are golden. Great content brother.

[@jamesbell8861]

I have no worries pouring up against steel. Make sure you vibe it well. You always want excellent consolidation. Too much Air is bad. The poly I always put up against the terra, which is where any moisture is going to originate from. I try not let concrete free fall out of the pump for more than a few feet and directly over rebar to avoid as much segregation as possible. Unless you are actually BLOWING YOUR CONCRETE INTO TIGHT SPOTS WITH A MIXTURE CALLED GUNITE. This technique is also used to free form the vertical walls of swimming pools and tunneling when you are not using steel forms. I always poly against the earth side no matter what. Before I put down an exterior slab I put a nice thick 6 ml poly down on my Compacted aggregate base, then steel, then mud. I am super excited to see how you tackle the next level down ... under the entire foot print of the property. We may need to do arched beams at 20 feet tall spanning the width of the property. A warehouse soccer pitch under the whole existing tunnel system !!! That will be Banananananans !!! And fun !!!

[@Badenhawk]

Man, I would love more of this type of content on this channel. Answering questions and such, providing some science, because that was awesome to learn about concrete and steel.

[@jameshogge]

I'd definitely go with a sacrificial anode. It won't interfere with the construction of the garage/tunnel at all and it should be fairly convenient to do. The entire steel structure is electrically connected so all you'll need is to do attach a cable at one place and link it to a block of zinc at the other end

[@MayaPosch]

Depending on the salinity level of the moisture, you might want to use aluminium instead of zinc, but yes.

[@stennis334]

Maybe a magnesium anode. I think that will work even better.

[@TheJoedirt6000]

why not all three

[@nalissolus9213]

I never understood how that stuff works, seems like magic.

[@DM-sx6ld]

@@nalissolus9213 Magnesium oxidizes easier than steel. So when electrically connected it "sacrifices" the magnesium first. Corrosion is an electrical process, you can also induce a current and stop the electrical potential for corrosion to occur.

[@darreno9874]

I'm looking forward to watching Colin Furze for the next 40 years not only for the great content but also to see how the tunnel is doing. Colin if your looking for ideas, what about putting an infinity mirror in the foot of the tunnel leading to the bunker, it would look like a shaft in the floor. Keep up the great work. God bless

[@jeno264]

Yes, awesome! Eighty year old Colin can show us tunnel updates! 😀💖

[@didierNYC]

hey Colin, love your content. I would encase the steel with the concrete and then cover the concrete with an additional water barrier (sheets or brushed on.) Perhaps some French drains for whatever comes. Since this will be under your driveway/deck, I assume there will be much more water penetration from rain then your previous tunnels. It does rain in your part of the woods. How thick will the finished roof be? Maybe one of your fancy elevation drawings to show your roof structure in the next vid. metal, concrete, sheeting, dirt, sand. pavers, surface thanx again

[@scbond]

French drains would do absolutely nothing.

[@dumuntai]

As a former submariner, we use sacrificial anodes all over the submarine. It should be pretty easy to stud weld the interior and mount the sacrificial anodes to the tunnels and the bunker. My thought on the plastic is it trapped want moisture was in the air before the concrete was poured.

[@gcopp81]

Yep! Zinc anodes!

[@Monkey_slapping_keys]

My first thought, he could cut in and modify fairly easily.

[@forrestfoxen7711]

Submarines once

[@EKEinc]

Unfortunately anodes wouldn’t work on the inside. Anodes need a conductive medium for them work. ( seawater, water) In air, they won’t work. Maybe if you put them on the outside where they have contact with the moist soil… But nah, wouldn’t make a significant difference.

[@dumuntai]

@EKEinc ya now that I think about it, they were in free flood areas and bilges.

[@brendontait6968]

Hey Colin, I use to work in a concrete laboratory at a concrete pipe factory. TBH, I was a little concerned with your original bunker with the polythene, with the thought that water may wick up between the steel and poly, glad to see it looks good so far. Generally speaking concrete protects steel from rust as you mentioned. In areas where we would build pipes for salt water, we would increase the reinforcing cover from like 20mm to 40mm which gave better protection from the salt. You have loads of cover... Interestingly enough, we would sit reinforcing outside for a few weeks to rust before using it as the rust would bond to the concrete much better than the mill scale. The concrete bonding well to the steel will reduce rust, so keep that in mind before pouring concrete. Delamination from the concrete will cause it to rust faster. Being that its in fairly low temperatures will significantly reduce the rusting rate, I think it's roughly log base10 on temperature where 10C increase in temperature will roughly double the corrosion rate. I would have tack welded reinforcing mesh to the walls of the bunker so it would become a big monocoque reinforcing structure. Good work ol chap... great project, have loved watching it.

[@divineoblivionx]

It feels like just yesterday as a teenager that I started watching your tunnel series. It doesn't feel like its been years and here you are, now building a secret garage. This type of content NEVER gets old and it will never not be fun to watch.

[@missmoode]

Didn’t he start posting it only a year and a half ago? Am I old? oh god

[@leprechaun3677]

What’s real crazy is that what you watched 8 years ago as a teenager, I binge watched in a day. For once, something didn’t make me feel old, instead it made me feel efficient. 🤗

[@divineoblivionx]

@@missmoode It feels like it's only been about that long. I'm 22 I shouldn't feel this old now 😂😂

[@kyleb161]

Love the giggidy you snook in there 😂😂😂😂

[@joonkim3320]

I was looking for the comment

[@jamielea3470]

Hi Colin, was intrigued to see you talking about rusting steel in concrete and how to prevent it because this is what I do for a job! If you are worried about the condition of the steel there is a method of non destructive testing you can do (known as a half-cell survey) that will tell you what condition the steel is in without having to visually inspect it. If you were looking to protect it there are several methods like you stated, but the one I and my company deal with is a Cathodic Protection system. (This is the method you mentioned) there are two main types of CP systems, Galvanic anode (sacrificial anodes) and Impressed current (the electricity one). both are viable options for protecting the steel. Both methods have their merits and draw backs. the galvanic anodes will run out eventually and will need replacing after time. Where as impressed current can be expensive to install and requires a constant power supply to ensure that it is working. There are many other factors that would affect the effectiveness of a CP system and how easy it would be to install on the tunnels and i'm not going to go into all of them in the comment as that would be too long. Good luck with the rest of the tunnels

[@renesolaire8319]

I own a electric protection device for trains railways. It’s simply a power supply. But you need an earth too. Very difficult to have an earth grounding to meet your bunker surface. Will have an electric bill not cheap by year.

[@Xyles7]

It seems like you've summoned the engineering task force on this one. Amazing how many engineers watch your videos

[@Craigzoidz]

As an engineer who approves water and sewer pipe infrastructure designs for a living, it's pretty cool to see another engineer build things that are far more interesting haha

[@Steve.._.]

​@@Craigzoidzyours is more interesting to some people. Just like how a lot of kids look at the garbage man being a fun looking job and enjoyable job. But they only think that because their trash doesn't stink so they don't experience the full job 😂

[@vinni40k]

It's like watching people play with the toys we always wanted but couldn't afford. These days only the CIA or support villains want secret tunnels and those contracts are hard to come by or ethically dubious

[@stevenyoung1999]

Armchair engineers….much like all the ex navy seals who comment on don Shipley’s posts, considering only a fraction of applicants make it into the navy seals, there’s seems to be tens of thousands of navy seals on KZbin

[@3nertia]

@@Steve.._. It's why my Mom used to say, "Hire a teenager now, while they still know it all!"

[@gemmarob26]

My wife is a structural engineer and she says: I've actually been thinking about this a lot since you started the tunnel videos, so I'm glad you brought it up. One of the worst things you can do for steel is put it through wet and dry cycles. All wet is better than cycling, so if the conditions around it are more consistent, then that would be better. I don't advise the plastic sheet for the same reason another commenter mentioned, trapping moisture between the sheet and the steel would accelerate rusting. I also agree with him that using the plastic as a vapor barrier to the soil would be a better use. This is actually why some states in the US will not allow epoxy coated rebar to be used in bridge construction. Little pin holes or gaps in the coating will allow moisture in and keep it concentrated in that specific area. This area is more likely to rust through and cause problems where as, if they just left it as metal, it would have developed a more even thin layer of rust without section loss. You could paint the back if you wanted, but seeing how the uncovered steel is doing after all this time, I don't know if I'd bother. Since this is your drive, I would maybe look into alternatives to salt for melting ice in case it seeps into the soil. Happy digging!

[@Kojara_SC]

In construction with reinforced concrete, the rebar has to have at least 1" of concrete around it. This is to protect the "coating" resulting from the reaction between concrete and rust from incoming water, be it from weather or from ground. Coworker just built a house and talked to the concrete specialists.

[@mattg9123]

Collin, I look at bridges! I am by no means a concrete expert, but what would be best is to pour the concrete directly against the raw steel. Attempting to then waterproof the concrete is the way to go, bitumen etc. I'd then look to paint the inside. I've been in some confined space box beam structures, they're painted inside and most of them are like new even today, most of them are pushing 60 years old now. The 'Bunker' it's difficult to tell. You could try some ultrasonic testing to find the residual thickness of the steel sheeting and determine if any section loss/corrosion has occurred. I'm sure some proper engineers can tell you more!

[@Red_Panda_Dragon]

There is actually "waterproof" concrete which is normal concrete with additives. It is used for underground structures precisely because it is otherwise difficult to put in a protective and watertight layer

[@wombatillo]

The alkalinity of the concrete and the lack of oxygen in a steel-concrete interface tends to inhibit rusting. Rebar typically rusts first near the outer face of the concrete where the concrete has carbonated with the atmoshpheric carbon dioxide. Carbonation happens at rate of something like a fraction of a millimeter per year. This eventually greatly lowers the concrete alkalinity around the outer rebar and allows for rust to start developing. Epoxy etc. are futile because there is always gaps in the epoxy allowing water and oxygen in. Epoxy layers actually cause faster rusting when it starts because the epoxy shell forms a nice little pocket where the rust can grow in peace.

[@jeremyburch5850]

I've seen a lot of uncoated rebar in concrete structures used to store/treat wastewater last well over 50 years here in the States. I would say you should be good to go with just steel/concrete. As others have said, galvanized steel would be a better long term solution, but it should be fine buried. However, I would roll on an asphaltic waterproofing coating on the outside of the concrete you put on top of the underground garage portion. Love the 2nd Channel, Colin!

[@erikdolerud]

This!

[@bobbyjenkins1321]

If I may offer an explanation as to why rebar is untreated in operations which are typically thought to be conducive to corrosion. When rebar is coated, most often in apoxy, it is really well protected against corrosion and so great! However if during the installation of the rebar the apoxy coating is chipped or scratched and not repainted again to cover the bare metal, it becomes a concentration point. So after extensive testing of this phenomenon, it is understood that the corrosion to be 10x as bad in that one spot because it has concentrated to a tiny area. So you would have areas of rebar with 1/10 the strength while other sections are in perfect condition. So it is better to leave the rebar untreated because you can be certain that the corrosion and rust will occur over the entire bar uniformly.

[@Newt2799]

Asphalt seems like a good idea

[@bytesizedengineering]

I'm sure this has already been said, but Grady from practical engineering has all of these answers in several videos. It would be fun to see him make an appearance on your channel.

[@dusseau13]

You could paint the outsides with softened roofing tar such as underground oil tanks. Might be a bit late now and also there is the welding heat to consider. The tar would also hold plastic in place on the sides for an added barrier. They also make rubberized cement.

[@andy123law]

I know a civil engineer and will forward this video after I comment. You can run a DC current through the whole steel structure as you mentioned. I've heard this helps with corrosion on bridges. Not sure what polarity but imagine it's like electroplating. You want to add ions to your metal. Another option might be a waterproof additive to your concrete. I know they use this on floating homes when making massive pontoons. Love this series Colin it's proper entertaining and most fellas would love to build something like this deep down 😂

[@matthewwilliams76]

Cathodic protection.....it's what they use to keep underground pipelines from rusting away

[@andy123law]

@@matthewwilliams76 there you go 👍

[@wombatillo]

Impressed cathodic current protection. It's not simple and requires a current source constantly running and you have to maintain it regulardly to make sure the reference electrodes and everything are working. Usually you use them in structures submerged in seawater but I suppose you could use them in wet or damp soil too. It's not trivial though because you can cause problems in the structure or nearby structure by having too much current and voltage.

[@andy123law]

@@wombatillo I will remember that when I build my bunker cheers 🤣👍 everyday is a school day 😀

[@matthewwilliams76]

​@@andy123lawjust putting the name of what you described is all. Sure it was on the tip of your tongue anyway!

[@llljoselll100]

Hi Collin, concrete mix design expert here. At our company we offer concrete chemical admixtures that can waterproof concrete and also something that will act as a corrosion inhibitor, this keeps the rebar in concrete from rusting and will probably work very well for your application.

[@tjvhigh09]

Use magnesium anodes. Make a little offshoot tunnel with a spot to dig down. Anode needs to be surrounded with clean dirt and soaked with water when installed. There's a piece of copper wire that comes off it which you can just weld to the wall. This is what's used to keep steel utility mains from rusting. Anode will be need to be replaced every so often depending on how many you use throughout your system

[@tjvhigh09]

If you look around the internet enough you'll be able to find a guide on how to read your anode with a volt meter to see if it needs to be replaced without digging it back up

[@gavlyons215]

@@tjvhigh09 Or zinc. I don't know which is cheaper but i know which one id rather have in case of a fire!

[@jjhack3r]

That’s a great idea. The iron could probably last forever if you had a few sacrificial anodes along the tunnel.

[@helgetippmann]

What the heck is „clean dirt“?

[@tjvhigh09]

@helgetippmann if you have to ask you wouldn't understand

[@SubMariner_]

As a former engineer on a diesel-electrical submarine for 7 years and a civil engineer for pipeline operations for 15 years, I have the following comment: Although, submarines and any metal boat / ship must have sacrificial anodes (various materials have been used), that is not always the case with buried pipes (or bunkers for this matter). Cathodic protection is mainly used to and one of the most effective methods for preventing corrosion on a metal surface. Due to the potential difference between the anodic (less noble) and the cathodic area (steel), positively charged metal ions leave the anode surface, while electrons leave the surface at the cathode. This results in reducing the thickness of metal. The simplest method to apply cathodic protection is by connecting the metal to be protected with another more easily corroded metal to act as the anode (passive cathodic protection). Zinc, aluminium and magnesium are the metals commonly used as anodes. For buried steel pipelines with large diameter we also use active protection that uses an external source of electrical power provided by a regulated DC power supply, often referred to as control panel. The control panel provides the current necessary to polarise the surface to be protected. With all that said if we use Reinforced Concrete Pipes (RCP) for buried applications, there is no need to provide cathodic protection for the steel rebars used inside the concrete, but the rebars must be properly galvanized preferably by the hot dip method and then given a protective coat of bitumen or epoxy paint to give you years of corrosion free service. In your case, you should benefit from investment in passive cathodic protection with zinc anodes directly connected to the steel inside. I can help you to calculate the amount of the anodes (by weight) for free if you need help with that. Amazing work Colin! Can't wait to see your new videos.. Keep up the good work!

[@GilgaFrank]

I believe oil rigs use a big magnesium sacrificial anode for corrosion protection. Sounds expensive but it would probably last a long time.

[@WyattMakes]

Two thoughts: Cathodic protection systems are tried and true in the oil and gas industry, but that's steel in dirt or rock. I've torn up a few foundations before, and rebar in concrete revealed after 100 years are still pretty good. Never actually took measurements but I'd say it's still structural at that age.

[@kierancronin7559]

You are spot on, no sheeting. When you pour the wet concrete the water seeps between the sheet and the metal, then is heated as the concrete cures. All that rust was from 8 years ago. So you're sorted! If you really want to make sure, you could paint the outside first with a waterproof polymer and that would seal off the steel completely. Even better I hear you say!

[@MarkkuS]

The welds would still rust

[@samael335]

It's pretty common to use sacrificial anodes on underground steel tanks and such. They're pretty cheap, like under $50US. Much easier than coating the steel in anything, and can be used on your existing tunnel and bunker as well.

[@andyshaw9205]

I came here to say this. We use sacrificial anodes on buried steel pipe all over the oil and gas industry

[@MrFARTSANDWICH]

A coating of synthetic 0w 20 or mineral oil plastic on top of that concrete with calcium chloride to absorb excess water on top of that plastic on top of that then your dirt. Oil is going to add some protection and also give something for the plastic to stick to.

[@robcape]

Colin! You could use “Sacrificial Anodes” by attaching zinc anodes to the steel like they use on battle ships. The zinc will corrode instead of the steel.

[@robcape]

Wow I made this comment 2 seconds before he said it in the video 😂

[@AdamTheJensen]

I think the issue there is that the anodes need to be on the outside of the steel where he wouldn't be able to change them. They'd potentially buy some time, but once they're gone, corrosion would resume as normal.

[@robogamer8]

Zinc is more for sea water, it would be magnesium

[@robogamer8]

@@AdamTheJensennot too sure as some anodes can last years just depends on the soil around and what it’s back filled with

[@jameshogge]

I'd definitely go with the sacrificial anode. Skip all the coatings/polythene. You can even put the anode somewhere convenient because the whole bunker/tunnel/garage complex will be electrically connected together: just bond a cable to it somewhere and lead it to a chunk of zinc elsewhere in the ground

[@piman13_71]

I was just thinking about this with the last episode as you will probably have more moisture coming in depending on how well sealed the lift garage and how often you use it

[@2MuchColinFurze]

i'm not worried about that, i'm sure if that did leak it could be fixable but once this is buried in concrete thats that

[@dahn57]

Some kind of dehumidifier or extractor might be a good idea, especially if you are going to use it as a working garage/workshop, you'll want some air extraction

[@RustNRestoration]

I was a concrete technician back in the late 80’s and have concrete technology quals, where did your concrete supply come from, down here in South Wales we use sea dredged sand which contains chlorides and salt, pit sand doesn’t contain as much chlorides so will not react as fast, cement has chemicals and silica’s in which react with moisture, I’d say it will outlast your lifetime Colin👍

[@PCMenten]

As I’m sure you know, the technical terminology of the chemical interaction between iron and concrete, the part where they neutralize each other, is called passivation. It’s good to learn how that works, to know that your tunnel will likely survive for a long time. I love your videos.

[@dielaughing73]

Thanks for reminding me what it's called. Colin might benefit from looking up the Pourbaix Diagram for steel, which shows the different regions of pH and electrical potential where passivation or corrosion are likely. I think if i were building something like this i would apply coatings to the outside of the steel then use an active method such as sacrificial anodes or impressed-current cathodic protection (applying electrical current) to make sure it's not rotting away where I can't see

[@Xeknos]

Man, this is so cool. I love this whole tunnel project. And its definitely good news that the bunker/tunnel system will apparently stand the test of time as well.

[@sampoore8501]

Usually when constructing a basement they will have to go for two methods of water protection, some sort of traditional tanking with a sump and probably a membrane!! Waterproof concrete has got a lot better though and is seen as a genuine second method of protection these days! Might be worth looking at

[@DrTheRich]

a sump need active control so it might only last if someone is paying for electricity... Colin won't live forever

[@IcyHell77mNRW]

@@DrTheRich how dare you suggesting Colin not being immortal :D you take that back at once ! ;)

[@Rogueruler]

You could use the Xypex admix product mixed into the concrete as a waterproofing, done in below grade tunnel building applications all the time.

[@tannerplays0.0]

You could add an additive like MasterLife CI 222 which makes steel last longer within concrete. There are other additives as well that can help add more protection for the steel.

[@tompw3141]

Good point - the concrete supplier should be able to provide some options

[@joemason6189]

Cathodic protection will look after your steel, sacrificial anode will do just fine (basically a bit of metal that is more reactive than the steel that floods the ground with electrons to protect your bunker. This will need a connection to your bunker). Although if you want to go fancy you could use an impressed current type which involves a transformer rectifier. My background - Gas pipeline engineer, looking after big bits of steel in the ground for years successfully. Hope this helps Colin, love the content. All the best, Joe

[@xiivillify]

do to the amount of exposed steel he'll have to use impressed current, sacrificial anodes will maybe last a month. hopefully he used the same grade of steel for the whole system, or the area with steel with the least native poetental will act like the sacrifical anoded and corrode fast

[@unlimitedspace113]

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

[@Spy653]

I'm still hoping he tries to do some TBM shit with the tunnel to the bunker and then just becomes a tunnel man

[@bruddaozzo]

So, a hole?

[@bruce-le-smith]

like the old multi story beach changing tent video :)

[@mikb277]

Wonder what the laws are for doing that..?

[@z3m0s]

He has to get to diamond level eventually once he's dug out his underground base lmao

[@itpros-z]

i like this builidng, your precision and you accuracy is great. This solution is incredible for me. Great job. Regards from Hungary.

[@cameron-johnbrady3768]

You're literally living every guy who grew up with Wallace and Gromit dream to be able to build a network of tunnels under your home and within reason have them go anywhere you want simply brilliant not only do you have the time to do it but the funds to do it too two things most of us will never have let alone at the same time 😅 admittedly both of these things are provided by your choice of profession and whilst you may feel the content is boring let I remind you of every hurdle you've faced along the way this is what we are all here for keep tunneling Colin I can hardly wait for the final finished product Side note, wouldn't it be funny if one of your friends or family members moved in nextdoor and wanted you to connect the "secret" tunnel to their house 😂 they'd never have to knock on again 😂😂😂

[@lordgunther4674]

New video idea! Buy out the neighborhood and turn it into a big tunnel network 😂

[@SeeItLikeItSub2It]

And girl's* 😂

[@ChrisLoew]

He is a real life Wallace.

[@Contariok]

Painting the outside will help a lot. Inside, you can get industrial dehumidifyer. I did this in my garage and it keps my tools rust free. This will also help a lot with your garage. You will get salt and water from your car, so its smart to be prepared! Love the content!

[@blbelt2001]

You may want to look at attaching some anodes to the steel. On bridges (at least in the US where I work on them) we use anodes that rust and are replacable, which prevents the rest of the structure from rusting.

[@TheBlacktom]

How does that look like? What are they made of?

[@nerfherder4284]

Also used in swimming pools to keep ladders from rushing

[@ReggieRG]

​@@TheBlacktomit is all about noble metals and such (so the sacrificial anodes are made of "nobler" metals such as platinum I guess)

[@AsthmaQueen]

​@@TheBlacktomzinc bricks

[@apveening]

@@ReggieRG Make that less noble, they are sacrificial and get used up, protecting the closer to noble iron. Most anodes are made of zinc.

[@greenlungo3996]

To your question at 4:32 about the plastic sheets on the wet steel, reminds me of videos where mechanics criticize the use of rubberized rust-proofing undercoats. Once hardened, they tend to peel away and crack a bit and leave this thin gap that draws in moisture by capillary action and then keeps it there with no air flow. Once rust starts to form, the rough and crusty steel surface wicks in water even more, while oxide formation pushes the gap wider. So I think you have better longevity on the bare-poured steel with its weather-facing surface chemically bonded and stabilized with the concrete.

[@steffenyount]

2 suggestions: 1) Safety: Add oxygen sensors and an automated ventilation system for your underground steal lined chambers. Your minimalist bunker/tunnel esthetic is lovely, but those steel walls totally remind me of the insides of a chain locker. There are too many sad stories of sailors and then their rescuers dying after entering rusty anchor chain lockers or other rusty enclosed/confined spaces. The risk is similar to the mortal dangers presented by grain silos. Just Google "anchor chain locker deaths" for examples. Please be safe and keep on digging! 2) Follow standard construction practices for sealing basement walls. Your underground garage really is just a fancy basement, and leak-free basement design is a pretty well understood in the industry. A proper treatment could include things like moisture barriers between dirt and concrete and/or weep holes with a sump system. Talk to your local basement builders for more info.

[@danwhiffen9235]

I think the issue typically with the chain locker asphyxiation is the oxidation process of the links themselves in an effectively stagnant atmosphere. He doesn’t actually have any rust forming in the inside, so that won’t scavenge the o2, and he actually has ventilation I think.

[@mattgraham1983]

😂😂 I guess you have just started watching the build. All that has been already addressed

[@rzb_uno]

Colin should clearly install an automatic system controlling O2, CO and CO2 levels and moving fans accordingly.

[@maxterjekale]

​@@mattgraham1983 do you know in which video this was addressed? I've enjoyed every episode of this project since the the start of the bunker and vaguely remember this being dealt with. Its certainly not an issue here but im interested in what the the conciderations were at the time

[@oliverlanchbery7148]

A gas monitor would be a sensible addition regardless given this is an enclosed space and at lower elevation than all the entry & ventilation points

[@Jimsads]

I applied to work in tescos 15 years ago and I can confirm you’ve got nothing to worry about 👍🏻👌

[@AndrewChristopherEnriquez]

in the oil feild we have steel pipe encased in concrete where we have to run tests to ensure a proper bond as to not contaminate the water table. further more we use cathodic protection to help prevent corrosion. definitely worth looking into because it's worth learning about and making a video about anyway.

[@leviharris7267]

Cathodic protection on the mainline pipelines across canada is the norm aswell

[@CanadianDirt]

Colin, this was really interesting and I might be able to help put your mind at ease regarding long-term success. I was demolishing a local sawmill from around 1920 so it was approximately 90 to 100 years old and they had disposed of a lot of old sawblades and various metal things in the massive concrete foundations for the machinery as they were pouring the concrete. I was very surprised that a lot of the sawblades which appeared to be between 1/8 and 3/16 of an inch thick we’re not rusted out at all. They all had a heavy layer of surface rust on them but as I was breaking them free with an excavator time after time, each one was remarkably structurally sound. Now, wherever pieces of steel were sticking out of the concrete and into the surrounding soil, the steel was always heavily rusted, and the saw blades were often just remnants of rusty steel.

[@4RILDIGITAL]

Wow, Colin! This video was incredibly informative and really fed into my curiosity about how different materials respond over time. It's fascinating to note that polyene and concrete used with bare steel can offer a considerable amount of rust protection. Also, the way you document your processes isn't just educational - it's downright entertaining. Keep up the great work!