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/diy/ - Do-It-Yourself - Concrete Wall Form

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Concrete Wall Form Anonymous 05/19/14(Mon)17:25 UTC+1 No.640332 Report

Hi /diy/

So I'm pouring a reinforced concrete wall, which isn't that hard in itself, but the wall needs to connect to the uneven surfaces next to it. I'd like to build a form so I can pour it all in one go, was hoping someone here would have a few pointers on this since wooden planks are a pain in the ass to carve down to fit correctly. Excuse the horrible paint skills.
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Anonymous 05/19/14(Mon)18:28 UTC+1 No.640344 Report

I'll assume your uneven surfaces are field stone, because anything else is easier to trim flatish than change your form.
I'd suggest one of those 'finger' things that you press against and uneven surface to get the profile, then mark it either on your plank siding or plywood, using a measuring stick to mark it all up.
Or you could do a 'rough cut', just something that will retain most of the aggregate and use an angle grinder to smooth off the surface after it does its initial set. Might be less work.
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Anonymous 05/19/14(Mon)19:07 UTC+1 No.640355 Report

>>640344
I was thinking of using a high viscosity concrete mix, but I fear that the amount will compress and force the concrete below out of the form as it's about 8m H x 7m L x 0.4m W . But if it does work the angle grinder idea to smooth it out would be a good way to tackle it.

Would be nice if someone who works in concrete could chime in on the concrete viscosity types.
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Anonymous 05/19/14(Mon)19:13 UTC+1 No.640360 Report

Get it close. And use a dryer, fortified mix. Add a bonding adhesive to the existing surface
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Anonymous 05/19/14(Mon)19:16 UTC+1 No.640362 Report

You want a 40-50mm slump mix, it will work well, then after it Drys grind it smooth
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Anonymous 05/19/14(Mon)23:49 UTC+1 No.640425 Report

>>640360
It's granite, I've drilled holes for rebars, it should be enough to bind the concrete after some rebar netting - I hope.
>pic

>>640362
Thanks, after some googling I'm a bit more confident, will drop by the nearest cement factory and have a talk to see what can be delivered.
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Anonymous 05/20/14(Tue)14:33 UTC+1 No.640722 Report

Spoke with the tech from the cement factory, they recommended that I'd use shotcrete at high psi to bind the concrete and granite together, add a rebar net and spray till I have the surface needed. I can then pour concrete into the original form and have them set into one large reinforced concrete piece.

Will probably take a few weeks to sort everything out. Will post pictures when it's done.
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Anonymous 05/21/14(Wed)14:37 UTC+1 No.641182 Report

>>640332
>wooden planks are a pain in the ass to carve down to fit correctly
you've never heard of sand paper?
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Anonymous 05/21/14(Wed)14:48 UTC+1 No.641187 Report

>>641182
Don't be a dick. This particular OP has more /diy/ in his veins than your entire family has shit in their brains.
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Anonymous 05/21/14(Wed)14:53 UTC+1 No.641188 Report

>>641182
> shaping wood.
> with sandpaper.

..Yeah, how about you finish your high school shop classes before you come here trying to tell adults how to work a material, kay?
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Anonymous 05/21/14(Wed)15:01 UTC+1 No.641190 Report

When I have to match wood to an uneven surface I use a large piece of cardboard as a pattern.
(water heater box, refrigerator box, etc.)

Use furring strips to make the cardboard stay flat while I trim to fit with a utility knife.

Transfer the pattern to plywood for the form.

I'm aware you've solved your problem already, OP. I just threw this out for someone else who may be looking for a similar solution.
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Anonymous 05/21/14(Wed)15:06 UTC+1 No.641193 Report

>>640722
is that springy station?
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Anonymous 05/21/14(Wed)15:49 UTC+1 No.641212 Report

1.Cut a straight notches, lay the planks inside.
2.Beat yourself up for probably doing more work than shaping individual planks.
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Anonymous 05/21/14(Wed)19:55 UTC+1 No.641311 Report

>>641182
You see the picture in >>640425 ?

That's inside the OPs own nuclear bunker. As in, he owns it. It's inside a mountain. The dude drilled the holes in the granite himself to insert the rebar you can see in that picture.

What I'm saying here is. bunkerbro knows about sandpaper, and we can all trust he knows that's not going to quite cut the mustard.
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Anonymous 05/22/14(Thu)00:08 UTC+1 No.641396 Report

>>641212
I guess that would be doable, but granite is harder than concrete and it would be a very tough job for my diamond chainsaw. Would require a lot of expensive chains to cut out and a few heads on the jackhammer to chip away the mid part - but still doable.

>>641190
Trying to shape the planks would take some time, pic for size reference.
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Anonymous 05/22/14(Thu)00:11 UTC+1 No.641398 Report

>>641396
It's getting late.
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Anonymous 05/22/14(Thu)01:04 UTC+1 No.641416 Report

Shotcrete? Holy shit op, you must have really deep pockets. If it was me, I'd use a rubber water-stop seal on the inside of the forms . Pour the wall slowly (but fast enough that you don't get cold joints).
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Anonymous 05/22/14(Thu)01:40 UTC+1 No.641425 Report

Why not use ICF instead of conventional forms. The foam blocks can easily by cut to fit any irregular surface. I do this all the time when building ICF basements on union footers
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Anonymous 05/22/14(Thu)03:25 UTC+1 No.641468 Report

>>640332
Polymer foam injection
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Anonymous 05/22/14(Thu)03:48 UTC+1 No.641486 Report

>>640332
why add when you can subtract?
the local museum had these giant machines like tunnel grinders come in and grind the walls flat. structural flaws like cracks in the rock were filled with concrete but it looks good.

it's the museum of new and old art in tasmania
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Anonymous 05/22/14(Thu)12:33 UTC+1 No.641625 Report

>>641396
Aye, so I guess this shotcrete thing allows you to basically form a nice square frame inside the arch for a decent frame to pour into?

I figure a strong solid concrete wall is your priority so dunno what you'd think of using concrete blocks to form a frame. Chipping a reasonable fit into the walls with them and a lintel. Maybe run some rebar into the granite and through the blocks, fill them with concrete as you go up. Then pump concrete into the gaps in the side. Cud b cheaper.
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Anonymous 05/23/14(Fri)08:29 UTC+1 No.642001 Report

>>641486
>Why?

Because OP can't afford a tunnel grinder and isn't about to chip away grind the walls back several feet with hand tools?
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Anonymous 05/23/14(Fri)16:56 UTC+1 No.642159 Report

>>642001
>OP can't afford a tunnel grinder
Are you sure about that? I'm pretty sure this guy didn't blow all of his money on just the bunker.
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Anonymous 05/23/14(Fri)17:10 UTC+1 No.642168 Report

>>642001
he's willing to purchase a few thousand dollars worth of concrete and rebar. why not rent some kind of mining drill and large masonry grinder for a week?
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Anonymous 05/23/14(Fri)17:42 UTC+1 No.642180 Report

>>642168
A few thousand dollars on concrete is cheap next to a tunnel anchor machine. They come in the price range of $50k per day. As for using handheld power tools it would take months and use up a great amount of diamond blades to remove the granite material. The cheapest way would be to cut the outlines, drill a few hundred holes and use expansive mortar and chip away with a small jackhammer. But this would also take quite some time. Much easier trying to tackle the form than the mountain.

Binding thin rebar netting to the larger rebars at the wall edges and spraying with shotcrete is most likely the best way. A small size shotcrete sprayer costs about $500 a day to rent.
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Anonymous 05/23/14(Fri)17:47 UTC+1 No.642183 Report

>>642180
how feasible the shotcrete is going to be will also depend on the geology. if the granite shifts slightly, wont this crack the concrete? how is bunker anon going to tackle the drainage/efflorescence?
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Anonymous 05/23/14(Fri)18:00 UTC+1 No.642188 Report

>>642183
I'd have to duck and cover if the shotcrete fails.
>pic

I wouldn't put much thought into it tho, most parts of the bunker is either partially or fully sprayed walls/ceiling as you reinforce bunkers (and tunnels) with anchor rods and spray. Might invest in a small shotcreter since I do have some parts that needs finishing. Scandivanian granite is one of the oldest rock formations in the world and as such the hardest.
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Anonymous 05/24/14(Sat)10:08 UTC+1 No.642530 Report

>>641486
Have you been there?
That place is amazing
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Anonymous 05/24/14(Sat)10:30 UTC+1 No.642536 Report

>>642530
I have a few more shots since you're interested.
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Anonymous 05/24/14(Sat)10:32 UTC+1 No.642538 Report

>>642530
this is the disguised entrance to the bunker museum
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Anonymous 05/24/14(Sat)10:45 UTC+1 No.642541 Report

>>642530
here's an idea for the bunker, bunker anon, giant trampoline with giant bells.
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Anonymous 05/24/14(Sat)10:58 UTC+1 No.642543 Report

>>642530
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Anonymous 05/24/14(Sat)16:52 UTC+1 No.642662 Report

>>640332
>since wooden planks are a pain in the ass to carve down to fit correctly

1. Make a stand so you can put a long piece of lumber standing straight up fairly close to the wall.
2. Cut out cardboard pieces that match the profile of the wall and staple them to the board.
3. Lay cardboard down on plywood and transfer profile.
4. Cut out profile with jigsaw.

You now have plywood pieces that will fit the rock wall well enough for normal 200 slump concrete. Caulk with silicone if you don't want any leaks at all. Build the rest of your form any way you want. Don't forget to put shittons of stiffeners on your form, since wet concrete exerts a huge amount of hydraulic pressure.
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Anonymous 05/24/14(Sat)18:51 UTC+1 No.642717 Report

I'm not seeing the problem, OP. Any carpenter with the skill to build the forms, should have the skill to scribe the boards to fit the pictured surfaces. Especially since it doesn't need to be perfect, just within 1/2" or so? The added time should be negligible, in the context of the time it'll take to build the form in the first place... maybe 20% extra time.
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