Casting a wall on rock, rustproofing rebar?

[Vadvadetjagsa]

Hello.
I've been trying to find an answer to my question without success, so now I'm trying to create my own thread.
I'm going to cast a retaining wall on a rock, like a "U" so that the rock, which slopes together with the wall, forms a pond that I can have water in.
The wall will be about 15m long and between 1m and 3m high. Reinforced with 12mm vertical at c/c 150 and 10mm horizontal at c/c 200.
Sand will be filled on the outside, so the pressure from the water is somewhat compensated by that.
But what I'm wondering about is if I need to protect the reinforcement from rust, which I plan to inject with r-ker into the rock. Someone told me that I should have stainless reinforcement, or alternatively, hot-dip galvanize what I have, because there is a risk that the rock contains water.
I could easily apply some cold galvanizing/zinc paint on the ends that will be injected into the rock, but I'm worried if it might negatively affect the adhesion. And I'm not very keen on hauling over 500kg of reinforcement steel to the galvanizing company unless it's absolutely necessary.
I'm fairly certain that I can keep the water from the basin or the ground away from the reinforcement. So it's any potential cracks in the rock that are the problem.
So if any of you have knowledge on how I should proceed, I would be very grateful if you could share it.

 

[bossespecial]

You can use "regular" reinforcement and drill an oversized hole and anchor the dowel with expanding concrete. This way, the iron gets a concrete cover that protects it. They can also "oversize" the iron so it doesn't matter if it rusts a little. In the joint between the wall and the rock, you wrap a protector bandage. Otherwise, go with stainless steel. I recommend adding a bit more horizontal reinforcement at the bottom edge against the rock, as a constraint arises against the rock when the concrete shrinks.

 

[Vadvadetjagsa]

You can use "regular" reinforcement and drill an oversized hole and cast the dowel with expanding concrete. This gives the iron a coating of concrete that protects. They can also "oversize" the iron so it doesn't matter if it rusts a little. In the joint between the wall and the rock, you wrap around a protectorbinda. Otherwise, go with stainless steel. I recommend adding a bit more horizontal reinforcement at the bottom against the rock since there's tension against the rock when the concrete shrinks.

Thanks for the quick response. I'll ditch the glue and drill... 25mm hole should be good for 12mm iron, right? No point messing with zinc paint then? It's a bit trickier when the horizontal reinforcement needs to go into the rock wall, but maybe it can be drilled diagonally down, that should be better regardless. Protectorbinda, is that the packing that's shot fast into the rock and expands when it comes into contact with water?

 

[bossespecial]

The lying reinforcement does not need to go into the rock; you just place it parallel to the rock surface. You thread the bind around the iron and "cast" it halfway down its height, the other half goes into the wall. This is to protect the iron at the junction between the rock and concrete.

 

[Vadvadetjagsa]

The horizontal reinforcement doesn't need to go into the rock; you just lay it parallel to the rock surface. You thread the band around the iron and "cast" it down halfway, the other half ends up in the wall. This is to protect the iron at the joint between rock and concrete.

Well, the rock has an L-shape, and the wall is like a U-shape. So the wall goes from one rock face to another and stands on rock. The result is therefore a dam with 3 concrete sides and one rock side and rock bottom. Then the horizontal reinforcement must be anchored in the rock at the beginning and end of the wall, so to speak.
Aha, Protectorbinda is the same as densotape. Now I get it. Genius solution. Then maybe I can skip that expanding seal that some ground company wanted me to install at the bottom of the wall, outside of the reinforcement. I was thinking of casting with concrete intended for water, and possibly lining the sides with pond liner and letting it go 2-3dm out on the bottom just in case. But if it turns out to be totally unnecessary, maybe I'll skip that step. A proper layer of protectorbinda should do the trick.
Thank you so much for the help, and have a wonderful day.

 

[FGLIN]

Well, the mountain has an L-shape, and the wall is like a U-shape. So the wall goes from one side of the mountain to another and simultaneously stands on the mountain. The result is thus a dam with 3 concrete sides and one mountain side as well as a mountain bottom. Then, the horizontal reinforcement must also be anchored in the mountain at the beginning and end of the wall, so to speak.
Aha, Protectorbinda is the same as densotape. Now I get it. Genius solution. Then maybe I can skip that expanding gasket that some market firm wanted me to install at the bottom of the wall, outside the reinforcement. I had planned to cast with concrete intended for water and possibly cover the sides with pond liner and let it go 2-3dm out on the bottom to be on the safe side. But if it turns out to be totally unnecessary, then maybe I'll skip that step. A proper layer of protectorbinda should do the trick.
Thank you so much for the help, and have a wonderful day.

I would guess that the expanding gasket is based on bentonite clay and is a good idea to have on the water side of the wall or possibly in the middle if you want to prevent the water from leaking out, partly to keep the water in the dam and perhaps partly to reduce corrosion attacks (but rust protection binding and casting probably do the most) and frost damage.

 

[Vadvadetjagsa]

I would guess that the expanding gasket is based on bentonite clay and a good idea to have on the water side of the wall or possibly in the middle if you want to prevent the water from leaking out, partly to keep the water in the pond and maybe also to reduce corrosion attacks (but rust protection binding and embedding probably do the most) and frost heaving,

Yes, maybe it's best to use all the tricks, hard to change your mind later. Thank you.

 

[sixten88]

At work, we've used vp-rör on the reinforcement which is dowelled 10cm down into the rock and 10cm up into the wall. Then it's also good to drill larger and let the concrete wall flow down into the hole or alternatively inject the iron in place.

 

[Vadvadetjagsa]

At work, we've used VP-pipes on the reinforcement that are pegged 10cm down into the rock and 10cm up into the wall. It's also good to drill larger and let the concrete wall flow down into the hole or alternatively inject the iron.

Interesting, what do you mean then? That the same mix used to cast the wall should also anchor the iron in the rock? So not first cast with expansion grout? Then you'd have to drill quite large holes or cast with quite a lot of flow to ensure it doesn't just form a big air bubble in the hole, right? I was thinking of drilling about 27mm and anchoring the iron with expansion grout, then building the form and tying. It would be nice to avoid the mess, but it sounds a bit risky to do as you suggest if I understand correctly. How large holes did you drill for how large iron?
And using VP-pipes instead of protector tape I assume? Yeah, that should work too. Probably cheaper as well. But then I would probably still want to tape the ends of the pipe so that water can't get in and the VP-pipe stays in position. Did you do that too?