Repair concrete staircase underside

[Gabsson]

I have a concrete staircase that also houses an old oil tank underneath. The underside of the staircase has a lot of frost damage and rusted reinforcement.

I need tips on how to address this in the best way. I want to ensure that the rusting stops. I've done some research and come up with the following suggestions.

Option 1:

1. Knock off loose concrete (as much as possible)
2. Use a wire brush to remove rust (probably impossible to remove it all, though)
3. Apply a slurry with something like https://www.bemix.se/produkt/bemix-korrohaft/
4. Apply repair mortar, e.g., https://www.bemix.se/produkt/bemix-betongspackel/

This will be quite a bit of work, of course, as it's pretty tricky to plaster upside down, so to speak?

Option 2:
1. Knock off loose concrete (as much as possible)
2. Use a wire brush to remove rust (probably impossible to remove it all, though)
3. Paint with anti-rust paint such as https://www.bygghemma.se/golv-och-v...MIoNetm73y9AIVCbp3Ch34SwntEAQYASABEgJn_PD_BwE

At the same time, I will treat the top of the stairs with cold asphalt (which I believe it was treated with previously) to reduce moisture load from above.

The staircase:


The staircase (underside):


Drilled into reinforcement/rebar to see how far the rust has gone:

 

[saiter]

I think you should paint the rebar with rust protection paint that contains zinc.
Then the question is if you can find a mason who is willing to help you?
Otherwise, this is probably what gives you the greatest chance of success. :
https://www.ardex.se/produkt/ardex-a-46/
You can check with their support if you should use primer first.

Ardex has good products and good support.

//AA

 

[Gabsson]

I think you should paint the reinforcement with rust protection paint that contains zinc.
Then the question is whether you can find a mason who wants to help you?
Otherwise, this is probably what gives you the greatest chance of success.:
[link]
You can check with their support if you should use a primer first.

Ardex has good products and good support.

//AA

I've also looked a bit at Ardex, but I would have liked to apply a slurry first to get that proper corrosion protection by increasing the alkalinity, which prevents rust. I can't see that Ardex has a specific slurry for this type of application?

I will email Ardex since their products are available in the local market where I live. Somehow it feels like a slurry is more appropriate than painting the reinforcement. I think the rust protection paint only protects locally, but the slurry changes the environment around the reinforcement.

 

[saiter]

Then you drive on the one you linked to.

//AA

 

[Gabsson]

Then you go with the one you linked to.

//AA

do you have experience with similar repairs?

 

[saiter]

No, not upside down.

//AA

 

[Gabsson]

It should be a mortar called tixopropt, as I understand it, that can be used from underneath (upside-down) without falling down.

https://www.bemix.se/produkt/bemix-r50/

"High-performance, fiber-reinforced, shrinkage-compensated thixotropic repair mortar for concrete repairs. Can be used on vertical surfaces without needing formwork. For repair of, for example, balconies, columns, and other concrete structures."

I don't intend to let a bricklayer do this, but I plan to try doing it myself...

 

[Gabsson]

I see now that other major suppliers like Combimix, Sika, and Weber also have similar systems.

https://www.se.weber/betong/reparationsbetong/weber-rep-05-slamningsmassa

https://www.se.weber/betong/reparationsbetong/weber-rep-25-reparationsbruk

It states that a 20mm layer of repair mortar rep25 provides 20 years of protection against carbonation. Rep50 provides 50 years of protection.

 

[saiter]

Let me know when you're done, and maybe I'll fix my own entrance stairs.

//AA

 

[Gabsson]

Since the tambourine/bay window in the house partially rests on the staircase's construction, it is important that this is done correctly.

The image below shows how the staircase is integrated into the tambourine/bay window.

 

[Gabsson]

Today I started addressing the rust damage on the reinforcement.

1. Chipped off all loose material
2. Sanded off rust with a brush
3. Sprayed with zinc anti-rust spray
4. Coated the surface with Bemix Korrohäft (two layers wet on wet).

Since this is the underside and not visible, I chose to skip the masonry. Especially as there is no mechanical wear there.

However, I had bought a bag of Bemix R50 thixotropic/fiber but will not do the masonry, as it requires formwork from below. Vertically works without problem (I've tried).

 

[Gabsson]

 

[Gabsson]

 

[ptk]

@Gabsson has it gone well? How thick of a layer of Korrohäft did you have in total?

 

[Gabsson]

@Gabsson has it gone well? How thick a layer of Korrohäft did you have in total?

Turned out very well but as mentioned, just anti-rust spray + two layers of slamma. Sufficient for the purpose in this case, which is to stop corrosion and further concrete flaking.

Regarding the repair mortar R50, it really is a quality mortar. I've used it to repair a concrete staircase. But building underneath on larger surfaces feels completely impossible without dealing with molds.