Restoring damaged concrete flights...

[jumbly]

At the front of our property is a flight of steps - 17 in total, 6 ft wide by around 30" deep. We believe they have been down since the 1960s or earlier and until this last Winter they were reasonably good, but the prolonged snow and frost has - like it did a lot of concrete - trashed many of the steps and the surface is now breaking up - quite considerably in places.

To replace them would be prohibitively expensive - our funds are very limited.

Would anyone have any ideas of what we could do to repair them, bearing in mind that parts of the existing concrete has reduced to powder and loose aggregate? Would stabiliser help to stop the deterioration with a new layer of fresh cement on top?

Any help or advice on this would be very welcome, thanks.

 

[PrenticeBoyofDerry]

What depth of repair are we talking about?
It is quite difficult to get small depth areas to key to each other and any remedial work done for this type of repair will only be temporary, the life of the repair will depend on usage and the extreme weather conditions.
But the basic method would be to build a former around the step/steps to be repaired to the correct height and make a repair mix, the design of this mix will depend on the depth of repair, as larger aggregates will give a stronger cured strength but we will be limited to what can be practicably used. I would go with a wet cast mix, this will help with self levelling and will give a strong curing strength.
The area should be clean and any loose materials removed. I would dampen down the area prior to any pour.
I would also sheet up after the pour has been made, then the following day wet down and re-sheet. This will help toughen the concrete up.

 

[jumbly]

Hi. Thanks for your response.

Not all the steps have been compromised, but the ones that have have surface damage that is just powdering off in areas.

We would probably scrape the surface off to get a reasonable depth of concrete on the top but we didn't want to have to replace the whole of the damaged steps - of which there is probably around 6 or 7 that warrant fairly major repair.

My concern is putting fresh cement on to the powdery base. No matter how much you brush it it is just crumbling away so we would need to try and stabilise it before we put anything on top otherwise the new stuff will just lift off.

 

[RedHerring2]

I'd coat the steps with a SBR/cement slurry before laying additional concrete. (Read the instructions on the can) This will help the new stuff to bond to the old. You could also add a bit of SBR to the mix.

As PBD asked, what depth of repair are we talking about?

 

[jumbly]

From just the 'skin' on the top down to around two inches or so in 'scoops' and some off the front edges of the step. Not that deep at the moment, but if we don't deal with it now it will just end up falling apart.

 

[PrenticeBoyofDerry]

two inch is not a great depth to deal with and long term bond could be difficult.
But a temp measure could still last a number of years.
SBR good idea, I am not a great fan of using PVA or bonding agents outside, I am not saying they don't work just not a fan.
So it could worth removing any loose stuff, even slightly scoring the surface could be beneficial.
Bond it and form out the step and a wet cast pour, 50mm depth I would be looking at fines 0-3mm and aggregates of about 6-10mm. or even a 0-10mm blended limestone.
1 fines - 2 aggregate - 1 cement, could be worth putting a waterproofing agent in it to.
You'll struggle with a colour match, some painting might be an option, unless you are prepared to take time matching.

 

[jumbly]

Ok, thanks very much for your help.

Sorry to be dim but what's SBR?

 

[Alarm]

Had a similar problem and bought some 10mm stainless steel rod cut to length (Metal Supermarkets) and drilled into the steps then did as above with a good mix of cement and PVA.

SBR http://www.constructionchemicals.co.uk/acatalog/sbrcomplete.pdf