Frost damage to 'stone' steps

The eighty-year old steps on the path to my front door seem to be made of some sort of composite cement casing over a much softer crushed red shale brick-like core. Over the last twenty years years some cracks in the vertical facing resulted in frost damage and some sections of the outer casing falling off the facing. I've repaired them as they happened, with mortar, sometimes with a bit more cement added, and sometimes padded out by mixing with small gravel to fill the deeper sections. Occasionally frost has caused a repaired bit to fall out again, and I've patched it up again. We're typically talking about sections up to 8 inches long and 4 high. though one is now about 15 inches long ( and up to about one inch deep)
In the recent severe weather, it's ALL fallen out again. I'd appreciate any advice on whether and how more effective and longer- lasting patching could be done - e.g any special mortar or cement/ concrete mix? Any hints on how to stop water penetration and frost damage at the seams between the repair and the original material, which I assume is what causes the weakness after a few years? Temperature here is supposed to be max of 4 or 5 celsius over the next few days, with no frost. Is that too low to attempt repairs now? I'd like to fix it to prevent further frost damage to exposed soft core material and edges of the damaged sections. Thanks Toom
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Toom Tabard wrote:

try epoxy 'mortars' to repair and possible use some form of anti-water penetration on it for next winter. I had a bot of frost spalling on some render, and the waterproofing stopped it completely. It was where water was being splashed onto it on the north side of the house.
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wrote:

Have you considered having the whole lot replaced with real stone?
Robert
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Other neighbours with similar steps and bigger problems have had major work done, but mine isn't at that stage. Thanks Toom
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Many thanks for that - looks promising - I'll look into it.
Thanks
Toom
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In article

When the weather gets better soak all the bits to be repaired in diluted PVA - the container should give the proportions. Think it's about 3:1 with the larger part water. Let it dry. Use the same mix as the gauging water for the mortar mix. I used this when repairing some stone mouldings some 30 years ago and they're still in place. But don't get the same wear as steps. Other thing which can look good is to repair then clad in real marble etc tiles. You can sometimes buy end of range boxes enough for this job at Wicks etc. Using a decent waterproof adhesive and grout should keep the water out.
--
*Sticks and stones may break my bones but whips and chains excite me*

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Many thanks for these ideas. Since stuff can't really stick to the soft core, and it all depends on the strength of the patch to the outer casing, I've also been wondering whether there's any kind of wire or metal mesh I could cut to size to embed in the repaired sections to reinforce them. If there's nothing designed for the purpose I might need to look around B&Q for something else suitable.
Thanks
Toom
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