Will Hydralime and sand ever set?

[TobleroneEater]

Hello,

I hope this is an ok place to ask this question. We have a builder installing an RSJ above a new opening in a ~170 year old lime stone house. We've asked them to use lime mortar for the external elements of the house, to maintain the breath-ability, strength, save the stone etc etc of the house (no need to go in to detail as to why we wanted this, I hope).

After installing the RSJ and back-filling above we found they used a 1:3 Hydralime / sand mix (the Tarmac / Bluecircle bagged hydrated lime you get at most builders merchants). After 3 days of good dry weather it's still very soft, turning to dust with little effort. We've found some places on the internet that say it will never set, the packaging says it must be used with cement, but the builder is insisting they've used it before and it will set.

Any advice on this? My instinct is to get them to redo it with a 1:3 cement and sand mix as standard – the area will be inside the property so I'm less worried about the breath-ability of the house than I am about the structure.

Thanks in advance!

 

[^woody^]

I was at Kenilworth Castle only the other week, and noted that the lime mortar there was pretty hard after 700 years or so.

It's the wrong choice of mortar, but if it was properly packed with slate as it should be, it will be fine. Otherwise cement mortar would be the better choice.

 

[TobleroneEater]

They'd have used a form of quick or lot lime mortar in the castle I reckon, not hydrated lime?

 

[stuart45]

Lime mortar should be kept damp(misting etc) and protected from the sun for at least a week. It cures from the outside first, so it's more difficult for the CO2 for reach the centre of the joints. Hydraulic lime would probably been a better choice in this instance. Don't know any lime specialists that use the bagged Hydrated lime instead of lime putty.

 

[23vc]

I was at Kenilworth Castle only the other week

Did you give em a quote? I’ll labour for you, round the corner from Leam
Joking aside when I take the kids there this summer which I’m meant to be doing, I’ll be checking out the mortar now.

 

[^woody^]

Did you give em a quote? I’ll labour for you, round the corner from Leam
Joking aside when I take the kids there this summer which I’m meant to be doing, I’ll be checking out the mortar now.

Yeah, there's a few damaged walls but the foundations look ok. I did give a good quote, but don't fancy lifting some of those stones with my bad back. I will sub it out to Stuart for £50 a day cash and provide some milk crates, and you'll have to negotiate a rate with him.