Lime mortar

robclay26

Hi,

I am looking to repair a brick window reveal and reset some stones on a limestone house wall with Lime motar.

I was wondering if hydrated lime mixed 1 lime to 2.5 sand is ok or do i need to use hydraulic lime? or whats the difference?

thanks

Roger Mellie Man on the Telly

Natural hydraulic lime (NHL) contains impurities which provide a degree of hydraulic set. The lime will also carbonate for millennia.

NHL 2 is feebly hydraulic, NHL 3.5 is moderately hydraulic, NHL 5 is eminently hydraulic. Porosity ("breathability") decreases with increasing hydraulicity.

Check the condition of the stone & brick - if it's soft/weak, use NHL 2. The mortar should never be stronger than the masonry. Don't go stronger than NHL 3.5.

You must use well graded sharp aggregate, not round sand.
5:2 mix is fine.
You must mix dry by volume in measured buckets, don't just throw it into a mixer 'by eye' with a spade.
You need to add water slowly and mix it properly for at least 20 minutes - you can't mix it like cementitious mortar.

Hydrated lime CL90 is very pure lime and has no hydraulic set (it will only cure by carbonation in the presence of carbon dioxide). It will also be too strong for the masonry. It will take forever to cure and is not practical - it's used to add plasticity to cementitious mortars.

robclay26

Super information,
Thanks a million 👠👠I

Roger Mellie Man on the Telly wrote: »

Natural hydraulic lime (NHL) contains impurities which provide a degree of hydraulic set. The lime will also carbonate for millennia.

NHL 2 is feebly hydraulic, NHL 3.5 is moderately hydraulic, NHL 5 is eminently hydraulic. Porosity ("breathability") decreases with increasing hydraulicity.

Check the condition of the stone & brick - if it's soft/weak, use NHL 2. The mortar should never be stronger than the masonry. Don't go stronger than NHL 3.5.

You must use well graded sharp aggregate, not round sand.
5:2 mix is fine.
You must mix dry by volume in measured buckets, don't just throw it into a mixer 'by eye' with a spade.
You need to add water slowly and mix it properly for at least 20 minutes - you can't mix it like cementitious mortar.

Hydrated lime CL90 is very pure lime and has no hydraulic set (it will only cure by carbonation in the presence of carbon dioxide). It will also be too strong for the masonry. It will take forever to cure and is not practical - it's used to add plasticity to cementitious mortars.

booooonzo

Roger Mellie Man on the Telly wrote: »

Natural hydraulic lime (NHL) contains impurities which provide a degree of hydraulic set. The lime will also carbonate for millennia.

NHL 2 is feebly hydraulic, NHL 3.5 is moderately hydraulic, NHL 5 is eminently hydraulic. Porosity ("breathability") decreases with increasing hydraulicity.

Check the condition of the stone & brick - if it's soft/weak, use NHL 2. The mortar should never be stronger than the masonry. Don't go stronger than NHL 3.5.

You must use well graded sharp aggregate, not round sand.
5:2 mix is fine.
You must mix dry by volume in measured buckets, don't just throw it into a mixer 'by eye' with a spade.
You need to add water slowly and mix it properly for at least 20 minutes - you can't mix it like cementitious mortar.

Hydrated lime CL90 is very pure lime and has no hydraulic set (it will only cure by carbonation in the presence of carbon dioxide). It will also be too strong for the masonry. It will take forever to cure and is not practical - it's used to add plasticity to cementitious mortars.

great post.. this should be pinned!

robclay26

booooonzo wrote: »

great post.. this should be pinned!

Agree! Followed his advice and it worked like a Dream. Nicer to work with than concrete.