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Lime mortar

  • 16-04-2021 10:04pm
    #1
    Registered Users Posts: 539 ✭✭✭ 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


Comments

  • Registered Users Posts: 1,074 ✭✭✭ 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.


  • Registered Users Posts: 539 ✭✭✭ robclay26


    Super information,
    Thanks a million 👠👠I
    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.


  • Registered Users Posts: 470 ✭✭ booooonzo


    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!


  • Registered Users Posts: 539 ✭✭✭ 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.


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