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Hydraulic lime is a variety of slaked lime used to make lime mortar
Lime mortar

Lime mortar is a type of mortar . It was used in the construction of the vast majority of brick and stone buildings worldwide from ancient times until the widespread adoption of Portland cement in the late nineteenth century....
. 'Hydraulicity' is the ability of lime to set under water. Hydraulic lime is produced by heating calcining limestone that contains clay
Clay

Clay is a naturally occurring material composed primarily of fine-grained minerals, which show plasticity through a variable range of water content, and which can be hardened when dried and/or fired....
 and other impurities. Calcium reacts in the kiln with the clay minerals to produce silicates
Belite

Belite is a name for dicalcium silicate, Ca2SiO4, sometimes formulated as 2CaO.SiO2 . It is a mineral present in Portland cement....
 that enable the lime to set without exposure to air. Any unreacted calcium is slaked to calcium hydroxide
Calcium hydroxide

Calcium hydroxide, traditionally called slaked lime, hydrated lime, or pickling lime, is a chemical compound with the chemical formula Calcium2....
. Hydraulic lime is used for providing a faster initial set than ordinary lime in more extreme conditions (including under water).








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Encyclopedia


Hydraulic lime is a variety of slaked lime used to make lime mortar
Lime mortar

Lime mortar is a type of mortar . It was used in the construction of the vast majority of brick and stone buildings worldwide from ancient times until the widespread adoption of Portland cement in the late nineteenth century....
. 'Hydraulicity' is the ability of lime to set under water. Hydraulic lime is produced by heating calcining limestone that contains clay
Clay

Clay is a naturally occurring material composed primarily of fine-grained minerals, which show plasticity through a variable range of water content, and which can be hardened when dried and/or fired....
 and other impurities. Calcium reacts in the kiln with the clay minerals to produce silicates
Belite

Belite is a name for dicalcium silicate, Ca2SiO4, sometimes formulated as 2CaO.SiO2 . It is a mineral present in Portland cement....
 that enable the lime to set without exposure to air. Any unreacted calcium is slaked to calcium hydroxide
Calcium hydroxide

Calcium hydroxide, traditionally called slaked lime, hydrated lime, or pickling lime, is a chemical compound with the chemical formula Calcium2....
. Hydraulic lime is used for providing a faster initial set than ordinary lime in more extreme conditions (including under water).

Hydraulic Lime in Construction


Hydraulic lime is a useful building material for the following reasons;

  • It has a low modulus of elasticity,
  • There is no need for movement joints,
  • It allows buildings to "breathe" meaning it doesn't trap moisture in the walls,
  • It has a lower firing temperature than Portland cement
    Portland cement

    Portland cement is the most common type of cement in general use around the world, because it is a basic ingredient of concrete, mortar , stucco and most non-specialty grout....
     thus much less polluting,
  • Stone and Brickwork bonded with lime is easier to re-use,
  • Lime acts as sacrificially in that it is weaker and breaks down more readily than the masonry, thus saving weaker stone such as sandstone and limestone from the harmful effects of temperature expansion and mortar freeze,
  • It is less dense than cement, thus less cold bridging,
  • Lime re-absorbs the CO2 omitted by its calcination (firing), thus partially offsetting the large amount emitted during its manufacture. The more hydraulic a lime, the less CO2 is reabsorbed during set, for example, 50% of CO2 is reabsorbed by NHL 3.5 during the set, compared to 100% of CO2 being reabsorbed by pure Calcium Carbonate
    Calcium carbonate

    Calcium carbonate is a chemical compound with the chemical formula CalciumCarbonOxygen3. It is a common substance found as Rock in all parts of the world, and is the main component of seashells, snails, and eggshells....
     (fat lime putty).


Classification

Natural Hydraulic Lime (NHL) is classified for different uses:

Feebly hydraulic lime

Feebly hydraulic lime (NHL 2) is used for internal work and external work in sheltered areas.

Moderately hydraulic lime

Moderately hydraulic lime (NHL 3.5) can be used for external work in most areas.

Eminently hydraulic lime

Eminently hydraulic lime (NHL 5) is used for external work in exposed areas, such as chimneys and for floor slabs/underpinning.

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