Preparation of Lime Mortar:

Lime is mixed with sand in a proportion of 1:3.
Some types of  mortar mills operating:

• One is diesel operated and has a capacity of 8cft; the mix is ground for a duration of 8 minutes.
• The second machine, 3 phase electrically operated, has a capacity of 2 cft

The finishing material of lime and sand in a proportion of 1:2 is mixed for 2 hours.
 

• The new mortar must match the historic mortar in color, texture and tooling.
  (If a laboratory analysis is undertaken, it may be possible to match the binder components and their proportions with the historic mortar, if those materials are available.)

• The sand must match the sand in the historic mortar.
  (The color and texture of the new mortar will usually fall into place if the sand is matched successfully.)

• The new mortar must be as vapor permeable and as soft or softer (measured in compressive strength) than the historic mortar.
  (Softness or hardness is not necessarily an indication of permeability; old, hard lime mortars can still retain high permeability.)

maturing lime

Use of Lime Mortar

• Roof of various types
• Wall masonry
• Floors
• Decorative elements ( cornice , mouldings etc )
• Finishes

Maturing of Lime :

Lime mortar is stored in mounds at the site.
The maturing period for the lime mortar is 6-9 days.
The top layer of the mortar, which has hardened is scraped and the mortar from the inner core is removed to be remixed before use.

Once lime and sand mortar is mixed and applied on a wall, it begins the process of carbonation, which is a very gradual process. If lime mortar is left to dry too rapidly, carbonation of the mortar will be reduced, resulting in poor adhesion and poor durability. In addition, lime mortar is slightly water-soluble and thus is able to re-seal any hairline cracks that may develop during the life of the mortar.

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