Why do old builders add lime to the cement mortar (pros, proportions)
Cement is used for construction work (foundations, brickwork, screeds, preparation of plaster solutions, etc.).
Cement is produced by crushing clinker. Various additives are added to the resulting powder: plasticizers, mineral additives, gypsum, etc.
Strength - an important property of cement. This indicator is influenced by the technology of preparation of the solution, styling. The most popular brands are M300-500. M100 - the minimum strength grade used for concreting curbs, fences. Brand M500 used where increased strength and resistance to heavy loads are required.
To obtain plasticity, liquid soap or plasticizers are added (5% of the total amount of cement).
Pros of lime in solution
Some add lime (no more than half the volume of sand).
- In addition to plasticity, lime gives "stickiness". When the solution pounces on the wall, then it no longer falls off and does not drain, but holds firmly.
- Another reason for adding lime is to save on cement.
- Lime imparts crack resistance to the surface.
- The solution takes on an interesting white-gray color.
By the way, when adding lime, soap, there is no white bloom (efflorescence) on the brick.
Cement-lime mortar is used mainly in damp places. A good mixture for plastering the bottom of the house: foundation, basement.
For masonry or plaster, slaked lime and sand are used. The main thing is to properly prepare lime (from 7 min. up to 30).
Stir occasionally and when the reaction completely stops, strain through a sieve. Then the lime must be left for 2 weeks (if for masonry) or for a month (if for plaster). If you buy ready-made slaked lime, then make sure that it is not frozen, otherwise the plaster will crumble when touched.
Proportions for solution preparation: 1 part cement, 1 part lime dough and 9 tsp. sand. Strength can be increased by using cement grade M400.
If the solution needs to be kept for several hours (up to 12 hours), then you can fill it with water on top.
The cement is mixed with sand and then lime is added. You can do this: first pour the cement with water, mix, and then add lime.
Long ago from the experience of old builders it is known that if you plaster a wall (concrete, wood or brick) with clay and lime, then even after 50 years it will be like new. And if you plaster with cement, then there will be mold, stains.