The technology of preparation and application of mortar for wall plastering
When decorating the external and internal walls, lime mortar is used. Despite the fact that in construction stores they offer various modern mixes for finishing work, this composition is worthy of attention. Consider what types of lime solutions are used in each case, how to properly prepare them, and what you need to remember when working with lime.
Lime: properties and application
Positive properties of lime – strength and high adhesive ability. One of its main advantages is its rather low cost, which, ultimately, will affect the overall construction budget.
Lime added to the mortar for plaster has antiseptic properties, preventing the formation of mold and fungi on the surface of the walls.
The most important property of lime is plasticity, which binds all the components of the batch into a homogeneous mass. The finest particles of calcium hydroxide are able to hold water on a rough surface, which reduces friction between the components, creating the so-called “lubricant”. Lime is put in a batch instead of synthetic plasticizers.
There are several basic recipes for making the mixture. But before you use them, you need to figure out how to pay the lime.
Extinguishing lime before mixing
For the preparation of various types of emulsions, hydrated (hydrant) lime is used – calcium hydroxide. First, it should be extinguished with water. To do this, take a container of a suitable size, for example, a barrel or a trough. The container must be metal without rust, wooden, or plastic.
Slaking lime in a metal container
Considering that the mass after the quenching will increase significantly, the container is taken three times more than the original amount of quicklime. To extinguish large portions of lime, a pit is prepared in the ground. Lumps of lime or ground powder are placed in the container and filled with a sufficient amount of water.
Attention! When combined with water, a chemical reaction immediately begins – lime begins to boil violently, so care must be taken not to get burned. Safety measures include special protective clothing, gloves made of rubber or silicone, safety glasses.
In the process of hydration, cold water is used in the following proportions:
Quenching “fluff” – 1 liter of water per 1 kg of lime;
Quenching of the “test” – 0.5 l of water per 1 kg of lime.
Rapid boiling lasts 36-48 hours, the mass is thoroughly mixed several times. After hydration, let stand for two weeks, then pass through a sieve to remove lumps. The hydrant mixture is ready for use.
Sand preparation for lime mortar
At the construction site, several types of sand are used:
Crushed mining waste.
Quartz sand is used for textured or artistic plaster.
Barite – for medical institutions and for protecting walls from radiation background.
Sometimes instead of sand, marble chips are used as a filler for decorative surface finishes.
Sand is selected, given the fraction and shape of the grains. Coarse-grained with interspersed shells is not suitable for the formation and alignment of walls.
A quarry with a small addition of clay will be an ideal filler for cement-lime plaster. Small cross section and irregular shape with sharp edges contributes to good adhesion to the surface. A small percentage of clay will not allow the emulsion to quickly settle.
Before mixing, sand is sieved through a frequent sieve with a small mesh of 3 to 5 mm. This fraction is suitable for starting plaster. For the finish sift through a sieve with a mesh of 1-1.5 mm. In the process, pebbles, shells and other foreign inclusions of a large fraction are eliminated. Shell inclusions are suitable for exterior decoration of facades.
Sand, sifted through a sieve
Types of lime solutions
In practice, several mixtures of lime are used:
The most common cement. With gypsum, the emulsion is used for finishing, when you need a perfectly smooth surface and quick drying. And with clay they use it rather rarely – for stoves, fireplaces and huts in the countryside. For each recipe, it is necessary to select and prepare all the constituent components.
A kind of lime mortar
Gypsum for mixtures
Lime-gypsum mortar for wall plastering is used only indoors with low humidity.
Advantages of gypsum plaster
This coating is used on ceilings due to its low weight. The walls are covered with a layer of about 5 mm, this allows you to spend significantly less material than when using plaster mortar with cement.