Self-leveling mortars, according to DIN 18550, are a special group of mortars that present a series of additives in their composition that are responsible for attributing outstanding qualities that make it different from the rest.
Self-leveling mortar is used as a coating to create flat and smooth surfaces, correcting any initial defects that it may have had. Adjustments in its composition are making it an ecological option, by omitting the traditional Portland cement for anhydrite.
What is a self-leveling mortar?
This is a special mortar, which stands out for being extremely liquid. Its composition is similar to other special mortars, consisting mainly of the union between cement or anhydrite and fine grain sand. The difference is due to the incorporation of certain additives, as expected.
The most commonly used additives to create self-leveling mortar are the following:
- Superfluidifiers, causing its characteristic liquid consistency.
- Retraction reducers, essential to control retraction due to excess water in the mix.
- Air entrainers, improving plasticity and reducing the density of the mixture.
- Viscosity modifiers, preventing aggregates from falling to the bottom.
The adverse consequence of using these additives is the mortar’s resistance reduction, being lower than conventional mixes.
It is fair to say that the name of this mortar is inaccurate since it requires manual smoothing to provide surface regularity, lacking mechanical self-sufficiency.
Anhydrite is a mineral that has recently gained ecological relevance, since it has been used as a substitute for Portland cement due to its low pollutant emissions, presenting interesting and positive results in many constructive aspects.
The main benefits of anhydrite as a mortar binder are that it allows to create a coating with a minimum thickness of 2.5 cm and it has great thermal conductivity. Also, it preserves the physicochemical qualities to level a surface.
Anhydrite is obtained from the residues of the fluorine industry, in the form of calcium sulfate, which must be properly subjected to a series of chemical reactions to isolate the precious mineral.
Uses of self-leveling mortar
The primary aim of a self-leveling mortar is to improve the base to be coated, ensuring continuity and uniformity throughout its surface. This mortar can be used both indoors and outdoors, and even on floors subject to high traffic.
Leveling mortars are used for various aspects of the construction sector, however, these are their most common uses:
- Projects that require anchoring bolts for machinery.
- Leveling base plates.
- Supporting machinery, columns, beams, and other structural elements.
- Repairing concrete, in structures affected by environmental agents, for example, saltpetre.
Main advantages of self-leveling mortar
In relation to the varied use of self-leveling mortars, there are also considerable advantages. Among the many benefits we have chosen the following as the most important:
- It has a good adhesion capacity.
- High mechanical and abrasive resistance.
- It is an affordable option and has a positive financial impact since it reduces the coating execution time, the number of workers needed, and tools.
- It offers quality and excellent finishes, creating compact floors.
- It allows leveling large surfaces, thanks to its great fluidity.
- Its average drying time is 24 hours. However, the pavement can be used by traffic 4 hours after pouring it if the environmental conditions for setting are ideal.
- It can be used on a variety of surfaces (carpets, vinyl flooring, laminate flooring, and others) and environmental conditions.
- It is compatible with thermoacoustic insulation, and underfloor heating.
How to use self-leveling mortars?
Before proceeding how to pour these mortars, it is important to mention some preliminary points necessary to apply the coating correctly:
- The surface to be coated must be clean. It has to be healthy and free of oils, dust and any other substance that may hinder the adherence of the mortar.
- The surface must be exposed to water, but puddles must be avoided.
- If metal surfaces are to be coated, they will need to be thoroughly cleaned to remove any remaining grease, rust, paint and any other residual material.
- The surface must be hard and consistent.
- If the presence of any cracks, these must be repaired with special products.
- Expansion joints must be maintained.
To pour self-leveling mortars, these are the following steps:
- Kneading the mortar mixture, which should reach an approximately liquid state, but should also be a thick mixture. For this you can use pumping machines or a concrete mixer.
- Depending on the thickness of the applied coating, it is necessary to wait an equivalent number of days to carry out any finishes, such as tiling or waterproofing the mortar.