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Mastic asphalt screed (AS)

Mastic asphalt screed consists of limestone or quartz sand filler, fine and coarse aggregates, bitumen and various additives. Bitumen, a substance obtained from the distillation of crude oil, serves as a binding agent and is responsible for the thermoplastic properties and the black color of the screed. If required, a different color is also possible, for which the screed must be given an appropriate pigmentation, sanding or coating.

A typical feature of mastic asphalt screed is its flowable consistency, which is obtained by heating the screed to approx. 250 °C. The elastic screed forms a dense structure with few cavities. It is not only insensitive to moisture and impermeable to water and water vapor, but also has relatively good thermal and sound insulation properties.

Areas of application for mastic asphalt screed

Mastic asphalt screed is mainly used in building construction and industrial construction, but is also used as a waterproofing material for buildings. Its use in residential construction is also theoretically possible, but is rather rare in practice. Nevertheless, it is suitable for all standard floor coverings and also for combination with underfloor heating. Compared to other types of screed, the thermal conductivity of mastic asphalt screed is lower than that of cement screed and calcium sulphate screed at 0.90 (W/(m-K)), but higher than that of magnesia screed. Mastic asphalt screed can also be laid in damp rooms (e.g. kitchen, bathroom).

Depending on the requirements, there are different hardness classes (IC10 to IC 100). If the screed contains hard aggregates, it can be used in industrial areas subject to high loads and traffic without any problems. Most people are probably familiar with mastic asphalt screed from road construction, as it is often used as a surface layer on freeways, but also in tunnels or on bridges.

Caution: Mastic asphalt screed cannot be pumped. It can therefore only be applied to higher floors with the aid of construction or inclined elevators, which transport the screed to its destination without it cooling down too quickly.

Laying techniques for mastic asphalt screed

The screed, heated to approx. 250 °C, is spread smoothly to create an even surface and rubbed down with sand. It hardens during the subsequent cooling process.

Possible laying techniques for mastic asphalt screed are:

- Bonded screed
- floating screed
- screed on separating layer
- screed on insulating layer
- heated screed

Important: If the mastic asphalt screed is laid on a separating or insulating layer, this must be made of a temperature-resistant material such as raw glass fleece or ribbed cardboard.

What to look out for when laying mastic asphalt screed

Mastic asphalt screed is laid manually, but this involves a lot of effort and physical exertion. Alternatively - although very rarely - it can also be laid by machine.

Depending on the laying technique, edge insulation strips of different thicknesses are required. For screeds on a separating or insulating layer, the edge insulation strips should be at least 8 mm thick, for heated screeds or hard surface coverings at least 10 mm.

Mastic asphalt screed is softer than other screeds. For this reason, elastic or textile floor coverings can theoretically deform under point loads. This can be avoided if the screed is leveled with a filler before the floor covering is applied.

Caution: Due to the high installation temperature, there is a certain risk for heat-sensitive materials in the vicinity. These include certain synthetic, insulating and plaster building materials.

Mastic asphalt screed and more from professionals

High quality advice, planning, choice of materials and implementation - this is what we stand for with our expertise and more than 25 years of experience in daily practice. We are proud to support you in your project with our screed work. Professional work, personal support and reliability in all matters are our quality features. See for yourself and contact us with your questions, requests or projects. We look forward to hearing from you and will be happy to discuss everything you need in a personal consultation. It's best to make an appointment now!


Questions and answers about mastic asphalt screed

Why is mastic asphalt screed black?

The binder in mastic asphalt screed is bitumen, which is obtained from crude oil and is black in color. This is why mastic asphalt screed is sometimes also referred to as black screed.

Is the application of mastic asphalt screed harmful to health?

When working with mastic asphalt screed, emissions that are hazardous to health may occur. It is therefore essential to observe health and safety measures when working with this screed.

Can mastic asphalt screed be recycled?

Yes, very well indeed. The prerequisite for this is that it is unmixed and free of impurities. In other words, it must not be covered with other materials and, above all, there must not have been a layer of tar underneath, which is the case in some older buildings.