In the production of soft coatings for the roof (roofing material) a fraction of 0.6-2.0 mm
performs the function of a protective layer – this is the coatings armor.
The functions of the top layer – dressing – just consist in protecting the bituminous binder from external influences.
The use of granulate or slag as an outer layer of a soft roof
considerably prolongs the service life of coatings, protecting them from ultraviolet radiation, intense oxidation, and also increases fire safety. Grains of dressing tightly interlock with bitumen, forming a virtually uniform stone shield, protective armor.
In addition to the shape, the grain size is important. In order to obtain a single-layer coating that completely protects the bituminous binder at any site, different fractions are mixed or a range from 0.6 mm to 2.0 mm is maintained. Too large grains will not be located close enough, that is, voids will form between them, and the protection will be unsatisfactory. At the same time, the small fraction is peeled off more quickly, the loss of its most part occurs during transportation and operation.
Another task of the stone shield is to increase the attractiveness of a soft roof.
Topping should be: hard; not transmitting sunlight; chemically inert; do not have dust fractions. To ensure that the granules adhere securely to the bitumen and do not fall off during transportation, rolling up the material into rolls and during the operation of the roof, they are treated in a special way.