As the name may or may not imply, roof mastic is based on bitumen. Since the requirements for waterproofing coverings are very rigid, bitumen requires special additives (polymers) to be added in order to improve its water proofing performance characteristics. Polymer additives make the original material elastic, heat-resistant and cold-resistant. Additionally, bitumen requires a thickening agent such as chalk, fragmented peat, ground slag, asbestos or wood meal to be added. These components are necessary to facilitate the laying of mastics, improve their heat-resistance and reduce the consumption of this binder. Roof mastics may be made of one or two components depending on its composition.
The main characteristics of a roof mastic include:
- high strength; and
- resistance to unfavourable conditions, wear and temperature extremes.
The characteristics of the final product are influenced by the characteristics of the original material
- (1) bitumen, (2) the quality and the amount of the introduced additives, solvent, emulsifiers and stabilizers as well as the peculiarities of the blending process.
The main criterion of high quality roof mastic is its dispersibility. It sould be able to have an even distribution of bitumen droplets in the polymer phase. If the dispersibility of the construction material was not achieved during its production, it means that it will lose its original characteristics very quickly after application. In practice, it is possible to produce a high quality mixture when applying homogenizers through the use of a colloid mill. A good quality colloid mill will serve to properly grind down the polymers.
The quality of the resulting substance may be checked with a special luminescence microscope that is usually a part of the equipment used at the bitumen mastic and rolled material production plants.
Bitumen mastics enjoy a wide application:
- bitumen and bitumen- polymer roofing repairs;
- bitumen shingles glueing;
- built-up roofing;
- waterproofing of rooms with limited ventilation; and
- rolled material glueing.