Waterproofing is the process of applying a material to an object or structure so that it resists the ingress of water or remains relatively unaffected by exposure to moisture under specific conditions. Waterproofing is typically used on structures that under normal circumstances would not be operable in wet or damp environments.
Bitumen is a generic term used to describe a category of minerals consisting primarily of hydrogen and carbon with traces of nitrogen, sulfur, and oxygen. It is a highly viscous liquid or semi-solid form of petroleum that could be found in natural deposits or as a refined product. Over 70% of bitumen consumption is directed towards roadway construction, where it is used as a binder to create hot mix asphalt. The remainder is primarily used for sealing, insulating, and waterproofing purposes.
Bitumen is a black, sticky substance with physical characteristics not unlike that of molasses at room temperature. As is typical with hydrocarbons, bitumen is highly hydrophobic in that they tend to repel or at the very least don’t mix well with water, hence their use as a material in waterproofing. Bitumen can be modified with polymers to enhance its performance and using as different forms of production in the building industry. It serves as the main component of waterproofing materials in the forms of sealants, mastics, adhesive, coating, etc.
Bitumen is a waterproof coating
Waterproofing coating systems are mostly employed to prevent the permeation of water and any soluble salts from penetrating the concrete to prevent the corrosion of reinforcing steel and interaction with the cement particles. These prevent the early deterioration of concrete structures exposed to adverse topographic conditions; severe ground and ambient salinity and a high temperature-humidity system. They have the advantages of good adhesion to the substrate, permeability to vapor, and crack bridging ability without decreasing the alkali resistance of the substrate.
In coating applications, bitumen is used as the foundation for bituminous paints, which are coating products consisting primarily of bitumen that is applied in liquid form. Bituminous paints are made up of bitumen mixed with a solvent, usually mineral spirits or naphtha but can also be mixed with other polymers such as polyurethane or acrylic-based polymers to give the other characteristics to enhance the performance of the coating. A specialized form of bitumen-based coating is also used in roofing in the form of waterproofing membranes.
Since bitumen is naturally insoluble in water, coatings derived from this material serve as an effective sealant or repellent against water ingress. This natural water resistance, combined with strong adhesive properties, allows bitumen to provide excellent barrier protection against corrosion by preventing air and moisture from coming into contact with the coated substrate. Additionally, bituminous paints are also relatively durable, economical, and resistant to chemical and ultraviolet (UV) degradation, thus making them well suited for coating structures that operate in harsh environments.
Due to their numerous desirable properties, bituminous paints are a viable solution for waterproofing a wide variety of structures, both above and below ground. In the construction industry, these paints are typically used to line reinforced concrete foundations and retaining walls to prevent moisture ingress, which can result in corrosion of the steel reinforcement.
The versatility of bituminous coatings makes them suitable for application on a broad range of materials including metals (iron, steel, zinc, lead, aluminum), concrete, felt, plastics, etc. Stairways, gutters, fences, railings, gates, ladders, and water tanks are just some of the other objects that are coated with bituminous paints to increase their longevity in harsh environments.
As they come in liquid form, bituminous paints can be applied just as easily as the common house paint. Depending on the shape and size of the surface, environment, coating requirements, and coating formulation, bituminous paints can be applied with a brush, roller, or sprayer (conventional, airless, or hot spray) as required.
Surface preparation is also important with bituminous paints. While they naturally have strong adhesive properties, they can be undermined by a dirty surface. When applying bituminous paints over existing paint, it’s also important to remove any loose or blistering paints beforehand. In an especially harsh environment, bituminous paints can also be applied as a topcoat with an additional anti-corrosive layer used as a primer to ensure adequate protection against corrosion.
Bitumen based polymer coating
These are a mixture of bitumen, mineral fillers, and polymers. Polymers commonly employed are either elastomeric or elastomeric. The addition of polymer to bitumen improves the flexibility even at low temperatures and provides a totally impermeable barrier against ingress of water, especially in the pavement in bridges, industrial washrooms, refurbishing of old bituminous roofs and tunnels. Since polymers also increase solvent and corrosion resistance, this system is employed on structures in underwater conditions, like pipelines, foundations, tanks, sewage works, effluent plants, docks, harbor installations, etc.
When elastomeric polymers are used, the coatings provide high resistance to cracking that can be caused due by structure movements. Its sealing properties do not change on exposure to a temperature between -25 and +100 degrees centigrade and UV radiation. Since it can be applied on damp surfaces by a brush, roller, or spray, this system has a wide range of applications. The major advantage is that it is very flexible and after application, it dries to form a uniform film that is perfectly impermeable to water. On aging, bitumen-based polymer coating remains flexible, non-toxic, and ecofriendly.
