Bitumen

Ordinary and modified bitumen (PMB)

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BITUMEN

It is known for its adhesive and cohesive assets, bitumen is mostly utilized in the construction industry.

Bitumen is a solid at ambient temperature and softens when heated, turning gradually into a viscous liquid. Therefore, Bitumen operates as the binder/glue for pieces of the aggregate. It is non-volatile at ambient temperature and atmospheric pressure. It is black or dark brown and it has waterproofing, and adhesive properties, the two other important characteristics are cohesiveness and durability.

The vast majority of refined bitumen is used in construction: primarily as a constituent of products used in paving and roofing applications. According to the requirements of the end use bitumen is produced to specification. This is achieved either by refining process or blending.

The bitumen is liquid at high temperature and solid at ambient temperature. The mayor part of bitumen is transported at high temperature, usually 160-180°C, but some part of bitumen is transported at ambient temperature, solid and packed (in big-bags, for example).

Bagged bitumen, big bags and blocks, represent relevant alternatives for transportation. Bags weight typically 20-30 kg and big bags 500 kg to 1 MT. Bitumen is filled in a polyethylene bag. 100% meltable without compromising the product characteristics. The bag is easy to carry by hand. Big bags are packed in an external bag and handled by forklift or small crane. No loss and no waste, thanks to the reusable packaging of big bags.

  • Bitumen BND 200/300 is used for the surface treatment of coatings in regions with cold climate, as well as for preparation of hot asphalt and bituminous crushed stone gravel mixtures.

  • Bitumen BND 130/200 is used for the surface treatment of coatings in regions with temperate climate, to impregnate macadam in regions with cold and temperate climates, for preparation of hot asphalt and bituminous mixtures in regions with cold climate.

  • Bitumen BND 60/90 is used to impregnate the macadam road in regions with warm climate, for preparation of hot asphalt and bituminous mixtures in regions with warm climate.

  • Bitumen BND 40/60 is used for the preparation of asphalt and bituminous mixtures in regions with summer temperature >30°C.

POLYMER MODIFIED BITUMEN (PMB)

Polymer modified bitumen (PMB) is one of the specially designed and engineered bitumen grades that is used in making pavement, roads for heavy duty traffic and home roofing solutions to withstand extreme weather conditions. PMB is a normal bitumen with added polymer, which gives it extra strength, high cohesiveness and resistance to fatigue, stripping and deformations, making it a favorable material for infrastructure.

The most common type of polymer that is added is styrene butadiene styrene (SBS), which acts as a binder modification agent. When a polymer is added to regular bitumen, it becomes more elastomeric, which provides it with additional elasticity. The primary objective of SBS polymer modified bitumen is to provide extra life to pavement, roads and construction designs. Some of the qualities exhibited by PMB are:

  • Higher rigidity

  • Increased resistance to deformations

  • Increased resistance to cracks and stripping

  • Better water resistance properties

  • High durability

Under traffic the film of bitumen hold the aggregates together may break, causing the aggregates to come off. This phenomenon is called raveling. PMB have increased cohesion energy: it requires much more energy to break because of their high elasticity or plasticity. As a consequence, the asphalt mix will be much less sensitive to raveling. SBS modified bitumen are typically more viscous than regular bitumen. This may become a problem if the viscosity is too high, because the product can no longer be pumped, or it will not coat the aggregates properly, or the asphalt mix can no longer be fully compacted. On the other hand, plastomer-modified bitumen are much less viscous.

Polymer modification improves the binder resistance to aging. Bitumen on the road is subjected to aggressive climatic conditions like oxidation by air, UV light, water, changes in temperatures. All this combined with traffic loads. Over time the bitumen tends to stiffen and come more brittle. In the case of PMB, this aging phenomenon is mitigated, which brings some extra durability to the pavement.

Finally, polymer modification improves the resistance to fatigue. Fatigue is the development of cracks by the repetition of loading cycles. It is responsible for the failure of many pavements. PMBs are more resistant to fatigue. They develop damage at a slower pace, bringing extended lifespan to the pavement.