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materials for the modification of road bitumen

Pavprene ® (SBS)

Styrene-Butadiene-Styrene based Thermoplastic Elastomer
Pavprene® is the trade name of the polymeric materials developed by SO.F.TER. for the modification of road bitumen.
Pavprene® is an elastomer based on SBS (Stirene-Butadiene-Stirene) thermoplastic rubber. which, when appropriately dispersed in the bitumen, allows to improve the mechanical characteristics of asphalt, such as elasticity, cohesion, indeformability, both at low and high temperatures.
Indeed, modified bitumen is becoming increasingly popular because it allows to significantly improve the quality, durability and performance of road surfaces, and to respond perfectly to problems of wear and maintenance caused by increasingly heavy traffic.
Moreover, the so-called draining asphalt, which can be obtained only by using modified bitumen, increases driving safety and comfort, thus allowing the number of accidents in rainy weather conditions fall by up to 30%.

 

ADVANTAGES OF BITUMEN MODIFIED WITH PAVPRENE®

Compared to traditional bitumen, modified bitumen allows to obtain the following benefits:
  • higher viscosity of the bituminous mixture and increased cohesion and adhesion to the aggregates;
  • higher ageing resistance and longer durability of the road surface;
  • lower deformability, that is improved resistance to ruts;
  • higher wear and fatigue resistance
  • higher stability of the asphalt; it improves its behaviour at high and low temperatures;
  • possibility of reducing the thickness of the road pavement without worsening its structural features;
  • possibility of counterbalancing the mediocre or variable quality of bitumen.
It is also possible to produce high-quality draining asphalt with further advantages, such as:
  • elimination of the aquaplaning effect;
  • improved adherence of tyres in rainy or very damp weather conditions;
  • improved diurnal and nocturnal visibility, thanks to a smaller amount of sprays and a reduced blinding effect of headlights on damp or wet asphalt;
  • a sound absorption effect: the noise reduction is possible thanks to dissipation of acoustic energy through the voids in the draining pavement (noise reduction of approximately 6 dB).

 

CHARACTERISTICS OF DRAINING AND NOISE ABSORBENT ROAD PAVEMENTS

With draining asphalt the characteristics of a wet road surface can assimilate to those of a dry surface.
In order to obtain a draining and sound absorption behaviour, the conglomerate must have an ‘open grade structure” and must contain over 15% voids , as shown in the image below.
The porous structure is of capital importance to drain rainwater and drastically reduce the noise caused both by the rolling of tyres and the engine.
Experimental and practical results confirm the effectiveness of an open grade structure: a well formulated conglomerate allows to reduce noise by about 6 dB which, being measured in a logarithmic scale, correspond to a 50% noise reduction measured with standard reading techniques.
The effectiveness of this particular texture can be verified through water permeability (I/min draining). Owing to this particular texture and the high content in voids, the use of high quality aggregates (basalt) is required.

SO.F.TER offers the market a range of products capable of meeting every need in the road paving sector. The products are divided into two groups which differ in molecular structure:

LINEAR STRUCTURE: enables to obtain bituminous blends that offer lower viscosity and improved sprayability, processability, emulsionability and storage stability, as well as better compatibility with the different types of bitumen.

RADIAL STRUCTURE: enables to obtain bituminous blends with improved physico-mechanical properties, first of all the softening point measured with the Ball-Ring test.

RANGE

Pavprene® 501 
Linear structure SBS elastomer, particularly suitable for bituminous emulsions. It can also be used for the waterproofing layer of draining surfaces (easy sprayability), and for both closed and open grade conglomerates.

Pavprene® 501P
Linear structure SBS elastomer: it has the same properties of Pavprene® 501 but with improvedprocessability thanks to added compatibilizing oil.

Pavprene® 511K
Radial structure SBS elastomer with high rheologic properties. It’s particularly suitable for modified bitumen such as high-technology “Hard” types (high tensile module).

Pavprene® 511P
Radial structure SBS elastomer: it has the same properties of Pavprene® 511K but with improved processability thanks to added compatibilizing oil.

Pavprene® 511C
Radial structure SBS elastomer: it has the same properties of Pavprene® 511P but with a very good processability due to higher content of compatibilizing oil

Precondition for a correct use of Pavprene® and for an optimum exploitation of its qualities, is that the bituminous blend be obtained with high shear mixers such as to achieve a continuous elastomeric phase, at temperatures around 180°C.
The following processing phases (preparation of the conglomerate, laying, rolling, spraying, etc.) must take into account the higher viscosity of modified bitumen, therefore the temperature will have to be slightly higher than the one normally used with non-modified bitumen.
Storage stability is the most critical parameter of the bitumen/SBS blends whose elements tend to separate after a certain amount of time. SO.F.TER. is developing special polymeric blends which can improve the storage stability of bituminous emulsions.
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