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Polymer modified bitumen

Polymer modified bitumen (PMB) are mixtures produced from:

  • bitumen
  • polymers

in which the polymers change the visco-elastic behavior of the bitumen and thus make this binder more suitable for different stresses.

Polymers can successfully improve the performance of asphalt pavements at low, intermediate and high temperatures by increasing mixture resistance to fatigue cracking, thermal cracking and permanent deformation.

The most commonly used polymer for bitumen modification is styrene–butadiene–styrene (SBS) followed by other polymers such as styrene–butadiene–rubber (SBR), ethylene–vinyl-acetate (EVA), and polyethylene. SBS block copolymers are classified as elastomers that increase the elasticity of bitumen.

Selected polymer or a blend of two or more modifiers shall have the following properties:

  • Compatible with bitumen
  • Resist degradation at mixing temperature
  • Capable of being processed by conventional mixing and laying machinery
  • Produce required coating viscosity at application temperature
  • Maintain premium properties during storage, application and in-service

ADVANTAGES AND USAGE OF MODIFIED BITUMEN:

Properties of modified bitumen depend upon type and quantity of modifier used and process adopted for their manufacture. The advantages of modified bitumen can include one or more of the following for road works:

 

  • Lower susceptibility to temperature variations
  • Higher resistance to deformation at high pavement temperature
  • Delay of cracking and reflective cracking
  • Better age resistance properties
  • Better adhesion between aggregates and binder
  • Higher fatigue life of mixes
  • Overall improved performance

According to these, polymer modified Asphalt needs much less maintenance work and Cost rather than a conventional Hot Mix Asphalt (HMA).

Polymer modified asphalt is mainly used in :

 

  • Main Roads & Highways
  • Airports
  • Roads with heavy traffic
  • Toll roads
  • Bus Lanes
polymer modified bitumen

Manufacturing process

Manufacturing process

Process Conditions:

Homogeneity is very important for desired performance of polymer modified binders. Hence, these should be prepared by appropriate industrial process and plant having high shear device. In high shear mixing, polymer particles are physically reduced in size by mechanical and hydrodynamic shear in a rotor-stator combination accompanied by significant input of heat energy to the mix. The polymer concentration up to the conditions and the polymer type may vary (e.g. SBS content is about 1%-7%).

 

The act of mixing base binder with polymer occur at elevated temperature (Min 160°C – Max 220°C) and the most appropriate temperature is about 180°C-200°C. also the shear rate is more than 2500 rpm. The time required to achieve a homogeneous blend of the polymer and the asphalt will vary with the type of polymer, its molecular weight, and (for thermoplastic rubbers) with the chemical composition of the polymer. A higher molecular weight will give rise to longer blending times.

SPECIFICATION

Test Method

(IS No)

PMB40 PMB70 PMB120 Characteristics/Grade
1203 30 to 50 50 to 90 90 to 150 Penetration at 25°C, 0.1 mm,100 g, 5 s
1205 60 55 50 Softening point (R&B), °C, Min
9381 -12 -16 -20 FRAASS breaking point, °C, Max
1209 220 220 220 Flash point, COC,°C, Min
70 70 70 Elastic recovery of half thread in ductilometer at 15°, percent, Min
3 3 3 Separation difference in softening point (R&B), °C,Max
1206 3-9 2-6 1-3 Viscosity at 150°C, poise

Thin film oven test and test on residue

9382 1.0 1.0 1.0 Loss in mass, percent, Max
1205 5 6 7 Increase in softening point, °C, Max
1203 35 35 35 Reduction in penetration of residue, at 25°C, percent, Max
50 50 50 Elastic recovery of half thread in ductilometer at 25°C, percent, Min
POLYMER MODIFIED BITUMEN Specification

 POLYMER MODIFIED BITUMEN Specification