Requirements of Bitumen

  • To avoid rutting due to high and overloaded traffic in India, we desire sufficient stiffness and flexibility of road surface at the desired temperature ( 60 degree C Considered maximum surface Temperature of the road in India )
  • To avoid the fatigue cracking ( bottom-up cracking ), we desire hardness at 25 degrees C at the bottom of the Bituminous layer.
  • For proper mixing and laying of Bituminous mix, we desire less stiffness at 135 degrees C
  • It has sufficient adhesion with the aggregates in the mix in the presence of water
  • It is desirable to maintain the stability under adverse weather conditions

Desirable Properties of Bitumen

  • Cohesion: means attractive forces between the two same particles of the bitumen basically it is a fundamental characteristic of bitumen binder. It is the main cause of shear stress in bitumen. The most important factor on which cohesion depends is “Temperature”. As we supply energy (temperature) to the bitumen, It decreases the cohesive forces. hence bitumen becomes liquid at high temperature.
  • Viscosity: It is resistance to movement between two adjacent layers due to intermolecular cohesive forces of attraction in liquid. It is expressed with a measuring unit of Ns/sqm or poise where 1 Ns/sqm is equal to 10 poise. The viscosity of the bitumen at the time of mixing and compaction should be adequate. It is achieved by heating the bitumen and aggregate prior to mixing or by use of cutbacks or emulsions of suitable grade.
  • Temperature Susceptibility: The bituminous material should not be highly temperature susceptible. During the hottest weather of the region the bituminous mix should not become too soft or unstable. During cold weather the mix should not become too hard and brittle, causing cracking. The material should be durable. It is better to use bitumen having a higher softening point which indicates lower temperature susceptibility.
  • Adhesion Property: The bitumen should not strip off from the aggregate in the presence of water. There has to be adequate affinity and adhesion between the bitumen and aggregate used in the mix.

Different Type of Bitumen Binder

  • Bitumen Binder or Asphalt Cement in US
  • Cutback Bitumen Binder
  • Emulsified Bitumen Binder
  • Modified Bitumen Binder

Bitumen Binder or Asphalt Cement

Viscosity grade bitumen is the most widely used bitumen in India. Viscosity grade bitumen may also be considered as the parent bitumen from which the Cutback Bitumen, Emulsified Bitumen and Modified Bitumen are produced. It is based on the viscosity at 60 degrees C As per Clause 5 page 1, IS 73: 2013, Bitumen shall be classified into four grades based on the viscosity, and suitability recommended for maximum air temperature as given below

VG : 10 Grade bitumen

  • Softest grade bitumen in India
  • Suitable for Cold climate
  • use for surface dressing
  • If Lowest daily mean air temperature More than – 10 Degree C ( ie -20 Degree C ), It can be used up to highest daily mean air temperature less than 20 degrees C
  • If the Lowest daily mean air temperature is up to 10 degrees C, It can be used up to the highest daily mean air temperature up to 30 degrees C
  • In a hot climate area where the daily mean air temperature is above 30 degrees C, VG 10 would not provide a good resistance to rutting.
  • Bitumen (VG 10 )should be heated in between 140 to 160 degree C before mixing with preheated Aggregate
  • Laying temperature of mix with VG 10 bitumen should not be less than 130 degrees C
  • Rolling Temperature of mix with VG 10 bitumen should not be less than 80 degrees C
  • the current price of VG 10 please visit https://www.bitumenindia.com/
  • IS 72 : 2013 test data as given below
VG 10 grade bitumen

VG : 20 Grade bitumen

  • Not available in Indian Market
  • Suitable in between daily mean air temperature of 20 degrees to 30 degrees C
  • At the site, it is prepared by mixing of VG 10 ( 50%) + VG 30 (50%), that is called Jugad technology
  • But as per IS 73: 2013 clause 4 pages 1, Bitumen shall be prepared by the refining of crude petroleum by suitable methods. hence It is preferable to avoid above jugad
  • Bitumen (VG 20 )should be heated in between 145 to 165 degree C before mixing with preheated Aggregate
  • Laying temperature of mix with VG 20 bitumen should not be less than 135 degrees C
  • Rolling Temperature of mix with VG 20 bitumen should not be less than 85 degrees C
  • IS 72: 2013 test data as given below

VG : 30 Grade bitumen.

  • Suitable in between daily mean air temperature of 30 degrees to 44 degrees C
  • It is a harder grade bitumen
  • It can withstand a higher traffic load.
  • As per IS 73: 2013 clause 6.2 pages 2, It is interesting to note that absolute viscosity between 3200 poise to 3600 poise can be identified as VG 30 as well as VG 40.
  • Bitumen (VG 30 )should be heated in between 150 to 165 degree C before mixing with preheated Aggregate
  • Laying temperature of mix with VG 30 bitumen should not be less than 140 degrees C
  • Rolling Temperature of mix with VG 30 bitumen should not be less than 90 degrees C
  • the current price of VG 30 please visit https://www.bitumenindia.com/
  • IS 72: 2013 test data as given below

VG : 40 Grade bitumen.

  • Hard grade bitumen
  • Suitable for heavy traffic roads.
  • a better option, in case of rutting issue
  • Bitumen (VG 40 )should be heated in between 160 to 170 degree C before mixing with preheated Aggregate
  • Laying temperature of mix with VG 40 bitumen should not be less than 150 degrees C
  • Rolling Temperature of mix with VG 40 bitumen should not be less than 100 degrees C
  • the current price of VG 40 please visit https://www.bitumenindia.com/
  • IS 72: 2013 test data as given below

Cutback Bitumen Binder

  • To reduce the viscosity, it is normal practice to heat the bitumen
  • . But from the environmental point of view, there is an emission of greenhouse gas (265 kg/ton source research paper ) during heating the bitumen and aggregate to prepare the mix.
  • Hence it is better to reduce the viscosity of bitumen by other means.
  • So The viscosity of bitumen is reduced by adding naphtha, kerosene, diesel, oil and furnace oil.
  • These solvents will evaporate after application and leave binder of similar hardness as bitumen
  • There are different types of cutback bitumen Like rapid curing(RC), medium curing(MC), And slow curing(SC)
  • Rapid Curing Bitumen (RC): Cut with high volatility solvents such as naphtha or gasoline. and it is classified into 4 grades a) RC 70, b) RC 250, c) RC 800, and d) RC 3 000. It is mainly used for tack coat and surface treatment. Refer IS 217: 1988.
  • Medium Curing Bitumen (MC): Cut with a moderate volatile solvent such as kerosene. and it is classified into 5 grade a) MC 30, b) MC 70, c) MC: 250, d) MC 800, and e) MC: 3 000. It is mainly used for Prime coat. As per IS 217: 1988 clause no 3.2.2.1 page no 1 MC 30 grade shall be used as a primer.
  • Slow Curing Bitumen (SC): Cut with a low volatile solvent such as low viscosity oil. and it is classified into 4 grade a) SC 70, b) SC 250, c) SC 800, and d) SC 3000. It is mainly used in cold mix and patching work
  • But there is a drawback to use Cutback bitumen
  • 1. As the solvent evaporates into the atmosphere which is a costly affair.
  • 2. The solvent which evaporates into the atmosphere is a cause of air pollution
  • 3. Due to the use of solvent, it has a low flash point and causes safety issues
  • Hence it is a good option to use Emulsified Bitumen