Comprehensive article on modified Bitumen with Gilsonite (Natural asphalt)


modified bitumen.Improving the properties of pure bitumen has attracted the attention of many researchers. In this study, researchers examined the effect of Gilsonite on the rheological properties of pure bitumen.

They used different percentages of Gilsonite powder to correct 60/70 pure bitumen.

In this study, they tested the viscosity, softening point, degree of permeability and degree of flammability.

The thermal sensitivity of the bitumens was also calculated.

Their results are as follows:

Adding Gilsonite to pure bitumen increases the viscosity and softness of the bitumen. It has also reduced its penetration rate.

So, adding this powder to pure bitumen has improved thermal sensitivity. But it has not affected the degree of bitumen ignition.

Gilsonite is a high-asphaltine natural hydrocarbon. It is also highly soluble in organic solvents and has a lot of nitrogen.

The researchers looked at the effect of Gilsonite on pure bitumen with a penetration rate of 30 and 50. They found that Gilsonite increased the softening point and reduced the degree of bitumen penetration.

They examined the effect of Gilsonite on bitumen performance at high, medium and low temperatures. The result was that Gilsonite had a positive effect on bitumen performance at high temperatures.

Other advantages and features of Gilsonite modified bitumen:

Gilsonite increases the Marshall resistance and the abrasion resistance of asphalt mixtures. It also increases the strength of asphalt mixtures, increases service life. So, it reduces maintenance costs.

Using Gilsonite as a modifier, also to the technical benefits, has many economic benefits.

An important factor in choosing Gilsonite is its solubility in carbon disulfide or gasoline. The lower the solubility of Gilsonite in carbon dioxide or gasoline, the better the mixing of Gilsonite with bitumen.



Reduce the cost of asphalt repair and replacement by up to 60%

Compensation for designing poor mixes

Improves resistance to deformation

Increases road life

Increases its resistance to water

Reduce the risk of breakage at low and cold temperatures

Insulation of fittings and sidewalks

Advantages of using Gilsonite in Waterproofing membrane

  • Increased shear strength
  • Increased resistance to layer movement
  • Flexibility is maintained at low temperatures
  • Reduce the tendency of Waterproofing membrane to move
  • suitable for sloping surfaces
  • Reduce lubrication at high temperatures
  • Cost-effectiveness and cost reduction
  • It is very impenetrable
  • It is light and has high insulation
  • Excellent adhesion properties
  • Odorless
  • Eco-friendly

Preparation of bitumen mixing with Gilsonite:

According to the proposal of the World Road Assembly (PIARC), Gilsonite powder used to modified bitumen must completely pass the sieve No. 50. To do this, the temperature of the mixture should be 140. C and mix for 150 minutes at a speed of 150 rpm.

Then the temperature of the mixture rises to 180 degrees Celsius. Then continue this process for 30 minutes at 4500 rpm. As a result, a homogeneous mixture of Gilsonite and bitumen is prepared.

Table 1 . Physical characteristics of Gilsonite

Experiment Volatiles (%) Solubility in Toluene Solubility in H2S (%) Specific gravity Softening point Powder color Moisture (%) Ash Mesh
Results 1 92 96 1.05 200 black 1 5-10 200

Table 2. Components of Gilsonite

Component SO3 MgO P2O5 Na2O K2O FeO3 SiO2 Al2O3 MnO T1O2 CaO N S H C
Percentage 9.467 0.029 0.008 0.035 0.067 0.502 0.774 0.174 0.001 0.024 1.23 2.63 10.31 79.08

Table 3. Physical characteristics of pure bitumen

Test type Test method (ASTM)  results
Specific gravity at 25. C D70 1/011
The degree of penetration is 25 degrees Celsius D5 69
Softness point in degrees Celsius D36 49/7
Kinematic viscosity in 135 (Santi Stoke) D2170 280
Flammable degree in degrees Celsius D92 311
Bitumen thermal sensitivity PI (in terms of penetration at 25 ċ and soft spot) -0/5
Bitumen thermal sensitivity PVN(Depending on the degree of penetration in 25 ċ and the concentration in Santi Stoke

135 ċ)


Table 4. Gilsonite modified bitumen test results

The amount of Gilsonite (g) Percentage of Gilsonite Net bitumen weight (g) viscosity Soft spot Degree of influence Degree of ignition
Sample 0 56/5 280 49/7 69 311
1.7 grams 3 54/8 280 49/8 68 310
3.4 grams 6 53/1 287 50/7 66 310
5 grams 9 51/5 430 52/6 61 310
6.8 grams 12 49/7 482 53/3 58 311
8.5 grams 15 48 651/9 55/3 54 310

Investigating the properties of modified and unmodified bitumen:

Researchers have studied viscosity, softening point, degree of penetration and degree of flammability.

They also calculated the thermal sensitivity of the modified and unmodified bitumen. You can see this comparison in Table 4 and Figures 1 to 4.

As you can see in Figure 1:

As the percentage of Gilsonite increases, the degree of penetration decreases. By adding Gilsonite at 15% by weight of bitumen, the degree of penetration has decreased by 25% compared to the unmodified sample.

You can also see in Figure 2 that the soft spot has also increased as the percentage of Gilsonite increases. With the addition of Gilsonite at 15% by weight of bitumen, the softening point has increased by 12% compared to the unmodified sample.

Figure 3 also shows the improvement of bitumen thermal sensitivity:

With the addition of Gilsonite at 15%, the thermal sensitivity of bitumen has increased by 24% compared to the unmodified sample.

You can also see in Figure 4:

Bitumen viscosity has also increased with increasing Gilsonite.

But as you can see in Figure 5:

Gilsonite has no effect on the degree of bitumen ignition.

Other results

Figure 2 shows the soft point changes of the modified bitumens The percentage increase is Gilsonite. In this chart you can see that sensitivity The heat of the modified bitumen has improved. That’s why sensitivity Heated and unmodified bitumen heat based on the index . The degree of penetration (PI) was calculated. Heat sensitivity with index PI is displayed and calculated from the following equation :

PI=[1952−500log(pen25)−20SP]/[50log (pen25)−SP−120]


where in:

Pen25: The degree of penetration of bitumen at 25. C

SP: The softening point is in degrees Celsius.

The amount of PI for bitumen used in road construction is usually in the range of 2 and +2. Figure 3 shows how PI changes with increasing Gilsonite percentage. We conclude that natural bitumen (Gilsonite) improves the thermal sensitivity of pure bitumen. Figure 4 shows how the viscosity changes with increasing Gilsonite percentage.

Table 5. PI values for quality determination

Bitumen type PI
Bitumen blown >2
Ordinary bitumen -2 to +2
Temperature sensitive bitumen <-2



According to experiments on pure bitumen 60/70 and bitumen-modified bitumens (different percentages):


1.Gilsonite Powder reduces the degree of penetration of pure bitumen by 60/70.

2.Gilsonite ( Natural Bitumen) Powder increases the softening point of 60/70 pure bitumen.

3.Gilsonite ( Natural Bitumen )Powder increases the viscosity of pure bitumen by 60/70.

4.Gilsonite powder increases the thermal sensitivity index of pure bitumen 60/70.

5.Natural bitumen powder does not affect the degree of ignition of pure bitumen 70/60.

Arya Gilsonite

Arya Gilsonite Co is ready to cooperate with you dear ones . So by giving Gilsonite a base price, it will make your job as easy as you need it to be. As a result, both you and your customer will be  satisfied. We offer customers high quality Gilsonite with 0 to 25% ash percentage.

Arya Co as one of the reputable Gilsonite suppliers in the Middle East

offers Gilsonite as follows:


  • in lump form like rock packed in the 500~1000 kg jumbo bag
  • 200 mesh packed in the 500~1000 kg jumbo bag
  • 300 mesh packed in the 500~1000 kg jumbo bag
  • 30-40 mesh packed in the 500~1000 kg jumbo bag
  • 100 mesh packed in the 500~1000 kg jumbo bag
  • 300 mesh packed in 25 kg pp bag
  • 200 mesh packed the 25 kg multi-paper bag
  • 200 mesh packed the 50 lbs multi-paper bag
  • 30-40 mesh packed pp bag on the pallet

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