Natural Asphalt
Natural asphalt is formed
gradually in the natural condition and open environment resulting from
evaporation and transformation of crude oil in nature with the passage of a
long time (millions of years). This type of bitumen is called natural asphalt
or mineral bitumen, which has a variety of applications.
As already mentioned, evaporation
of crude oils from natural bitumen within a long period of time is one of the
causes of the formation of natural asphalt. Natural asphalt is a natural
resinous hydrocarbon and it is also called uintaite or asphaltum. Its
durability is more than the petroleum asphalts, which is also called lake
asphalt such as asphalt of Behbahan Lake or Lake Asphalt of Trinidad in the US.
Natural asphalt in our country is
usually known as Gilsonite, which actually originates from the solidification
of crude oil under pressure. To determine the characteristics of natural
asphalt, its odor and softening point, moisture, level of ash and carbon, and
solubility are measured.
There are many natural asphalt
mines under exploitation in Iran, especially in the west of the country such as
Kermanshah, Ilam, and Kordestan. The level of ash in the natural asphalt is of
great importance. The lower the level of ash, the higher the quality of bitumen.
The softening point of bitumen is another significant parameter in measuring
the quality of the natural asphalt.
Bitumen’s level of sulfur and natural
asphalt’s oxygen are crucial as well.
In comparison to petroleum
asphalts, the natural asphalts include more sulfur and some level of ash, while
petroleum asphalt contains no ash at all. Natural asphalt is used in the drilling
mud to control well walls and to aggregate in the asphalt and the walls of the casting
molds or printer ink.
Considering that natural asphalt
is hydrophobic and both acid resistance and base resistance, it is used in the production
of rooftop asphalt, bituminous waterproofing, and moisture insulations.
Natural asphalt is in lump form, a
shiny and black substance, and in powder form, it is a dark brown micronized
powder, which can be collected using an excavator and compressor. It is highly
soluble in organic solvents.
Even though coal and natural
asphalt are similar in appearance, coal is formed from the decomposition of
plants and trees through the passage of time and natural asphalt originates
from the evaporation of crude oil, which is produced from the remains of planktons.
Natural asphalt is mostly used in bituminous
waterproofing, in which by adding petroleum asphalt the level of penetration is
decreased, and its viscosity and the softening point are increased, which can
result in reducing bitumen’s thermal sensitivity and enhancing its function in
the higher degrees and reducing the damages caused by the low temperature.
Using natural asphalt in warm mix
asphalt can result in enhancing the strength and resistance of pavements
against traffic load and prevents the asphalt from cracking in the lower
temperature. However, considering that natural asphalt contains ash, it is
recommended to add it to petroleum asphalt for the purposes of asphalt production
and road construction.
The percentage of ash of natural
asphalt is the most important index in its analysis,
which is determined by ASTM 3174
standard.
Read more:
What Is Bitumen?
Introduction of Various Bitumen Tests