GILSONITE
1.
What is
Gilsonite
GILSONITE is a pure
hydrocarbon, with a melting point between 160°C and 220°C. The mineral is natural
bitumen and geologically petroleum based solid and therefore extremely
compatible with petroleum bitumen.
When blended, a very
intimate molecule of GILSONITE and bitumen is formed, one that takes on some
hardness and durability of GILSONITE while still retaining the flexibility of
the bitumen.
Gilsonite is mined in
underground shafts and resembles shiny, black substance similar in appearance
as the mineral Obsidian It is brittle and usually micronized into dark brown
powder. It is mainly composed of asphaltenes; thus, Gilsonite Is classified as a Natural Asphalt and also known as Gilsonite or Uintaite. Discovered in the 1860s, it was first marketed as a
lacquer, electrical insulator, and waterproofing compound. This unique mineral
is used in more than 160 products, primarily in dark-colored printing inks and
paints, oil well drilling muds and cements, asphalt modifiers, foundry sand
additives, and a wide variety of chemical products.
2. What
makes GiLSONITE different from other natural Asphalts
1
|
high purity and consistent properties
|
2
|
high nitrogen content
|
3
|
high molecular weight
|
4
|
high asphaltene content
|
5
|
high solubility in organic solvents
|
GILSONITE doesn’t contribute
to low temperature cracking. This is contrary to logic and experience with
other bitumen modifiers that also impart hardness, The semi-polymeric nature of
GILSONITE and its unique chemical composition are responsible for this unusual
behavior.
The high asphaltene
content and high molecular weight function mainly as a solution thickener or
flow controller, These two factors are the main reason for the improvement in
the pavement stability characteristics.
The high nitrogen
content of GILSONITE gives the modified bitumen better adhesion to aggregate
which improves stripping characteristics, as well as oxidation resistance.
The minimal sulphur
content also means that GILSONITE is a low odor product
GILSONITE only needs
1/3 of other natural asphalts to give even better performance. Due to its
pureness, only a replacement of 5 — 15 % of the actual bitumen content shows
significant improvement in stiffness and resistance to deformation as well as
ductility and viscosity.
3. Where
to use GILSONITE
GILSONITE is a very
economic and cost effective way to modify road construction bitumen for high
performance roads.
Sophisticated test
methods such as Indirect Tension Stress Test, Cryonic Tensile Stress Test and
the Splitting and Erectile Tension Test have proved that GILSONITE modified
bitumen offers superior properties in:
- ·
fatigue behavior
- ·
stiffness modulus
- ·
cold temperature
performance
Special computer
software for the dimensioning of traffic surfaces of asphalt was used to
calculate and compare the utilization period of Gilsonite and Polymer modified
binder courses; result was that the calculated
life time of binder courses on US federal motorways increased from 18 to 29
years.
GILSONITE modified
bitumen will increase the susceptibility to deformation from static or slow
moving loads at
Toll Plazas, Airport
Taxiways, Exit Ramps, Container Terminals, Sharp Curves, Port Facilities,
Intersections, Truck Terminals, Bus Stops and Lanes, Bridge Decks, Roundabouts,
Park Decks.
GILSONITE modified
bitumen will help against moderate rutting caused by high speed, heavy volume
traffic at Truck Lanes, Racing Circuits, Highways, Airport Runways
A GILSONITE
modification makes the most sense when used in high performance binder courses,
but can also be used in a wide variety of asphalt surface courses such as Stone
Mastic Asphalt, Asphalt Concrete, Gussasphalt, Hot Rolled Asphalt.
Gilsonite can significantly improve the high
temperature properties of asphalt binders.
Gilsonite increases the Ring & Ball Softening
Point, the Absolute Viscosity and reduces the Penetration values of both neat
and modified asphalt binders.
Consequently, it also increases the high temperature
stiffness and reduces the phase angle of the base asphalt
GILSONITE has been
used widely in addition to up to 50 % with recycled asphalt.
4. How
to use GILSONITE
GILSONITE is a free
flowing granular material which will not cake or block during storage.
Because of the
nature of this hydrocarbon, GILSONITE is completely soluble in bitumen, forming
a very intimate molecule that will NOT separate. It can be used:
·
in bitumen
pre-blend: a pre-blend of GILSONITE and bitumen in the proper percentage (5-15
%) can be produced in the bitumen tank with temperatures maintained around
170°C. During the GILSONITE solution, agitation and recirculation under heat
should be maintained for 12 — 24 hours.
·
in pug mill:
addition of GILSONITE to a pug mill can be accomplished by the introduction of
pre-weighted plastic bags, or in bulk by using an automatic dosage system. The
GILSONITE should be added onto the hot aggregate before the bitumen is added.
The wet mix circle must be extended by 15 sec. to ensure proper blending.
·
in drum plants:
GILSONITE may be added to a drum plant, either by the master batch method or
with a dry mineral feeder at the correct rate of flow along with the bitumen.
Paving conditions
should remain identical to non-modified bitumen, except that mix temperatures
should be maintained at a minimum of 160°C to compensate for the addition of
the GILSONITE. Lay down and compaction should be normal providing this slightly
higher temperature is maintained.
GILSONITE is
available in 25 kg meltable plastic bags, 30 kg craft paper bags and 1,000 kg
big bags.
5. Purpose
of GILSONITE modification of Asphalt Pavement Mixtures
1
|
Improved
resistance to deformation
|
2
|
Improved the
economic performance of the road
|
3
|
Improved
resistance to stripping
|
4
|
Improved resistance
to fatigue
|
5
|
Improved
durability
|
6
|
Compensation for
poor mix design
|
7
|
Compensation for
poor aggregates
|
6. Gilsonite
in Hot Mix Asphalt
According
to FHWA (U.S. Federal Highway Administration) research data, up to 80% of
pavement flexibility is lost during the first 5 years. When the aging process
is halted and the pavement is preserved early on, maintenance is less invasive
and much less expensive.
Furthermore,
FHWA, FAA (Federal Aviation Administration), NAVFAC (Naval Facilities
Engineering Command), MDOT (Michigan Department of Transportation), and AzDOT
(Arizona Department Transportation), research shows agencies that used
Gilsonite-based treatments reduced pavement replacement costs by up to 60%
compared to using the worst first-practices.
While
HMA (Hot Mix Asphalt) pavements perform poorly when they become hard (like
cement), when Gilsonite is applied to the surface of asphalt pavement it
maintains oils, resiliency, and flexibility by filling micro-voids and keeping
asphalt binders soft and pliable. The use of Gilsonite lowers viscosity by over
30%, increases ductility by 30%, and increases Marshall Stability by almost 40%
(strength of binder) after just 5 years. Contrary to many engineers’ belief,
Gilsonite does NOT harden pavement. However, it DOES toughen the surface to
better withstand traffic and the aging process. The stability of
Gilsonite-fortified pavements makes them more resistant to problems, such as
rutting and shoving, and increases the pavement’s load carrying ability. In some
cases these high-performance mixes will halt, and reverse the effects of aging
and degradation from water penetration, oxidation, and UV radiation. In
addition, other benefits include increased resistance to water stripping,
oxidation and the aging process.
7. Notes
on Ashes and Volatiles
GILSONITE is an
Organic matter; a hydrocarbon consisting of Carbon and volatile gases like
Methane. With very special characteristics defining it as Bituminous matter.
These characteristics are very similar to those, which are synthetically
produced in the refineries.
This chemistry,
which defines this bitumen without its volatile gases, is nothing but something
similar to a Coal. Then “the higher the volatile matter Ratio to Carbone the
closer it is to synthetic Bitumen”.
In the laboratory
the test procedure is defined to quantify these matters. We slowly apply heat
to GILSONITE to initially reach to its softening points 170-220 degrees C . The
heat is applied further at a constant rate in order to reach the temperature of
350 degrees C at which the volatile gases are fully evaporated. At this stage
we reach a point referred to as FIXED CARBON.
The Temperature is
still increased beyond 350 degrees C at a constant rate until all Fixed Carbone
is disintegrated fully at temperatures above 800 degrees C. The specimen is
kept at this temperature for a while and then cooled off. The remaining balance
is then analyzed and measured.
The balance is
collectively referred to “ASH” which, are basically Ferrous Silicate: FeSi2,
Calcium Carbonate: CaCo3 , SO2, MgO, Al2O3 and SIO2
8. Notes
on Asphaltene content
Asphaltenes are molecular substances that are found
in crude oil, along with resins, aromatic hydrocarbons, and alkanes (i.e.,
saturated hydrocarbons). The word "asphaltene" was coined by
Boussingault in 1837 when he noticed that the distillation residue of some bitumen
had asphalt-like properties. Asphaltenes in the form of distillation products
from oil refineries are used as "tar-mats" on roads.
Asphaltenes consist primarily of carbon, hydrogen,
nitrogen, oxygen, and sulfur, as well as trace amounts of vanadium and nickel.
The C:H ratio is approximately 1:1.2, depending on the asphaltene source.
Asphaltenes are defined operationally as the n-heptanes (C7H16)-insoluble,
toluene (C6H5CH3)-soluble component of a
carbonaceous material such as crude oil, bitumen or coal. Asphaltenes have been
shown to have a distribution of molecular masses in the range of 400 u to 1500
u with a maximum around 750 u.
Unique natural hydrocarbon is high in asphaltenes and
nitrogen. It makes it fully compatible with bitumen. It be melted into hot
bitumen, added during the hot-mix manufacturing process, or blended into a
preservation treatment. In either case, GILSONITE dissolves easily in bitumen
and achieves a uniform, easily workable product.
Gilsonite
resin is often used by asphalt producers, road paving engineers and paving
contractors who are concerned with PG specifications, high-performance and
cost-effectiveness. Gilsonite, long known as a bitumen re-enforcer and
strengthening agent, also offers a unique combination of high-performance and
economy for high-stress paving, and preservation applications. Gilsonite is an
approved mineral by the U.S. Food & Drug Administration for use in resinous
and polymeric coatings that come into direct contact with food. Gilsonite falls
under Section 175.300 (formerly Section 121.2514) of the FDA regulations, Part
3, subpart (iv), which lists Gilsonite as one of several approved natural
resins. Besides being non-toxic, Gilsonite products are non-carcinogenic and
non-mutagenic.
9. Gilsonite
Solubility
A variety of sophisticated analytical tests have been
run on Gilsonite to characterize its unique properties. For reference, the test
methods include vacuum thermal gravimetric analysis (TGA), nuclear magnetic
resonance (NMR), Fourier transform infrared spectrometry (FTIR), vapor pressure
osometry (VPO), high performance liquid chromatography (HPLC), rapid capillary
gas chromatography (RCAP), and several fractionation techniques. H/C ratios and
NMR analysis indicate the presence of a significant aromatic fraction. Most of
the aromatics exist in stable, conjugated systems, probably porphyrin-like
structures that relate to the geologic source of the product. The remainder of
the product consists of long, paraffinic chains. A very unique feature of
Gilsonite is its high nitrogen content, which is present mainly as pyrrole,
pyridine, and amide functional groups. Phenolic and carbonyl groups are also
present. The law oxygen content relative to nitrogen suggests that much of the
nitrogen has basic functionality. This probably accounts for Gilsonite special
surface wetting properties and resistance to free radical oxidation. The
average molecular weight of Gilsonite is about 3000. This is very high relative
to other asphalt products and to most synthetic resins. This may relate to
Gilsonite "semi-polymeric" behavior when used as a modifying resin in
polymeric and elastomeric systems. There is some reactive potential in
Gilsonite. Crosslinking and addition type reactions have been observed.
Gilsonite is known to react with formaldehyde compounds under certain
conditions
Gilsonite is an
important component of today's printing inks, paints & industrial coatings.
Gilsonite is used as a hard resin and carbon black dispersant in a variety of
coatings. Solutions of Gilsonite (sometimes called cutbacks or varnishes) are
an excellent starting point for blending Gilsonite with other components of a
final product formulation. Some formulators convert dry Gilsonite into liquid
solution in their own facilities. Others will request a pre-made solution.
Converting dry, granular Gilsonite to a liquid solution also provides the
opportunity to remove the small amount of abrasive grit that occurs in natural
asphalt. Stabilizing additives can also be added if a poor solvent is used or
if high concentrations of Gilsonite are desired.
Solubility:
Gilsonite is soluble in aliphatic, aromatic and chlorinated hydrocarbon
solvents. It has limited solubility in most ketones, but is soluble in mixed
aromatic solvents that contain a ketone component. Gilsonite is not soluble in
water, alcohols, or acetone.
Solution
Preparation: Three basic procedures are used to dissolve Gilsonite. In each
case, precautions for flammable materials should be used. Cold-cutting:
Gilsonite is generally soluble in aliphatic and aromatic solvents at ambient
temperatures. Some agitation should be used. The rate of solution will depend
on the type of solvent, the type and severity of mixing, and the grade of
Gilsonite. The solution rate can be increased by using a high shear mixer, such
as a Cowles disperser. When a ball mill or a paddle mixer is used, lump grade
Gilsonite is recommended. When high energy mixing is available, either lump or
pulverized grades may be used. Care must be taken to avoid "dry
balls" of undissolved solid when using pulverized grades. Hot-cutting: The
rate of solution can be increased by heating. Steam coils or hot oil is
preferred. Direct-fired heating can be hazardous. Care must be taken to avoid
or make up for vaporized solvent.
Facilities for
solvent containment are often necessary. The maximum processing temperature
will depend on the boiling range of the solvent. Hot fluxing: Gilsonite can be
hot fluxed into asphalts and high boiling oils. Once blended, the combination
can then be let down with a solvent to reach the desired viscosity. This hot
fluxing with another product can help overcome limitations of solubility.
Selecting the correct blend or co-solvent can yield compatibility with a
solvent that is normally of limited solubility. Hot Fluxing Procedure: Heat the
oil to 200 °F or more. Most of the high boiling, law aromatic ink oils in use
today will require a temperature of at least 300-330 °F. With good agitation,
add dry Gilsonite at a rate that maintains constant dispersion of the particles
until they dissolve. Be alert for foaming that can be caused by traces of
moisture in the Gilsonite. Continue to agitate for 15 to 30 minutes beyond the
point when the last of the Gilsonite particles is detected. The Gilsonite
should now be completely dissolved and the solution ready for discharge.
Filtration: The varnish must be filtered to remove the grit that is a natural
component of Gilsonite. There are two common filtration methods. Each provides
a different degree of cleanliness. Both methods are normally preceded by
passing the hot varnish through a course wire screen (approx. 1/4") to
remove any large stones. For a normal degree of cleanliness, the prescreened,
hot varnish is passed through wire screen baskets of about 200 mesh (74
microns). Cloth bag filters can also be used, at a higher cost, when the
company doesn’t have the personnel to clean the wire baskets. Disposal of the
bags is also a consideration. Be careful to use bags that can tolerate elevated
temperatures if hot cutting is performed.
For extra
cleanliness, the prescreened, hot varnish is passed through cartridge filters
of about 5 to 25 microns. These filters are also disposable. Viscosity
Modification: Some Gilsonite solutions can be quite viscous at ambient
temperature. Also, some solutions can steadily increase in viscosity over time.
These characteristics are usually observed when using law aromatic oils with
poor solvent power or when high percentages of Gilsonite are used. In these
cases, small amounts of viscosity modifiers are often added to (1) keep the hot
varnish sufficiently fluid for easy filtration and (2) to reduce and stabilize
the ambient viscosity so the solution remains fluid until it is used. The
following is a partial list of modifiers that are effective at stabilizing the
viscosity of Gilsonite solutions.
Soft asphalt flux.
This is often substituted for 15 to 20 % of the Gilsonite in the varnish. At
this level, it reduces the softening point of the Gilsonite by about 30 °F. It
should not be used when maximum hardness and rub resistance is desired, or when
fast solvent release is required, or when restrictive health safety regulations
are in effect.
Tridecyl alcohol
(TDA). More volatile than some modifiers (a flash point of 180°F), but
effective. Generally used at 3-10%, based on the Gilsonite content.
Low molecular weight
alcohols. Examples are n-propanol and n-butanol. These are effective, but their
high volatility usually restricts their use to fast drying systems or products
that are stored and used at ambient temperature.
Tall oil fatty acids. These are mainly oleic and
linoleic acids with small amounts of rosin acids present. They are used for
their high flash point and law volatility. In some cases, stearic or oleic
acid, or vegetable oils such as linseed or soya bean oil, can be substituted
for tall oil fatty acids with comparable performance.
Surfactants. A wide
variety of commercial surfactants are also effective. Care must be taken to
avoid any undesirable side effects on the performance of the final product.
GILSONITE SOLUBILITY
|
Chemical
Group
|
Item
|
Solubility
|
Aliphatic
Hydrocarbons
|
VM&P Naphtha
|
S
|
----
|
Mineral Spirits
|
S
|
----
|
Solvents with KB
|
S
|
Aromatic
Hydrocarbons
|
All
|
S
|
Alcohols
|
All
|
I
|
Chlorinated
Hydrocarbons
|
All
|
S
|
Esters
|
Methyl Acetate
|
I
|
----
|
Ethyl Acetate
|
Slight
|
----
|
n-Butyl Acetate
|
Slight
|
Glycols
|
All
|
I
|
Glycol
Ethers
|
All
|
I
|
Glycol
Ether Esters
|
All
|
I
|
Ketones
|
Acetone
|
I
|
----
|
MEK
|
I
|
----
|
MIBK
|
I
|
Other
Solvents
|
Carbon Disulfide
|
S
|
----
|
Carbon
Tetrachloride
|
S
|
10. Gilsonite
Compatibility
Adhesive/
coating system
|
Compatibility
|
Adhesive/
coating system
|
Compatibility
|
Natural rubber
|
FAIR
|
Ethylene/vinyl acetate
|
GOOD
|
Cellulose esters
|
POOR
|
SBS rubber
|
EXCELLENT
|
Phenolic
|
GOOD
|
Polychloroprene rubber
|
EXCELLENT
|
Resorcinol formaldehyde
|
FAIR
|
Nitrile rubber
|
FAIR
|
Urea formaldehyde
|
GOOD
|
Butyl rubber/polyisobutylene
|
GOOD
|
Melamine formaldehyde
|
GOOD
|
Silicone
|
GOOD
|
Alkyd
|
GOOD
|
Polyurethane
|
FAIR
|
Epoxy
|
FAIR
|
Vinyl ethers
|
GOOD
|
Polyurethane
|
FAIR
|
Resinates
|
GOOD
|
Acrylic
|
FAIR
|
Resin modified
|
EXCELLENT
|
Unsaturated polyester
|
FAIR
|
C9 aromatic
|
GOOD
|
Polyaromatic
|
GOOD
|
DCPD
|
EXCELLENT
|
Acrylic acid diester
|
POOR
|
Terpene
|
EXCELLENT
|
Polyvinyl acetate
|
FAIR
|
Terpene phenolic
|
GOOD
|
Polyvinyl alcohol
|
FAIR
|
Phenolic modified
|
GOOD
|
Polyvinyl chloride
|
GOOD
|
maleic-fumaric modified
|
EXCELLENT
|
Acrylic
|
FAIR
|
Alkyd
|
GOOD
|
Polyamide
|
POOR
|
Shellac
|
POOR
|
Phenoxy
|
POOR
|
|
|
11. Typical
Gilsonite Laboratory Test
TEST
|
UNIT
|
SAM-1
|
SAM-2
|
SAM-3
|
SAM-4
|
ENRICHED
|
Ash
|
wt%
|
12.4
|
14.88
|
4.71
|
1.87
|
0
|
Moisture
|
wt%
|
0.12
|
0.14
|
0.15
|
0.18
|
0.10
|
Volatile
|
wt%
|
68.9
|
71.6
|
68.45
|
72.6
|
75.0
|
Fixed
Carbon
|
wt%
|
18.7
|
13.52
|
26.51
|
25.25
|
30
|
Density
|
g/qcm
|
1.18
|
1.21
|
1.12
|
1.08
|
1.10
|
Softening
point
|
c
|
190-200
|
230-245
|
180-195
|
200-210
|
160
|
Flash
point
|
c
|
430
|
440
|
410
|
430
|
430
|
Sulphur
|
wt%
|
1.77
|
3.74
|
0.74
|
0.67
|
1
|