What is Natural Asphalt?
The first thing that involves mind once you hear asphalt is roads. However, the versatility of asphalt makes it the ideal material for different applications and locations: from driveways to runways, from the barn floor to the ocean floor.
HMA is additionally used worldwide as a practical solution to water storage, flood control, erosion, and conservation issues. Asphalt has been approved by the Environmental Protection Agency and used with success as a primary liner for each sanitary and hazardous waste landfill.
You'll find asphalt all around you in a very sort of uses, including:
• Transportation - highways, railbeds for transit systems, airport runways
• Recreational - running tracks, greenway trails, playgrounds, bicycle, golf cart paths, racetracks, basketball & tennis court
• Aquatic - fish hatcheries, reservoir liners, industrial retention ponds, sea walls, dikes & groins to manage beach erosion
• Residential - driveways, subdivision roads
• Agricultural - cattle feed lots, poultry house floors, barn floors, greenhouse floors
• Industrial - work sites, log yards, ports, freight yards, landfill caps
Gilsonite sale to asphalt mixer to make modified asphalt. Gilsonite and other asphaltites are used as performance-enhancing agents for asphalt mixes. Gilsonite-modified paving mixes achieve higher performance grades (PG) and incorporate into an asphalt mix with no need for high shear milling as in the case with some other modifiers. the use of SBS (styrene-butadiene-styrene) polymers may be partially or totally replaced by or complemented by, the presence of gilsonite. Gilsonite-modified asphalts will have higher stability, reduced deformation, reduced temperature susceptibility and increased resistance to water stripping as compared to non-modified asphalts.
On the other hand, a wide sort of polymers is used as additives in bitumen compositions. for example, copolymers derived from styrene and conjugated dienes, like butadiene or isoprene, are particularly useful, since these copolymers have good solubility in bitumen compositions and the resulting modified bitumen compositions have smart rheological properties.
Gilsonite, Glance Pitch and Graliamite are natural occurring hydrocarbon substances characterized by a high softening point (above 110Â° C) in the class known as asphaltite. They are mined much like other minerals and sold essentially in their native state.
They are fully compatible with asphalt and have long been known as asphalt hardeners and reinforcing agents. Gilsonite is currently sold all over the world as an asphalt modifier in the form of a dry bulk solid granular powder.
Gilsonite benefits to asphalt pavements include increased stability, resistance to deformations problems such as rutting and shoving, resistance to water striping and increased load bearing ability. Gilsonite functions by making the pavements harder, stronger and increases asphalt’s adhesion to aggregates.
It is generally regarded that Gilsonite reduces pavements’ low-temperature properties making them susceptible to thermal cracking. Gilsonite melted into hot asphalt will reduce penetration and increase the viscosity of the asphalt binder. Gilsonite may also be mixed with aggregate prior to combining with the asphalt binder.
Gilsonite modified asphalt pavements have been particularly successfully in highly stressed traffic areas. Gilsonite, as the majority constituent, has been combined with virgin polymers such as styrene – butadiene – styrene (SBS) and Ethyl Vinyl Acetate (EVA). Gilsonite modified asphalt binders generally do not increase asphalt binder content requirement in pavement mixtures.
Performance grading of asphalt binders and pavement mixtures became a reality with the conclusion of the “FHWA” 50 million $, Strategic Highway Research Program, “SHRP”, in March of 1993. “SHRP” developed new asphalt binder specifications and test criteria based on the engineering properties related to pavement performance. The new emphasis is on the low-temperature performance of aged binder materials.
The low-temperature flexibility of aged asphalt binders became significant. Performance Grade “PG,” asphalt is based on the predicted temperature performance both high and low of asphalt binders. Neither Gilsonite nor post vulcanized crumb rubber have performed well under “SHRP” evaluations. “SHRP” specifications will cause increased demand for modified asphalt as state departments of transportation adopt the “PG” specifications
Asphalt has been the subject of exhaustive study to improve characteristics for use in paving. Various properties of asphalt are manipulated to produce a product that has the appropriate wear properties, resistance, fatigue and low temperature cracking resistance, adhesion strength, viscosity and pour point. Rut resistance is resistance to longitudinal surface depressions in the wheel paths.
Adhesion strength is the maximum adhesion strength of the joint sealant and the joint reservoir, including but not limited to, between the aggregate and the binder.
Shove resistance is resistance to permanent, longitudinal displacement of a localized area of the pavement surface caused by traffic pushing against the pavement. Heavy hydrocarbon that can be derived from, without limitation, natural asphalt (Gilsonite), shale asphalt, bottoms from a solvent deasphalting process, hard asphalt, blown asphalt, stiff refined asphalt, a flux. Asphalt is usually the base ingredient for the primer and the binder.
A primer can be asphalt, fibers (including but not limited to, mineral or cellulose), processing agent (including but not limited to, oligomeric wax, carboxilated, derivative of oligomeric wax, or low molecular weight polyolefin), polymeric or elastomeric additive, or asphalt derived.
A primer melts to the aggregate. Asphalt binders without polymers are referred to as “neat”.
Mixing Gilsonite into Bitumen
This is a simple procedure. A bitumen tank with a propeller stirrer with enough agitation action to create a vortex is recommended. The best choice is a “lightning” mixer or some other type of electrically powered mixer. An explosion proof motor is preferred if large dust concentrations are likely to occur.
Gilsonite should be added slowly at the vortex. Provisions should be made to recirculate the hot bitumen through recirculation piping. The most important item is that the minimum temperature should be about 170 to 175Â° C. Anything significantly less than this will extend mixing time. For typical (5-10%) substitution concentrations, 2-4 hours of mixing after the addition is completed should be sufficient. For master batch concentrations (over 10% Gilsonite) recirculation overnight is preferred.
If the bitumen cannot be heated higher than 170Â°C then you may consider using Selects other Grade (60/70 mesh) or Selects Grade (200mesh) rather than HMA Modifier Grade (175Â°C softening point) for modification. However, each one of these Selects grades will require slightly more Gilsonite to be added, relative to HMA Modifier grade, to achieve the same level of bitumen modification. The dry Gilsonite should be poured into the hot bitumen slowly. If it is added too fast then it may agglomerate, or “ball up” on the surface. If this happens then some manual stirring to disperse the agglomerations may be required.
If a horizontal, cylindrical tank is used, then Gilsonite should be added at an opening at the top (about 0.5-1.0 meters in diameter). Again, it should be poured in slowly and stirred with a propeller mixer or a manual paddle so it does not “ball up” or agglomerate. Recirculation piping will be necessary to insure some agitation effect and proper dissolving.
Recirculation is very important to achieve proper dissolution. If mixing is done in a horizontal tank then it is essential that the Gilsonite-modified bitumen be recirculate from the front of the tank to the back or vice versa. This should be accomplished, even if some re-plumbing of the tank is necessary. Gilsonite does not dissolve instantly. Mixing a tank containing 10-15 MT bitumen and 5% Gilsonite addition will take about 2-4 hours to add in, and additional 2-4 hours mixing time afterward. Naturally, higher Gilsonite dosage levels will require longer mixing times.
Unfortunately, during mixing, there is no test or checklist to determine whether the Gilsonite is blending well in the bitumen. However, if it is not, then large balls or chunks will be visible in the bitumen if it is in an open tank.
Afterward, the best method to check whether Gilsonite was fully mixed into the bitumen is by comparing the original and final penetrations of the bitumen.
Batch Plant (Pug Mill) Mixing
First, Gilsonite should be added during the dry cycle of the mixing procedure, onto the hot aggregate rocks, before the bitumen is added. We recommend extending the total cycle time by about 15 seconds to insure proper dissolution.
Eagle petrochem Company has found that 5 additional seconds of dry mixing and 10 additional seconds of wet mixing maximized the Marshall Stability of the paving mix.
The Gilsonite can be stored in an additional silo at the pug mill and sprayed into the mixer. In Iran, there is frequently a dry mineral (ground limestone) silo and this material is sprayed onto the mix. Gilsonite would be handled in this same manner. A screw feeder or vane feeder that measures the amount of Gilsonite per batch can be calibrated to measure the dosage level of Gilsonite per batch. Afterward, the only residue left behind in the silo will be Gilsonite powder that can be easily cleaned out.
It may be much easier to pre-package Gilsonite into small, polyethylene bags with a measured amount of Gilsonite and toss them onto the hot aggregate in a batch plant. The sidewall thickness of the bag should be about 2 mils (0.005 cm). The aggregate temperature should be around 180Â°C. It is the aggregate temperature that is melting the bags and the Gilsonite, not the heat from the bitumen. Therefore, a temperature of 150-165Â°C entering the pug mill is acceptable, as long as the aggregate is sufficiently heated.
In either case, spraying Gilsonite onto aggregate or tossing bags into the pug mill, we conservatively recommend increasing the mixing time an extra 15 seconds. This will insure the Gilsonite is melted properly and dissolving into the bitumen. Finally, it is possible to just scoop or shovel a precise number of kilos of Gilsonite per batch onto the hot aggregate, no re-packaging — just hand labour.
Continuous Plant (Drum) Mixing
Gilsonite may be introduced into a via a screw auger. It should be added at a point inside the drum where the bitumen is added. The screw auger should be controlled by a drive motor that is calibrated to the plant’s production rate. The auger should enter the drum at the opposite end from the flame. Care should be taken to ensure that Gilsonite is not caught up in the air stream and delivered to the bag house. It should be added right under the bitumen output so that a part of the Gilsonite is taken down by the bitumen to mix with the aggregate.
Eagle petrochem Gilsonite does not recommend any special paving procedures just because Gilsonite resin has been added to the paving mix. After modification with Gilsonite, the final bitumen will have a significantly lowered penetration, a significantly increased viscosity and a moderately increased softening point. Gilsonite modification creates a highly stable, easily workable paving mix.
We recommend normal paving procedures and normal lay-down temperatures. If the increase in viscosity resulting from Gilsonite modification presents any flow ability problems, we recommend the contractor operates at the higher end of his normal operating lay-down temperature range. During cold weather, 5 to 10Â°C, Gilsonite-modified mixes may tend to set-up slightly faster than standard mixes. In this case, the initial roller may follow the paver a little close and the finish roller may not have to stay back as far.