asphalt with and without asphaltite
How to use Asphaltite in asphalt
Asphaltite use in road asphalt , is performance-enhancing agents for asphalt mixes. asphaltites modified paving mixes achieve higher performance grades (PG) and incorporate into an asphalt blend 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 asphaltites. asphaltites-modified asphalts can have higher stability, reduced deformation, reduced temperature susceptibility and increased resistance to water stripping as compared to non-modified asphalts. A difficulty in using asphaltites as an asphalt modifier is that it is a solid, which is more difficultly handled and incorporated into a viscous bitumen.
The present invention is related to hydrocarbon-based binders, such as bitumens, asphalts and tars, modified with asphaltites such as asphaltites, and is more particularly related to processes and compositions for incorporating asphaltites into asphalt binders.
aggregate compositions
The use of bitumen (asphalt) compositions in preparing aggregate compositions (including, but not just limited to, bitumen and rock) useful as road paving material is complicated by at least three factors, each of which imposes a serious challenge to providing an acceptable product. First, the bitumen compositions must meet certain performance criteria or specifications in order to be considered useful for road paving. For example, to ensure acceptable performance, state and federal agencies issue specifications for various bitumen applications including specifications for use as road pavement. Current Federal Highway Administration specifications require a bitumen (asphalt) product to meet defined parameters relating to properties such as viscosity, toughness, tenacity and ductility. Each of these parameters defines a critical feature of the bitumen composition, and compositions failing to meet one or more of these parameters will render that composition unacceptable for use as road pavement material.
Conventional bitumen compositions frequently cannot meet all of the requirements of a particular specification simultaneously and, if these specifications are not met, damage to the resulting road can occur, including, but not necessarily limited to, permanent deformation, thermally induced cracking and flexural fatigue. This damage greatly reduces the effective life of paved roads.
In this regard, it has long been recognized that the properties of conventional bitumen compositions can be modified by the addition of other substances, such as polymers and asphaltites such as asphaltites.
performance-enhancing agents
Asphaltites and other asphaltites are used as performance-enhancing agents for asphalt mixes. asphaltites-modified paving mixes achieve higher performance grades (PG) and incorporate into an asphalt blend 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 asphaltites. asphaltites-modified asphalts can have higher stability, reduced deformation, reduced temperature susceptibility and increased resistance to water stripping as compared to non-modified asphalts. A difficulty in using asphaltites as an asphalt modifier is that it is a solid, which is more difficultly handled and incorporated into a viscous bitumen.
On the other hand, a wide variety of polymers have been used as additives in bitumen compositions. For example, copolymers derived from styrene and conjugated dienes, such as butadiene or isoprene, are particularly useful, since these copolymers have good solubility in bitumen compositions and the resulting modified-bitumen compositions have good rheological properties.
Asphaltite mixture with road bitumen
It is also known that the stability of polymer-bitumen compositions can be increased by the addition of crosslinking agents such as sulfur, frequently in the form of elemental sulfur. It is believed that the sulfur chemically couples the polymer and the bitumen through sulfide and/or polysulfide bonds. The addition of extraneous sulfur is required to produce the improved stability, even though bitumens naturally contain varying amounts of native sulfur.
A second factor complicating the use of bitumen compositions concerns the viscosity stability of such compositions under storage conditions. In this regard, bitumen compositions are frequently stored for up to 7 days or more before being used and, in some cases, the viscosity of the composition can increase so much that the bitumen composition is unusable for its intended purpose. On the other hand, a storage stable bitumen composition would provide for only minimal viscosity increases and, accordingly, after storage it can still be employed for its intended purpose.
Bitumen composition
A third factor complicating the use of bitumen compositions concerns the use of volatile solvents in such compositions. Specifically, while such solvents have been heretofore proposed as a means to fluidize bitumen-polymer compositions containing relatively small amounts of sulfur which compositions are designed as coatings, environmental concerns restrict the use of volatile solvents in such compositions. Moreover, the use of large amounts of volatile solvents in bitumen compositions may lower the viscosity of the resulting composition so that it no longer meets viscosity specifications designated for road paving applications. In addition to the volatile components, reduction of other emissions during asphalt applications becomes a target. For example, it is desirable to reduce the amount of sulfur compounds that are emitted during asphalt applications.
Asphaltic concrete
Asphaltic concrete, typically including asphalt and aggregate, asphalt compositions for resurfacing asphaltic concrete, and similar asphalt compositions must exhibit a certain number of specific mechanical properties to enable their use in various fields of application, especially when the asphalts are used as binders for superficial coats (road surfacing), as asphalt emulsions, or in industrial applications. (The term “asphalt” is used herein interchangeably with “bitumen.” Asphaltic concrete is asphalt used as a binder with appropriate aggregate added, typically for use in roadways.) The use of asphalt or asphalt emulsion binders either in maintenance facings as a surface coat or as a very thin bituminous mix, or as a thicker structural layer of bituminous mix in asphaltic concrete, is enhanced if these binders possess the requisite properties such as desirable levels of elasticity and plasticity.
mechanical performance
As noted, various polymers have been added to asphalts to improve physical and mechanical performance properties. Polymer-modified asphalts (PMAs) are routinely used in the road construction/maintenance and roofing industries. Conventional asphalts often do not retain sufficient elasticity in use and, also, exhibit a plasticity range that is too narrow for use in many modern applications such as road construction. It is known that the characteristics of road asphalts and the like can be greatly improved by incorporating into them an elastomeric-type polymer which may be one such as butyl, polybutadiene, polyisoprene or polyisobutene rubber, ethylene/vinyl acetate copolymer, polyacrylate, polymethacrylate, polychloroprene, polynorbornene, ethylene/propylene/diene (EPDM) terpolymer and advantageously a random or block copolymer of styrene and a conjugated diene. The modified asphalts thus obtained commonly are referred to variously as bitumen/polymer binders or asphalt/polymer mixes. Modified asphalts and asphalt emulsions often are produced utilizing styrene/butadiene based polymers, and typically have raised softening point, increased viscoelasticity, enhanced force under strain, enhanced strain recovery, and improved low temperature strain characteristics as compared with non-modified asphalts and asphalt emulsions.
bituminous binders
The bituminous binders, even of the bitumen/polymer type, which are presently employed in road applications often do not have the optimum characteristics at low enough polymer concentrations to consistently meet the increasing structural and workability requirements imposed on roadway structures and their construction. In order to achieve a given level of modified asphalt performance, various polymers are added at some prescribed concentration.
More specifically, to be used in road materials, however, asphalt must first meet certain specifications. For example, as a result of the Strategic Highway Research Program (SHRP), the Federal Highway Administration (FHA) has developed a battery of tests and specifications for asphalt, designed to ensure that road materials have a longer lifetime before requiring maintenance or replacement. Such specifications may be categorized as comprising high, intermediate and low temperature Performance Grade (PG) tests, and compatibility tests, when a polymer, such as rubber, is added to the asphalt. Further information about the specifications can be found in the booklet SUPERPAVE Series No. 1 (SP-1), 1997 printing, published by the Asphalt Institute (Research Park Drive, P.O. Box 14052, Lexington, Ky. 40512-4052), which is hereby incorporated by reference in its entirety, and is hereinafter referred to as MP1 (Standard Specification for Performance Graded Asphalt Binder). In addition, some agencies have adopted Compatibility tests to prevent separation of polymer and asphalt.
hot mix plant
If a particular asphalt does not pass the minimum specifications for all of the above-described MP1 tests, then the asphalt will not be shipped from an oil refinery to a hot mix plant for use as road material. Various procedures have therefore been developed to improve the rheological properties of asphalt, so that it will meet the minimum requirements of the MP1 tests. The development of such procedures has a direct impact on the cost effective production of asphalt because it allows for greater amounts of Asphaltens to be included in the asphalt shipped to the hot mix plant.
As noted, one procedure to alter asphalt’s rheological properties, for example, is to add polymers to asphalt to produce PMA. There is a risk, however, of PMAs failing the compatibility test. As noted, this may necessitate further processing steps, such as cross-linking of the polymer to thereby improve the asphalt’s compatibility. Furthermore, because the cost of polymers and cross-linking agents are substantially higher than the cost of asphaltene, and there are costs for the additional processing steps, it may be difficult to produce PMA for profit.
asphaltenes
Another procedure is to add conventional flux oil to soften asphaltenes to a desired consistency and therefore affect the rheological properties of the resulting asphalt. The improvement in performance grade by adding such flux oils is problematic, however. For instance, certain conventional flux oils may decrease both the high intermediate and low temperature PG test values, in proportion to the amount of flux oil present in asphalt. Thus, while an asphalt containing a high amount of flux oil may have an acceptable intermediate or low temperature PG test value, the asphalt may not have an acceptable high PG test value. In addition, because flux oil is substantially more expensive than asphaltenes, an asphalt having a high flux oil content may be difficult to make profitable. Conversely, an asphalt with a low flux oil content, while being less expensive to produce, may not have acceptable PG test values.
asphaltites,asphaltum, uintaites or uintahites
As noted, the addition of solid asphaltites, also known as asphaltum, uintaites or uintahites, such as asphaltites, to asphalt is another procedure known to alter the rheological properties of asphalt. As noted, the use of solid asphaltites, however, is not ideally suited for an oil refinery environment. Rather, in a refinery, it is more desirable to handle and mix fluids. Moreover, the properties of solid asphaltites may vary from sample to the next. Therefore, the conventional addition of solid asphaltites may not provide a predictably uniform change in the rheological properties of asphalt.
As can be seen from the above, the art is replete with methods to improve asphalt compositions. The needed elements for the commercial success of any such process include keeping the process as simple as possible, reducing the cost of the ingredients, and utilizing available asphalt cuts from a refinery without having to blend in more valuable fractions, or at least reduce the amounts of those fractions. In addition, the resulting asphalt composition must meet the above-mentioned governmental physical properties and environmental concerns. Thus, it is a goal of the industry to reduce the cost of adding or the proportion of any modifiers added to the asphalt without sacrificing any of the other elements.
SUMMARY OF THE INVENTION
There is provided, in one form, a method for improving an asphalt composition comprising adding to an asphalt a synthetic flux oil, where the synthetic flux oil comprises at least one asphaltite and a carrier oil comprising either a naphthenic or paraffinic hydrocarbon oil.
In another embodiment of the invention, there are provided asphalt compositions made by the process described above. A further embodiment of the invention includes the effective synthetic flux oils per se.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to a synthetic flux oil that improves the MP1 PG test results of asphalts as compared to asphalts not containing the synthetic flux oil, which in turn contains asphaltites such as asphaltites. In particular, the synthetic flux oil improves the MP1 temperature spread. The term “MP1 spread” as used herein refers to difference between the minimum of the high temperature PG test values and the maximum of the low temperature PG test values. The synthetic flux oil by improving the rheological properties of asphalt allows, for example, larger amounts of asphaltenes to be included in asphalt compositions than previously possible.