Asphalt coating composition and asphalt coating method

Abstract

The present disclosure includes systems and methods for applying a coating system to a surface. An exemplary method includes applying an asphalt emulsion to a surface at a rate of approximately 0.12 to 0.20 gallons per square yard, the asphalt emulsion including Gilsonite, at least a portion of which includes an asphalt blend modified to have a positive charge, one or more polymers, and one or more surfactants. The method may also include applying fine aggregate onto the asphalt emulsion. The fine aggregate may be applied at a rate of approximately 2.5 pounds per square yard. In such an embodiment, the asphalt emulsion may be applied at a rate of approximately 0.18 gallons per square yard, and the asphalt emulsion may include approximately 56% solid asphalt residue by weight. In another embodiment, the fine aggregate may be applied at a rate of about 1.25 pounds per square yard, the asphalt emulsion may be applied to the pavement at a rate of about 0.17 gallons per square yard, and the asphalt emulsion may comprise about 37% solid asphalt residue by weight of the asphalt emulsion.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to U.S. Application No. 17 / 937,213, filed September 30, 2022, the contents of which are incorporated herein by reference in their entirety for all purposes as if fully set forth herein.

[0002] [Technical field] FIELD OF THE DISCLOSURE The present disclosure relates to coating systems and related methods for asphalt pavements. [Background technology]

[0003] Asphalt pavement is a composite material containing mineral aggregate and asphalt binder, which hardens to form a strong surface. Asphalt pavement deteriorates over time due to oxidation of the asphalt binder, heavy loads, and fluctuating climatic conditions. One method for restoring or repairing deteriorated asphalt pavement is to remove the existing pavement and replace it with newly prepared or reused pavement. However, removal and replacement is costly and wasteful. However, asphalt pavement repair products exist that can be used to repair pavement surfaces.

[0004] A typical asphalt repair product includes a coating composition, such as a uintaite-asphalt composition, and aggregate. Generally, the composition can be spread onto the asphalt pavement, and then aggregate is applied over the composition using a spreader or other similar device. However, there is a wide variety in the methods by which the composition and framework can be prepared. The components of the composition, the type of aggregate, and its application rate (gals. / yd) 2 and / or lbs. / yd. 2) can all be modified to achieve specific performance goals. Additionally, in some cases, the coating composition and aggregate can be combined together and then applied to the pavement. However, in many cases, the specific product applied to the pavement and its application rate will depend on the method used to pave.

[0005] The asphalt pavement industry has two somewhat separate segments: aviation and road. Aviation pavements, such as those used in the construction of airport runways, have greater demands compared to road pavements. For aviation pavements, safety is paramount, construction projects and schedules are more difficult to meet, and the challenges are greater and more costly to address. Furthermore, aviation pavements are used to support airplanes, while roads are used for cars and trucks. The two pavement types also age differently. In general, airport pavement requirements (e.g., performance requirements, specifications, quality control systems, etc.) are generally more stringent and extreme than those used for road pavements.

[0006] Conventional road asphalt repair surface treatments are not always suitable for airfield pavements. Conventional road treatments designed for durability beyond 3-5 years typically are not suitable for the demanding aviation pavements. As road treatments increase over time, safety performance issues also arise, such as the generation and increase of foreign object debris (FOD), and favorable friction characteristics decrease. Airfield asphalt pavements, even those previously treated with a conventional uintaite-asphalt coating or other repair coating, begin to deteriorate in terms of their surface condition characteristics and must be retreated to maintain minimum safety requirements. Without further treatment, the pavement would have to undergo much more extensive, costly, and destructive restoration procedures. Conventional road treatments can be modified to improve road conditions and enhance friction characteristics, thereby addressing the safety issues mentioned above. Unfortunately, such treatments (or treatments) have a relatively short lifespan, lasting 2-5 years or less. Other more substantial (heavily applied) asphalt repair treatments can provide service lives longer than 3-5 years. However, these substantial treatments are not well suited to the demands of airfield pavement applications. There is a lack of coating systems with increased useful service life that can be applied at relatively heavy rates and are suitable for both road and aviation pavements. Summary of the Invention

[0007] The present disclosure includes a method for applying a coating system to a surface. In one or more embodiments, the method includes spreading an asphalt emulsion onto the surface at a rate of about 0.12 to 0.20 gallons per square yard. The asphalt emulsion includes an asphalt blend containing Gilsonite, at least a portion of which has been modified to have a positive charge, one or more polymers, and one or more surfactants. The method may include applying fine aggregate to the stable cationic emulsion applied to the surface. In one embodiment, the fine aggregate may be applied at a rate of about 2.5 pounds per square yard. In such an embodiment, the asphalt emulsion may be spread onto the surface at a rate of about 0.18 gallons per square yard, and the asphalt emulsion may contain about 56% by weight of solid asphalt residue. In another embodiment, the fine aggregate may be applied at a rate of about 1.25 pounds per square yard. In another embodiment, the asphalt emulsion may be applied at a rate of about 0.17 gallons per square yard, and the asphalt emulsion may comprise about 37% by weight of solid asphalt residue.

[0008] In one embodiment, an asphalt emulsion containing about 37% solid asphalt residue by weight of the asphalt emulsion may be spread on a surface at a rate of about 0.12 gallons per square yard, and fine aggregate may be applied at a rate of about 0.6 pounds per square yard. In another embodiment, an asphalt emulsion containing about 37% solid asphalt residue by weight of the asphalt emulsion may be spread on a surface at a rate of about 0.20 gallons per square yard, and fine aggregate may be applied at a rate of about 2.0 pounds per square yard.

[0009] The present disclosure also includes a system for treating pavement. In one embodiment, the system can include an asphalt emulsion. The asphalt emulsion can include an asphalt blend including a first asphalt naturally containing a major amount of nitrogen-containing polar resin, the asphalt blend being modified so that at least a portion of the nitrogen-containing polar resin has a positive charge; one or more polymers; and one or more surfactants. The system can include an aggregate material for application to the pavement coated with the asphalt emulsion. The application rate of the asphalt emulsion can be about 0.12 to 0.20 gallons per square yard. At least a portion of the nitrogen-containing polar resin can be pyrrole. An acid modifier can be added in an amount such that the pH of the asphalt emulsion is 6.5 or less. In another embodiment, the acid modifier can be added in an amount such that the pH of the asphalt emulsion is 5.0 or less. The acid modifier can include hydrochloric acid. The acid modifier can include polyphosphoric acid.

[0010] As one example, the aggregate in such a system may be sized so that 98% or more of the aggregate material passes through a No. 14 sieve and 15% to 45% of the aggregate material passes through a No. 30 sieve. In another example, the first asphalt may be Gilsonite.

[0011] In one embodiment, the asphalt emulsion may contain about 56% by weight of solid asphalt residue and may be applied to the pavement at a rate of about 0.18 gallons per square yard, and the aggregate material may be applied at a rate of about 2.5 pounds per square yard.

[0012] In another embodiment, the asphalt emulsion may contain about 37% by weight of solid asphalt residue and may be applied to the pavement at a rate of about 0.17 gallons per square yard, and the aggregate material may be applied at a rate of about 1.25 pounds per square yard.

[0013] In another embodiment, the asphalt emulsion may contain about 37% by weight of solid asphalt residue and may be applied to the pavement at a rate of about 0.12 gallons per square yard, and the aggregate material may be applied at a rate of about 0.6 pounds per square yard.

[0014] In another embodiment, the asphalt emulsion may contain about 37% by weight of solid asphalt residue and may be applied to the pavement at a rate of about 0.2 gallons per square yard, and the aggregate material may be applied at a rate of about 2.0 pounds per square yard. [Brief explanation of the drawings]

[0015] The above and other features of the present disclosure will become more fully apparent from the following description taken in conjunction with the accompanying drawings. The present disclosure will be described with additional specificity and detail using the accompanying drawings, with the understanding that these drawings illustrate only some embodiments in accordance with the present disclosure and, therefore, are not intended to limit its scope. Those skilled in the art will appreciate that certain features are optional and that features or aspects of one embodiment can be utilized or combined with other features highlighted in another embodiment. Furthermore, each and every aspect shown and described is not necessarily required; rather, various aspects are shown and / or described as features of potential embodiments that may be included.

[0016] [Figure 1] FIG. 1 is an exemplary graph showing the coefficient of friction in a section of pavement where bleeding or flushing occurs, resulting in an extremely slippery and dangerous area. [Figure 2] FIG. 2 is a graph showing friction data for a road wheelpath, which serves as a control sample, a road in deteriorated but "good" condition, exhibiting typical but acceptable friction characteristics. [Figure 3] FIG. 3 is a graph showing roadway friction data, showing friction measurements of existing coating systems less than one month after application. [Figure 4]FIG. 4 is a graph showing roadway friction data, showing friction measurements of existing coating systems 11 months after application. [Figure 5] FIG. 5 is a graph illustrating roadway friction data showing friction measurements of a coating system according to one embodiment of the present disclosure 11 months after application. [Figure 6] FIG. 6 is a graph illustrating roadway friction data showing friction measurements of a coating system according to one embodiment of the present disclosure less than one month after application. [Figure 7] FIG. 7 is a graph illustrating roadway friction data showing friction measurements of a coating system according to one embodiment of the present disclosure 11 months after application. DETAILED DESCRIPTION OF THE INVENTION

[0017] In this detailed description, reference is made to the accompanying drawings, which form a part of the detailed description. In the drawings, like symbols typically indicate similar elements unless otherwise noted. The illustrative examples, drawings, and potential points of novelty set forth in the detailed description are not intended to be limiting. Alternative embodiments may be utilized, and other changes may be made, without departing from the concept or scope of the subject matter described herein. It will be readily understood that the aspects of the present disclosure, as described herein and shown in the drawings, may be variously arranged, substituted, combined, and designed in various configurations, all of which are expressly contemplated and made a part of this disclosure.

[0018] In one embodiment of the present disclosure, an asphalt emulsion composition for coating a paved surface is provided. In another embodiment of the present disclosure, an asphalt emulsion composition and aggregate for coating a paved surface are provided. In another embodiment of the present disclosure, a method for making an asphalt emulsion composition for coating a paved surface is provided. In another embodiment of the present disclosure, a method for applying an asphalt emulsion and / or aggregate to a paved surface is provided.

[0019] Specific tests and methods are known for characterizing asphalt pavements, particularly aged or deteriorated asphalt pavements. Pavements can be rated according to a pavement condition index. Roads and parking lots can utilize a pavement condition index according to ASTM D6433-20. Airport tarmac can utilize a pavement condition index according to ASTM D5340-20. The pavement condition index can be rated on a scale of 0 to 100. An index rating of 85 to 100 can be considered good, an index rating of 70 to 85 can be considered satisfactory, an index rating of 55 to 70 can be considered fair, and an index rating of 40 to 55 can be considered unsatisfactory. A pavement classified as "unsatisfactory" is highly undesirable and impedes traffic. The lower the rating, the worse the pavement condition.

[0020] Thus, asphalt pavements can be characterized according to a pavement condition index, but they can also be characterized according to surface density, porosity, texture, permeability, traffic volume, travel speed, climate, weather, temperatures typically experienced, snow and ice removal processes, cleaning processes, whether the pavement has previously undergone surface treatment, etc.

[0021] Characterization of an asphalt pavement may take into account the typical use of the pavement as well as the physical condition of the pavement, and this characterization can inform those skilled in the art as to how to treat the pavement to make it safer or to have more generally desirable properties. Examples of pavement treatments include fog sealing (applying an asphalt emulsion to the pavement), slurry treatment (applying an asphalt emulsion containing aggregate in a slurry form), chip sealing (sequentially applying layers of asphalt emulsion and crushed stone chips), microsurfacing (similar to a slurry treatment), scrub sealing (a treatment similar to a chip seal in which asphalt emulsion is rubbed into the damaged portion of the pavement), or a sequential combination of treatments (e.g., scrub sealing followed by a slurry treatment). Various asphalt treatments may use asphalt emulsions with different properties, and the selection of which treatment to use may depend on the properties of the asphalt pavement being treated.

[0022] However, many existing treatments have been observed to have certain drawbacks. For example, some treatments suffer from negative first-order effects or impacts that become apparent within a very short period of time after treatment. Negative first-order effects can include improper breakage and curing, overapplication of asphalt emulsion resulting in very slippery pavements or "black ice," and overapplication of aggregate that causes the new treatment to spall within a short period of time.

[0023] Additionally, many existing treatments can have negative secondary effects that become apparent over time. Negative secondary effects can include bleeding or flushing, which results in a thin film of asphalt or oil appearing on the surface, making the pavement very slippery and reducing friction over time, leading to pavement densification or rutting of the roadway surface. The reduction in surface friction characteristics can be observed in Figure 1, as measured by the coefficient of friction in pavement sections that have undergone bleeding or flushing. Bleeding or flushing can significantly reduce surface friction and result in dangerous areas of the roadway.

[0024] Even when it is determined that pavement properties or properties of a pavement portion need to be adjusted in existing processes, adjusting certain parameters can be difficult, if not impossible. For example, slurry and microsurfacing processes cannot be adjusted by the amount of aggregate after the process is prepared; the only adjustable factor is the application rate. Such limitations can result in suboptimal treatment for the pavement or portion thereof, and can result in negative primary or secondary effects. Furthermore, chip seals may be adjustable by the asphalt emulsion application rate and aggregate application rate, but they may be subject to certain minimum values ​​for each, which can also result in negative primary or secondary effects.

[0025] Negative primary and secondary effects are not insignificant. For example, a section of asphalt road in Maine was treated with fog seal. Negative primary and secondary effects (one or more of reduced friction, bleeding, or overapplication of asphalt emulsion) occurred, and the treated pavement became slippery. It was determined that the slipperiness of the pavement contributed to a traffic accident. Following the accident, the Maine Department of Transportation suspended its statewide fog seal treatment program due to safety concerns. A December 2, 2019, Morning Sentinel article titled "Maine to stop using certain road sealant on travel lanes after dangerous road conditions reported" reported the Maine Department of Transportation's decision to stop using fog sealant on roadways. This was due to a section of road treated with fog seal experiencing bleeding events where the fog seal did not penetrate deep enough into the pavement, resulting in a "glassy surface," which caused numerous crashes.

[0026] Embodiments of the present disclosure provide pavement surface treatments that mitigate negative primary impacts, negative secondary impacts, or both. To mitigate such impacts, embodiments of the present disclosure adjust one or more of the following: the amount of solids and water in the asphalt emulsion, the application rate of the asphalt emulsion, and the application rate of the aggregate. Additionally or alternatively, embodiments of the present disclosure may be suitable for treating asphalt pavements that have undergone densification in specific portions of the pavement, such as roadways.

[0027] For asphalt pavements, including both airfield and road pavements, there are a range of pavement characteristics for which existing surface treatments may result in overapplication of asphalt emulsion or may exhibit negative primary or secondary effects similar to those caused by overapplication. As one example, if the pavement surface is compact (e.g., an average surface texture (or unevenness) of about 2 mm or less), relatively dense (e.g., roadway), and / or has relatively low porosity and permeability, the existing treatment may not be able to fully penetrate the pavement surface. In such cases, over time and with traffic, the surface treatment itself may densify the pavement surface without penetrating into it. In such cases, the existing surface treatment may initially provide improved properties, including frictional properties. In one example, improved frictional properties include higher friction measurements or higher measured coefficients of friction. However, over time, the existing surface treatment may result in deteriorating pavement properties, leading to the entrenchment of suboptimal pavement treatments. For example, an existing surface treatment may initially exhibit increased coefficient of friction measurements, but these measurements may decrease over time as a result of the treatment densifying and setting in a much lower coefficient of friction. This set-in pavement surface may thus become more slippery. In certain applications (e.g., roads), friction measurements may become suboptimally low. In other applications (e.g., airport pavements), friction measurements may become unacceptably low. Even on roads, particularly dense pavement sections with existing treatments may subsequently densify to the point where the coefficient of friction is so low that it becomes unsafe.

[0028] Embodiments of the present disclosure provide asphalt emulsion-based (or utilizing) surface treatments (or treatments) that contain a higher proportion of water and / or other non-asphalt liquids than existing surface treatments. Such treatments can exhibit significantly improved pavement properties for densified pavements both immediately after treatment and long-term after treatment. In one embodiment, such treatments can provide treated pavements with relatively high coefficient of friction measurements both immediately after treatment and for up to at least 11 months after treatment.

[0029] In one embodiment of the present disclosure, an improved asphalt emulsion is provided. In one embodiment according to the present disclosure, the asphalt emulsion may comprise about 35% to about 50% solid asphalt residue by weight of the asphalt emulsion. In another embodiment, the asphalt emulsion may comprise about 37% solid asphalt residue by weight of the emulsion. In another embodiment, the asphalt emulsion may comprise about 1.75% polymer (undiluted) by weight of the emulsion. In another embodiment, the asphalt emulsion may comprise about 38.25% solid asphalt residue by weight of the emulsion. In another embodiment, the asphalt emulsion may comprise about 40% solid asphalt residue by weight of the emulsion.

[0030] In one embodiment, the asphalt blend before emulsification may include Gilsonite. About 20% by weight of the asphalt blend may include Gilsonite.

[0031] In one embodiment of the present disclosure, the improved asphalt emulsion may be applied to the pavement surface treatment at a rate of approximately 0.12 to approximately 0.20 gallons per square yard. In another embodiment of the present disclosure, the improved asphalt emulsion may be applied to the pavement surface treatment at a rate of approximately 0.15 to 0.18 gallons per square yard. In another embodiment of the present disclosure, the improved asphalt emulsion may be applied to the pavement surface treatment at a rate of approximately 0.17 gallons per square yard.

[0032] In one embodiment of the present disclosure, aggregate, such as fine aggregate, may be applied to the pavement surface treatment at a rate of about 0.6 to about 2.0 pounds per square yard. In another embodiment of the present disclosure, aggregate, such as fine aggregate, may be applied to the pavement surface treatment at a rate of about 1.0 to about 1.5 pounds per square yard. In another embodiment of the present disclosure, aggregate, such as fine aggregate, may be applied to the pavement surface treatment at a rate of about 1.25 pounds per square yard.

[0033] In one embodiment of the present disclosure, the pavement surface treatment may include treating the pavement by uniformly applying an asphalt emulsion to the entire pavement surface at a rate of 0.12 gallons per square yard, and then applying fine aggregate to the asphalt emulsion at a rate of 0.6 pounds per square yard. In one embodiment of the present disclosure, the pavement surface treatment may include treating the pavement by uniformly applying an asphalt emulsion to the entire pavement surface at a rate of 0.20 gallons per square yard, and then applying fine aggregate to the asphalt emulsion at a rate of 2.0 pounds per square yard. In one embodiment of the present disclosure, the pavement surface treatment may include treating the pavement by uniformly applying an asphalt emulsion to the entire pavement surface at a rate of 0.17 gallons per square yard, and then applying fine aggregate to the asphalt emulsion at a rate of 1.25 pounds per square yard.

[0034] An asphalt emulsion according to the present disclosure may include an asphalt blend containing Gilsonite. In another embodiment according to the present disclosure, the Gilsonite in the asphalt blend of the asphalt emulsion is modified (or modified) to have a positive charge (e.g., in the presence of an acid or in a low pH environment). In one example, Gilsonite may be included as asphalt (i.e., not a fraction, distillate, or derivative), and a modifying agent such as an acid may impart a positive charge to one or more nitrogen-containing moieties (including pyrrole). One example of an acid that may be used is hydrochloric acid. Another example of an acid that may be used is polyphosphoric acid. Gilsonite may have a relatively large amount of nitrogen-containing moieties. Such modified Gilsonite can impart a cationic effect to the asphalt emulsion without the need to include a cationic surfactant.

[0035] Gilsonite is a naturally occurring asphaltite hydrocarbon mineral resin. It is a unique composition that is notoriously difficult to incorporate into asphalt emulsions. Gilsonite is a combination of various molecules that function in asphalt compositions in a variety of ways. Gilsonite contains a relatively large number of polar components and resins. For this reason, Gilsonite is able to solvate the asphaltenes typically present in asphalt cements. In one embodiment, lowering the pH of the emulsion to acidic conditions in the presence of a modifier such as an acid activates one or more nitrogen moieties (e.g., pyrroles) and becomes positively charged (N+) on the surface of the Gilsonite-asphalt droplets. In this way, portions of the Gilsonite possess a positive or partial positive charge. This allows Gilsonite to share its ability to behave in a manner consistent with cationic surfactants without the need to add cationic surfactants to the asphalt emulsion. Additionally, the positive or partial positive charge of Gilsonite can also act as an adhesion agent.

[0036] Asphalt can be described as a colloidal system containing various components. For example, asphalt may contain asphaltenes, aromatics, resins, and oily / waxy saturates, among other components. In most cases, hard asphaltenes are surrounded (solvated) by aromatics, resins, oily / waxy saturates, etc.

[0037] The emulsion may include one or more polymers. Polymers can be used to enhance the durability and toughness of the finished coating system and to help retain fine aggregate materials in the coating applied to the pavement. Exemplary polymers or copolymers include those that help impart desired properties to the asphalt emulsion residue by, for example, providing a stress-absorbing layer that adheres strongly to the underlying pavement, providing a non-stick surface, or providing a polymer with non-swelling properties. In one example, the polymer may include a combination of polymers and copolymers, such as acrylic, styrene-butadiene rubber, or a combination thereof. The polymer or polymers may comprise from about 0.5% to about 5.0% by weight of the emulsion.

[0038] Exemplary acrylic polymers or copolymers may include those derived from acrylate monomers. The acrylic monomers may be based on, for example, (meth)acrylic acid, (meth)acrylic acid esters, (meth)acrylamide, (meth)acrylonitrile, and derivatives of these acrylate monomers. Exemplary (meth)acrylic acid esters include, but are not limited to, alkyl and hydroxyalkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hydroxyethyl (meth)acrylate, isobornyl (meth)acrylate, and longer-chain alkyl (meth)acrylates such as ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, and stearyl (meth)acrylate. Derivatives of (meth)acrylamide include, but are not limited to, alkyl-substituted (meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, t-butyl(meth)acrylamide, N-octyl(meth)acrylamide, and longer-chain alkyl(meth)acrylamides such as N-lauryl(meth)acrylamide and N-stearyl(meth)acrylamide. Acrylic polymers also include polymers commonly known as acrylics, acrylate polymers, polyacrylates, or acrylic elastomers. Acrylate polymers belong to a group of polymers commonly known as plastics, while acrylic elastomers are a generic term for a type of synthetic rubber whose main component is an alkyl acrylate ester (e.g., ethyl ester or butyl ester).

[0039] Exemplary copolymers may include polymers derived from, for example, vinyl acetate, vinyl chloride, vinylidene chloride, styrene, substituted styrenes, butadiene, unsaturated polyesters, polyolefins such as ethylene, etc. In some embodiments, the acrylic copolymer is derived from acrylate monomers and mixtures thereof, polymerized with styrene or ethylene. In yet other embodiments, the acrylic copolymer is derived from butyl acrylate, copolymerized with styrene or ethylene. In yet other embodiments, the copolymer is acrylonitrile butadiene.

[0040] In one embodiment, the asphalt emulsion can include one or more surfactants to establish stability, viscosity, and other properties during storage, transportation, application, curing, and curing. The surfactants can promote short-term and long-term strengthening of the polymer binder in the pavement. Preferably, the surfactants are non-cationic surfactants.

[0041] The surfactant may be a nonionic surfactant and / or an amphoteric surfactant. However, in most cases, the emulsion does not contain a cationic surfactant due to its adverse effect on emulsion stability and for reasons explained elsewhere in this disclosure. Therefore, an amphoteric surfactant and / or a nonionic surfactant is preferred instead of a cationic surfactant. An amphoteric surfactant and / or a nonionic surfactant shortens the break time / cure time of the emulsion when applied to the pavement. An amphoteric surfactant is a surfactant that can be cationic at low pH and anionic at high pH, ​​while a nonionic surfactant has no inherent charge. In contrast, typical cationic surfactants, such as fatty alkylamines, are always cationic. A cationic surfactant has a strong positive charge except at very high pH.

[0042] Exemplary amphoteric surfactants may include alkoxylated alkylamines, betaines and imidazolinium derivatives.Exemplary nonionic surfactants may include ethoxylated compounds and esters, such as ethoxylated fatty alcohols, ethoxylated fatty acids, sorbitan esters, ethoxylated sorbitan esters, ethoxylated alkylphenols, ethoxylated fatty amides, glycerin fatty acid esters, alcohols, alkylphenols, and mixtures thereof.In one example, noncationic surfactants may include nonylphenol ethoxylates or ethoxylated alcohols.

[0043] In one embodiment, one or more surfactants may comprise from about 0.25% to about 4.0% by weight of the emulsion. In one example, the surfactant comprises from 0.25% to about 2.5% by weight of the emulsion. Additionally, the amphoteric surfactant comprises from about 0.25% to about 2.0% by weight of the emulsion. The non-cationic surfactant may comprise from about 0.25% to about 4.0% by weight of the emulsion. In one example, the non-cationic surfactant comprises from 0.375% to about 2.0% by weight of the emulsion.

[0044] In one embodiment, the asphalt emulsion may contain sufficient modifier to charge the Gilsonite contained therein. In one example, an acid is added to the asphalt emulsion to lower the pH to less than about 6.5. In another example, an acid is added to the asphalt emulsion to lower the pH to less than about 5.0. In one example, the modifier may be an acid present in an amount of about 0.025 to about 1.5% by weight of the emulsion. In one example, the modifier may be hydrochloric acid.

[0045] Additionally or optionally, the asphalt emulsion according to the present disclosure may contain other optional additives to tailor the properties of the emulsion for its intended use, application method, and storage conditions, including, for example, mineral salts, thickeners, stabilizers, antifreeze agents, adhesion promoters, fungicides, pigments, etc.

[0046] Pavement surface treatments according to one or more embodiments of the present disclosure may include aggregate or fine aggregate materials. Fine aggregate materials may include, but are not limited to, crushed chert, quartzite, or carbonate. Other types of fine aggregate may be used as well. The fine aggregate may be dry, clean, firm, durable, and angular in shape with a highly textured surface (or rough surface). The fine aggregate material may be derived from taconite ore. In one example, the fine aggregate may comprise at least 50% silicon dioxide and up to about 5% calcium oxide by weight.

[0047] In embodiments of the present disclosure, fine aggregate may be applied to the pavement surface after the asphalt emulsion. As the emulsion hardens and curing progresses, the fine aggregate can become embedded and fully bound within the asphalt emulsion. The fine aggregate can improve the frictional properties of the treated pavement surface. In embodiments, the fine aggregate can have the classification boundaries shown in Table 1 when tested according to ASTM C136. Additionally, exemplary fine aggregate materials can include the properties shown in Table 2 below.

[0048] Table 1. Particle sizes of fine aggregate materials [Table 1]

[0049] Table 2. Properties of fine aggregate [Table 2]

[0050] An embodiment of the present disclosure includes a method for producing an asphalt emulsion. The method may first include mixing Gilsonite with asphalt cement. This mixing may be performed using a standard vat mixer or similar. This mixing step may include adding an optional light oil, such as atmospheric diesel, to the asphalt blend. The light oil can aid in the penetration of the emulsion into the underlying pavement. Next, an optional chemical may be added to the asphalt blend. This optional chemical can be used to aid in the melting and mixing of the Gilsonite in the asphalt blend. The asphalt blend composition may be exposed to a temperature of at least about 300°F for a period of time. In one example, the asphalt blend may be exposed to a temperature of about 350°F and mixed at that temperature for 24 to 48 hours. In another example, the asphalt blend may be exposed to a temperature of about 400°F and mixed at that temperature for 24 hours.

[0051] The method may include preparing an aqueous solution containing water, a modifier (e.g., an acid), one or more surfactants, and / or one or more other additives. In one example, an acid may be added to water or a solution of water and surfactant(s) and mixed. In one embodiment, the method may include sending the asphalt blend and aqueous solution to an emulsion mill to form an asphalt emulsion. In one embodiment, one or more polymers may be added to the aqueous solution or the asphalt emulsion.

[0052] In one embodiment, the method may include adding a modifier such as hydrochloric acid to water along with one or more surfactants and / or other additives to form an aqueous solution, which may be added to an asphalt blend to emulsify the asphalt therein.

[0053] In another aspect, the method may include adding a modifying agent, such as polyphosphoric acid, to the asphalt blend. In this aspect, polyphosphoric acid may be added to the asphalt blend, where it can modify the Gilsonite therein to impart a positive or partial positive charge of nitrogen-containing moieties, such as pyrrole. The aqueous solution (if not acidic) may then be mixed with the asphalt blend. This modified Gilsonite can have surfactant-like properties, reducing, if not eliminating, the need to add a separate surfactant.

[0054] In one embodiment according to the present disclosure, an asphalt emulsion according to the present disclosure was applied to a densified pavement roadway. The asphalt emulsion contained approximately 56% solid asphalt residue. Frictional properties were measured for an untreated control pavement roadway, which was also measured. The asphalt emulsion was applied at 0.22 gallons per square yard and fine aggregate was applied at a rate of approximately 2.5 pounds per square yard, corresponding to the existing pavement treatment. The existing pavement treatment was also modified to contain the same asphalt emulsion (approximately 56% solid asphalt residue) but at a lower rate of 0.18 gallons per square yard and fine aggregate applied at approximately 2.5 pounds per square yard. Therefore, the modified treatment applied less asphalt emulsion to the densified pavement roadway. The data in Table 3 were obtained.

[0055] Table 3. Asphalt emulsion containing approximately 56% solid asphalt residue at existing and revised treatment rates [Table 3]

[0056] In another embodiment according to the present disclosure, an asphalt emulsion according to the present disclosure was applied to the pavement roadway of a densified pavement. The asphalt emulsion contained approximately 37% solid asphalt residue, with a corresponding increase in water content within the emulsion. The more dilute asphalt emulsion was applied to the densified roadway at a rate of approximately 0.17 gallons per square yard. Following application of the asphalt emulsion, fine aggregate was applied at a rate of approximately 1.25 pounds per square yard. Thus, the modified treatment applied a smaller amount of more diluted asphalt emulsion to the densified roadway, followed by the application of a smaller amount of fine aggregate compared to the existing pavement treatment. The following data, shown in Table 4, was obtained:

[0057] Table 4. Asphalt emulsion containing approximately 37% solid asphalt residue at lower treatment rates. [Table 4]

[0058] The data from the test was graphed and is included in the figure. The graph reflects the results of measurements of the coefficient of friction made at 60 mph.

[0059] FIG. 2 is a graph showing friction data for a roadway, providing a control sample representing a typical roadway in deteriorated but "fair" condition with typical but acceptable friction characteristics. The graph includes the coefficient of friction, μ (mu), on the y-axis 101. The graph includes distance traveled across the sample pavement on the x-axis 102. The graph background includes regions 110 indicating pavement surface conditions that are "excellent" or "good" with respect to friction characteristics, region 120 indicating pavement surface conditions that are "good" or "fair" with respect to friction characteristics, region 130 indicating pavement surface conditions that are "poor" or "unsafe for airfield tarmac," and region 140 indicating pavement characteristics that are "unsafe for roadways." The y-axis 101, x-axis 102, and regions 110, 120, 130, and 140 are similar throughout the graphs in each figure. Notwithstanding the foregoing summary of regions 110, 120, 130, and 140, a coefficient of friction (μ) between 0.72 and 1.00 is considered excellent, a μ between 0.52 and 0.71 is considered good, a μ between 0.42 and 0.51 is considered fair, a μ between 0.30 and 0.41 is considered insufficient and unsafe for airport tarmac, and a μ below 0.30 is considered unsafe for roads. Notwithstanding the foregoing classification and labeling of regions 110, 120, 130, and 140, higher μ generally represent more favorable surface friction characteristics than lower μ. At very low μ levels, a pavement surface may become unsafe because it is very slippery. Thus, while a μ of 0.45 does not technically place a surface at an "unsafe" level, a μ of 0.60 may be more favorable than a μ of 0.45.

[0060] The untreated control sample in FIG. 2 exhibits a relatively stable pavement surface coefficient of friction 100 along a "good" region 110.

[0061] Figure 3 is a graph of roadway friction data, showing friction measurements of an existing coating system less than one month after application. The pavement in Figure 2 was treated with an existing surface treatment consisting of an asphalt emulsion with approximately 56% solid asphalt residue applied at a rate of approximately 0.22 gallons per square yard, and fine aggregate applied at a rate of 2.5 pounds per square yard. Less than one month after treatment, a measured coefficient of friction of 200 indicates a general initial improvement in frictional properties compared to the control, while the 350-400 meter section indicates potential initial densification, which may indicate future negative secondary effects.

[0062] Figure 4 is a graph depicting roadway friction data, showing friction measurements of an existing coating system 11 months after application. The pavement in Figure 3 had an existing surface treatment consisting of an asphalt emulsion with approximately 56% solid asphalt residue applied at a rate of approximately 0.22 gallons per square yard, and fine aggregate applied at a rate of 2.5 pounds per square yard. At 11 months after application, a measured coefficient of friction of 300 indicated significant degradation of frictional properties across the pavement, which generally fell into the "poor" and "unsafe for airfield tarmac" regions 130. This may reflect a negative secondary effect of densifying the surface treatment across the pavement.

[0063] FIG. 5 is a graph illustrating friction data for a roadway, showing friction measurements of a coating system according to one embodiment of the present disclosure 11 months after application. The pavement in FIG. 5 was surface-treated according to one embodiment of the present disclosure, using an asphalt emulsion with approximately 56% solid asphalt residue applied at a rate of approximately 0.18 gallons per square yard, and fine aggregate applied at a rate of 2.5 pounds per square yard. Approximately one year after surface treatment, the measured coefficient of friction (500) is uniform and within the acceptable "good" or "fair" range 120, with a μ average value of just below 0.5. Compared to the existing surface treatment, the modified treatment graphed in FIG. 5 exhibits improved frictional properties without significant localized reductions in the coefficient of friction, which could result in dangerously slippery areas on the pavement.

[0064] Figure 6 is a graph illustrating friction data for a roadway, showing friction measurements of a coating system according to one embodiment of the present disclosure less than one month after application. The pavement in Figure 6 was surface-treated according to another embodiment of the present disclosure, using an asphalt emulsion having about 37% solid asphalt residue applied at a rate of about 0.17 gallons per square yard, and fine aggregate applied at a rate of 1.25 pounds per square yard. Less than one month after application, the measured coefficient of friction of 600 was extremely uniform across the entire pavement, indicating very significantly improved frictional properties.

[0065] Figure 7 is a graph illustrating roadway friction data, showing friction measurements of a coating system according to one embodiment of the present disclosure 11 months after application. The pavement in Figure 6 was surface-treated according to another embodiment of the present disclosure, using an asphalt emulsion having about 37% solid asphalt residue applied at a rate of about 0.17 gallons per square yard, and fine aggregate applied at a rate of 1.25 pounds per square yard. Approximately one year after surface treatment, the measured coefficient of friction of 700 is very uniform throughout the pavement, with significantly improved frictional properties reflecting "excellent" or "good" frictional properties.

[0066] Thus, to varying degrees, surface treatments according to aspects of the present disclosure provide improved frictional properties for pavements that are longer lasting and that significantly reduce the occurrence of negative secondary effects that are prevalent in existing surface treatments and that can result from densifying the surface treatment.

[0067] While various embodiments have been disclosed herein, other embodiments will be apparent to those skilled in the art. The various embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims

1. 1. A method of applying a coating system to a surface, the method comprising: applying an asphalt emulsion to the surface at a rate of about 0.12 to 0.20 gallons per square yard; and applying fine aggregate onto the asphalt emulsion applied to the surface; Asphalt emulsion is a) an asphalt blend comprising Gilsonite, wherein at least a portion of the Gilsonite has been modified to have a positive charge; b) one or more polymers, and c) one or more surfactants.

2. 10. The method of claim 1, wherein the fine aggregate is applied at a rate of about 2.5 pounds per square yard.

3. 10. The method of claim 1, wherein the fine aggregate is applied at a rate of about 1.25 pounds per square yard.

4. 3. The method of claim 2, wherein the asphalt emulsion is applied at a rate of about 0.18 gallons per square yard.

5. 4. The method of claim 3, wherein the asphalt emulsion is applied at a rate of about 0.17 gallons per square yard.

6. 10. The method of claim 1, wherein applying the fine aggregate and spreading the asphalt emulsion are performed using the same application vehicle.

7. 10. The method of claim 1, wherein the asphalt emulsion comprises about 56% by weight of solid asphalt residue.

8. 10. The method of claim 1, wherein the asphalt emulsion comprises about 37% by weight of solid asphalt residue.

9. 3. The method of claim 2, wherein the asphalt emulsion comprises about 56% by weight of solid asphalt residue.

10. 4. The method of claim 3, wherein the asphalt emulsion comprises about 37% by weight of solid asphalt residue.

11. 5. The method of claim 4, wherein the asphalt emulsion comprises about 56% by weight of solid asphalt residue.

12. 6. The method of claim 5, wherein the asphalt emulsion comprises about 37% by weight of solid asphalt residue.

13. 10. The method of claim 1, wherein the asphalt emulsion is spread at a rate of about 0.12 gallons per square yard and the fine aggregate is applied at a rate of about 0.6 pounds per square yard.

14. 10. The method of claim 1, wherein the asphalt emulsion is spread at a rate of about 0.20 gallons per square yard and the fine aggregate is applied at a rate of about 2.0 pounds per square yard.

15. 14. The method of claim 13, wherein the asphalt emulsion comprises about 37% by weight of solid asphalt residue.

16. 15. The method of claim 14, wherein the asphalt emulsion comprises about 37% by weight of solid asphalt residue.

17. 1. A system for surfacing a pavement, the system comprising: an asphalt emulsion and an aggregate material for application to a pavement coated with the asphalt emulsion; Asphalt emulsion is an asphalt blend comprising a first asphalt that naturally contains a major amount of a nitrogen-containing polar resin, wherein at least a portion of the nitrogen-containing polar resin has been modified to have a positive charge; one or more polymers, and one or more surfactants, The system wherein the asphalt emulsion is applied to the pavement at a rate of about 0.12 to about 0.20 gallons per square yard.

18. 20. The system of claim 17, wherein at least a portion of the nitrogen-containing polar resin is pyrrole.

19. 20. The system of claim 17, further comprising an acid modifier in an amount such that the asphalt emulsion has a pH of 6.5 or less.

20. 20. The system of claim 17, further comprising an acid modifier in an amount such that the asphalt emulsion has a pH of 5.0 or less.

21. 14. The system of claim 13, wherein greater than 98% of the aggregate material passes through a No. 14 sieve and between 15% and 45% of the aggregate material passes through a No. 30 sieve.

22. 14. The system of claim 13, wherein the first asphalt is Gilsonite.

23. 14. The system of claim 13, The asphalt emulsion comprises about 56% by weight of solid asphalt residue; The asphalt emulsion is applied to the pavement at a rate of about 0.18 gallons per square yard; and The aggregate material is applied at a rate of approximately 2.5 pounds per square yard, system.

24. 14. The system of claim 13, The asphalt emulsion contains about 37% by weight of solid asphalt residue; The asphalt emulsion is applied to the pavement at a rate of about 0.17 gallons per square yard; and The aggregate material is applied at a rate of approximately 1.25 pounds per square yard, system.

25. 14. The system of claim 13, The asphalt emulsion contains about 37% by weight of solid asphalt residue; The asphalt emulsion is applied to the pavement at a rate of about 0.12 gallons per square yard; and The aggregate material is applied at a rate of approximately 0.6 pounds per square yard, system.

26. 14. The system of claim 13, The asphalt emulsion contains about 37% by weight of solid asphalt residue; The asphalt emulsion is applied to the pavement at a rate of about 0.20 gallons per square yard; and The aggregate material is applied at a rate of approximately 2.0 pounds per square yard, system.

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