Patent Application
20240141602
The present invention relates to a pavement paving process. More specifically, the present invention is directed to a pavement paving process that effectively incorporates asphalt millings and reduces the need for new materials that make up pavements suitable to support vehicular and heavy equipment traffic.
Modern recycling techniques offer a means of recovering desirable pavement properties without replacing the entire pavement with new materials. Additionally, they enable reuse of production waste from the asphalt pavement industry. By recycling asphalt pavements, the demand for natural resources can be decreased, reducing the production of waste material and costs. Desirably the amount of the asphalt pavement that is recycled is maximized and the amount of new material that is added to the recovered asphalt is minimized. Reclaimed asphalt pavement, also known as RAP, can be recycled “in-place,” i.e., at the road location, or can be recycled “in-plant,” i.e., the RAP is removed from the road surface and transported to an asphalt mix plant. In a hot in-place recycling process, the existing pavement is reheated and milled and virgin aggregate and preferably a rejuvenating agent is added to the RAP. This process is primarily used for resurfacing the top layer of a pavement and can re-use up to 100% of the RAP. In a hot in-plant recycling process, the RAP is broken, milled, and fractionated, and virgin aggregate, and preferably a rejuvenating agent and, in some instances, fresh bitumen are added. The in-plant process may be used for the construction of new base layers, but it can be difficult to incorporate a high level of RAP into the final product due to constraints of the asphalt mix plant, and typically the final product consists of up to about 50% RAP, but more commonly 25-35% RAP. The function of the rejuvenating agent, also known as a recycling agent, is to modify the properties of the aged binder contained in the RAP so that the recycled asphalt or asphalt millings has properties resembling those of the original asphalt. It may not be possible to restore the asphalt to its former state, but it should be possible to significantly improve those properties that have been subject to deterioration. In-plant rejuvenation of RAP also involves transportation of asphalt millings to plant and distribution of rejuvenated RAP to site at which it is used. Therefore, in cases where RAP can be recycled in place, using e.g., a cold planer, a tremendous amount of savings can be realized, not only in the cost of transportation but also logistics required to get the RAP to where it is needed and often, just in time. Among other examples, several disclosures detail chemical compositions of various rejuvenators, their uses and the conditions under which they may be utilized to bind with recycled asphalt.
U.S. Pat. Pub. No. 20160376440A1 of Naidoo et al. (hereinafter Naidoo) discloses an asphalt additive comprising an oil component comprising vegetable oil and/or a crude tall oil, an amine component, and an organosilane component, the disclosure incorporated herein by reference. Asphalt compositions and products comprise asphalt binder, aggregate, and the additive. Treatment methods include contacting asphalt compositions or asphalt products with the additive. According to Naidoo, asphalt pavements deteriorate over time due to the impact of traffic, water and sunlight. The deterioration in pavement quality can lead to permanent deformation or rutting, cracking or brittleness and can lead to binder stripping and inferior skid resistance. The deterioration is evident from a decrease in penetration value, e.g., measured at 25° C. in accordance with EN 1426 or ASTM D5-97 and an increase in softening point, e.g., measured using the Ring and Ball technique in accordance with EN 1427 or ASTM D36-95. More recent testing demonstrates the deterioration through Performance Grade testing on asphalt mixes taken from commercial pavements where m-value and creep stiffness are negatively impacted (measured using testing equipment in accordance with AASHTO M320). Although Naidoo discloses at least an asphalt additive, an asphalt binder, a method for forming an asphalt mix, a method of treating an asphalt article, a method of treating recycled asphalt and a method of forming a foam, Naidoo fails to disclose a complete pavement construction process to form a pavement suitable for supporting vehicular and heavy equipment traffic.
Naidoo further discloses that the cost of thermal energy to achieve suitable conventional paving mixes for paving is considerable as a mixture of a suitable aggregate comprising stones, gravel, sand, and the like, is heated at an elevated temperature of about 270-370° F. and mixed with a similarly hot, bituminous binder such as an asphalt-based binder, e.g., asphalt or asphalt plus polymer and additives, until the aggregate particles are coated with the binder. Paving mixes made in this temperature range are often referred to as a hot mix. The mixing typically occurs away from the paving site, and the mixture is then hauled to the site and supplied to a paving machine, further exacerbating the significantly elevated thermal energy consumption problem. The mixture of asphalt and aggregate applied by the paving machine to a surface is then usually roller-compacted by additional equipment while still at an elevated temperature. The compacted aggregate and asphalt material eventually hardens upon cooling. As the paving of a roadway or commercial parking lot involves a large mass of paving mixes, a large portion of the paving cost can be attributed to the need for hot mixes.
U.S. Pat. No. 5,578,663 to McGovern (hereinafter McGovern) discloses a pavement rejuvenating and/or conditioning composition in which particular coal tar derivatives and other optional ingredients are supplemented with an elastomeric constituent, the disclosure incorporated herein by reference. A rejuvenating or conditioning composition containing an elastomer will reliably hold in place a top layer of fine aggregate, whereas a rejuvenating or conditioning composition without elastomer does not, and also allows for early restoration of traffic, prompt resistance to rain, and good repair and wear resistance of and in the pavement to be maintained. The elastomer is preferably acrylonitrile-butadiene polymer although other polymers can also be substituted including natural and nitrile-rubbers, polyorganosiloxane and, less preferably, styrene-butadiene, neoprene- and polybutadiene polymers. Again, although McGovern discloses a pavement rejuvenating and/or conditioning composition in which particular coal tar derivatives and other optional ingredients are supplemented with an elastomeric constituent, McGovern fails to disclose a complete pavement construction process to form a pavement suitable for supporting vehicular and heavy equipment traffic.
U.S. Pat. Pub. No. 20210230818 of Fennell et al. (hereinafter Fennell) discloses a method for repairing/treating a pavement with the use of a rheology modifier is disclosed, the disclosure incorporated herein by reference. The method comprises first applying a layer of a rheology modifier composition comprising a rejuvenating component onto the top surface of the pavement that needs repair, then applying a second layer of a binder onto the rheology modifier layer. The second layer of binder effectively seals the rheology modifier layer with the rejuvenating component for intimate contact with the top pavement surface, thus penetrating the surface layer to extend the life of the pavement surface, arresting the deterioration of visco-elastic properties and restoring some of those properties. Again, although Fennell discloses a pavement repair/treatment method using a rejuvenating component, Fennell fails to disclose a complete pavement construction process to form a pavement suitable for supporting vehicular and heavy equipment traffic. Fennell discloses an application of a second layer of a binder onto a first layer in order to protect the first layer.
There exists a need for a process for constructing a pavement suitable for supporting vehicular and heavy equipment traffic where the process reduces the amount of required new materials, e.g., by reusing milled asphalt in place or reusing asphalt millings transported to location. Further, there exists a need for a process for constructing a pavement suitable for supporting vehicular and heavy equipment traffic where the process is less energy intensive.
In accordance with the present invention, there is provided a pavement paving process including:
In one embodiment, the layer of asphalt millings includes compacted asphalt millings. In one embodiment, the rejuvenator is configured to be applied at a rate of about 0.06 gallon per cubic yard of the compacted asphalt millings. In one embodiment, the layer of asphalt millings includes millings of about 0.5-3.0 inches. In one embodiment, the layer of aggregate includes crushed stone of sizes 0.25-3.0 inches. In one embodiment, the crushed stone can be limestone, granite, basalt, quartz, sandstone or any combinations thereof. In one embodiment, the compacting step is configured to be performed within about 1 hour of the start of the incorporating step and any one of the layer of rejuvenated asphalt millings and the layer of aggregate is disposed at at least about 70 degrees F. In one embodiment, the incorporating step includes spraying the layer of asphalt millings.
An object of the present invention is to provide a paving process to construct a pavement, e.g., a road, parking lot, etc., suitable for supporting vehicular and heavy equipment traffic that reduces the use of asphalt and increases the use of recycled asphalt, i.e., millings.
An object of the present invention is to provide a paving process to construct a pavement, e.g., a road, parking lot, etc., suitable for supporting vehicular and heavy equipment traffic that is cost effective.
Another object of the present invention is to provide a pavement paving process that results in pavements that are more durable than pavements constructed with asphalt.
Whereas there may be many embodiments of the present invention, each embodiment may meet one or more of the foregoing recited objects in any combination. It is not intended that each embodiment will necessarily meet each objective. Thus, having broadly outlined the more important features of the present invention in order that the detailed description thereof may be better understood, and that the present contribution to the art may be better appreciated, there are, of course, additional features of the present invention that will be described herein and will form a part of the subject matter of this specification.
In order that the manner in which the above-recited and other advantages and objects of the invention are obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
As a substitute for an asphalt-based paving process, the present paving process reduces the use of asphalt, reducing or eliminating the part of the paving process that traditionally incurs the highest cost while providing a paved surface suitable for vehicular and heavy equipment traffic.
Unlike an application of asphalt or asphalt sealer over an aggregate foundation, an application of rejuvenator in asphalt millings allows the rejuvenator to penetrate, flux and co-mingle with the existing asphalt binder of asphalt millings, instead of adding another layer to the substrate, restoring asphalt binder, e.g., maltenes that have been lost due to aging in the asphalt millings. An asphalt rejuvenator penetrates the asphalt well below the surface to chemically revitalize and protect the asphalt binder.
The term “about” is used herein to mean approximately, roughly, around, or in the region of. When the term “about” is used in conjunction with a numerical range, it modifies that range by extending the boundaries above and below the numerical values set forth. In general, the term “about” is used herein to modify a numerical value above and below the stated value by a variance of 20 percent up or down (higher or lower).
In order to reduce the amount of pavement construction waste and the need for new pavement construction materials, used asphalt is increasingly being recycled and merged in asphalt-producing processes in the form of asphalt millings. Asphalt is a mixture of various sizes of rock and oil as a binder. Asphalt pavements that have been damaged over a period of use can be milled to produce asphalt millings which are typically sorted according to their sizes and used according to certain weight or volume percentages in a reconstituted asphalt mixture. While reconstitution of asphalt millings and new aggregate with an appropriate asphalt binder to form asphalt theoretically can be used to reduce the amount of new aggregate required, this process is fraught with shortcomings in practice. Ideally, asphalt millings should be interspersed evenly with new aggregate and an appropriate asphalt binder to result in asphalt consistent in its quality throughout the mixture. However, in practice, asphalt millings tend to get added to the mixture in clusters or clumps. While it is easy to assume recycled asphalt millings would behave identically or similarly to aggregate, recycled asphalt millings include a used asphalt binder interspersed within the millings which may not be revived in their function as a binder in the reconstituted asphalt mixture, therefore resulting in noticeable differences in appearance and function in the resulting asphalt mixture between the portions of asphalt made with fresh aggregate and portions of asphalt made with asphalt millings. The Applicant discovered a new process in which asphalt millings used therein can be properly rejuvenated with a rejuvenator to provide strength and longevity when combined with a fresh layer of aggregate atop a layer of millings being rejuvenated, thereby prolonging the service life of the pavements constructed from the asphalt millings and removing the need for additional and new asphalt.
A rejuvenator, as used herein, shall refer to any compositions or materials capable of providing the features in the rejuvenator itself or any materials it interacts with. The purpose of a rejuvenator is to rejuvenate aged asphalt binder and provide a fuel resistant surface. Rejuvenation, as used herein, is defined as an act which significantly lowers viscosity, increases ductility, lowers softening point and increases penetration, without disturbing the asphalt's capacity to bind aggregate and without significantly lowering skid resistance of the asphalt and/or aggregate it interacts with.
First, a layer of asphalt millings 4 is laid down cold (e.g., without external heating) on the ground upon which a pavement is to be constructed or an existing bed of stone foundation as shown in
Upon application of the rejuvenator 6, an aggregate layer 8 is laid over the layer of millings 4 as shown in
Referring back to
The detailed description refers to the accompanying drawings that show, by way of illustration, specific aspects and embodiments in which the present disclosed embodiments may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice aspects of the present invention. Other embodiments may be utilized, and changes may be made without departing from the scope of the disclosed embodiments. The various embodiments can be combined with one or more other embodiments to form new embodiments. The detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, with the full scope of equivalents to which they may be entitled. It will be appreciated by those of ordinary skill in the art that any arrangement that is calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of embodiments of the present invention. It is to be understood that the above description is intended to be illustrative, and not restrictive, and that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Combinations of the above embodiments and other embodiments will be apparent to those of skill in the art upon studying the above description. The scope of the present disclosed embodiments includes any other applications in which embodiments of the above structures and fabrication methods are used. The scope of the embodiments should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
