Patent Publication Number: US-9890299-B1

Title: Spray paving coating and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     FIELD OF THE INVENTION 
     The field of the invention relates to asphalt spray paving. 
     SUMMARY 
     Embodiments of the present invention are defined by the claims below, not this summary. This summary merely presents a high-level overview of various aspects of the invention and a selection of concepts that are further described below in the detailed description section. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in isolation to determine the scope of the claimed subject matter. The scope of the invention is defined by the claims. 
     In a first aspect, a paving mixture for application to a road surface is provided, in accordance with an embodiment of the present invention. The mixture comprises a binding material layer applied to the surface to form a base layer on the surface, and an aggregate material layer applied on top of the binding material layer. The binding material layer comprises at least 15% of the bitumen in the paving mixture by weight. The aggregate material layer contains a mixture of aggregate and bitumen that provides a road surface. When constructed the paving mixture can be 1 inch thick or greater. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Illustrative embodiments of the present invention are described in detail below with reference to the attached drawing figures, wherein: 
         FIG. 1  depicts a paving mixture applied to a surface, in accordance with an embodiment of the present invention; 
         FIG. 2  depicts a first method of applying a paving mixture to a surface, in accordance with an aspect of the present invention; and 
         FIG. 3  depicts a second method of applying a paving mixture to a surface, in accordance with an aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The subject matter of the various embodiments of the present invention is described with specificity in this disclosure to meet statutory requirements. However, the description is not intended to limit the scope of claims. Rather, the claimed subject matter may be embodied in various other ways to include different features, components, elements, combinations, and steps, similar to the ones described in this document, and in conjunction with other present and future technologies. Terms should not be interpreted as implying any particular order among or between various steps disclosed herein unless the stated order of steps is explicitly required. Many different arrangements of the various components depicted, as well as use of components not shown, are possible without departing from the scope of the claims below. 
     In one aspect, a paving mixture for application to a surface is provided. The mixture comprises a binding material layer that is applied to the surface to form a base layer on the surface. An aggregate material layer is then applied on top of the binding material layer, the binding and aggregate layers mixing to form a solid surface resistant to cracking and deformation. The binding material layer comprises at least 15% of the bitumen within the paving mixture by weight. The aggregate material layer contains an asphalt mixture of bitumen and aggregate that provides a road surface. The aggregate material layer and the binding material layer can be combined on the surface within 30 seconds of application of the binding material layer to allow for adequate mixing of the layers and prevent undesired diffusion of the binding material layer on the surface. 
     The paving mixture described herein can be used with any number of surfaces to provide an even, strong, water impermeable layer that is resistant to erosion and cracking. Surfaces to which the paving mixture may be applied include roads, streets, interstates, parking lots, airport runways, and other similar surfaces. For simplicity, all of these surfaces are described as “road surfaces” herein. These surfaces do not need to be a particular consistency, composition, or texture. The binding material layer combines with the aggregate material layer to give it elasticity, strength, and cohesion. The binding material layer also fills in cracks on the surface to which the paving mixture is applied. The aggregate material provides a firm structural component that will resist deformation. 
     The binding material layer provides a moisture barrier that prevents cracks under the applied paving mixture from deteriorating or expanding. Additionally, the combination of a binding layer and an aggregate layer provides a surface with a degree of elasticity that will resist cracking, molding, rutting, or similar deformation or damage, due to the binding layer providing a dynamic element to the aggregate material. In this regard, the binding material fills in the space, or gaps, between aggregate materials, providing a more consistent aggregate base material that has less air gaps and more cohesion. 
     The binding material may form a certain percentage of the overall bitumen in the paving mixture to provide adequate adhesion of the aggregate elements and proper dispersion of the binding material into the cracks on the surface. The amount of binding material used in the paving mixture may vary based on the desired performance and adhesion of the aggregate material. An ideal percentage of the binding material is at least 15% of the bitumen in the paving mixture by weight, which provides sufficient bonding and elasticity, while maintaining structural integrity from the aggregate material. The binding material may contain bitumen and other materials that form asphalt or similar surface forming materials, including sand, polymers, cross-linking agents, vulcanization agents, accelerators, extenders, and fluxing agents. The binding material may also form a polymer modified asphalt emulsion (PMAE) or hot-asphalt cement, a petroleum solvent cutback asphalt, and other similar or analogous compositions. The viscosity of the binding material layer may be varied with the addition of different materials or heat. Varying the viscosity provides different diffusion properties of the binding material across the surface to which it is applied, which may be desirable based on the amount of wear of the surface or the textural irregularities of the surface. 
     Heating the binding material decreases the viscosity, and helps to increase penetration of the binding material into cracks on the surface. Heating the binding material and/or aggregate material also helps to increase mixing of the binding material and the aggregate material once the layers are combined, providing a more uniform, durable paving mixture. When a liquid asphalt emulsion is used as the binding material, the asphalt emulsion may be formulated to have a low viscosity to help the binding material (i.e., asphalt emulsion) penetrate throughout the aggregate mixture, coating a higher percentage of the aggregate material in the aggregate material layer. 
     The aggregate material layer provides a structural component with compressive strength and durability. The aggregate material may comprise sand, gravel, crushed stone, slag, rock dust, and the like. The aggregate material may also include small or micro sized aggregate materials, or rather a pulverulent material, to provide a more densely packed or organized paving mixture. Exemplary pulverulent materials may include fine sand or dust, which enhance the consistency of the paving mixture by better distributing the aggregate materials throughout the paving mixture. This also allows the aggregate material to mix with the binding material more effectively, and reduces air gaps in the paving mixture. In addition to the materials listed, the aggregate material may include a synthetic aggregate. 
     An asphalt solution comprising bitumen may be added to the aggregate mixture. The asphalt solution may be the same as or similar to the binding material, providing an adhesive or bonding element in the aggregate material layer. By including the asphalt solution, or binding element, in the aggregate mix, there is also enhanced bonding between the aggregate materials prior to distribution over the binding material layer. A pulverulent material, such as sand or fine rock dust, may be added to the asphalt mix to help control the diffusion of the asphalt mix during application when the aggregate particles are otherwise large. Larger aggregate particles are desirable for structural support reasons, but may allow an asphalt mix to spread or run too quickly when the aggregate is applied to the surface. The asphalt solution or asphalt mixture may further comprise a bituminous material comprising at least one of asphalt cement, pitch, coal tar, vacuum tower bottoms, resin, performance grade asphalts, flux, and petroleum based products. The asphalt solution can include antistrip and other additives, including those that prevent excessive running or dispersion of the asphalt solution. The asphalt solution may comprise less than 15%, such as 5%, of the aggregate material layer. Additionally, the asphalt contained in the aggregate mixture may coat some or all of the aggregate particles in the mixture to create a Hot Mix Asphalt (HMA), which may be appropriate in circumstances that require a high amount of diffusion of the binding material. An aggregate mixture is considered a HMA asphalt when the temperature of the aggregate mixture is at least 230 degrees Fahrenheit. A HMA provides increased distribution and uniformity of the binding material amongst the aggregate material in the aggregate material layer, due to the heat. A Warm Mix Asphalt (WMA) may also be used for similar purposes. An asphalt mix is considered a WMA when the asphalt is heated to at least 100 degrees Fahrenheit. A Cold Mix Asphalt (CMA) may also be used where the asphalt is approximately ambient temperature, and no enhanced diffusion of the binding material is desired. The type of asphalt used, and the heat applied, may be determined based on ambient conditions and the desired diffusion or mixing of the binding and aggregate materials, prior to any compaction. 
     The portion of the paving mixture that comprises the binding material or asphalt solution may be varied based on the amount of adhesion needed to allow the paving mixture to withstand wear, movement, deformation, and/or cracking. In a preferred embodiment, the binding material may be at least 15% of the paving mixture by weight. Additionally, the aggregate material may be applied such that the paving mixture forms a layer at least 1 inch thick or greater after application, and/or compaction, for example 1.25 inches, 1.5 inches, 2 inches, 3 inches, or 4 inches. 
     The amount of binding material applied to the surface depends on the desired amount of surface treatment, and the desired thickness of the paving mixture product. In one embodiment, a distribution of 0.02 gallons/ft 2  0.03 gallons/ft 2  0.04 gallons/ft 2  of binding material may be applied to the surface. In another embodiment, a distribution of 0.05 gallons/ft 2  of binding material may be applied to the surface. In yet another embodiment, a distribution of 0.06 gallons/ft 2  of binding material may be applied to the surface. The depth of the aggregate material layer may be two or more times the depth of the binding material layer. This provides a stable surface and allows varying degrees of mixture between the binding material and the aggregate material, depending on the desired structural characteristics of the paving mixture. 
     The aggregate material may be applied to the binding material layer within a relatively short amount of time so that the binding material does not become too dispersed or diffuse on the surface after application. This time period may be less than 30 seconds, and even as short as a few seconds. As the aggregate material layer is applied to the binding material layer, the layers may be compacted into a tighter, more uniform layer of paving mixture, removing air gaps. This compacting can be accomplished mechanically, such as with a roller, pressing device, and/or machine. Compacting the binding layer and the aggregate layer together provides an even, uniform paving surface and also helps to distribute the binding material amongst the aggregate, providing a more stable, even paving mixture on the surface to which the paving mixture is applied. 
     In another aspect, a method for application of a paving mixture to a surface is provided. The method comprises applying a binding material layer to the surface to form a base layer on the surface, and applying an aggregate material layer on top of the binding material layer, wherein the binding material layer comprises at least 15% of the bitumen in the paving mixture by weight, the aggregate material layer contains an asphalt mixture that provides a road surface, and the aggregate material layer and the binding material layer are combined on the surface within 30 seconds of application of the binding material layer. 
     The paving mixture may be applied by a vehicle that contains a binding material application component and an aggregate material application component. The binding material application component may apply the binding material layer ahead of the aggregate material layer, such as by spray paving, and may heat the binding material to a temperature that provides the desired viscosity or fluid properties. The aggregate material application component may apply the aggregate material on top of the binding material layer within 30 seconds or less of the binding material layer being applied to the surface. The aggregate material application component may also heat the aggregate material. The binding and aggregate layers may subsequently be compressed or compacted by a roller or a pressure application component. The binding material layer may comprise 15% or more of the bitumen in the paving mixture by weight, in a desired aspect. 
     In another aspect, a method for applying a paving mixture to a surface is provided, in accordance with an embodiment of the present invention. The method comprises applying a binding material layer to the surface to form a base layer on the surface, applying an aggregate material layer on top of the binding material layer, and compacting the binding material layer and the aggregate material layer together, wherein the binding material layer comprises at least 15% of the bitumen in the paving mixture by weight, the aggregate material layer contains an asphalt mixture that provides a road surface, and the aggregate material layer and the binding material layer are combined on the surface within 30 seconds of application of the binding material layer. As discussed herein, compacting of the binding material layer and the aggregate material layer may be accomplished using a roller machine or a mechanical compaction apparatus. 
     Referring to  FIG. 1 , an exemplary paving mixture applied to a surface is shown, in accordance with an embodiment of the present invention. In  FIG. 1 , a surface  108  is depicted with a paving mixture  100  applied on top of the surface  108  with an even distribution, which may result after mechanical compaction of the paving mixture  100 . The paving mixture  100  includes a binding material layer  102  proximate to the surface  108 , and an aggregate material layer  104  applied on top of the binding material layer  102 . The paving mixture  100  has a thickness  106  of 1.25 inches after application and/or after compaction of the layers. 
     Referring to  FIG. 2 , a flowchart of a first exemplary method  200  of applying a paving mixture to a surface is provided, in accordance with an aspect of the present invention. In  FIG. 2 , at a first step  202 , a binding material layer is applied to a surface to form a base layer on the surface. At a second step  204 , an aggregate material layer is applied on top of the binding material layer, wherein the binding material layer comprises at least 15% of the bitumen in the paving mixture by weight, the aggregate material layer contains an asphalt mixture that provides a road surface, and the aggregate material layer and the binding material layer are combined on the surface within 30 seconds of application of the binding material layer. 
     Referring to  FIG. 3 , a second exemplary method  300  of applying a paving mixture to a surface is provided, in accordance with an aspect of the present invention. In  FIG. 3 , at a first step  302 , a binding material layer is applied to a surface to form a base layer on the surface. At a second step  304 , an aggregate material layer is applied on top of the binding material layer. At a third step  306 , the binding material layer and the aggregate material layer are compacted, wherein the binding material layer comprises at least 15% of the bitumen in the paving mixture by weight, the aggregate material layer contains an asphalt mixture that provides a road surface, and the aggregate material layer and the binding material layer are combined on the surface within 30 seconds of application of the binding material layer. 
     Embodiments of the technology have been described to be illustrative rather than restrictive. Alternative embodiments will become apparent to readers of this disclosure. Further, alternative means of implementing the aforementioned elements and steps can be used without departing from the scope of the claims below, as would be understood by one having ordinary skill in the art. Certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations, and are contemplated as within the scope of the claims.