VOID REDUCING ASPHALT MEMBRANE COMPOSITION, METHOD AND APPARATUS FOR ASPHALT PAVING APPLICATIONS

Abstract

A method of sealing pavement joints includes the steps of dispensing a first band of void reducing joint composition on a substrate. Applying a first pass of pavement over at least a portion of the void reducing joint composition. Dispensing a second pass of void reducing joint composition on the substrate. Applying a second pass of pavement of the second band of void reducing joint composition and against an edge of the first pass of pavement.

Claims

1-11. (canceled)

12. A method of forming a pavement construction joint, comprising: dispensing a band of a void reducing joint composition on a substrate using at least one spray application vehicle; permitting the application of a paving pass over the band of joint composition, wherein the paving pass is positioned against an edge of a previously laid portion of pavement to form a pavement construction joint having a volume of air voids; and allowing at least a portion of the joint composition to migrate upward to reduce the volume of air voids.

13. The method of claim 12, wherein the substrate comprises a pre-existing pavement roadway.

14. The method of claim 12, wherein the void reducing joint composition comprises at least one asphaltic binder, at least one elastomeric polymer, at least one thickener, and at least one additive to reduce tackiness.

15. The method of claim 12, wherein the band of joint composition comprises a thickness of about 1/16 to about ⅜ inch.

16. The method of claim 12, wherein the void reducing joint composition consists essentially of at least one asphaltic binder, at least one elastomeric polymer, at least one thickener, and at least one additive to reduce tackiness.

17. The method of claim 16, wherein the at least one elastomeric polymer comprises a styrene-butadiene-styrene polymer.

18. The method of claim 12, wherein the substrate comprises at least one of an asphalt concrete, a cement concrete, a milled asphalt concrete, a brick surface, or a chip seal surface.

19. The method of claim 12, wherein the substrate comprises a milled asphalt concrete.

20. The method of claim 16, wherein the joint composition comprises about 85 to about 97 wt. % of the least one asphalt binder.

21. The method of claim 12, wherein the joint composition is resistant to lateral flow across the substrate.

22. The method of claim 12, wherein the previously laid portion of pavement is positioned over the band of joint composition.

23. The method of claim 12, wherein the band comprises a width of about 4 to about 24 inches.

Description

BEST MODE FOR CARRYING OUT THE INVENTION

[0019] The present invention is directed to a new preventative maintenance product and process for pavement construction involving hot mix asphalt and particularly to the construction of joints between adjacent pavements and non-asphaltic surfaces such as concrete.

[0020] The present invention provides void reducing asphalt membrane compositions which, when used in pavement applications, are placed below the new lift of asphalt mixture pavement and/or against a cold joint on the vertical face of a newly created lift of asphalt mixture pavement before an adjacent hot mix is put down against or over the cold joint to form a good bond between the cold joint and hot mix and reduce air voids and water permeability and create better crack resistance in the area of the joint. The void reducing asphalt membrane compositions of the present invention have been formulated so as to be resistant to lateral flow prior to paving over with hot mix asphalt in order to remain in the joint area in sufficient quantity to fill voids. At the same time the void reducing asphalt membrane composition is formulated so that it can be applied in a sufficient thickness to allow it to migrate upward into a freshly placed asphalt overlay during a paving process to reduce air voids and reduce water permeability. In multi-pass pavement applications the void reducing asphalt membrane composition can be provided between adjacent passes of asphalt, including on the vertical face or edge of a first or previous pass. Further a conventional tack coating can be provided under a first or previous pass alone or together with a band of the void reducing asphalt membrane composition.

[0021] The void reducing asphalt membrane composition is sufficiently non-tracking or loses its tackiness quickly so as to allow for construction traffic to drive over the applied composition during placement of an asphalt overlay or an adjacent pass and avoid work stoppage during a paving operation. Generally after application the void reducing asphalt membrane composition may be driven across by construction traffic or other vehicular traffic within 30 minutes of placement or as within as little as 15 minutes or less of placement. This ability to be non-tracking or quickly lose any tackiness solves constructability issues that plague other approaches to pavement joint construction.

[0022] The composition includes polymerized asphalt which allows a joint formed therefrom to expand and contract elastically, thus dissipating expansion and contraction forces. The highly compliant material behaves like an expansion joint in pavement applications which prevents stresses from building up at the joint which would otherwise tend to cause cracks to form and subsequent pavement failure.

[0023] The void reducing asphalt membrane composition of the present invention generally comprises a mixture of an asphalt binder, elastomeric polymers, a thickener and a wax modifier. Other embodiments comprise an asphalt binder, elastomeric polymers, a thickener, a wax modifier and fumed silica and/or fumed alumina. Further embodiments include an asphalt binder, elastomeric polymers, a thickener, a wax modifier and a saponified fatty acid and a resin acid gelling compound. Still further embodiments comprise an asphalt binder, elastomeric polymers, a thickener, a wax modifier fumed silica and/or fumed alumina and a saponified fatty acid and a resin acid gelling compound.

[0024] The asphalt binder is the main component of the composition and provides the material strength or foundation to fill voids in the area of the longitudinal asphalt pavement construction joint. The asphalt binder can comprise 85 to 97 wt. % of the composition and more preferably 90 to 93 wt. % of the composition. Suitable asphalt binders include paving grade asphalts including; performance graded, viscosity graded or/or penetration graded.

[0025] The composition includes an elastomeric polymer component that allows the area in and around the longitudinal asphalt pavement construction joint formed therefrom to expand and contract elastically. The polymer component creates a polymer modified asphalt binder in combination with the asphalt binder component. Suitable examples of this polymer component include Styrene-Butadene-Styrene (SBS), Styrene-Butadene Rubber (SBR), Ethylene-Styrene-Interpolymers (ESI), Evaloy (an ethylene terpolymer available from Dupont), and other elastomeric polymers that are used in polymer modified asphalt compositions. This polymer component can comprise 1 to 6 wt. % of the composition and more preferably 2 to 5 wt. % of the composition.

[0026] The wax modifier reduces the viscosity of the composition at the paving temperature so that during a paving process the composition can migrate upward into a freshly placed asphalt overlay to reduce air voids and reduce water permeability. Futhermore, at pavement surface temperature, the wax modifier provides stiffness to the void reducing asphalt membrane which reduces issues with tracking. Suitable wax modifiers include, but are not limited to, waxes of vegetable (e.g. carnuba wax), animal (e.g. beeswax) mineral (e.g. Montan™ wax from coal, Fischer Tropsch wax from coal) or petroleum (e.g. paraffin wax, polyethylene wax, Fischer-Tropsch wax from gas) origin including oxidised waxes; amide waxes (e.g. ethylene bis stearamide, stearyl amide, stearylstearamide); fatty acids and soaps of waxy nature (e.g. aluminum stearate, calcium stearate, fatty acids). The wax modifier also improves cohesion properties of the composition. The wax modifier can comprise 1 to 5 wt. % of the composition and more preferably 2 to 4 wt. % of the composition.

[0027] The fumed silica and/or fumed alumina function as fillers and impart resistance to flow immediately after application and give a non-tacky character to the composition that prevents pick-up by construction and non-construction equipment before paving is complete.

[0028] The fumed silica and fumed alumina can be used alone or together in any desired proportion. The total amount of fumed silica and/or fumed alumina can comprise 1 to 10 wt. % of the composition and more preferably 3 to 6 wt. % of the composition.

[0029] The saponified fatty acid and resin acid gelling compound functions to control the rate at which the composition sets or cures. Suitable saponified fatty and resin acid gelling compounds include but are not limited to crude tall or distilled tall oil. The total amount of saponified fatty acid and resin acid gelling compound can comprise 0 to 3 wt. % of the composition and more preferably 1 to 2 wt. % of the composition.

[0030] A typical formulation of the void reducing asphalt membrane composition is made by adding the polymer component to the heated asphalt binder while shearing the mixture. After or before the polymer component and asphalt binder are thoroughly mixed the wax modifier can be added while shearing the mixture followed by the addition of the fumed silica and/or fumed alumina are and saponified fatty acid and resin acid gelling compound. The mixed void reducing asphalt membrane should be stored under conditions of agitation and heating until application.

[0031] During the course of the present invention the inventors discovered that when the final polymer composition included fumed silica and/or fumed alumina the resulting polymer composition demonstrated improved heat stability. Furthermore the polymer properties imparted to the composition remained more consistent over time while at an elevated temperature as compared to a similar composition that did not include fumed silica and/or fumed alumina.

[0032] In a typical application the void reducing asphalt membrane composition of the present invention is placed in a band from 4 to 24 inches wide on the surface to be paved (also referred to as a cold joint portion) in the area where a longitudinal construction joint of an asphalt overlay or pass will develop. Subsequently the asphalt overlay or pass is laid down. In the case of multi-pass pavement installations before an adjacent paving pass is placed, a band of the void reducing asphalt membrane composition having a width of 4 to 24 inches is applied over and against the vertical face portion of a previously laid pavement pass in the area where the longitudinal joint will occur under the adjacent paving pass. The thickness of applied band of void reducing asphalt membrane compound in any situation can be 1/16 to ⅜ of an inch depending on the overlay type and thickness. These widths and thickness ranges are exemplary of typical applications; however, it is to be understood that other widths and thicknesses and combinations thereof could be used. The thickness of the applied band can be adjusted to allow migration of a volume of the void reducing asphalt membrane composition into the asphalt overlay and reduce the air void volume and ability for water to infiltrate and damage the overlay and underlying structure. The band of void reducing asphalt membrane composition can be applied to any existing surface to be paved including asphalt concrete, Portland cement concrete, milled asphalt concrete or milled Portland cement concrete, brick or a chip seal surface as well as metal structures.

[0033] For paving of adjacent lanes the void reducing asphalt membrane composition can be applied to the vertical face of the first paving pass as well as on an area where the second application of the product as described above will be placed.

[0034] The air void volume in the finished asphalt overlay in the area of the longitudinal asphalt pavement construction joint above the void reducing asphalt membrane composition can be reduced to about 7% or lower due to the migration of the product into the finished asphalt overlay. In preferred embodiments the air void volume of the finished asphalt overlay will be reduced to 4% in the finished asphalt overlay in the area above the void reducing asphalt membrane composition.

[0035] In the area of the longitudinal asphalt pavement construction joint the asphalt overlay mixture will be of low permeability to water infiltration as a result of the void reducing asphalt membrane composition migration into the asphalt overlay. The area of the longitudinal asphalt pavement construction joint over the void reducing asphalt membrane composition will be resistant to crack initiation and propagation.

[0036] The void reducing asphalt membrane composition can be applied using various coating methods such as coating, rolling, spraying, etc. According to one embodiment of the present invention the void reducing asphalt membrane composition can be applied using a strike off box that may be mounted on mobile equipment that can be pulled or pushed either manually or mechanically driven. Strike off boxes that are designed for use in narrow width paving projects are exemplified by U.S. Pat. No. 8,506,204 to Reames et al. incorporated herein by reference. Alternatively conventional paving equipment downsized to apply the void reducing asphalt membrane composition in desired widths can be used.

[0037] In other embodiments a spraying system can be used which can be mounted on mobile equipment that can be pulled or pushed either manually or mechanically driven. Otherwise the spraying can be achieved using a handheld spraying device such as a wand.

[0038] Although the present invention has been described with reference to particular means, materials and embodiments, from the foregoing description, one skilled in the art can easily ascertain the essential characteristics of the present invention and various changes and modifications can be made to adapt the various uses and characteristics without departing from the spirit and scope of the present invention as described above and encompassed by the attached claims.