BACKGROUND

Trillions of dollars have been invested in our Nation's highway infrastructure. It is therefore vital to maintain and improve pavement performance to reduce the overall life-cycle costs of our roadway systems and to ensure the safety of motorists. Present-day pavements generally consist of asphalt, concrete, and/or composites thereof, which can be damaged for many reasons, including weather and traffic loading. The infiltration of water into a roadway is a major contributor to roadway damage because this weakens the base and subgrade support. Traffic loading is another contributor, which induces cracking in new and rehabilitated pavements.

Current highway repair programs have a few options for maintaining and preserving roadway pavements, however, these options suffer from significant shortcomings. The most common repairs are the placement of an additional new asphalt concrete overlay on the roadway or the milling and replacement of an existing overlay. Another repair strategy is the placement of a geosynthetic interlayer between new asphalt concrete layers or between an existing pavement and an asphalt concrete overlay or a chip seal surface treatment to extend the service life of the pavement.

The most widely used geosynthetic interlayer is a needle-punched nonwoven paving fabric made from thermoplastic staple fibers. These fabrics are combined in the field with an asphalt cement to form a thick interlayer to retard fatigue and reflective cracking in pavements and to act as a pavement moisture barrier. The paving fabric construction also makes it appropriate for use beneath a chip seal surface treatment by providing a durable fibrous seat for the chip seal surface treatment. A chip seal surface treatment involves the spraying of an asphalt emulsion onto the roadway surface, then immediately coating the surface with a layer of stone to build up pavement thickness, as opposed to placing a thickness of a plant-mixed asphalt concrete.

Although these measures can provide some relief, the pavements containing these paving fabric interlayers must eventually be resurfaced, and before resurfacing, a milling operation is frequently used to reduce the pavement thickness and to reestablish the correct pavement profile. Milling machines use large rotating drums with teeth to remove the top several inches of the existing pavement. Current paving fabric constructions are problematic because they can result in large pieces of the paving fabric that can wrap and clog milling drums so that milling operations are halted. Further, the millings containing the larger pieces of paving fabric, such as greater than 1.5 inches, can disrupt reprocessing operations and often render these millings unusable as a valuable asset for recycling back into new asphalt concrete.

Another existing option for roadway repair is the use of fiberglass or fiberglass composite geosynthetic interlayers within asphalt concrete pavements. These paving mats or composites were developed using brittle fiberglass fibers to create interlayers that are millable to recycle back into new asphalt concrete. Although easily milled and recycled, these fiberglass-based products have significant shortcomings that limit their effectiveness to extend pavement service life. Most of the fiberglass-based paving mats are very thin and, as such, cannot absorb a sufficient amount of stress from underlying cracking for long term prevention of fatigue and reflective cracking in the surface layer. Further, these thin fiberglass-based mats are unable to absorb and retain an adequate amount of asphalt cement to function as an effective moisture barrier. A pavement moisture barrier should have a water permeability of no more than 1×10−4cm/sec to effectively keep surface moisture from penetrating the pavement.

Additionally, working with the brittle fiberglass-based paving mats is quite difficult. The mats are easily damaged during installation and under construction traffic. Also, fiberglass-based paving mats readily tear and split open upon pavement cracking, which renders them ineffective as long-term moisture barriers. Due to the low elongation to rupture of fiberglass-based interlayers and their inability to stretch and bend, such products do not conform well to an uneven surface, such as a milled surface. A milled surface is the remaining corrugated pavement surface after cold milling, grinding, or planing a pavement surface with a milling machine. This milled surface is at least 15% longer than a flat pavement surface and these fiberglass-based pavement interlayers can elongate only 3 to 5% before rupturing. Thus, the use of fiberglass paving mats requires additional time, effort, and money to first prep the roadway surface before a repair is made. This initial prep commonly involves smoothing out the surface or placing an additional asphalt concrete layer to level the top of the surface. The fiberglass-based interlayers are also not appropriate for use beneath a chip seal surface treatment due to their thin nature and their vulnerability to construction and in-service damage.

One configuration for fiberglass-based interlayers is a composite of nonwoven fabric with a fiberglass grid or scrim. These products demonstrate strength principally in the machine and cross-machine directions and only a small fraction of their strength is demonstrated in any bias direction, such as at 45 degrees to the machine direction. This limits their ability to provide strength to resist pavement cracking due to traffic stresses applied in other than the machine or cross-machine orientations of the interlayers.

Moreover, the use of fiberglass paving mats can be injurious to workers as the fiberglass mats shed needle-like, glass fibers. This requires additional protective equipment and/or safeguards for workers engaged in the storage, handling, and installation of such materials. Still, workers coming in contact with these fiberglass paving mats complain of irritating glass fibers.

Milling and repaving of roadways has become very common-place and the ability of the geosynthetic interlayer to be easily milled and recycled into new asphalt concrete greatly influences the choice of product. It is therefore desirable to develop alternatives to overcome the shortcomings of existing geosynthetic interlayers for the repair, maintenance, and preservation of pavements. The present application is directed to an interlayer that is easily milled and recycled, like the fiberglass-based products, yet has all the features and benefits of a needle-punched, nonwoven thermoplastic paving fabric interlayer, such as thickness, asphalt cement absorption, elongation, 360 strength homogeneity, and durability. This application addresses the composition and method of use for a new geosynthetic interlayer fabric or composite system compatible with the current state of the practice in asphalt concrete paving and the placement of a chip seal surface treatment, and the subsequent milling and recycling of these pavements.

SUMMARY Provided herein is an easily millable, recyclable, waterproofing, paving fabric interlayer system comprising a flexible, nonwoven, paving fabric and a tack coat wherein the paving fabric includes (a) about 50-99% by weight of thermoplastic fibers having a length in the range of about 1-3 inches; and (b) an asphalt retention capacity between about 0.1-0.3 gallons/square yard.

This application is also directed to a method of waterproofing, repairing, or constructing a roadway or other hard surface that includes: (a) applying a tack coat onto the surface of the roadway; (b) placing a flexible, nonwoven, paving fabric interlayer onto the tack coat, wherein the paving fabric includes about 50-99% by weight of thermoplastic fibers having a length in the range of about 1-3 inches and an asphalt retention capacity between about 0.1-0.3 gallons/square yard, when tested per ASTM D6140; and (c) applying a new asphalt concrete layer or a chip seal surface treatment onto the paving fabric.

The present application is also directed to a millable, recyclable, waterproofing, paving fabric interlayer system made of a flexible, nonwoven, paving fabric and a tack coat wherein the fabric includes: (a) about 50-99% by weight of thermoplastic fibers having a length in the range of about 1-3 inches; (b) a strip tensile strength of about 40-50 pounds with an elongation of about 20 to 60% tested per ASTM test method D5035, Type 2C-E; (c) a grab tensile strength of about 75 to 100 pounds with an elongation of between about 30 and 70%, tested per ASTM D4632; (d) a thickness in the range of about 30-50 mils tested per ASTM D5199 and in the range of about 60-80 mils when asphalt saturated, when tested per ASTM D6140 and D5199; (e) a trap tear strength of about 30-45 pounds, when tested per ASTM D4533 and an asphalt saturated trap tear strength of 15-30 pounds when tested per ASTM 6140 and ASTM D4533; and (f) an asphalt retention capacity between about 0.1-0.3 gallons/square yard, tested per ASTM D6140.

Also, this application contemplates a millable, recyclable, waterproofing paving fabric conjoined with a scrim or grid and installed with an asphalt tack coat as an effective interlayer system.

In addition, the present application is directed to a prefabricated, millable, recyclable, waterproofing, paving fabric interlayer system made of a flexible, nonwoven, paving fabric including: (a) a mastic coating on at least one surface of the paving fabric; (b) about 50-99% by weight of thermoplastic fibers having a length in the range of about 1-3 inches; and (c) an asphalt retention capacity between about 0.1-0.3 gallons/square yard, when tested per ASTM D6140.

Also, the present application is directed to a composite of a layer or layers of sheet like material(s) composited with a millable, recyclable, waterproofing, paving fabric interlayer system made of a flexible, nonwoven, paving fabric including: (a) a mastic coating on at least one surface of the paving fabric; (b) about 50-99% by weight of thermoplastic fibers having a length in the range of about 1-3 inches; (c) a strip tensile strength of about 40-50 pounds with an elongation of about 20 to 60% tested per ASTM test method D5035, Type 2C-E; (d) a grab tensile strength of about 75 to 100 pounds with an elongation of between about 30 and 70%, tested per ASTM D4632; (e) a thickness in the range of about 30-50 mils tested per ASTM D5199; (f) a trap tear strength of about 30-45 pounds, when tested per ASTM D4533; (g) an asphalt saturated trap tear strength of about 15-30 pounds when tested per ASTM 6140 and ASTM D4533; and (h) an asphalt retention capacity between about 0.10 and 0.30 gallons/square yard, tested per ASTM D6140.

The millable, recyclable, waterproofing, paving fabric interlayer system and method of waterproofing, repairing, or constructing a roadway and other hard surface described herein have several benefits and advantages. One particular benefit is that the disclosed system provides an effective waterproofing moisture barrier, defined as having a permeability of no more than 1×10−4cm/sec for roadways. A disadvantage of thin fiberglass-based interlayers is that they cannot absorb enough asphalt cement to achieve sufficient waterproofing. Another benefit is that the disclosed system provides high elongation to rupture, as much as 70%, so that it can stretch over minor bumps, milled pavement surfaces, or undulations. In contrast, fiberglass products have a maximum elongation to rupture of only 3-5%. Placement directly onto a milled surface, a common cost-saving design configuration, requires at least 15% interlayer elongation. Therefore, the disclosed system offers a significant cost saving advantage over fiberglass-based interlayers. Elongation of the paving fabric system is necessary to maintain continuous moisture barrier integrity, even if the pavement in which it is embedded cracks open. Also, the disclosed system, when placed around a curve, can be stretched so as not to have to be cut and restarted several times, which is the case for the fiberglass paving mats. Cutting and restarting the fabric increases the complexity of installation and introduces additional seams thereby providing more chances for pavement overlay shoving and surface water ingress; and requires additional money, time, and effort to install properly. Another benefit of the disclosed system is that it provides excellent asphalt absorption/retention due to the thickness and needle-punched fibrous formation of the interlayer. Greater asphalt retention permits more stress absorption that better resists fatigue and reflective cracking in comparison to thinner fiberglass-based interlayers. Furthermore, thickness and asphalt retention of the paving fabric system provide a better seat for an overlying chip seal surface treatment to help minimize stone loss. An additional benefit of the disclosed system is that the light color of the interlayer reflects solar energy and remains cooler, which is not only beneficial for the workers but also for the hot tack coat to cool sufficiently and solidify properly to avoid paving equipment tracking and pick up. An extra benefit is that the disclosed system is easily millable and recyclable in subsequent roadway repairs owing to the fabric construction and the short length of the thermoplastic fibers therein, and the heat and pressure treatment, resulting in lower tensile and tear strengths and elongations. These features are unlike traditional AASHTO M 288 Type II paving fabric, which has longer fibers and a more entangled construction making it stretch and narrow-down to produce rope-like strands and large pieces, which can cause milling and recycling problems. In particular, the trapezoidal tear strength as tested on an in-service simulated asphalt saturated sample per ASTM D4533shows less than half the tear strength of the traditional paving fabric. Furthermore, the present fabric is better able to withstand and survive construction and in-service stresses without losing more than 10% of its original strength, in stark contrast to fiberglass-based fabrics that can degrade and weaken dramatically under such conditions.

