Method of reinforcing and waterproofing a paved surface

0001The present invention is related generally to methods of reinforcing and waterproofing paved surfaces such as roads and parking lots, and more particularly to a method which includes the use of a reinforcement mat.

0002Paved surfaces such as roads and parking lots are commonly constructed with a top surface layer of asphalt paving material. Over a period of time, the paved surface usually deteriorates due to the effects of traffic, temperature cycles, and other environmental causes. Cracks develop in the paved surface, and the cracks can spread and cause further deterioration. Water can penetrate the paved surface by flowing into the cracks, causing further damage.

0003Damaged paved surfaces are usually repaired by applying a new surface layer of paving material over the damaged portions or over the entire paved surface. After a paved surface having cracks is resurfaced, many times the new surface layer cracks directly over the cracks in the old surface. This is known as "reflective cracking." One way to address this problem is to make the new surface layer thicker, but this is not very effective.

0004Consequently, various reinforcement materials and methods have been tried for preventing or repairing cracks and other deterioration in paved surfaces. One commercial product (an example of which is Petromat® available from BP Amoco) is a reinforcement mat constructed from nonwoven needle-punched polypropylene fibers. The polypropylene mat is applied over a tack coat of asphalt, and then a surface layer of paving material is applied over the mat. The paving material is heated prior to its application over the mat. Unfortunately, the polypropylene mat tends to melt and/or shrink when it is exposed to the hot paving material, which detracts from its ability to provide reinforcement and waterproofing. Additionally, if the tack coat is applied at too high a temperature, the polypropylene mat may likewise shrink or melt.

0005Various patents describe reinforcement materials and methods of reinforcing paved surfaces. For example, <patcit id="pcit0001" dnum="US2115667A"><text>U.S. Patent No. 2,115,667 to Ellis</text></patcit> discloses reinforcing an asphalt road with a reinforcing agent made from woven glass. A woven reinforcement material is usually less porous than a nonwoven material. This impedes the ability of the asphalt to penetrate the reinforcement material to create a strong paved surface. A woven material is also usually more expensive to manufacture than a nonwoven material.

0006<patcit id="pcit0002" dnum="US4637946A"><text>U.S. Patent No. 4,637,946 to Shah et al</text></patcit>. discloses a road repair membrane comprising a glass fiber mat impregnated with a blend of asphalt, block copolymer, and mineral filler. An impregnated mat would not be very effective in soaking up asphalt to create a strong bond with the road. A weakly bonded mat could delaminate from the asphalt layers, enabling the road surface to come apart.

0007<patcit id="pcit0003" dnum="US6235136B"><text>U.S. Patent No. 6,235,136 to Kittson et al</text></patcit>. discloses a water-resistant mastic membrane. The membrane comprises a carrier layer and a grid of glass fibers, both embedded in molten mastic material. The carrier layer is designed to provide only limited performance to the mastic membrane, and can be destroyed, or melted, by the molten mastic material. The membrane is bulky, having a thickness of 50 mm to 150 mm, and consists primarily of mastic material.

0008<patcit id="pcit0004" dnum="DE19543991A"><text>DE-A-19543991</text></patcit>, discloses a method of reinforcing and waterproofing a paved surface comprising the steps of applying a layer <i>of bitumen</i> on a surface, applying a reinforcement mat over the surface having a first layer comprising a nonwoven mat produced from polymer fibers and a second layer of mineral fibers attached to the first layer, forming a water barrier by pre-impregnating the mat with bitumen and applying a layer of paving material over the reinforcement mat.

0009In view of the above, it would be desirable to provide an improved method of reinforcing and waterproofing a paved surface.

0010The above object is achieved by a method of reinforcing and waterproofing a paved surface according to claim 1.

0011In a preferred embodiment the first layer and the second layer of the reinforcement mat are attached to each other by any one of sewing, knitting, needling, heat treating, and adhering with an adhesive, or combinations thereof.

0012In one embodiment of the method, the reinforcement mat is applied to the paved surface after the liquefied asphalt is applied to the paved surface.

0013In another embodiment of the method the reinforcement mat is applied to the paved surface before the liquefied asphalt is applied to the paved surface.

0014In another embodiment of the method, the second layer of the reinforcement mat comprises continuous strands of glass fiber. The strands of glass fiber are oriented along one direction and are substantially parallel to one another.

0015In another embodiment of the method, the second layer of the reinforcement mat comprises a randomly-oriented continuous-strand glass fiber mat.

0016In another embodiment of the method, the second layer of the reinforcement mat comprises randomly-oriented chopped stands of glass fiber.

0017Various objects and advantages of this invention will become apparent to those skilled in the art from the hollowing detailed description of the preferred embodiments, when read in light of the accompanying drawings. <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Fig. 1</figref> is a cross-sectional view in elevation of a paved surface which is reinforced and waterproofed according to the method of the invention.</li><li><figref idref="f0002">Fig. 2</figref> is a plan view of a first embodiment of a reinforcement mat illustrated in <figref idref="f0001">Fig. 1</figref> showing a second layer of continuous strands of glass fiber.</li><li><figref idref="f0002">Fig. 3</figref> is a plan view of a second embodiment of the reinforcement nat illustrated in <figref idref="f0001">Fig. 1</figref> showing a second layer of randomly-oriented continuous-strand glass fiber mat.</li><li><figref idref="f0002">Fig. 4</figref> is a plan view of a third embodiment of the reinforcement mat illustrated in <figref idref="f0001">Fig. 1</figref> showing a second layer of randomly oriented chopped strands of glass fiber.</li></ul>

0018The present invention relates to an improved method of reinforcing and waterproofing a paved surface such as a road, a parking lot, or any other type of paved surface. The method can be used in the construction of a new paved surface, in the rejuvenation of an existing paved surface.

0019Referring now to the drawings, <figref idref="f0001">Fig. 1</figref> shows a paved surface 10 which is reinforced and waterproofed according to the method of the invention. A first step of the method is to apply a layer of liquefied asphalt 12 on the paved surface 10. The liquefied asphalt 12 can be any type of bituminous material which is fluid at the time of application but which is able to firm up after application. For example, the liquefied asphalt can be a molten asphalt; for example, asphalt heated to a temperature above about 250°F (121°C), an asphalt emulsion (typically asphalt dispersed in water with an emulsifier), or an asphalt cutback (typically asphalt diluted with a solvent to make the asphalt fluid).

0020The layer of liquefied asphalt 12 can be applied in any amount which is suitable for penetrating and soaking the reinforcement mat 14, described below. Preferably, the liquefied asphalt is applied at a rate within a range of from about 0.1 gallon/square yard (0.32 liter/square meter) to about 0.5 gallon/square yard (1.58 liter/square meter), the optimum rate depending on the weight of the reinforcement mat. The liquefied asphalt can be applied by any suitable method, such as by spraying it as a layer or by pouring and spreading it into a layer.

0021A second step of the method is to apply the reinforcement mat 14 over the liquefied asphalt 12, while the liquefied asphalt is still in the fluid condition. The reinforcement mat 14 is sufficiently porous such that the liquefied asphalt penetrates and soaks the reinforcement mat 14. In the embodiment shown, the layer of liquefied asphalt 12 includes a bottom portion 16 below the reinforcement mat 14 and a top portion 18 which saturates the reinforcement mat 14. However, the liquefied asphalt could also be located entirely inside the reinforcement mat after it is applied. Preferably, the reinforcement mat can absorb at least about 0.1 gallon/square yard (0.32 liter/square meter) of the liquefied asphalt.

0022A sufficient amount of liquefied asphalt 12 is applied, and the reinforcement mat 14 absorbs enough liquefied asphalt, to form a strong bond with the paved surface 10 and with the layer of paving material 20, described below. The reinforcement mat 14 also forms a water barrier that prevents water from penetrating into the paved surface from above. Preferably, the reinforcement mat 14 is substantially completely saturated with the liquefied asphalt, such that the liquefied asphalt penetrates from a bottom surface 22 to a top surface 24 of the reinforcement mat 14.

0023As shown in <figref idref="f0001">Fig. 1</figref>, the reinforcement mat 14 includes a first layer 30 and a second layer 32. The first layer 30 is a nonwoven fibrous mat made from mineral fibers such as glass fibers, polymer fibers, or mixtures thereof. Preferably, the first layer is a nonwoven fibrous mat as disclosed in <patcit id="pcit0005" dnum="US79577401A" dnum-type="L"><text>U.S. Patent Application Serial No. 09/795,774, filed February 28, 2001</text></patcit>, owned by the assignee of this invention.

0024In a first embodiment, the first layer 30 of the reinforcement mat 14 is made of glass fibers, and has a width w, as shown in <figref idref="f0002">Fig. 2</figref>. Such a glass fiber mat is thermally stable, and does not melt and/or shrink when it is exposed to hot paving material. At the levels of strain encountered in the movement of pavements, the glass fiber mat comprising the first layer 30 carries much higher tensile loads than the polypropylene mats typically used. Preferably, the glass fiber mat has a basis weight within a range of from about 0.5 to about 10 pounds per hundred square feet (about 0.02 kg/m² to about 0.42 kglm²), and more preferably from about 1 to about 5 pounds per hundred square feet (about 0.04 kg/m² to about 0.21 kg/m²).

0025A first embodiment of the second layer is generally shown at 32 in <figref idref="f0002">Fig. 2</figref>. The second layer 32 includes a plurality of continuous strands 34 of glass fibers disposed on a surface of the first layer 30. The strands 34 can be oriented in a desired direction relative to the first layer 30, and relative to one another. Preferably, the strands 34 are oriented along one direction, and are substantially parallel to one another, as shown in <figref idref="f0002">Fig. 2</figref>. The strands 34 can also be oriented in any desired direction relative to the first layer 30 and relative to one another. The orientation as shown in <figref idref="f0002">Fig. 2</figref> is preferred for reasons that will be explained in detail below.

0026Adjacent parallel strands 34 can be spaced at any desired distance relative to one another. Preferably, the strands 34 are spaced within the range of about 0.5 to about 12 strands per inch of width w (19.7 to 472 strands/meter of width w) of the first layer 30. More preferably, the strands 34 are spaced at about 2.0 strands per inch of width w (78.8 strands/meter of width w) of the first layer 30.

0027Each bundle 34 can contain any desired amount of filaments of glass fibers. The strands 34 preferably have a linear density within the range of from about 100 to about 1000 yards per pound (241 to 2411 meters/kilogram) of glass. More preferably, the strands 34 have a linear density within the range of from about 200 to about 450 yards per pound (482 to 1085 meters/kilogram) of glass. Additionally, the second layer 32 preferably weighs within the range of from about 0.5 to about 15 ounces per square yard (17 to 512 grams/square meter) of reinforcement mat 14. More preferably, the second layer 32 weighs within the range of from about 4.5 to about 6.5 ounces per square yard (153 to 220 grams/square meter) of reinforcement mat 14.

0028The strands 34 comprising the second layer 32 can be attached to the first layer 30 by any desired method. Knitting, as shown in <figref idref="f0002">Fig. 2</figref>, is a preferred method of attaching the strands 34 to the first layer 30. As used herein, knitting is defined as a method of attaching by interlacing yam or thread 35 in a series of connected loops with needles. The strands 34 can also be attached to the first layer 30 by other methods, such as, for example, sewing, needling, heat treating, adhering with an adhesive, or any combination thereof. The thread 35 can be any desired natural or synthetic material. Preferably the thread 35 is synthetic. More preferably, the thread 35 is polyester or nylon because of the relatively high melting temperatures of both polyester and nylon.

0029A second embodiment of the reinforcement mat is generally shown at 14' in <figref idref="f0002">Fig. 3</figref>. The reinforcement mat 14' includes the first layer 30, and a second layer 36. The second layer 36 is formed from a randomly-oriented continuous strand of glass fiber applied to a surface of the first layer 30 by any conventional method. The layer 36 formed from the continuous strand of glass fiber is commonly known as a continuous filament mat (CFM). The second layer 36 can have any desired weight. Preferably, the second layer 36 weighs within the range of from about 4.5 to about 45 ounces per square yard (154 to 1535 grams/square meter) of reinforcement mat 14. More preferably, the second layer 36 weighs within the range of from about 9.0 to about 18 ounces per square yard (307 to 614 grams/square meter) of reinforcement mat 14.

0030The second layer 36 can be attached to the first layer 30 by any desired method. Knitting is a preferred method of attaching the second layer 36 to the first layer 30, as described above for attaching the second layer 32 to the first layer 30. As shown in <figref idref="f0002">Fig. 3</figref>, threads 38 attach the second layer 36 to the first layer 30 in a series of connected loops.

0031A third embodiment of the reinforcement mat is generally shown at 14" in <figref idref="f0002">Fig. 4</figref>. The reinforcement mat 14" includes the first layer 30, and a second layer 40. The second layer 40 is formed from randomly-oriented chopped strands of glass fiber applied to a surface of the first layer 30 by any conventional method. The random orientation of the chopped strands of the layer 40 provide improved strength to the reinforcement mat 14 in a first, x, dimension and a second, y, dimension. The second layer 40 can include chopped strands of any desired length. Preferably, the chopped strands have a length within the range of from about 0.5 to about 8.0 inches (0.013 to 0.20 meters). More preferably, the chopped stands have a length within the range of from about 2.0 to about 4.0 inches (0.05 to 0.1 meters). Most preferably, the chopped stands have a length of about 2.0 inches (0.05 meters).

0032The second layer 40 can have any desired weight. Preferably, the second layer 40 has a weight within the range of from about 0.5 to about 15 ounces per square yard (17 to 512 grams/square meter) of reinforcement mat 14. More preferably, the second layer 40 weighs within the range of from about 5.0 to about 8.0 ounces per square yard (171 to 273 grams/square meter) of reinforcement mat 14. The second layer 40 can be attached to the first layer 30 by any desired method. Knitting is a preferred method of attaching the second layer 40 to the first layer 30, as described above for attaching the second layer 32 and 36 to the first layer 30. As shown in <figref idref="f0002">Fig. 4</figref>, threads 42 attach the second layer 40 to the first layer 30 in a series of connected loops.

0033The reinforcement mat 14, 14', and 14" can be wrapped in a continuous roll, although a continuous roll is not required. Preferably, such a continuous roll has a width within a range of from about 5 feet (1.52 meters) to about 20 feet (6.1 meters). The continuous roll may also have any desired width. The reinforcement mat 14, 14', and 14" is applied over the liquefied asphalt by unrolling the reinforcement mat 14, 14', and 14" from the roll onto the liquefied asphalt.

0034The liquefied asphalt is allowed to become firm, or at least partially solidify, at some time after the application of the reinforcement mat. Usually, the liquefied asphalt is allowed to become firm before the application of the paving material described below. For example, molten asphalt can be allowed to become firm by cooling, asphalt emulsion can be allowed to become firm by the evaporation of water, and cutback asphalt can be allowed to become firm by the evaporation of solvent. The open porosity of the first layer 30 of the reinforcement mat 14 facilitates the evaporation of water or solvent.

0035A third step of the method is to apply a layer of paving material 20 over the reinforcement mat 14, 14', and 14". The paving material 20 can be any material suitable for providing a top surface layer of a paved surface, such as an asphalt paving material, typically a mixture of asphalt 26 and aggregate 28, or a concrete paving material. The paving material is usually applied in a heated condition, and then allowed to cool. When the heated paving material is applied over the reinforcement mat the heat of the mix partially liquefies the asphalt in the reinforcement layer, drawing it up into the mat, and forming a monolithic waterproof bond with the overlying pavement layer. It is during this heating step (that is unavoidable when placing an asphalt paving mixture over the mat) that damage from melting and shrinking can occur with polypropylene mats.

0036When the reinforcement of the paved surface is completed, the penetration of the reinforcement mat by the liquefied asphalt 12 (now at least partially solidified) forms a strong bond between the reinforcement mat 14, 14', and 14", the asphalt 12, the paved surface 10, and the layer of paving material 20. This creates a strong, monolithic paved surface structure that is very resistant to damage. The high tensile and mechanical strength of the reinforcement mat 14, 14', and 14" provides mechanical reinforcement to the paved surface. Additionally, the penetration of the reinforcement mat by the asphalt forms a water barrier or waterproof membrane that prevents water from penetrating into the paved surface from above and causing damage.

0037The principle and mode of operation of this invention have been described in its preferred embodiments. However, it should be noted that this invention may be practiced otherwise than as specifically illustrated and described. The drawings show a particular type and size of reinforcement mat, but other types and sizes of reinforcement mat can also be used. The drawings also show particular types and amounts of liquefied asphalt and paving material, but it is recognized that other types and amounts of liquefied asphalt and paving material can be used in the invention.