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You are an expert at summarizing long articles. Proceed to summarize the following text: 
FIELD OF THE INVENTION 
     The present invention relates generally to recreational ramps and, more particularly, to recreational ramps for use with wheeled vehicles such as skateboards and the like. 
     BACKGROUND OF THE INVENTION 
     Skateboard ramps provide an ideal way for allowing skateboarding enthusiasts to practice their sport away from the hazards of traffic. Such ramps are typically installed by municipalities in skate parks, which are usually located in residential areas. To ensure maximum usage of these parks by skateboarding enthusiasts, the skateboard ramps must provide a smooth ride. At the same time, by virtue of the fact that skateboard ramps are outdoor installations, these must be made resistant to severe changes in the weather, particularly as occur in northern latitudes. In addition, municipalities must be conscious of the effects of noise pollution on nearby residences and hence the surface of the ramp must be designed with a quiet ride in mind. 
     It is therefore not surprising that skateboard ramps have undergone a considerable evolution from a time when the ride surface was made of wood. Such wooden ramps, although simple to construct and capable of providing riders with a pleasant “feel”, require a high degree of maintenance as they tend to decay rather quickly, especially in areas where rain or snow are prevalent. Moreover, as they perish, wooden ramps subject skaters to the risk of injury from splinters and exposed screw heads. 
     By moving from a wooden ramp to one made of painted steel, one reduces the maintenance requirements of the ramp and thus significantly increases its safety and durability, although rust now becomes a significant impediment to the commercial success of this type of ramp. This is especially problematic in humid climates or in the presence of salt used to melt snow in some regions. Moreover, the rolling of wheels on a steel surface causes a much greater amount of noise than on a wooden ramp. Thus, even with the advent of the stainless or galvanized steel ramp, noise remains a critical issue, along with the added cost of treating the large amounts of metal necessary to create stainless steel skateboard ramps. 
     Another material that has been used in the construction of skateboard ramps is aluminum. Such a ramp offers the advantage of being more durable than one made of stainless steel. However, aluminum is afflicted by an even greater cost than stainless steel and retains the poor noise performance usually associated with metal surfaces. As a result, aluminum is often not the choice of a cash-strapped municipality in search of skateboard ramps to populate a skate park. 
     Thus, in search of the ideal skateboarding surface, manufacturers of skateboard ramps have turned to concrete. A concrete surface provides quiet, long-lasting skating pleasure with a superior ride “feel”. However, as can be readily imagined, the extreme weight of a concrete structure of the size necessary to provide appropriate elevations and radii of curvature is the most serious drawback of this type of ramp. In particular, the weight of such a structure renders it virtually impossible to account for shifts in the level of the earth that may occur after the ramp is placed, not to mention the disadvantage of requiring special heavy equipment to position the structure in the first place. Moreover, a conventional concrete structure is typically unattractive, not only because of its natural discoloration and liability to graffiti, but also because it curtails the field of view of individuals in its vicinity. 
     Against this background, it is apparent that the need exists for a skateboard ramp that is capable of providing the durability, safety, noise absorption and “feel” of a conventional concrete ramp, while benefiting from a greatly reduced weight and reduced physical volume. 
     SUMMARY OF THE INVENTION 
     The present invention recognizes that the durability, safety, noise absorption and “feel” of the surface provided by a skateboard ramp need not be compromised by excessive weight and/or expense. Accordingly, the present invention may be broadly summarized as providing a recreational ramp suitable for use with wheeled vehicles, including a support structure and a molded concrete layer mounted on the support structure. The molded concrete layer includes a sloping region that extends from a ground level to an above-ground level. 
     The present invention may also be broadly summarized as a process for the fabrication of a molded concrete layer for use in construction of a recreational ramp suitable for use with wheeled vehicles. The process includes preparing a mold from complementary parts, closing the parts onto one another, thus defining an interior space representative of a concrete layer, pouring concrete mixture into the mold, allowing the concrete to settle and separating the complementary parts of the mold to expose the molded concrete layer. The concrete layer is then mounted onto a support structure. 
     Embodiments of the invention offer the advantages of conventional concrete, i.e., a smooth, quiet and durable surface for riding, while the ramp as a whole is lighter and less bulky than a conventional concrete ramp. A particularly advantageous embodiment is one in which the concrete is self-leveling concrete, allowing the production of a thin, yet strong molded concrete layer. 
     These and other aspects and features of the present invention will now become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIGS. 1A ,  1 B and  1 C are perspective views of three example ramps in accordance with respective embodiments of the present invention; 
         FIG. 2  is a perspective view of a support structure forming part of the ramp of  FIG. 1A ; 
         FIG. 3  is a perspective view of the underside of the molded concrete layer forming part of the ramp of  FIG. 1B ; and 
         FIG. 4  is a flowchart showing an example sequence of steps in the process of manufacturing a ramp in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to  FIGS. 1A ,  1 B and  1 C, there are shown three example embodiments of a recreational ramp  100  for use with wheeled vehicles such as skateboards, in-line skates, roller skates, roller-skis, bicycles (e.g., BMX), and so on. In each case, the ramp  100  includes a support structure  110  and a molded concrete layer  120  mounted on the support structure  110 . The molded concrete layer  120  includes a sloping region  130  that extends from a ground level to an above-ground level. The molded concrete layer  120  also includes a platform  140  which acts as a braking surface. The dimensions of the platform  140  depend on the design parameters of the ramp  100 , such as the elevation of the platform  140  with respect to the ground level. 
     The platform  140  may be integral with the sloping region  130 . Alternatively, the platform  140  may be molded separately from the sloping region  130  and these two portions of the molded concrete layer  120  may be independently attached to the support structure  110  in a manner to be described later in further detail. A similar protective band  165  made of steel or other suitable material may protect a juncture  125  (best seen in  FIG. 3 ) where the sloping region  130  and the platform  140  meet. 
     Likewise, an optional protective band  160  may surround a portion of the periphery  170  of the molded concrete layer  120 . The protective band  160  may be made of steel treated against rust and may be affixed to the periphery  170  in any conventional way. A suitable thickness for the protective band is 1.5 inches, although other thicknesses are within the scope of the invention. 
     The sloping region  130  and the platform  140  can be said to define a top surface  150  of the molded concrete layer  120 . Due to the texture of concrete, this top surface  150  is quiet when subjected to a rolling motion of wheeled vehicles such as skateboards. This makes the ramp  100  suitable for installation in residential areas. In addition, due to the fact that the concrete supported by the support structure  110  is in the form of a thin slab, the ramp  100  of the present invention will be considerably lighter in weight than conventional solid concrete ramps of the same size, and will not obstruct the field of view of a user proximate the ramp  100 . 
     Moreover, by making the molded concrete layer  120  out of high-performance (high-compressive-strength) self-leveling concrete, it is possible to obtain a smoother and thinner surface than with traditional concrete, which is of particular advantage when vehicles with small wheels, such as skateboards, are used. 
     Additionally, as shown in  FIG. 1A , a barrier  180  can surround the platform  140 . The barrier  180  is not essential, although it may be advantageous, for example, in order to provide a sense of security to skateboarding enthusiasts who are coming out of a maneuver or waiting to use the ramp  100 . The barrier  180  may take the form of a solid wall or, as illustrated in  FIG. 1A , the barrier  180  may take the form of a grille, which has the advantage of being less dense, and thus lighter, than a solid wall. 
     Also, in some designs, the ramp  100  may include various additional features, such as boxes (see box  190  in FIG.  1 C), islands, gaps, rails (see rail  195  in FIG.  1 C), and so on. Such features are fastenable to the molded concrete layer and/or to the support structure  110  in any known way. 
     In some embodiments of the ramp  100 , such as the one shown in  FIG. 1A , the sloping region  130  will present a straight surface (i.e., at a constant gradient), while in other embodiments, such as the one shown in  FIG. 1B , the sloping region  130  will present a curved surface. When a curved surface is presented, the radius of curvature may be constant or variable. Several particularly popular ramp designs include sloping regions  130  with a constant radius of curvature, in which the curved surface presents an arc of substantially 90 degrees (known as a “quarter-pipe” and shown in  FIG. 1B ) or 180 degrees (known as a “half-pipe”). Alternatively, a half-pipe may be constructed by placing two quarter-pipes adjacent one another, with the ground-level portions of the respective sloping regions in contact with one another. 
     As shown in greater detail in  FIG. 2 , the support structure  110  may typically include an arrangement of vertical legs  210  and diagonal cross-braces  220  joining the legs  210 . The legs  210  may have a rectangular tube-like structure with dimensions of three inches by three inches, although solid legs and legs having other dimensions are within the scope of the invention. The legs  210  have feet  230  which are adjustable in height. Such height adjustment may be achieved by providing multiple possible levels defined by buttons or by screwing the feet  230  in one direction to increase the leg height and in another to reduce the leg height. The adjustment of the feet  230  can also serve to level the support structure  110  where the ground on which it is placed is not level. 
     In a non-limiting example embodiment of the ramp  100  in  FIG. 1A , known as a “six-foot bank”, the length of the platform  140  is about four feet, the height of the platform  140  is about six feet, the length of the sloped region  130  of the ramp  100  is about fourteen to fifteen feet and the thickness of the molded concrete layer  120  varies between 1.5 and 6.5 inches. In a non-limiting example embodiment of the ramp  100  in  FIG. 1B , known as a three-foot quarter pipe”, the length of the platform  140  is about 30 inches, the height of the platform  140  is about three feet, the radius of curvature of the sloped region  130  is about six feet and the thickness of the molded concrete layer  120  varies between 1.5 and 6.5 inches. Other dimensions are of course possible, and the above examples merely serve to illustrate two of the myriad designs that will appeal to today&#39;s skateboard enthusiast and which are within the scope of the present invention. 
     The support structure  110  can be made of steel treated against rust (e.g., stainless or galvanized steel) or any other suitably rigid material that is resistant to corrosion. In order to attach the molded concrete layer  120  to the support structure  110 , any suitable fastening mechanism can be used. For example, the legs may have holes  240  through which tamper-proof masonry fasteners can be inserted. An example of a suitable tamper-proof masonry fastener is the Torx® Tamper-Resistant TapCon® Concrete Screw available from Tanner Bolt &amp; Nut Corp., Brooklyn, N.Y. 
     Because the molded concrete layer  120  has a finite thickness, the portion of the molded concrete layer  120  which meets the ground level would ordinarily present a step that is not always easy to overcome by a vehicle with small wheels, such as a skateboard. To this end, the portion of the molded concrete layer  120  at the ground level may be gradually thinned out so as to present a much smaller step to the user of the ramp. However, the reduction in thickness of the molded concrete layer  120  at an edge thereof increases the fragility of the layer  120  and may lead to erosion or damage of the concrete layer at its thinnest point around the periphery  170 . Accordingly, a more desirable solution is to provide a transition plate  105  in order to bridge the step presented by the thickness of the molded concrete layer  120 . 
     Thus, with continued reference to  FIGS. 1A ,  1 B and  1 C, the molded concrete layer  120  is recessed around a portion of its periphery  170 . The depth of the recessed portion may be about ⅛ of an inch deep, although other depths are within the scope of the present invention, as long as the molded concrete layer  120  remains sufficiently thick in the recessed portion. The transition plate  105  is secured to the recessed portion of the molded concrete layer  120 . The transition plate  105  could be secured to the recessed portion of the molded concrete layer  120  by any suitable masonry fastener or in any other suitable way known to those of ordinary skill in the art. The transition plate  105  may be made of neoprene, metal or plastic, although other materials are within the scope of the present invention. 
     In the most interior area of the recessed portion, the transition plate  105  has a thickness substantially equal to the thickness of the recess, so that there is a smooth transition between the top surface  150  of the molded concrete layer  120  and a top surface of the transition plate  105 . The transition plate  105  can be curved so that there is also a smooth transition between the top surface of the transition plate  105  and the ground level. It should be noted that it is not necessary to affix the transition plate  105  to the ground, although to do so would not depart from the spirit of the present invention. 
     Reference is now made to  FIG. 3  of the drawings, in which there is shown a perspective view of the underside of the molded concrete layer  120  in accordance with the embodiment shown in FIG.  1 B. To provide additional support where necessary, an armature (shown in dotted outline at  135 ) may be provided within the molded concrete layer  120  around its periphery  170  and also through one or more cross-paths. In a non-limiting embodiment, the armature  135  may be composed of steel wires. Accordingly, the underside of the molded concrete layer  120  may include a plurality of ribs  310 ,  320  and a border  330  which occupy the volume in the neighbourhood of the armature  135 . 
     The molded concrete layer  120  should have a thickness which allows sufficient rigidity to support the weight of multiple users as well as the pressure resulting from skateboard maneuvers. It has been found that a 1.5 inch thick molded concrete layer  120  with a thickness of 6.5 inches in the neighbourhood of the armature  135  and having a compressive strength of at least 40 MPa (Megapascals) provides a suitable degree of rigidity. Other combinations of thickness and compressive strength are of course within the scope of the invention. Generally speaking, higher compressive strength is preferred in order to afford an increased resistance to shock and allow for a reduction in thickness of the molded concrete layer  120 . 
     One example of concrete having a suitable compressive strength and capable of being molded into a thin layer (on the order of a few inches) is self-leveling concrete. In particular, it has been found that a self-leveling concrete compound having a slump flow of at least 20 inches and a considerable degree of homogeneity is advantageous. Greater slump flow is preferred in order to afford a layer that fits the mold more accurately and has a smoother surface with fewer air pockets. However, it has been observed that too high a slump flow may lead to an inherent weakness in the compound once it solidifies. Therefore, if a self-leveling concrete is used, it is desirable although not essential that such concrete have a slump flow of between 20 and 28 inches. 
     A non-limiting example process for manufacturing the molded concrete layer  120  is now described with reference to FIG.  4 . Specifically, a mold having several complementary parts is prepared at step  410 . The mold is the negative of the intended shape of the molded concrete layer  120 . Thus, of importance is the shape of the inside surface of each part of the mold. The inside surface of the mold can also be provided with recesses in the positions where it is desired to place the optional armature  135 , around which will appear the reinforcement ribs  310 /beams  320 /border  330 . To avoid the onset of rust, the armature  135  may undergo a pre-processing step, e.g., one which involves pre-coating the armature  135  with epoxy and bathing it in an electrolytic solution. At step  420 , the complementary parts are closed onto one another, defining an interior space that has the desired shape of the concrete layer being manufactured. 
     A mixture of concrete is poured into the mold at step  430 . Due to the relatively small amount of the space between the parts of the mold (providing a thickness of the ensuing concrete layer that ranges from about 1.5 inches to about 6.5 inches in an example embodiment), suitable rigidity is provided through the use of a high-performance concrete compound having a compressive strength of preferably at least 40 MPa (Megapascals) and, even more preferably, greater than 60 MPa. To this end, it is advantageous to use a self-leveling concrete compound, which typically exhibits a higher compressive strength than ordinary concrete for a given thickness. Also, the use of self-leveling concrete is advantageous because it will have a relatively high degree of fluidity compared to ordinary concrete, allowing it to enter various areas of the mold that occupy a space that is too small to accommodate a slurry of ordinary poured concrete. Moreover, self-leveling concrete has a tendency to produce a mirror-like surface having a desirable smoothness. A non-limiting example of a self-leveling concrete compound that is suitable for use with the present invention is Domflex™, which has been developed by Tessier Récréo-Parc Inc., Nicolet, Quebec, Canada. 
     Next, a curing period  440  ensues, during which the concrete settles and acquires a smoothness and a rigidity. During this phase the mold and its contents are heat-treated and kept at a high humidity level. A temperature of 60 degrees Celsius and a humidity level of greater than 90% have been found to be suitable, although other combinations are within the scope of the present invention. At step  450 , the parts of the mold are removed and the remaining molded concrete layer  120  is allowed to cool down at step  460 . At this point, the molded concrete layer  120  is ready to be mounted onto a support structure  110  using the fastening techniques described previously. 
     While specific embodiments of the present invention have been described and illustrated, it will be apparent to those skilled in the art that numerous modifications and variations can be made without departing from the scope of the invention as defined in the appended claims.

Summary:
A recreational ramp suitable for use with wheeled vehicles, including a support structure and a molded concrete layer mounted on the support structure. The layer includes a sloping region that extends from a ground level to an above-ground level. Also, a process for the fabrication of a molded concrete layer for such a recreational ramp. The process includes preparing a mold from complementary parts, closing the parts onto one another, thus defining an interior space representative of a concrete layer, pouring concrete mixture into the mold; allowing the concrete to settle and separating the complementary parts of the mold to expose the molded concrete layer. Embodiments of the invention offer the advantages of conventional concrete, i.e., a smooth, quiet and durable surface for riding, while the ramp as a whole remains lightweight and less bulky as compared with conventional concrete ramps. A particularly advantageous embodiment uses self-leveling concrete.