Patent Application
20130089374
The present invention relates to the field of compositions and methods used in connection with the application, maintenance and repair of asphalt paving. More particularly, the present invention relates to methods and materials used in sealing seams in asphalt paving.
One of the major problems that arises in applying the top course paving of a roadway is the sealing of the joint or “seam” between pavement sections or “lanes”. Since pavement sections are applied in widths determined by the width of the paver, they are typically applied in multiple passes of the paver, with each pass loosely referred to as a “lane”. This means that there is time interval between paving one lane and the next adjacent lane, during which time the asphalt of the preceding lane has cooled to ambient temperature. The temperature difference between the cooled pavement of the preceding lane and the fresh asphalt of the next adjacent lane makes for a weak bond between the two sections along the seam. This weakness often leads to cracking in the seam area, which allows water to penetrate into the seam and, with freezing and thawing, produces progressive deterioration and separation of the pavement sections.
Even when a strong bond is initially achieved in the seam between lanes, the expansion and contraction of the adjacent lanes under varying weather conditions will subject the seam to stresses and shear forces that will tend to degrade the joint over time and cause it to fail, due to the limited elasticity and tensile strength of asphalt paving materials. In effect, a paving seam has to function as an “expansion joint” between adjacent lanes, but the asphalt concrete typically applied in the seam area does not have the right mechanical properties to serve this function.
In an effort to address the problems associated with seam sealing, two approaches have been tried. The first approach is to reheat an area of the previously cooled lane adjacent to the seam to approximately the same temperature as the hot asphalt applied to the new lane, so that the reheated area will fuse with the fresh paving. An example of this method is taught by the patent application of Chandler (US2010/0021233). But the limited extent to which applied heat can penetrate downward and laterally into the asphalt of the preceding lane means that there will always be some juncture along which hot asphalt is interfacing with cooled asphalt, thereby producing a deficient bond.
The second approach to the seam sealing dilemma involves the use of a joint-sealing tape. Such tapes typically comprise a mixture of soft asphalt and rubber, and they are inserted into the seam after the two adjoining pavement sections have been laid down. An example of this method is described in the Hegemann U.S. Pat. No. 5,981,061. Problems associated with this method include gaps between the tape and the asphalt and failure of the tape to penetrate deeply enough into the seam. Furthermore, since this method involves applying adhesive between two pavement sections at ambient temperature, it misses the opportunity to use the elevated temperature of the fresh hot asphalt to improve the curing of the adhesive so as to form a stronger bond.
The present invention introduces a new method of sealing the seam between two adjacent sections of asphalt pavement. Instead of a tape applied after the adjoining sections have been paved, the present invention deploys an adhesive elastomeric gasket which completely envelopes the vertical faces of the adjacent lanes on three sides—i.e., above, below and along each face. Since the gasket extends partly underneath each section of paving, it is laid down before each lane is paved, thereby taking advantage of the heat of the fresh asphalt to effectively and rapidly cure the adhesive component of the gasket to insure a strong bond on both sides of the seam.
The present invention comprises a gasket “carpet” that is laid down prior to the paving of the initial section or lane of a roadway. An example of such a gasket is shown in
The first and second hinge means 1718 preferably comprise a flexible strip of the same elastomeric material from which the entire gasket 10 is fabricated. Each of the two top flanges 1516 is a rectangular sheet, which is flat or, as depicted in
The gasket 10 is made of a water-impermeable elastomeric material that is resistant to environmental extremes of temperature and humidity and can withstand prolonged exposure to heat, cold, ozone, ultra-violet radiation, and hydrocarbons. The gasket elastomer must also must have high tensile and tear strength and remain flexible under compression and elongation over a broad temperature range. Preferred gasket materials are nitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), and/or hydrogenated carboxylated nitrile butadiene rubber (HXNBR). In order to increase its adhesiveness and protect it from oxidative and chemical degradation, the contact surfaces of the gasket 10 is coated with an adhesive resin 19 (
The foregoing summarizes the general design features of the present invention. In the following sections, specific embodiments of the present invention will be described in some detail. These specific embodiments are intended to demonstrate the feasibility of implementing the present invention in accordance with the general design features discussed above. Therefore, the detailed descriptions of these embodiments are offered for illustrative and exemplary purposes only, and they are not intended to limit the scope either of the foregoing summary description or of the claims which follow.
As shown in
Next, as depicted in
The foregoing process is repeated when the second pavement section 12 is laid down over the other side of the footing sheet 13, as depicted in
The resulting configuration of the gasket 10, as shown in
Although the preferred embodiment of the present invention has been disclosed for illustrative purposes, those skilled in the art will appreciate that many additions, modifications and substitutions are possible, without departing from the scope and spirit of the present invention as defined by the accompanying claims.
