MONOLITHIC PROTECTIVE WATERPROOFING SYSTEM

A monolithic protective waterproofing system for light rail and intermodal class I railroad bridges comprehends a multiple layer product installed in-situ. It includes a sprayed on primer, a sprayed on membrane having a thickness of between 60 and 120 mils, a second sprayed on layer of membrane having a thickness of about 20 mils that is utilized as an adhesive that is rapidly covered with a resilient mat having a thickness of between approximately 6 and 12 mm, a second layer of a sprayed on primer and a top coat of sprayed on membrane of approximately 30 to 50 mils. Both the product and method of installation are disclosed.

FIELD

The present disclosure relates to a waterproofing system for railroad bridge decks and similar structures and more particularly to a monolithic protective waterproofing system or product for light rail and intermodal class I railroad bridges and similar structures and a method of installing same.

BACKGROUND

As the nation's transportation infrastructure ages, attention is returning to enhancing the service life of existing structures and ensuring that new structures are built with the most modern techniques and materials to provide the maximum attainable service life.

One of the most difficult service environments exists on light rail transit bridges and intermodal class I railroad bridges. Heavy loads, exposure to high humidity and often salt spray and the placement of rock ballast on the bridge deck which supports the railway ties and track all contribute to aging of the structure. The ballast has a particularly deleterious effect on concrete bridge decks as sharp corners and edges of the ballast (which is crushed rock) concentrates loads. What begins as surface cracking and spalling leads to significant deterioration of the concrete as water and often salt flows into the deck itself. Deterioration through the freeze-thaw cycle and corrosion of reinforcing steel in the concrete follow. Even steel bridge decks are not immune from such deterioration as the ballast is capable of puncturing, abrading and wearing even the most rugged deck coatings. Cracks, gouges and discontinuities in a deck coating commence a process of deterioration by rusting.

From this background, it is apparent that materials, systems, products and processes of application which extend the service life of railroad bridges and similar structures are highly desirable. The present invention is so directed.

SUMMARY

The present invention provides a monolithic protective waterproofing system or product for light rail and intermodal class I railroad bridges and similar structures and a method of installing same. The waterproofing system is a multi-layer product installed in-situ on either new structures or structures previously in service. It includes a primer, an elastomeric membrane having a thickness of between approximately 60 and 120 mils, a second layer of elastomeric membrane having a thickness of 20 mils that is utilized as an adhesive that is rapidly covered and upon which is pressed a rubber mat having a thickness of approximately 8 mm, a second layer of a primer and a top coat of elastomeric membrane of between approximately 30 to 50 mils.

Before the various layers are applied to a bridge deck, the deck is cleaned by, for example, sand blasting to remove any loose material such as rust, spalled or damaged concrete, previous coatings and anything that might interfere with achieving a tight and continuous bond between the bridge deck and the product. New bridge decks or recently replaced decks may only require inspection. Then, the first layer of primer is applied and allowed to dry followed by the first layer of membrane which is also allowed to dry. A second, thinner layer of membrane, which functions as an adhesive, is next applied followed quickly by application of adjacent strips of a resilient, preferably rubber, mat. The resilient mat is supplied in rolls of, for example, four or six feet by fifty feet (1.219 or 1.829 meters by 15.24 meters). A second layer of primer is then applied to the top of the resilient mats and a final layer of membrane is sprayed onto the primer and mats, completing the installation process. The track ballast, railroad ties and railroad track are then installed and the bridge is placed in or returned to service.

It is thus an aspect of the present invention to provide a monolithic protective waterproofing product for railroad bridges and the like.

It is a further aspect of the present invention to provide a method of building up a monolithic protective waterproofing product in-situ on a railroad bridge or similar structure.

It is a still further aspect of the present invention to provide a monolithic protective waterproofing product having layers of primer, membrane and resilient mat.

It is a still further aspect of the present invention to provide a monolithic protective waterproofing product having first layers of primer and membrane, a resilient, rubber mat and additional layers of primer and membrane on a railroad bridge or similar structure.

It is a still further aspect of the present invention to provide a method of building up a monolithic protective waterproofing product having layers of primer, membrane and resilient mat on a railroad bridge.

It is a still further aspect of the present invention to provide a method of building up a monolithic protective waterproofing product having first layers of primer and membrane, a resilient, rubber mat and additional layers of primer and membrane on a railroad bridge or similar structure.

DETAILED DESCRIPTION

With reference toFIG. 1, a railroad bridge or similar structure either new or undergoing updating, repair, refurbishment or rehabilitation is illustrated and generally designated by the reference number10. The bridge10may be disposed across a river or a stream12or other obstacle and includes a horizontal deck14which may be fabricated of wood, concrete or steel upon which one or multiple railroad tracks20are supported and carried. Each railroad track20includes ballast (crushed rock)22which supports ties24which, in turn support and locate the rails26of the track20. Because the bridge10is undergoing repair or rehabilitation, the ballast22, the ties24and the rails26have been removed from the bridge deck14, as illustrated.

It will be appreciated that the product40and the method of the present invention is intended for and is usable on both new construction and bridges10that have been in service and are undergoing updating, repair, refurbishment or rehabilitation. In the latter case, a first or preliminary step to the in-situ installation of the waterproofing product40of the present invention is cleaning the bridge deck14and removal of any loose material such as rust, spalled or damaged concrete, previous coatings and anything that might interfere with achieving a tight and continuous bond between the bridge deck14and the waterproofing product40. If the bridge deck14is concrete and is spalled, pitted or contains other defects, it must be sand blasted or metal shot blasted through the use of conventional sand or metal shot blasting equipment32and an operator or technician34to remove laitance and other contamination and then patched with a concrete patching material. If the bridge deck14is steel it should be prepared similarly to SP6or near white. If the bridge deck14is new or has been recently replaced, this step may simply involve inspection of the bridge deck surface to ensure its integrity and relative smoothness and cleanliness.

Referring now toFIGS. 2 and 3and7, the building up or in-situ installation of the waterproofing product40according to the present invention begins with the spraying, squeegeeing or rolling of a first layer of primer42onto the bridge deck14. The first layer of primer42is preferably applied at a rate of approximately 130 to 200 square feet per gallon (3.12 to 4.8 square meters per liter) over concrete surfaces and at a rate of approximately 200 to 400 square feet per gallon (4.8 to 9.6 square meters per liter) over steel surfaces. If the bridge deck14is steel and has a 5 mil profile or better, i.e., less, use of the first layer of primer42is not necessary. The first layer of primer42is preferably one of polyurethane, polyurea, methyl methacrylate, a polyurethane hybrid or an acrylic. The first layer of primer42is preferably allowed to become tack free before the next step is undertaken.

The first layer or base coat of membrane44is then sprayed on the first layer of primer42at a rate of approximately 20 square feet per gallon (0.48 square meters per liter) to a minimum thickness of approximately 80 mils and allowed to cure. The thickness of the first layer or base coat of membrane44may be increased to 120 mils and even thicker if desired. The first layer of membrane44is preferably an elastomer and is one of polyurethane, polyurea, methyl methacrylate, a polyurethane hybrid, bitumen or an acrylic.

Referring now toFIGS. 2,4,6and7, a second, thinner layer of elastomeric membrane46is sprayed onto the surface of the first layer of membrane44by an operator or technician34just prior to the application of a layer of a resilient mat50. The resilient mat50is unrolled, preferably in closely adjacent transverse or longitudinal strips, on the bridge deck14. Transverse strips or panels of the resilient mat50are illustrated in solid lines inFIG. 2and longitudinal strips or panels of the resilient mat50are illustrated by a phantom line inFIG. 2. The strips or panels of the resilient mat50are pressed into position by a cushioned roller52on a moveable frame or trolley54that also carries a roll56of the resilient mat50. As such, the second layer of membrane46functions as an adhesive which, because it is still liquid and the resilient mat50is pressed into it, will flow and enter surface irregularities, interstices and voids51in the resilient mat50, intimately bonding it to the first layer of membrane44.

The resilient mat50(and the roll56thereof) is preferably rubber and is, or is similar to, a product sold under the trademark Regupol 6010 for a type of impact sound acoustic underlayment manufactured by Regupol Pty. Ltd., Smeaton Grange, N.S.W. The resilient mat50may also be constituted of or include reclaimed rubber, ground rubber, virgin rubber, vinyl, polyvinylchloride or polyvinyl acetate preferably having approximately 40% air filled interstices or voids51by volume that has been formed into a continuous sheet that, for ease of handling and installation, is preferably four or six feet (1.219 or 1.829 meters) wide and is cut and rolled into rolls of, for example, fifty feet (15.24 meters) in length. It will be appreciated that the spring rate of the resilient mat50may be increased by reducing the volume of the air filled voids51to 30% or less or may be reduced by increasing the volume of the air filled voids51to 50% or more. Different materials and combinations thereof will also provide differing spring rates. The thickness of the resilient mat50may be varied from 6 millimeters (0.236 inches) or less to 12 millimeters (0.472 inches) or more, 8 millimeters (0.315 inches) having been found to be a widely useful, nominal thickness.

If desired, the resilient mat50, in the same or various thicknesses, may be installed in additional layers depending upon protection, sound transfer, vibration dampening and load carrying requirements. To install multiple layers of the resilient mat50, an additional layer of the thinner membrane layer46is applied to the upper surface of each previous layer of the resilient mat(s)50and an additional layer of resilient mat50is installed while the additional thinner membrane layer46is still liquid and pressed into intimate contact with the thinner membrane layer46on the upper surface of the previous layer of the resilient mat50by the cushioned roller52so that a portion of the additional thinner membrane layer46is forced into the voids and interstices of the resilient mat50, as described above. If multiple layers of the resilient mat50are installed, care should be taken to stagger or offset the seams between adjacent resilient mats50of each layer.

Referring now toFIGS. 5,6and7, after the bridge deck14is completely covered by the resilient mats50, a second layer of primer62is sprayed onto the surface of the resilient mats50at a rate of 30 to 50 square feet per gallon (0.72 to 1.2 square meters per liter). When the second layer of primer62is only slightly tacky, a third layer of elastomeric membrane64of one of the materials previously listed is sprayed on the second layer of primer62to a thickness of approximately 30 to 50 mils and preferably about 40 mils.

After these steps, installation of the monolithic waterproofing product40is complete and the ballast22, the ties24and the rails26of the railroad track20may all be installed or re-installed on the waterproofing product40on the bridge deck14.

It will be appreciated that the monolithic waterproofing product40of the present invention provides numerous benefits. The waterproofing product40, particularly because of the resilient mat(s)50, is thicker than similar products and the resilient mats50may be applied, as noted above, in multiple layers. Such increased thickness is projected to provide better sound and vibration attenuation than competing products. The preferred resilient mat50, described above, contains approximately 40% air filled voids or interstices which allow the membrane layers to penetrate the resilient mats50and achieve an intimate bond therewith. This stiffens the entire waterproofing product40and provides a mechanical lock with the resilient mats50.

Additionally, because of the material and surface finish of the third and final layer of membrane64, namely tough and stiffly resilient, which is also the result of the resilient mats50, the ballast22will create small depressions or pits in the surface of the membrane64but will not puncture it. This action tends to hold the ballast22in place, thereby providing a more stable roadbed and generating less noise as trains pass. Finally, because of the ease of building up the various layers of the waterproofing product40and the speed and uniformity with which the resilient mats50are installed, not only is the final product better from the standpoints of strength, durability and resistance to water penetration but its total cost (material and installation) is also less than competing products.