Abstract:
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.

Description:
FIELD 
       [0001]    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 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0003]    As the nation&#39;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. 
         [0004]    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. 
         [0005]    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 
       [0006]    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. 
         [0007]    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. 
         [0008]    It is thus an aspect of the present invention to provide a monolithic protective waterproofing product for railroad bridges and the like. 
         [0009]    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. 
         [0010]    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. 
         [0011]    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. 
         [0012]    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. 
         [0013]    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. 
         [0014]    Further aspects, advantages and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0015]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0016]      FIG. 1  is a perspective view of a light rail bridge or similar structure from which the ballast, railroad ties and railroad track have been removed which is undergoing a cleaning step prior to installation of the waterproofing product of the present invention; 
           [0017]      FIG. 2  is a top, plan view of a railroad bridge or similar structure schematically and sequentially showing certain steps of the method of installation of the waterproofing product according to the present invention; 
           [0018]      FIG. 3  is a fragmentary, sectional, schematic view illustrating the application of the first layer of primer and the first layer of membrane to the bridge deck; 
           [0019]      FIG. 4  is a fragmentary, sectional, schematic view illustrating the application of the second layer of membrane and the resilient mat to the bridge deck; 
           [0020]      FIG. 5  is a fragmentary, sectional, schematic view illustrating the application of the second layer of primer and the second layer of membrane to the bridge deck; 
           [0021]      FIG. 6  is a greatly enlarged, fragmentary, sectional view of the layers of a monolithic waterproofing product according to the present invention installed on a bridge deck or similar structure; and 
           [0022]      FIG. 7  is a flow chart presenting the installation steps of a monolithic waterproofing product according to the present invention, including a bridge deck preparation step. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0024]    With reference to  FIG. 1 , a railroad bridge or similar structure either new or undergoing updating, repair, refurbishment or rehabilitation is illustrated and generally designated by the reference number  10 . The bridge  10  may be disposed across a river or a stream  12  or other obstacle and includes a horizontal deck  14  which may be fabricated of wood, concrete or steel upon which one or multiple railroad tracks  20  are supported and carried. Each railroad track  20  includes ballast (crushed rock)  22  which supports ties  24  which, in turn support and locate the rails  26  of the track  20 . Because the bridge  10  is undergoing repair or rehabilitation, the ballast  22 , the ties  24  and the rails  26  have been removed from the bridge deck  14 , as illustrated. 
         [0025]    It will be appreciated that the product  40  and the method of the present invention is intended for and is usable on both new construction and bridges  10  that 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 product  40  of the present invention is cleaning the bridge deck  14  and 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 deck  14  and the waterproofing product  40 . If the bridge deck  14  is 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 equipment  32  and an operator or technician  34  to remove laitance and other contamination and then patched with a concrete patching material. If the bridge deck  14  is steel it should be prepared similarly to SP  6  or near white. If the bridge deck  14  is 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. 
         [0026]    Referring now to  FIGS. 2 and 3  and  7 , the building up or in-situ installation of the waterproofing product  40  according to the present invention begins with the spraying, squeegeeing or rolling of a first layer of primer  42  onto the bridge deck  14 . The first layer of primer  42  is 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 deck  14  is steel and has a 5 mil profile or better, i.e., less, use of the first layer of primer  42  is not necessary. The first layer of primer  42  is preferably one of polyurethane, polyurea, methyl methacrylate, a polyurethane hybrid or an acrylic. The first layer of primer  42  is preferably allowed to become tack free before the next step is undertaken. 
         [0027]    The first layer or base coat of membrane  44  is then sprayed on the first layer of primer  42  at 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 membrane  44  may be increased to 120 mils and even thicker if desired. The first layer of membrane  44  is preferably an elastomer and is one of polyurethane, polyurea, methyl methacrylate, a polyurethane hybrid, bitumen or an acrylic. 
         [0028]    Referring now to  FIGS. 2 ,  4 ,  6  and  7 , a second, thinner layer of elastomeric membrane  46  is sprayed onto the surface of the first layer of membrane  44  by an operator or technician  34  just prior to the application of a layer of a resilient mat  50 . The resilient mat  50  is unrolled, preferably in closely adjacent transverse or longitudinal strips, on the bridge deck  14 . Transverse strips or panels of the resilient mat  50  are illustrated in solid lines in  FIG. 2  and longitudinal strips or panels of the resilient mat  50  are illustrated by a phantom line in  FIG. 2 . The strips or panels of the resilient mat  50  are pressed into position by a cushioned roller  52  on a moveable frame or trolley  54  that also carries a roll  56  of the resilient mat  50 . As such, the second layer of membrane  46  functions as an adhesive which, because it is still liquid and the resilient mat  50  is pressed into it, will flow and enter surface irregularities, interstices and voids  51  in the resilient mat  50 , intimately bonding it to the first layer of membrane  44 . 
         [0029]    The resilient mat  50  (and the roll  56  thereof) 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 mat  50  may 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 voids  51  by 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 mat  50  may be increased by reducing the volume of the air filled voids  51  to 30% or less or may be reduced by increasing the volume of the air filled voids  51  to 50% or more. Different materials and combinations thereof will also provide differing spring rates. The thickness of the resilient mat  50  may 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. 
         [0030]    If desired, the resilient mat  50 , 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 mat  50 , an additional layer of the thinner membrane layer  46  is applied to the upper surface of each previous layer of the resilient mat(s)  50  and an additional layer of resilient mat  50  is installed while the additional thinner membrane layer  46  is still liquid and pressed into intimate contact with the thinner membrane layer  46  on the upper surface of the previous layer of the resilient mat  50  by the cushioned roller  52  so that a portion of the additional thinner membrane layer  46  is forced into the voids and interstices of the resilient mat  50 , as described above. If multiple layers of the resilient mat  50  are installed, care should be taken to stagger or offset the seams between adjacent resilient mats  50  of each layer. 
         [0031]    Referring now to  FIGS. 5 ,  6  and  7 , after the bridge deck  14  is completely covered by the resilient mats  50 , a second layer of primer  62  is sprayed onto the surface of the resilient mats  50  at a rate of 30 to 50 square feet per gallon (0.72 to 1.2 square meters per liter). When the second layer of primer  62  is only slightly tacky, a third layer of elastomeric membrane  64  of one of the materials previously listed is sprayed on the second layer of primer  62  to a thickness of approximately 30 to 50 mils and preferably about 40 mils. 
         [0032]    After these steps, installation of the monolithic waterproofing product  40  is complete and the ballast  22 , the ties  24  and the rails  26  of the railroad track  20  may all be installed or re-installed on the waterproofing product  40  on the bridge deck  14 . 
         [0033]    It will be appreciated that the monolithic waterproofing product  40  of the present invention provides numerous benefits. The waterproofing product  40 , particularly because of the resilient mat(s)  50 , is thicker than similar products and the resilient mats  50  may 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 mat  50 , described above, contains approximately 40% air filled voids or interstices which allow the membrane layers to penetrate the resilient mats  50  and achieve an intimate bond therewith. This stiffens the entire waterproofing product  40  and provides a mechanical lock with the resilient mats  50 . 
         [0034]    Additionally, because of the material and surface finish of the third and final layer of membrane  64 , namely tough and stiffly resilient, which is also the result of the resilient mats  50 , the ballast  22  will create small depressions or pits in the surface of the membrane  64  but will not puncture it. This action tends to hold the ballast  22  in 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 product  40  and the speed and uniformity with which the resilient mats  50  are 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. 
         [0035]    The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.