Abstract:
The present invention relates generally to an improved expansion joint construction and a method for creating an expansion joint between adjacent roadway slabs. The invention relates specifically to the use of an epoxy blend having improved set times that can be applied in cold weather.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to an improved expansion joint construction system and a method for creating an expansion joint for bridges, roadways, parking structures and the like wherein adjacent slabs are subject to movement and a flexible seal is required in the expansion gap between adjacent slabs. The invention relates specifically to an expansion joint system which provides a high strength, impact resistant and semi-flexible joint nose, allows various liquid or preformed seals to be used in the gap to absorb movement, can be applied in cold weather, and sets in a short amount of time. 
       BACKGROUND OF THE INVENTION 
       [0002]    Roadways, bridges, and parking structures are typically built of sections or slabs arranged with expansion gaps between adjacent sections to account for the natural expansion and contraction of the sections as temperatures change, and vertical movement caused by vehicular traffic. The expansion gaps need to be sealed to prevent water from getting beneath the sections and leading to rusting of steel substructures, heaving in freezing temperatures, or otherwise deteriorating components of the slabs. Seals are also needed to prevent corrosives, such as salt, and other debris from getting in the joint and causing damage to the sections. When gaps or seals are damaged, or have deteriorated over time, it is necessary to repair the expansion joint and create a new seal to prevent any additional damage. When repairing expansion gaps it is advantageous to be able to complete the repair process as quickly as possible to minimize the time that traffic must remain off the expansion gap. 
         [0003]    Various materials and systems have been implemented to provide flexible seals that can move with the movement of adjacent slabs and prevent water and/or debris from getting into the expansion gap and causing damage. For a discussion of prior systems see Cathey et al. (U.S. Pat. No. 5,190,395). 
         [0004]    In new roadway, bridge, or parking structure construction, time may not be a critical factor in the installation of a joint seal. However, in remedial applications, time is a critical factor, and repair and roadway down time should be minimized so that vehicle traffic can return. However, if traffic is returned before the nosings and seal materials are set, additional damage may be done to the nosings and seal, significantly diminishing the usable life of the seal. In addition, in colder weather prior systems generally take longer to set and may require additional steps and components to install, effectively making the systems commercially infeasible when temperatures drop below 40 degrees Fahrenheit. For example, at 40 degrees Fahrenheit a prior system may take around nine hours to cure or set. Some systems have added supplemental heat and used additives to accelerate the set time, however, even with these additional steps, prior systems do not set as quickly as the present invention and add to the expense of installation. For example, at 40 degrees Fahrenheit a prior system may mix in an accelerator agent and provide supplemental heat and still may take around three and a half hours to cure or set. Such a system would, therefore, not be recommended for installation in colder temperatures. 
       SUMMARY OF THE INVENTION 
       [0005]    It is an object of the present invention to provide a joint construction system that sets quickly to minimize down time. 
         [0006]    It is a further object of the present invention to provide a joint construction system that can set quickly in cold temperatures. 
         [0007]    It is a further object of the present invention to provide a joint construction system that can set quickly in cold temperatures without the need to include additives for accelerating the set time. 
         [0008]    It is a further object of the present invention to provide a joint construction system that can set quickly in cold temperatures without the need to add supplemental heat during the installation process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIGS. 1 through 3  illustrate sectional views showing an installation sequence of an expansion joint system of the present invention; and 
           [0010]      FIGS. 4 through 6  illustrate sectional views showing an installation sequence of an expansion joint system of the present invention in a remedial application having concrete slabs with an asphalt overlay. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    The figures and the following description describe two examples of the installation sequence of an expansion joint system of the present invention. As one having skill in the art will recognize, the installation sequence may be varied, may be applied to new constructions or may be applied in other remedial applications and remains within the scope and spirit of the invention. In addition, the installation sequence may be applied in a number of uses, including but not limited to roadways, bridges, and parking structures. 
         [0012]      FIG. 1  shows sectional views of a pair of adjacent slabs  12  and  14 . In between slab  12  and slab  14  is an expansion gap to permit necessary movement of the slabs. Recesses  16  and  18  are shown in each adjacent slab  12  and  14 . The bases of recesses  16  and  18  are approximately parallel to the surface of the roadway  20  and  22 . The sidewalls of recesses  16  and  18  are approximately parallel to the walls of slab  12  and  14  that define the expansion gap and approximately perpendicular to the surface of roadway  20  and  22 . 
         [0013]    This is the general starting point for the installation sequence between two adjacent concrete slabs. One can arrive at this point through a variety of ways. In new construction the slabs may be created with the appropriate recesses and placed such that they define an appropriate expansion gap. In remedial applications, a prior seal may need to be removed and the recesses cleared of prior header material or cut out of the concrete through means known in the art. 
         [0014]    Once recesses  16  and  18  are defined in slabs  12  and  14 , they should be prepared for the installation sequence. Preparation of the recess requires the surfaces of the recess to be cleaned and dried sufficiently to allow the mortar to adhere to the recess surfaces. In a preferred embodiment, recesses  16  and  18  will be thoroughly cleaned to remove all rust, corrosion, and debris and will be fully dried. For example, one may first sandblast the recess to remove rust and corrosion. Then the sand and other debris can be removed by blowing the recesses with oil free compressed air. As one having skill in the art will recognize, any level of preparation that allows the mortar to adhere to the recess surfaces falls within the scope and spirit of the invention. 
         [0015]    After recesses  16  and  18  have been prepared, temporary form  24  is installed in the gap between slab  12  and slab  14  with the top flush with or above the surface of roadway  20  and  22 . Temporary form  24  is preferably made of extruded polystyrene, but may be made of other lightweight materials. In some embodiments, other materials may be attached to temporary for  24  to facilitate the removal of the form later in the process. 
         [0016]    Prior to filling recesses  16  and  18 , the mortar is mixed. The mortar must be an epoxy-urethane blend that can be applied in various temperatures, including temperatures under 40 degrees, and set in less than two hours. An example of one such mortar is Silspec 1000 from Silicone Specialties, Inc. In a preferred embodiment the epoxy-urethane blend, when set, has a tensile strength of approximately 1500 pounds per square inch (psi), elongation properties of approximately 30% to 40%, a compressive strength of approximately 3500 psi, and a Shore D hardness of approximately 60 to 70. In a preferred embodiment, the mortar is kept in two components that are mixed to create the epoxy-urethane blend prior to installing the mortar. In a preferred embodiment, after the components of the mortar are mixed, sand and other aggregate such as crushed stone or flint is mixed with the mortar. As one having skill in the art will recognize the mortar does not need to include the sand or other aggregate to remain within the scope and spirit of the present invention. 
         [0017]    Once the mortar and any desired aggregate are mixed together, it is poured into recesses  16  and  18 .  FIG. 2  shows mortar mixture in recesses  16  and  18 . The mortar mixture is poured to fill recesses  16  and  18  near or up to the surface of roadway  20  and  22 . Unlike prior systems, there is no need to provide a primer layer between the mortar and the concrete, however, the inclusion of a primer step remains within the scope and spirit of the present invention. In a preferred embodiment, once the mortar mixture is poured into recesses  16  and  18 , it is compacted. 
         [0018]    The mortar mixture is then allowed to set and/or cure throughout to create nosings  26  and  28 . In 40 degree Fahrenheit weather, the mortar mixture can set in approximately one hour. In 10 degree Fahrenheit weather, the mortar mixture can set in approximately one and a half hours. If the mortar mixture is only filled to near the level of the roadway surface, a separate layer of mortar that corresponds to the finish of roadway  20  and  22  may be applied up to the level of the surface of roadway  20  and  22 . As one skilled in the art will recognize, the additional layer of mortar is not necessary and remains within the scope and spirit of the invention. 
         [0019]    Once nosings  26  and  28  are set, temporary form  24  is removed as is illustrated by the dotted lines in  FIG. 2 . In a preferred embodiment, the edges of nosings  26  and  28  may be beveled using a grinder or other tool. As one having skill in the art will recognize, the edges may be beveled in other ways or the beveling step may be skipped and remain within the scope and spirit of the present invention. 
         [0020]    Next, a seal is created between slabs  12  and  14 , preferably at nosings  26  and  28 . In this embodiment a seal is created by inserting and wedging backer rod  32  in the gap between the nosings as shown in  FIG. 3 . Backer rod  32  may be made of a closed cell polyethelene foam or other similar materials. Backer rod  32  is used as a shelf to hold silicone sealant  30  in place while silicone sealant  30  is applied in liquid form into the gap and on top of backer rod  32 . As one having skill in the art will recognize, any temporary or permanent backing may be used in place of backer rod  32  to provide a base for applying the seal and remains within the scope and spirit of the invention. In addition, one having skill in the art will recognize that other seals such as compression seals, pre-compressed foams, closed cell foam seals, pre-formed silicone profile seals, pressurized compression seals, liquid applied seals, liquid applied joint sealants, or other seals may be used in place of or in conjunction with the described seal and remain within the scope and spirit of the invention. 
         [0021]      FIGS. 4 through 6  illustrate the use of the present expansion joint system to install an expansion joint in a concrete slabs  40  and  42  which have been overlaid with asphalt overlay  48  and  50 .  FIG. 4  shows sectional views of a pair of adjacent slabs  40  and  42  with asphalt overlay  48  and  50  on top of slabs  40  and  42  respectively. In between slab  40  and slab  42  is an expansion gap to permit necessary movement of the slabs. In this embodiment, recesses  44  and  46  are shown as an area of the roadway adjacent to the expansion gap where asphalt overlays  48  and  50  are missing above each adjacent slab  40  and  42 . The bases of recesses  44  and  46  are the top surfaces of slab  40  and slab  42 . The sidewalls of recesses  44  and  46  are approximately parallel to the walls of slab  40  and  42  that define the expansion gap and approximately perpendicular to the surface of the surface of asphalt overlays  48  and  50 . 
         [0022]    As discussed above, one can arrive at this point through a variety of ways. In a remedial application with an asphalt overlay, sections of asphalt overlay  48  and  50  may cut out down to the surface of concrete slabs  40  and  42  and removed. 
         [0023]    Once recesses  44  and  46  are defined, they should be prepared for the installation sequence. As discussed above, preparation of the recess requires the surfaces of the recess to be cleaned and dried sufficiently to allow the mortar to adhere to the recess surfaces. In a preferred embodiment, one may first sandblast the recess to remove rust and corrosion, and then blow recesses  44  and  46  with oil free compressed air to remove the sand and other debris. After recesses  44  and  46  have been prepared, temporary form  52  is installed in the gap between slab  40  and slab  42  with the top flush with or above the surface of asphalt overlay  48  and  50 . 
         [0024]    Prior to filling recesses  44  and  46 , the mortar is mixed. As discussed above, the mortar must be an epoxy-urethane blend that can be applied in various temperatures, including temperatures under 40 degrees, and set in less than two hours. An example of one such mortar is Silspec 1000 from Silicone Specialties, Inc. In a preferred embodiment the epoxy-urethane blend, when set, has a tensile strength of approximately 1500 pounds per square inch (psi), elongation properties of approximately 30% to 40%, a compressive strength of approximately 3500 psi, and a Shore D hardness of approximately 60 to 70. In a preferred embodiment, the mortar is kept in two components that are mixed to create the epoxy-urethane blend prior to installing the mortar. In a preferred embodiment, after the components of the mortar are mixed, sand and other aggregate such as crushed stone or flint is mixed with the mortar. 
         [0025]    Once the mortar and any desired aggregate are mixed together, it is poured into recesses  44  and  46 .  FIG. 5  shows mortar mixture in recesses  44  and  46 . Mortar mixture fills recesses  44  and  46  up to the surface of asphalt overlay  48  and  50 . Unlike prior systems, there is no need to provide a primer layer between the mortar and the concrete, however, the inclusion of a primer step remains within the scope and spirit of the present invention. In a preferred embodiment, once the mortar mixture is poured into recesses  44  and  46 , it is compacted. 
         [0026]    Mortar mixture is then allowed to set and/or cure throughout to create nosings  54  and  56 . In 40 degree Fahrenheit weather, the mortar mixture can set in approximately one hour. In 10 degree Fahrenheit weather, the mortar mixture can set in approximately one and a half hours. Once nosings  54  and  56  are set, temporary form  52  is removed as is illustrated by the dotted lines in  FIG. 5 . In a preferred embodiment, the edges of nosings  54  and  56  may be beveled using a grinder or other tool. 
         [0027]    Next, a seal is created between adjacent slabs  40  and  42  at nosings  54  and  56 . In this embodiment a seal is created by inserting and wedging backer rod  60  in the gap between the nosings as shown in  FIG. 6 . Backer rod  60  may be made of a closed cell polyethylene foam rubber or other similar materials. Backer rod  60  is used as a shelf to hold silicone sealant  58  in place while silicone sealant  58  is applied in liquid form into the gap and on top of backer rod  60 . As one having skill in the art will recognize, other seals such as compression seals, pre-compressed foams, closed cell foam seals, pre-formed silicone profile seals, pressurized compression seals, liquid applied seals, liquid applied joint sealants, or other seals may be used in place of or in conjunction with the described seal and remain within the scope and spirit of the invention. 
         [0028]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.