Patent Publication Number: US-2004055235-A1

Title: Concrete construction with control joint protective strip

Description:
FIELD OF THE INVENTION  
       [0001] The present invention pertains to concrete building materials, and more particularly to a concrete construction having one or more crack control/expansion joints and having a crack control/expansion joint protective strip.  
       BACKGROUND OF THE INVENTION  
       [0002] Concrete is often used as a building material in the construction of commercial buildings and other structures. It is common to form individual concrete wall sections by pouring concrete into forms which have been arranged on a horizontal surface, such as a slab of concrete forming the floor of a building. When the concrete has cured, the wall sections are lifted, or tilted to a vertical orientation to form the walls of the building. An inherent characteristic of concrete is that it will shrink as it cures, due to the loss of moisture during the curing process. Shrinkage of the concrete creates internal stresses which, if not addressed in the formation of the concrete slab, will cause random stress cracks to develop throughout the concrete slab. Therefore, a common practice in the formation of concrete slabs is to control the location of shrinkage cracks by forming expansion control joints which, if properly formed, will define where stress cracks develop in the curing concrete slab. Generally, control joints are formed by saw-cutting a relatively narrow channel in one or more selected locations along a poured concrete slab. The cut is preferably made while the concrete is still “green” and as soon after pouring when the concrete will support the weight of persons performing the cutting.  
       [0003] One drawback of control joints, as described above, is that uncured edges of the control joint are susceptible to damage at the upper edges by personnel or vehicular traffic over the joint prior to cure, whereby edges of the saw-cut joint may be broken. This type of damage to the control joint is known as spalling. Another problem is that control joints are susceptible to the accumulation of unwanted debris in the joint. Such debris must be removed prior to filling the control joint with an appropriate joint sealer.  
       [0004] As mentioned above, wall sections are commonly formed atop the floor slab. Once the slab has sufficiently cured and control joints have been cut, forms for the wall sections are assembled on the slab, a release agent is applied, and concrete is poured into the forms.  
       [0005] One drawback of forming the wall sections on the floor slab, as described above, is that the control joints in the floor slab become filled with concrete used to form the wall sections. When the wall sections are eventually raised, the sides of the walls have protruding ridges where the concrete entered the control joints. These ridges must be ground flush with the surface of the sides of the walls. The additional effort required to patch damaged control joints, remove unwanted debris from control joints, and to grind off protruding ridges of formed wall sections contribute to the expense and time required to construct a building from concrete materials.  
       [0006] There is thus a need for a concrete construction which overcomes the drawbacks of the prior art, such as those described above.  
       SUMMARY OF THE INVENTION  
       [0007] The present invention provides a concrete construction for use in erecting buildings and other structures and which provides concrete wall sections having a clean appearance and which do not require subsequent grinding or patching finishing steps. In an exemplary embodiment, the concrete construction includes a concrete section, or slab which has at least one control joint formed into a surface of the slab. The concrete section further includes a control joint protective strip which is removably inserted into the control joint to protect the edges of the control joint while the concrete slab cures and to prevent the accumulation of unwanted debris within the control joint. Advantageously, the control joint protective strip prevents unwanted spalling of the corner edges of the control joint due to human or vehicular traffic over the slab.  
       [0008] The control joint protective strip is an elongate member having a head portion and an adjoining stem portion. The head portion overlies the upper edges of the control joint when the protective strip is installed to the concrete construction. The stem portion extends from the head portion and is configured to engage frictionally side walls of the control joint. In one exemplary embodiment, the stem portion of the control joint protective strip includes one or more flanges which are configured to engage the side walls of the control joint to retain the protective strip therein. In another exemplary embodiment, the stem portion itself is shaped to engage the side walls of the control joint. For example, the stem portion may have an arcuate shaped section or an angled section which engages the side walls of the control joint. In yet another exemplary embodiment, the stem portion has a bulbous shape which engages the side walls of the control joint.  
       [0009] The invention also comprises a method of forming a concrete construction including the steps of forming a first concrete section, forming a control joint in the concrete section, and inserting at least one control joint protective strip in the control joint.  
       [0010] The features and objectives of the present invention will become more readily apparent from the following Detailed Description taken in conjunction with the accompanying drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention.  
     [0012]FIG. 1 is a perspective cross-sectional view of an exemplary embodiment of the concrete construction of the present invention;  
     [0013] FIGS.  2 A- 2 J depict various exemplary cross-sectional shapes of the control joint protective strip of the present invention;  
     [0014]FIG. 3 depicts the exemplary concrete construction of FIG. 1, with a wall section formed on an upper surface; and  
     [0015]FIG. 4 depicts the concrete construction and wall section of FIG. 3, with the wall section separated and the reveal patched with filler. 
    
    
     DETAILED DESCRIPTION  
     [0016] Referring to FIG. 1, there is shown an exemplary embodiment of a concrete construction  10  including a control joint protective strip  12 . The concrete construction  10  includes a concrete section, or slab  14  in which a control joint  16  has been formed to control the development of stress cracks in the slab  14 . While a single control joint  16  is depicted, it is understood that more than one control joint  16  may be formed in a given concrete slab  14  to control the location of stress cracks as may be required. In the exemplary embodiment, the control joint  16  is depicted as a relatively narrow channel having opposing side walls  18 ,  20  and upper edges  22 ,  24  defined on an upper surface  26  of the concrete slab  14 . The concrete construction  10  further includes an elongate control joint protective strip  12  which has been removably installed into the control joint  16  of the concrete slab  14 . The control joint protective strip  12  includes a head portion  30  which covers the upper edges  22 ,  24  of the control joint  16 , and a stem portion  32  which is received into the control joint  16  to engage frictionally the side walls  18 ,  20  of the control joint  16 . Thus installed, the control joint protective strip  12  protects the upper edges  22 ,  24  of the control joint  16  from contact with personnel or vehicular traffic passing over the control joint  16 . The control joint protective strip  12  also prevents unwanted debris from entering and accumulating in the control joint  16  once the protective strip  12  has been installed.  
     [0017] Referring to FIGS.  2 A- 2 J, various exemplary configurations of a control joint protective strip  12   a - 12   j  according to the present invention are depicted in cross-section. FIGS.  2 A- 2 D and FIG. 2J depict exemplary cross-sections of control joint protective strips  12   a - 12   d  and  12   j  having head portions  30 , stem portions  32 , and one or more flanges  34  extending from the stem portions  32 . The flanges  34  extending from the stem portion  32  are configured to engage the side walls  18 ,  20  of the control joint  16  when the stem portions  32  have been inserted into the control joint  16 . FIGS.  2 E- 2 G depict cross-sections of exemplary control joint protective strips  12   e - 12   g  wherein the stem portions  32  are shaped to engage the side walls  18 ,  20  of the control joint  16  when the protective strips  12  are installed therein. FIGS. 2E and 2G depict cross-sections wherein the stem portions  32  have an arcuate shape, and FIG. 2F depicts an exemplary cross-section wherein the stem portion  32  has an angled shape configured to engage the side walls  18 ,  20  of the control joint  16 .  
     [0018]FIGS. 2H and 2I depict cross-sections of exemplary control joint protective strips  12   h ,  12   i  wherein the stem portions  32  have a generally bulbous configuration to engage the side walls  18 ,  20  of the control joint. In FIG. 2H, the stem portion  32  comprises opposing arcuate portions joined at a distal end  36  of the protective strip  12  to form the bulbous stem portion  32 . FIG. 2I depicts a cross-section similar to that of FIG. 2H, but wherein the opposed arcuate portions of the stem  32  are not connected at their distal ends  36 .  
     [0019] With reference to FIG. 1, a method of forming a concrete construction  10 , including a concrete slab  14  and a removable control joint protective strip  12 , will now be described. An exemplary concrete construction  10 , as described above, may be formed by forming a concrete slab  14 , forming at least one control joint  16  in the concrete slab  14 , and inserting at least one control joint protective strip  12  into the control joint  16 . In general, the concrete slab  14  may be formed by pouring concrete into a form which has been arranged on a horizontal surface, as is known in the art. Once the concrete slab  14  has cured to a degree sufficient to support weight on its upper surface, the control joint  16  is formed, such as by saw cutting along a predetermined path, as is known in the art. The joint protective strip  12  is installed to form the concrete section  10  by inserting the stem portion  32  into the control joint  16  to engage frictionally the side walls  22 ,  24  thereof.  
     [0020] Referring to FIGS.  3 - 4 , one or more wall sections  38  may be formed on an upper surface  26  of the concrete construction  10 . First, a concrete construction  10  is formed, as described above. After the control joint  16  has been formed and the control joint protective strip  12  has been installed into the control joint  16 , forms for the wall sections  38  are arranged on the upper surface  26  and concrete is poured into the forms to create the wall sections  38 .  
     [0021] A release agent  40  is applied to concrete construction  10  to prevent fusion between the concrete construction  10  and wall sections  38  and to facilitate separation once the wall sections  38  have cured. Once the wall sections  38  atop the concrete construction have cured sufficiently, additional wall sections may be formed successively on top of wall sections  38  by arranging forms atop the wall sections  38 , coating wall sections  38  with a release agent, and pouring concrete into the forms, as described above. Control joints  16  are not generally formed into the successive wall sections  38 , but may be if the size of the wall sections  38  requires control joints  16  to control stress cracks. If control joints  16  are formed in the wall sections  38 , they may be provided with control joint protective strips  12  as was described above for the underlying slab  14 .  
     [0022] Advantageously, the control joint protective strip  12  prevents concrete used in the formation of the wall sections  38  from filling the control joints  16  of the slab  14  below. Rather, the head portions  30  of the protective strips  12  form slight indentations, or reveals  42 , in the side surfaces of the wall sections  38 . These reveals  42  may easily be filled with patching material  44 , as depicted in FIG. 4, once the wall sections  38  have cured and have been raised into position to form a wall. Alternatively, the reveals  42  may be left unfilled to provide architectural detail, as may be desired. To this end, the control joint protective strip  12  may include a design, provided in relief, on the head portion  30  to thereby create a desired architectural reveal  42  in a wall section  38  which is formed atop an underlying concrete construction  10  that includes the control joint protective strip  12 .  
     [0023] Advantageously, the reveal  42  formed into the wall section  38 , whether filled with patching material or left unfilled as an architectural reveal, eliminates or reduces the need to grind the surface of a wall section to remove undesirable ridges as required when the strip  12  is not used to protect control joint  16 .  
     [0024] After the wall sections have been raised, the protective strip  12  may remain in the control joint  16  to protect the control joint  16 . Alternatively, the protective strip  12  may be removed from the control joint  16  and the control joint  16  may be filled with a joint sealer.  
     [0025] While the present invention has been illustrated by the description of the various embodiments thereof, and while the embodiments have been described in considerable detail, it is not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope or spirit of Applicant&#39;s general inventive concept.