Abstract:
A cast wall system comprising at least two modular units, each having a front surface, a back surface, and opposing edge surfaces. A first edge surface (e.g., an upper edge surface) of one modular unit is positioned adjacent to a second edge surface (e.g., a lower edge surface) of another modular unit. A compression system (e.g., a threaded rod under tension) and coupled to elongated beams) provides a force to compress the first edge surface of the one modular unit toward the second edge surface of the other modular unit, and a hardened backing (e.g., concrete) is positioned on the back surface of the at least two modular units. Preferably, the first and second edge surfaces are ground in order to improve the surface contact between those two edge surfaces. When producing the cast wall, the hardened backing is preferably poured onto the back of the modular units. Prior to and during the pouring, it is preferred to support a first end of the one modular unit and a second end of the other modular unit on a common rail. In one embodiment, the common rail includes a base portion and an upright portion (e.g., a T-rail), and the step of supporting includes positioning the base portion on a support surface, and setting the first end of the one modular unit and the second end of the other modular unit on the upright portion. Preferably, the second end of the one modular unit and the first end of the other modular unit are supported on rails different than the common rail.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to the field of concrete walls having veneered surfaces. 
       BACKGROUND 
       [0002]    Due to the expense of building a conventional brick wall from brick, block, stone, or other hard modular unit, veneered building panels with a hardened backing (e.g., concrete) arc becoming more popular in building construction. In one common process, thin modular units, such as thin bricks or blocks, are laid out face down, and a concrete backing layer is poured into the track of the units to form a cast wall. The veneered brick building panels can either be pre-cast (i.e., constructed off-site and then transported to the building site) or tilt up (constructed on-site and tilted up into place) to be attached to an exterior wall. 
         [0003]    In the past, simulated brick veneered building panels were made of thin modular units that are arranged on an object retention liner. U.S. Pat. No. 5,268,137 to Scott, et al. shows an object retention form liner that holds and transfers objects, such as thin bricks, to the finished surface of concrete structures. Thin bricks are placed in recesses in the form liner. Concrete is poured into the form liner to completely cover the backs of thin bricks. The concrete fills the spaces along the sides of the thin bricks and additional cavity areas to simulate the grout line in conventional masonry construction. Once the concrete has properly hardened, the wall is raised and the form liner can be pulled away from the outer surface of the concrete wall to expose the outer surface of the bricks having grout lines to give the appearance of a conventional masonry construction. 
         [0004]    U.S. Pat. No. 5,009,387 to Scott, et al. shows a form liner with recesses that are closely sized to fit the face of a standard brick or a thin brick that is about one-half the depth of a standard brick. The recesses are arranged in staggered rows in the surface of the form liner to resemble the normal grout line between bricks. Ridges between the bricks fill the area around each side of the brick to a desired depth to form the grout recesses. Retainers such as clips hold the bricks in position in their individual recesses. The retainers are flexible and resilient enough to maintain proper spacing between bricks by absorbing the vibration that occurs during the cement pouring process. 
       SUMMARY 
       [0005]    Although the systems described above increase efficiency in the construction of walls, the thin modular units do not effectively transfer compressive loads. Therefore, the thin modular units are not able to be taken into account while measuring the load bearing capabilities and structural rigidity of the wall. The result is that the poured concrete must be sufficiently thick to take the full design load of the wall. In addition, some existing pre-cast systems allow concrete to leak between the modular units and into the front face of the modular units and onto the casting deck. 
         [0006]    A need exists for a precast wall that is load bearing and can add to the structural rigidity of the wall. A precast wall whereby the concrete modular units act as an integral structure and where the concrete modular units absorb and transfer a compressive load to each other will allow the precast wall to be calculated as a load bearing structure. In addition, there is a need for a precast system that inhibits the leakage of concrete onto the front face of the modular units. 
         [0007]    The present invention provides a cast wall system comprising at least two modular units, each having a front surface, a back surface, and opposing edge surfaces. A first edge surface (e.g., an upper edge surface) of one modular unit is positioned adjacent to a second edge surface (e.g., a lower edge surface) of another modular unit. A compression system (e.g., a threaded rod under tension and coupled to elongated beams) provides a force to compress the first edge surface of the one modular unit toward the second edge surface of the other modular unit, and a hardened backing (e.g., concrete) is positioned on the back surface of the at least two modular units. Preferably, the first and second edge surfaces are ground in order to improve the surface contact between those two edge surfaces. 
         [0008]    The above-described cast wall system can be produced by positioning the first edge surface of the one modular unit adjacent to the second edge surface of the other modular unit, compressing the first edge surface toward the second edge surface, and pouring a backing (e.g., concrete) on the back surface of the at least two modular units. Preferably, the method also includes grinding the first and second edge surfaces prior to compressing. 
         [0009]    In another aspect, the invention provides an improved method of forming a cast wall system that is made up of at least two modular units, each modular unit having at least a first end and a second end, and each end having an edge surface. The method comprises positioning an edge surface of the first end of one modular unit adjacent an edge surface of the second end of the other modular unit, supporting the first end of the one modular unit and the second end of the other modular unit on a common rail, and pouring a backing (e.g., concrete) onto the modular units. In one embodiment, the common rail includes a base portion and an upright portion (e.g., a T-rail), and the step of supporting includes positioning the base portion on a support surface, and setting the first end of the one modular unit and the second end of the other modular unit on the upright portion. Preferably, the second end of the one modular unit and the first end of the other modular unit are supported on rails different than the common rail. 
         [0010]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0011]      FIG. 1  is a rear perspective view of a tray and cast wall with a portion broken away. 
           [0012]      FIG. 2  is a perspective view of a load-bearing modular unit shown in  FIG. 1 . 
           [0013]      FIG. 3  is a cross-section view of the cast wall taken along line  3 - 3  in  FIG. 1 . 
           [0014]      FIG. 4  is a close-up view of the cross-section of the cast wall shown in  FIG. 3 . 
           [0015]      FIG. 5  is a rear perspective view of a second embodiment of a cast wall with a portion broken away. 
           [0016]      FIG. 6A  is a perspective view of a first type of a load-bearing modular unit shown in  FIG. 5 . 
           [0017]      FIG. 6B  is a perspective view of a second type of a load-bearing modular unit shown in  FIG. 5 . 
           [0018]      FIG. 7  is a cross-section view of the cast wall taken along line  7 - 7  in  FIG. 5  with a portion of the concrete removed for clarity. 
           [0019]      FIG. 8  is a close-up view of the cross-section of the cast wall shown in  FIG. 7 . 
           [0020]      FIG. 9  is a section view of a third embodiment of the present invention. 
           [0021]      FIG. 10  is an enlarged end view of a T-rail used in the embodiment of  FIG. 9 , 
           [0022]      FIG. 11  is a section view of a fourth embodiment of the present invention. 
           [0023]      FIG. 12  is a section view of a fifth embodiment of the present invention. 
       
    
    
       [0024]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
       DETAILED DESCRIPTION  
       [0025]      FIG. 1  illustrates a veneered building panel, or a cast wall  10 , embodying the present invention. The cast wall  10  includes load-bearing modular units  14 , inserts  18  coupled to some of the modular units  14 , and connection bars  22  extending between the inserts  18 . The cast wall  10  can be either pre-cast, in which case the cast wall  10  is constructed off-site and then transported to the building site, or tilt up, in which case and the cast wall  10  is constructed on-site and tilted up into place. Whether the cast wall  10  is pre-cast or tilt up, the construction of the cast wall  10  is generally the same for both cases. 
         [0026]    In constructing the cast wall  10 , a frame  24  having the dimensions of the desired cast wall  10  is placed on a generally horizontal surface, such as the ground. The frame  24  can be constructed of many different of materials, including without limitation steel, wood, rigid plastic, and other types of synthetic or non-synthetic materials, and any blend or combination thereof. The frame  24  should be rigid to withstand any shear or normal forces that may be present once the modular units  14  are placed inside the frame  24  and the concrete backing is poured. 
         [0027]    The modular units  14  illustrated in  FIGS. 1-4  are constructed of concrete. However, in other embodiments of the invention, the modular units  14  can be constructed of various materials or combinations of materials, including brick or stone. Most of the modular units  14  have a common rectangular size like the unit shown in  FIG. 2 , but the cast wall  10  also includes smaller modular units  27  to facilitate the construction of a rectangular wall using a staggered pattern. Each modular unit includes a rear surface  26  and a front surface  28  that may include surface roughness or contours not present on the rear surface  26 . The front surface  28  and the rear surface  26  are connected by four edge surfaces  30 . In the embodiment shown in  FIGS. 1-4 , the edge surfaces  30  are smaller in area than the front surface  28  and the rear surface  26 . 
         [0028]    The edge surfaces  30  of the modular units  14  are qualified, or ground, to provide surfaces that will effectively mate with adjacent edge surfaces for transfer of loads. More specifically, in the illustrated embodiment, the top and bottom edge surfaces  30  are ground so that they are substantially parallel to each other, and the side edges are ground so that they are substantially parallel to each other and perpendicular to the top and bottom surfaces. Edge surfaces  30  that are not in contact with other surfaces can function properly without grinding. For example, the top edge  34  and left edge  38  of the modular unit  42  at the top left corner of the cast wall  10  may function properly without being ground. 
         [0029]    The front surfaces  28  of the illustrated modular units  14  are commonly colored to provide a desired appearance. For example, the front surface  28  can be colored and textured to provide the appearance of brick, granite, and other building materials. The color of the modular units can be mixed throughout the modular units or, alternatively, can be at the surface only. 
         [0030]    Referring to  FIGS. 2 and 3 , the front corners  29  of each modular unit  14  are chamfered to give the appearance of a mortar joint when abutted next to another modular unit  14 . In the illustrated embodiment, the chamfering is accomplished by grinding the sharp corners, but the chamfering could also be molded into the modular unit  14  or formed in any suitable manner. When combined with surface coloring, the grinding operation will expose the underlying material, which is commonly a gray-colored concrete, resulting in the appearance of a mortar joint having a color different than the front surface  28  of the modular unit  14 . 
         [0031]    In the embodiment illustrated in  FIGS. 1-4 , a top row  46  and a bottom row  50  of modular units  14  of the cast wall  10  have a groove  54  formed in the rear surface  26 . In other embodiments, variations in the location and amount of grooves  54  can occur. The groove  54  is precision ground into the modular units  14  and is toleranced square to the edge surfaces  30  of the modular unit  14 . As illustrated in  FIGS. 2-4 , the cross-section of the groove  54  is rectangular with rounded ends  62 . In other embodiments, the groove  54  can be square, cylindrical, oval, elliptical, triangular, or any other suitable shape. 
         [0032]    The insert  18  includes a tongue portion  66 , a stabilizer portion  70 , and a receiving portion  74 . The tongue portion  66  is dimensioned to fit securely into the groove  54 . In the embodiment illustrated in  FIGS. 1-4 , the shape of the tongue portion  66  is cylindrical with rounded ends  78 , similar to the groove  54 . The illustrated tongue portion  66  is slightly smaller than the groove  54  to achieve a snug fit. The size of the tongue portion  66  can be the same as the groove  54  to yield a press-fit for insertion, or the size of the tongue portion  66  can be slightly larger than that of the groove  54  to yield an interference-fit, depending on the material of the insert  18 . The insert  18  of the embodiment of the invention illustrated in  FIGS. 1-4  is metal. However, in other embodiments, the material of the insert  18  can include, but is not limited to steel, iron, ceramic, plastic or polymer materials, or a combination of such materials. 
         [0033]    The stabilizer portion  70  is coupled to the tongue portion  66  and is designed to be positioned flush with the rear surface  26  of the modular unit  14  when the tongue portion  66  is inserted into the groove  54 . The stabilizer  70  serves to inhibit excess bending of or torque on the insert  18  when the insert  18  is coupled to the connection bar  22 . In the embodiment illustrated in  FIGS. 1-3 , the stabilizer  70  is generally flat, circular, and of a larger size than the receiving portion  74  and tongue portion  66 . In other embodiments, the stabilizer  70  can be of a different shape, size, or thickness to inhibit bending or excess torque of the insert  18 . 
         [0034]    As illustrated in  FIG. 1 , the receiving portion  74  of the insert  18  is cylindrical in shape and has a flat circular face  82  and a cylindrical edge  86 . In other embodiments, the shape of the receiving portion  74  can be square, rectangular, oval, elliptical, triangular or any suitable shape. In the embodiment illustrated in  FIGS. 1-4 , upper and lower apertures  90 ,  94  are present in the receiving portion  74 . In the embodiment illustrated in  FIGS. 1-4 , the upper apertures  90  in the inserts along the top row  46  of modular units  14  are not threaded and the lower apertures  94  in the inserts  18  along the bottom row  50  of modular units  14  are threaded. The size of each lower aperture  94  is large enough to receive a first end  106  of a connection bar  22 . The first end  106  of connection bar  22  is threaded to screw into the threaded lower aperture  94 . A second end  114  of the connection bar  22  is not threaded and has a stopper  110 . The stopper  110  is of a size larger than that of the upper aperture  90 . In the embodiment illustrated in  FIGS. 1-4 , the stopper  110  is a threaded nut. In other embodiments, the stopper  110  can be welded or otherwise secured to the second end  114  of the connection bar  22 . In other embodiments, both apertures  94 ,  90  can be threaded in opposite directions to provide insertion of a connection bar  22  having two threaded ends  106 ,  114  within the apertures  94 ,  90 , respectively. Alternatively, both of the apertures  94 ,  90  can be smooth, while both ends  106 ,  114  of the connection bar  22  can be threaded with threaded nuts securing the connection bar  22  through the apertures  94 ,  90 . 
         [0035]    In constructing the cast wall  10  illustrated in  FIG. 1 , the modular units  14  with ground edge surfaces  30  are placed inside the frame  24  and arranged in staggered rows. The modular units  14  placed in the top row  46  and the bottom row  50  have grooves  54  for receiving the inserts  18 . The inserts  18  can be placed in the modular units  14  prior to being placed in the frame. Alternatively, the inserts  18  can be placed in the grooves  54  of the modular units  14  after the modular units  14  have been arranged in the frame. 
         [0036]    After the top row  46 , bottom row  50 , and middle rows  118  have been arranged in the frame, the connection bars  22  can be installed. As illustrated in  FIG. 1 , the first end  106  of the connection bar  22  is inserted through the aperture  94  in the insert  18  in the bottom row  50 . The second end  114  of the connection bar  22  is inserted into the aperture  90  of the insert  18  in the top row  46  of modular units  14 . The stopper  110  is connected onto the second end  114  of the connection bar  22 , and the connection bar  22  is then rotated to engage the threads in the aperture  94 . The connection bar  22  is rotated until a desired tension is achieved in the connection bar  22 . 
         [0037]    In embodiments wherein both ends  106 ,  114  of the connection bar  22  are threaded and both apertures  94 ,  90  are threaded, a first end  106  of the connection bar  22  is inserted into a first aperture  94  and the second end  114  of the connection bar  22  is inserted into a second aperture  90 . Because the first aperture  94  is threaded opposite to that of the second aperture  90 , when the connection bar  22  is rotated, both ends  106 ,  114  of the connection bar  22  will engage the respective threads and thereby tighten and compress the cast wall  10 . In this embodiment, the connection bar  22  can be threaded partially into the inserts  18  before the inserts  18  are engaged with the grooves  54 . 
         [0038]    In other embodiments of the invention wherein both ends  106 ,  114  of the connection bar  22  are threaded and the apertures  94 ,  90  are not threaded, the first end  106  of the connection bar  22  can be inserted into a first aperture  94  independent from or simultaneously with the second end  114  of the connection bar  22  being inserted into a second aperture  90 . Stoppers  110  can then be screwed onto the threaded ends  106 ,  114  of the connection bar  22  until the modular units  14  are compressed. Other methods of compressing the modular units  14  are available in alternative arrangements of the connection bar  22  and inserts  18 . 
         [0039]    After compressing the modular units  14  with the connection bar  22 , concrete  88  is poured into the frame  24  and onto the back of the assembled modular units  24 . The concrete  88  is evenly spread on the rows  46 ,  50 ,  118  of modular units  14 . The concrete  88  sits for a time period until the concrete  88  is hardened to a desired drying point. The cast wall  10  can then be tilted up to be used as a structural building wall. It should be understood that any other suitable hardened backing can be used instead of concrete. 
         [0040]    Another embodiment of the invention is shown in  FIGS. 5-8 .  FIG. 5  illustrates a veneered building panel, or a cast wall  210 , made up of load-bearing modular units  214  having a similar arrangement to the cast wall  10  illustrated in  FIGS. 1-4 . Analogous to the cast wall  10  of  FIGS. 1-4 , the cast wall  210  of  FIGS. 5-8  can be either pre-cast or tilt up in construction. The illustrated modular units  214  are constructed of concrete, but can be constructed of other materials or various combinations of material as described for the modular units  14  of  FIGS. 1-4 . The modular units  214  also have a similar shape, edge characteristics, corner design, and surface features as the modular units  14  of the embodiment illustrated in  FIGS. 1-4 . The cast wall can also include smaller modular units  227 , similar to the smaller modular units  27 , to facilitate the construction of a rectangular cast wall  210  using a staggered pattern. 
         [0041]    The modular units  214  have chamfered edges  229  that are aligned with the chamfered edges  229  of the adjacent modular unit  214 . In the embodiment illustrated in  FIGS. 5-8 , the chamfered edges  229  are squared off to form a rectangular chamfer. In other embodiments, the chamfered edges  229  can be round, oval, beveled, triangular, or square. 
         [0042]    The chamfered edges  229  allow for a U-shaped chair, or riser  236 , to be inserted into the chamfered edges  229 . The riser  236  has two arms  240  that each fit within the chamfered edge  229  of a modular unit  214 . A base portion  244  of the riser  236  rests on a flat surface  245  (e.g., the ground G) within a frame  252 . As illustrated in  FIGS. 7-8 , a front surface  256  of the modular units  214  is not entirely smooth. The risers  236  allow for the modular units  214  to be at an equal height off the ground, or other flat surface, and aligned with one another during construction of the cast wall  210 . The illustrated risers  236  include a solid base portion  244  that helps to capture any concrete that may leak between the joints and keep the concrete off of the casting deck. In an alternative embodiment, the base portion  244  can be semi solid. 
         [0043]    In the embodiment illustrated in  FIGS. 5-8 , the modular units  214  are arranged in the frame  224  similar to the embodiment illustrated in  FIGS. 1-4 . The modular unit  214  for insertion into a top row  246  or a bottom row  250  of the cast wall  210  is illustrated in  FIG. 6A . The modular unit  214  has a horizontal groove  254  formed in a rear surface  226 , similar to the groove  54  of the illustrated embodiment of  FIGS. 1-4 . The horizontal groove  254  is precision ground to be parallel to the top and bottom edges  256 . The modular unit  214  shown in  FIG. 6A  also has a set of vertical grooves  326 ,  330  formed in the rear surface  226  that extend perpendicular to the horizontal groove  254 . The modular unit  214  (shown in  FIG. 6B ) used for middle rows  318  of the cast wall  210  also has vertical grooves  326 ,  330 . One vertical groove  326  is located one-quarter of the length of the modular unit  214  in from a first parallel side edge  334  of the modular unit  214 . The other vertical groove  330  is located one-quarter of the length of the modular unit  214  in from a second parallel side edge  338  of the modular unit  214 . As shown in  FIG. 5 , when the modular units  214  are arranged into staggered rows, a top edge  342  of a first modular unit  346  contacts one half of a lower edge  350  of second and third modular units  354 ,  358 . One vertical groove  326  of the first modular unit  346  is aligned with a vertical groove  330  of the second modular unit  354 , and the other vertical groove  330  of the first modular unit  346  is aligned with a vertical groove  326  of third modular unit  358 . 
         [0044]    As illustrated in  FIGS. 7-8 , an L-shaped elongated beam  218  is inserted into the groove  254  of the top row  246  such that a first face  220  of the elongated beam  218  engages a bottom sidewall  221  of the groove  254 . A second face  222  of the elongated beam  218  engages a back wall  223  of horizontal groove  254 . Another elongated beam  218  is inserted into the bottom row  250  such that a first face  220  of the elongated beam  218  engages a top side wall  225  of the horizontal groove  254 , and a second face  222  engages the back wall  223  of the horizontal groove  254 . In other embodiments, the first face  220  of the elongated beam  218  can engage the bottom sidewall  221  and the second face  222  can engage the rear surface  226  of the modular units  214  of the top row  246 . Likewise, for the bottom row  250 , the first face  220  can engage the top sidewall  225  of the horizontal groove  254 , and the second face  222  can engage the rear surface  226  of the modular units  214 . With any arrangement of the elongated beam  218 , adhesive (e.g., epoxy—not shown) can be added between any surface of the modular unit  214  and the elongated beam  218  to keep the elongated beam  218  from moving prior to concrete  288  being poured onto the rear surface  226  of the cast wall  210 . 
         [0045]    The elongated beam  218  has apertures  294  that are spaced to align with the grooves  326 ,  330 . The apertures  294  are located on either the first face  220  or the second face  222  of the elongated beam  218 , depending on which face  220 ,  222  is adjacent the grooves  326 ,  330 . The apertures  294  are large enough to receive a first end  306  or a second end  314  of the connection bar  322 . The first end  306  and second end  314  of the connection bar  322  are threaded and can be connected to a threaded nut  310 . In other embodiments, variations in the connection between the elongated beam  218  and the connection bar  322  can exist as long as the construction allows for compression of the modular units  214  by the connection bar  322 . 
         [0046]    The cross-section of the connection bar  322  illustrated in FIGS.  5  and  7 - 8  is generally round. The vertical grooves  326 ,  330  for receiving the connection bar  322  are of a round shape, or a shape that can fully accommodate the round connection bar  322 . In other embodiments, the shape of the connection bar  322  and grooves  326 ,  330  can vary. The horizontal groove  254  has a more squared shape to receive at least one face  220 ,  222  of the elongated beam  218 . However, the horizontal groove  254  can be shaped in various ways to receive alternative shapes of the faces  220 ,  222  of the elongated beam  218 . 
         [0047]    In constructing the cast wall  210  of  FIG. 5 , the modular units  214  are arranged in the frame  224  in staggered rows  246 ,  250 ,  318 . The too row  246  and bottom row  250  include the modular units  214  having the vertical and horizontal grooves  254 ,  326 ,  330  (shown in  FIG. 6A ), and the middle rows  318  include the modular units  214  having only the vertical grooves  226 ,  330  (shown in  FIG. 6B ). The connection bars  322  are placed in the aligned vertical grooves  326 ,  330  such that the first end  306  and the second end  314  of the connection bar  322  extend into horizontal grooves  254  of the top and bottom rows  246 ,  250 . One of the elongated beams  218  is placed into the horizontal groove  254  of the top row  246  of modular units  214  such that the first end  306  of the connection bar  322  is received within the corresponding aperture  294  of the elongated beam  218 . The second elongated beam  218  is placed into the horizontal groove  254  of the bottom row  250  of modular units  214  to receive the bottom end  314  of the connection bar  322  within the corresponding aperture  294  of the elongated beam  218 . Other variations and sequences for constructing the cast wall  210  are possible. 
         [0048]    Upon the connection bar  322  being fully inserted within the vertical grooves  326 ,  330  of the modular units  214  and into the apertures  294  in the elongated beams  218 , the threaded nuts  310  can now be screwed onto the first or second ends  306 ,  314  of the connection bar  322  to cause the connection bar  322  to compress the modular units  214  together. When the modular units  214  are compressed by the connection bar  322  to the desired force, the cast wall  210  is ready for concrete  288  to be poured. The concrete  288  is not shown to be entering grooves  326 ,  330  of cast wall  210  in  FIGS. 7-8  for purposes of clarity and viewing of the interaction between components of the assembled cast wall  210 . However, in practice, concrete  288  will seep into the grooves  326 ,  330 . The concrete  288  sits for a time period until the concrete  288  is at a specific drying point, similar to the cast wall  10  illustrated in  FIGS. 1-4 . The cast wall  210  is then tilted up to be used as a structural building wall. 
         [0049]    In should be understood that the vertical compression of the modular units structurally integrates the modular units as a structural component of the building wall, and further inhibits leakage of concrete between the top and bottom edges of adjacent modular units. The modular units can also be compressed in the horizontal direction in order to inhibit the leakage of concrete between the side edges of adjacent modular units. Because the side edges are precision ground, horizontal compression of the modular units will provide the desired seal to deter concrete leakage. The horizontal compression is not illustrated in the drawings, but can be performed in a manner similar to that described above for the vertical compression. For example, the horizontal compression can be performed using an apparatus similar to that illustrated in  FIGS. 1-4  (with appropriate vertical slots formed in the modular units), and the vertical compression can be performed using the apparatus of  FIGS. 5-8 . Alternatively, the horizontal compression can be performed using a carpenter&#39;s pipe clamp engaging the side edges of each row. 
         [0050]    In one embodiment, the horizontal compression is performed first, followed by the vertical compression. After the vertical compression is added, the apparatus for creating the horizontal compression can be removed. Due to the overlapping nature of the modular units, the vertical compression will maintain at least a portion of the horizontal compression. In this manner, only the apparatus that creates the vertical compression will be embedded into the concrete backing. 
         [0051]    In a modification of this embodiment, a small vertical compression is applied first, followed by horizontal compression of each row (either simultaneously or sequentially). The horizontal compression of each row is strong enough to overcome the friction created by the vertical compression and move the units horizontally into intimate contact with each other. The horizontal compression is then removed, and the small vertical compression will hold the units in place. Concrete can then be poured into the back of the assembled units. 
         [0052]    In another embodiment of the invention, the compression of the units can be performed by the frame  24 . More specifically, the side rails of the frame can be designed to be movable so that a compressive force can be applied by the rails on the assembled units. For example, a pipe clamp can be applied to force the rails into contact with the units, or some other system (e.g., manual, hydraulic, pneumatic, etc.) can be used to move the rails and apply a compressive force to the units. 
         [0053]      FIG. 9  illustrates a third embodiment of the present invention including a cast wall  400  having a mixture of split face blocks  402  and smooth face blocks  404  (for clarity, the blocks  402 , 404  are not shown in section) and a concrete backing  405 . As with the previously-described embodiments, the system of  FIG. 9  utilizes a frame  406  that forms the outer periphery of the cast wall  400 . In addition, the illustrated system is design to work with modular units having ground edges. 
         [0054]    The embodiment of  FIG. 9  utilizes a compression system that applies a compressive force to the blocks. The illustrated compression system includes L-shaped beams  410  and threaded compression rods  412  (for clarity, the rod  412  is not shown in section). The L-shaped beams  410  fit into horizontal grooves  414  in the blocks, and one leg  416  of each beam  410  extends beyond the back surface  418  of the corresponding modular unit. The long leg  416  of each beam  410  is provided with a hole (not shown) that receives a compression rod  412 , which positions the rod  412  slightly spaced from the back surface  418  of the modular units. This alleviates the need for the vertical grooves in the back surface of the modular units. 
         [0055]    The embodiment of  FIG. 9  further includes T-rails  420  in place of the riser  236  of the previous embodiment. Referring to  FIG. 10 , each T-rail  420  includes a base portion  422  having a width W 1  of about 1.50 inches and an upright portion  424  having a height H of about 1.188 inches from the bottom of the base portion  422 . The upright portion  424  of the illustrated T-rail  420  includes a narrow section  426  having a width W 2  of about 0.19 inches and a wide section  428  having a width W 3  of about 0.31 inches. Referring back to  FIG. 9 , a series of T-rails  420  are used to support the edges of the modular units. On each end of the wall  400  adjacent the frame  406 , L-rails  430  are used to support the end of the top and bottom rows of modular units. 
         [0056]      FIG. 11  shows the use of the compression system concept of the present invention with a more conventional cast brick system (for clarity, the concrete backing is omitted from  FIG. 11 ). The illustrated system will produce a cast wall  500  having three rows of split face block  502  on the top, six rows of brick  504  in the middle, and one row of split face block  506  on the bottom (for clarity, the blocks  502 , 504 , 506  are not shown in section). The top three rows of block  502  are set up in the manner described above with respect to  FIGS. 9 and 10 . The rows of brick are set using a foam riser  508  that supports brides having brick snaps  510  to reduce concrete leakage between the bricks  504 , as is known in the art. The bottom row of block  506  is supported on rails  512 , but no vertical compression is applied. With the system of  FIG. 11 , the blocks  502 , 506  and bricks  504  can be integrated into the same wall, and the relative depths of the blocks  502 , 506  and bricks  505  can be adjusted by changing the heights of the rails  512  and the foam riser  508 . 
         [0057]      FIG. 12  illustrates application of some of the concepts of the present invention to a cast wall  600  that is formed upside down from the conventional manner. More specifically, in the embodiment of  FIG. 12 , the concrete  602  is poured into the frame  604  before the blocks  606  are set in place. The blocks  606  are then place right side up onto the concrete  602  with an appropriate compression system. In this embodiment, the threaded rods  608  (for clarity, the threaded rod  608  is not shown in section) of the compression system are accessible through tubes  610  that extend through holes in the sidewall of the frame  604  and engage the beams  612 . Due to the close fit of the frame  604 , the rods  608 , the tubes  610 , and the beams  612 , only a small amount of concrete is likely to leak out of the holes in the frame  604 . 
         [0058]    Thus, the invention provides, among other things, a cast wall having a veneered surface that is load bearing and able to transfer compressive loads. The invention further provides a system for building a cast wall wherein the amount of concrete leaking between the modular units is reduced. In addition, the invention provides a rail system that supports the modular units while a backing is being poured. Various features and advantages of the invention are set forth in the following claims.