Patent Publication Number: US-9896838-B2

Title: Concrete panel and concrete panel connector structure for forming reinforced concrete building components

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/992,483, filed Jan. 11, 2016, now U.S. Pat. No. 9,546,484 which claims the benefit under 35 U.S.C. § 120 of U.S. patent application Ser. No. 14/475,229, filed Sep. 2, 2014, now U.S. Pat. No. 9,234,349 which claims the benefit, under 35 U.S.C. § 119(e), of U.S. Provisional Patent Application No. 61/959,717 filed Aug. 30, 2013, and entitled “Hybrid Wall System Using Steel Framing Modules and Concrete Panels.” The entire content of each of these prior applications is incorporated herein by this reference. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The invention relates to building construction methods including precast concrete panels and especially lightweight concrete panels with reinforcement provided in the connections between the panels. 
     BACKGROUND OF THE INVENTION 
     Building walls, retaining walls and perimeter fence-type walls are often made with concrete block. These construction methods are easily done manually, but are time consuming and create a product that has many mortar joints, which are inherently weak. In cases where joints are eliminated by the use of concrete panels, the panels are often massive and require heavy machinery to assemble into the desired structure. If smaller panels are used, it is still necessary to incorporate structural reinforcement within the panel, complicating the panel manufacturing process. What is needed are improved precast concrete panel systems and constructions methods using precast concrete panels. 
     SUMMARY OF THE INVENTION 
     The present invention encompasses concrete panels, connector structures for concrete panels, concrete panel systems, concrete panel assemblies, and methods of producing concrete panel assemblies. The concrete panel systems, assemblies, and methods may be used together with suitable reinforcing bars to form building components comprising walls (including stand-alone walls used as fences), floor structures, and roof structures. 
     A concrete panel system according to one form of the invention includes first, second, and third rectangular precast concrete panels, each defining a respective top edge, bottom edge, and first and second lateral edges. A first type connector is formed in the concrete material at least along the top edge of the first panel and along the first lateral edge of the first panel. A second type connector is formed in the concrete material at least along the second lateral edge of the second panel, and along the bottom edge of the third panel. The first type connector and the second type connector are configured so that when the first type connector along the first lateral edge of the first panel is placed in a connected position with the second type connector along the second lateral edge of the second panel, and the first type connector along the top edge of the first panel is placed in the connected position with the second type connector along the bottom edge of the third panel, a cavity is formed between the respective panel edges. This cavity extends along both the top edge of the first panel and the first lateral edge of the first panel. The portion of the cavity extending along the first lateral edge of the first panel is adapted to receive at least a lower portion of a first reinforcing bar with an upper portion bent at approximately 90 degrees to the lower portion so as to extend either along the top edge of the second panel or in the portion of the cavity extending along the top edge of the first panel. That is, the connection produced by the two connector types allows the reinforcing bar to be placed in the cavity extending along the first lateral edge of the first panel so that the bar may then traverse a corner of the first or second panel and then extend along the top edge of the first or second panel. In some forms of the invention, each cavity formed in the connections between panels is adapted to receive at least two side-by-side (roughly parallel) extending portions of reinforcing bars, together with a suitable encasement material such as a mortar or non-shrink grout to encase the reinforcing bars in the cavity. Also, a suitable adhesive material may be applied so as to reside in portions of the edge connections external to the respective cavity. 
     The ability to receive a reinforcing bar in position traversing a corner of the connected panels and encase the reinforcing bar in encasement material produces a very robust connection between adjacent panels of the panel system. The connection in the panel system resists forces such as wind loading and earthquake accelerations that would tend to produce cracks in standard mortar joints between traditional concrete blocks. Furthermore, the concrete panel system may be used to form a wall which may be connected to a wood or metal framed wall via connectors incorporated in the concrete panel edge connections. The hybrid concrete and framed wall system has the structural and other benefits of both the concrete panel wall and framed wall. 
     A concrete panel assembly according to one or more embodiments is made up of the first, second, and third rectangular precast concrete panels. The panels are positioned in an assembly plane with the first panel adjoining the second panel with the first type connector along the first lateral edge of the first panel in a connected position with the second type connector along the second lateral edge of the second panel, and with the third panel adjoining both the first and second panels with the second type connector along the bottom edge of the third panel in the connected position with the first type connector along the top edge of the first panel and the first type connector along the top edge of the second panel. In this assembled arrangement, a respective edge cavity is formed between the respective adjoined panel edges, so that a respective edge cavity extends along the top edge of the first panel, the top edge of the second panel, and the first lateral edge of the first panel. Also a corner cavity is formed at the junction of the first lateral edge of the first panel and the second lateral edge of the second panel with the bottom edge of the third panel. The panel assembly also includes a length of first reinforcing bar extending along at least a portion of the cavity formed between the first and second panels. The first reinforcing bar is bent at approximately 90 degrees so as to traverse the corner cavity and extend parallel to the top edge of the first panel, either along the tope edge of the first panel or the top edge of the second panel. In the panel assembly, at least a portion of each respective edge cavity is filled with encasement material and at least a portion of each adjoined edge has an adhesive material applied thereon. 
     According to one form of the invention, a method of constructing a concrete building component includes placing the first, second, and third precast rectangular concrete panels in the assembly plane in the configuration described for the panel assembly above. These placements produce the cavities between the panel edges. As the panels are being placed in the assembled configuration, reinforcing bars are placed in the cavities formed between the panels. At least some of these reinforcing bars traverse a respective corner of a panel and run side-by-side with other reinforcing bars in the respective cavities. Encasement material is applied in the cavities either after the cavities are formed or as the panels are placed together to form the cavities. The encasement material serves to encase the reinforcing bars in the edge connections and help provide a connection between the reinforcing bars and the panels. The construction method may also include applying a suitable adhesive material in portions of the panel edge structure external to the respective cavity to help adhere the panels in their connected position in the panel assembly. 
     The present invention also encompasses a particular panel edge connection structure with a tongue and groove arrangement which produces the reinforcing bar receiving cavities. This tongue and groove arrangement together with other advantages and features of the invention will be described below in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded front view showing a number of precast concrete panels according to one example embodiment. 
         FIG. 2A  is a front view of the panels in  FIG. 1  assembled with reinforcing bars included in the connections between panels. 
         FIG. 2B  is an enlarged view of a portion of the panel assembly shown in  FIG. 2A , the enlarged view showing a vertical connection between panels and intersecting horizontal connections between panels. 
         FIG. 3  is an enlarged section view along line  3 - 3  in  FIG. 2A , showing details of connectors formed in the edges of the panels and a cavity formed in the connection to receive reinforcing bars. 
         FIG. 4  is a flow chart of an assembly process according to an example embodiment. 
         FIG. 5  is a perspective view of the top corner of two wall panels, with corner and cap elements that tie the panels together according to another embodiment. 
         FIG. 6  is a perspective view of and assembled wall incorporating column elements employing a tongue and groove connection according to the present invention. 
         FIG. 7  is a perspective exploded view of a mold for use in casting concrete panels with edge connectors according to the present invention. 
         FIG. 8  is a cross sectional view of a panel according to another embodiment with a utility void cast therein. 
         FIG. 9  is a view in section through an alternative panel edge connector structure according to another embodiment. 
         FIG. 10  is a view in section through another alternative panel edge connector according to a further embodiment. 
         FIG. 11  is a perspective view of a wall constructed using precast concrete panels and posts according to another embodiment. 
         FIG. 12  a perspective view of a hybrid wall constructed using a frame structure in addition to the precast panels and posts of the embodiment of  FIG. 11 . 
         FIG. 13  is a perspective view showing a connector for attaching a concrete panel to a steel frame wall structure. 
         FIG. 14  is a side view of the concrete panel connector of  FIG. 13 . 
         FIG. 15  is a diagrammatic representation of a wall structure that may be produced from concrete panels according to the present invention. 
     
    
    
     DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
       FIG. 1  shows precast concrete panels  10   a - d  and  20  which may be assembled to form a wall according to one example embodiment. It will be appreciated that the invention is not limited to systems or methods for producing walls. Rather, panel systems according to various forms of the invention may be used to produce walls, floor structures, and roof structures. As used in this disclosure and the following claims, the designation “building component” will be used to describe the assembled panel structure which may be produced according to the present invention, and this designation will be understood to encompass building walls, free-standing walls (such as fences), retaining walls, floor structures, roof structures, and the like. Various embodiments of the invention will be described below in the context of a “wall” for the purpose of simplifying the discussion only, and this description in the context of a “wall” is not intended to be limiting. Also, relative terms such as top, bottom, lateral, shallow, and deep, are used in this disclosure and the claims simply to assist in identifying and distinguishing the various components, and these relative terms are not intended to be limiting. 
     The vertical panels  10   a - d  and horizontal panel  20  shown in  FIG. 1  are each made up of a panel body provided with opposing side, tongue and groove elements in which the tongue is formed by parallel ridges (described in detail below in connection with  FIG. 3 ) and represents a first type connector  11 . These ridges of the first type connector  11  are adapted to project into an opposing groove of a second type connector  12 . Details of this groove structure will also be described below in connection with  FIG. 3 . Preferably the connectors are located on three or four edges of the panels  10   a - d  and panel  20  as shown in  FIG. 1 , but this may vary according to the panel position and use in the final assembly. Panels  10   a - d  can be made with varying widths, lengths, and thicknesses depending on the functional requirements of the intended assembly. 
       FIG. 2A  is a somewhat diagrammatic front view of the panels of  FIG. 1  in an assembled state in an assembly plane which runs parallel to the plane of the drawing sheet. Panels  10   a - d  are joined with vertical connections to each other, and with a horizontal connection to panel  20  resting at the top of the assembly. There would also be a horizontal connection between the lower edges of the panels  10   a - d  and the support surface on which the panel assembly rests, such as a suitable concrete foundation. Reinforcing bars  19   a - f  employed inside the joints are depicted as dotted lines in  FIG. 2A . Reinforcing bars  19   a - d  are shown as projecting below the assembly to indicate that those reinforcing bars can be set in a slab or other foundation or floor assembly under the panels  10   a - d.  Reinforcing bars  19   e - f  run horizontally in the example of  FIG. 2A . As can be seen in the drawing, there are several places in the assembly where a connection contains two reinforcing bars overlapping and running adjacent (that is, side-by-side or roughly parallel) to each other in the connection. This arrangement will be described further below with reference to  FIG. 2B  and  FIG. 3 , and elsewhere. 
       FIG. 2B  is an enlarged somewhat diagrammatic view of an edge connection intersection of the embodiment of  FIG. 2A  showing reinforcing bar  19   d  curved through the connections between panels  10   c,    10   d,  and  20 . This particular connection intersection is selected just as an example of the connection intersections between the vertical panels  10   a - d  and the horizontal panel  20 . Reinforcing bar  19   d  extends vertically inside a vertical edge connection cavity  13   a  formed between panels  10   c  and  10   d,  and includes a 90 degree curved section to allow the reinforcing bar to traverse the corner formed at the upper left hand corner of panel  10   d.  A portion  9  of reinforcing bar  19   d  then extends horizontally through cavity  13   b  of the horizontal edge connection between panel  20  and panels  10   c  and  10   d.  This portion  9  of reinforcing bar  19   d  extends side-by-side with reinforcing bar  19   e  in cavity  13   b.  The enlarged view of  FIG. 2B  shows cavity  13   a  is formed by the tongue and groove connectors formed in the panel edges, and particularly in this embodiment with ridges  15   a  and groove  17   a  formed in opposing panel edges. Similarly, cavity  13   b  is formed by a tongue and groove arrangement provided by ridges  15   b  and groove  17   b.  It is noted that although panels  10   c  and  10   d  are shown with right angle corners at the intersection of their respective top edge and lateral side edge, these intersections may be cast with a curve or a bevel at the corner to help facilitate the traversal of the reinforcing bar around the corner. Also, although not labeled separately in  FIG. 2B , it will be appreciated that the intersection of cavity  13   a  and cavity  13   b  produces essentially a corner cavity that facilitates the positioning of reinforcing bar  19   d  around the corner of panel  10   d  (or around the corner of panel  10   c  if it was desired for the bar to extend in that direction). 
     The section view of  FIG. 3  shows adjacent tongue and groove elements as well as the cavity  13   a  facilitating placement of rebar or reinforcing bar  19   d  according to an embodiment of the invention. First panel  10   c  is illustrated as having a first type connector generally shown at  11  in  FIG. 3 . First type connector  11  comprises the two spaced-apart ridges  15   a  protruding from a base plane  8  of the first type connector. The two ridges  15   a  define a V-shaped first type connector channel there between, which as shown forms one side of the walls for cavity  13   a  defined between adjacent panels  10   c  and  10   d  in the connected position. That is, the walls of cavity  13   a  are formed in part by the surfaces of the first type connector channel between ridges  15   a.  In this embodiment, the entire first type connector channel resides outside the first type connector base plane  8  (to the right of plane  8  in the figure), however other embodiments may provide a channel between ridges  15   a  which extends past the plane  8  into the structure of panel  10   c.    
     Referring still to  FIG. 3 , second type connector  12  is formed in the edge of panel  10   d  which meets the opposing panel  10   c  edge face on. The second type connector  12  comprises the groove  17   a  recessed inside a base plane of the second type connector. In this particular example the edges of panels  10   c  and  10   d  abut each other such that the base plane  8  of first type connector  11  coincides with the base plane of second type connector  12 . Thus both base planes are shown as the plane at reference numeral  8 . As will be described in an alternative connector embodiment below, the respective connector base planes need not coincide as shown in the example of  FIG. 3 . As will also be described below, some embodiments may include a thin layer of adhesive between portions of the panel edges external to the cavity  13   a  and thus the connector type base planes may also not coincide for this reason. 
     In the embodiment shown in  FIG. 3 , groove  17   a  of second type connector  12  comprises a first shallow groove  18  and a second deep groove  16  formed along an interior of the first shallow groove  18 . Cavity  13   a  defined between adjacent panels  10   c  and  10   d  in the connected position is formed in part by the surfaces of the second deep groove  16 . The deep groove  16  in this version is a V-shaped groove having two walls as shown, while the shallower groove  18  in which groove  17  is formed includes slanted walls and an inside face in which deep groove  16  is formed. This is not limiting and actual manufactured shapes may contain smoothly transitioning angles of cast concrete to form the shallow and deeper grooves. Other embodiments may use other groove shapes to form the shallow and deep grooves or may use a single groove which cooperates with ridges  15   a  to form the desired cavity  13   a.  The V-shaped deep groove  16  joining to the V-shaped channel formed by ridges  15   a  in the example shown in  FIG. 3  establishes a diamond-shaped cavity  13   a  into which one, two, or more reinforcing bars may be placed. 
     In some preferred versions of the invention, the panel edge connections as shown in  FIG. 3  are of a design, profile, and size such that it is possible to accommodate up to two pieces of #4 (½ inch) rebar in the resulting edge cavity ( 13   a  in  FIG. 3 ) when the first and second type connectors  11  and  12 , respectively, are in the connected position. Thus the example of  FIG. 3  shows that reinforcing bar  19   d  fills less than half of cavity  13   a.  In this embodiment, the size of cavity  13   a  allows for at least two reinforcing bars to fit in the cavity side-by-side, and still allow encasement material to flow down the cavity (or otherwise be placed in the cavity) to fill the cavity around the reinforcing bar or bars. The encasement material is indicated by the horizontal section lines in  FIG. 3 . While in this embodiment only one reinforcing bar  19   d  is shown, other versions use two or even more reinforcing bars in at least portions of the vertical joints. At the junction with the cavity formed between panel  20  and panels  10   c  and  10   d  (for example) each vertically extending length of reinforcing bar may be one bent in a different direction. 
     Some forms of the present invention may include a suitable adhesive in the connections between adjacent panel edges to help hold the panel edges in the desired connected position. For example, a suitable adhesive may be applied along respective adjacent edges of the two panels external to the surfaces defining the reinforcing bar receiving cavity  13   a  in  FIG. 3 . The particular first and second type connector arrangement shown in  FIG. 3  includes a predefined gap between the outer surface of each ridge  15   a  and the surface of shallow groove  18  to provide space for retaining a suitable amount of adhesive in the connection. Adhesive may also be applied to closely abutting surfaces in the connection such as the surfaces of the panel edges external to the ridges  15   a  for panel  10   c  and shallow groove  18  (again using the example of  FIG. 3 ). In any case, the adhesive may be applied prior to bringing the opposing panel edges together in the desired connected position. 
     Panels  10   a - d  and  20  may be manufactured (precast) in molds by any suitable molding technique. Preferably the concrete is selected to create panels between  40  and  90  pounds per cubic foot, enabling construction techniques disclosed herein to be accomplished with two construction personnel lifting and assembling the panels to create walls and other structures. This may be accomplished with a suitable known lightweight concrete or “foamcrete” techniques which involve casting concrete with air bubbles or fillers to create a lighter weight structure than typical concrete. Heavier weight concrete,  150  pound per cubic foot concrete for example, may also be used to form panels within the scope of the invention. The panels  10  may have various texture applied to selected faces of the panel by either casing on a profiled surface or applying the texture after the panel has been cast. The profile surface can be part of the mold or part of the supporting surface. Further, the panel may be colorized during the casting process or colored after it has been cast. The panels can be reinforced during the casting process, with material inserted before or during the pouring process, however, some embodiments do not employ reinforcing inside the panels or use only light reinforcing, and rely on the reinforcing bars positioned in the edge connections to provide strength to the finished assembly of panels. 
       FIG. 4  shows a process flowchart for assembling a panel system according to one embodiment. The illustrated process may be used, for example, to assemble three panels on a foundation, in an arrangement such as that in  FIG. 2B . The techniques herein are repeated and combined to create larger structures such as building walls for example. The process begins at step  402  where the reinforcing bar (such as  19   d  in  FIG. 2A ) is set in the foundation by any suitable method (such as during the foundation pour or by affixing the reinforcing bar in a drilled hole in the foundation concrete). With the reinforcing bar extending vertically in the desired position, at step  404  the process for forming a wall vertically stands two precast panels ( 10   c  and  10   d  in  FIG. 3  for example) aligned with each other in an assembly plane, with the first type connector ( 11  in  FIG. 3 ) facing the second type connector ( 12  in  FIG. 3 ), preferably with the vertical reinforcing bar positioned between the ridges of the first type connector ( 15   a  in  FIG. 3 ). Preferably this step can be done by two personnel lifting the panels and placing them by hand, but machine lifting may also be used. An additional reinforcing bar may be inserted in the cavity ( 13   a  in  FIG. 3 ) or set in place to put multiple reinforcing bars in the joint as discussed above and shown at step  710 . Referring to step  406 , an adhesive may be applied to the opposing panel edges and the connector surfaces outside the cavity wall portions (of cavity  13   a  in  FIG. 3  for example). Various embodiments use different arrangements of adhesive as further discussed below. Next at step  408 , the panels are connected by pushing them together such that the first panel first type connector  11  is placed in a connected position with the second panel second type connector  12 , with the reinforcing bar placed in the cavity formed by the connectors. The process is designed in preferred versions to allow personnel to push the panels in place by hand such that the adhesive seal and connection is formed along the length of the joint on the panel  10  edge portions external to the surfaces forming the cavity in the connection. The process at step  409  also places a 90 degree bend in the reinforcing bar to traverse a corner defined at the top of the respective panel. The 90 degree value given here (and referenced elsewhere in this disclosure and the claims) is an approximate value as allowed by tolerances to facilitate placement in the connection cavities as described. Traversing the corner in either direction in the plane in which the panels are assembled places a portion of the reinforcing bar extending generally parallel to the top edge of the respective panel. The reinforcing bar may be pre-bent or bent in situ in the vertical cavity. Where two reinforcing bars are used in the vertical joint between adjacent panels, the second bar may run vertically to reinforce additional panels placed atop the current assembly, or may be bent the opposite direction as the other reinforcing bar. At step  412 , the process includes adding encasement material into the vertical cavity ( 13   a  in  2 B and  FIG. 3  for example), preferably (but not necessarily) by filling from the top and packing down to ensure there are no voids around the reinforcing bar(s) in the cavity. 
     After the encasement material is applied, the vertical edge connection cavity of two side-by-side panels is complete, and a third panel (such as panel  20  in  FIGS. 1 and 2B ) may be placed atop the lower assembly. Depending on the desired structure the third panel may be placed horizontally spanning two or more vertical panels (such as  10   c  and  10   d  in  FIGS. 1-3 ). At step  414 , the process vertically stands a third precast rectangular concrete panel in a position at least partially atop the first panel in the assembly plane. The third panel has a second type connector (such as connector  12  shown best in  FIG. 3 ) formed in the bottom edge, and connectors formed on other edges as needed for the desired structure. Step  416  applies adhesive to the joint, which may occur before the third panel is stood in place, or after by tilting the panel and applying adhesive into the resulting gaps. The encasement material is applied into the horizontal joint at step  418 , which may be done again before or after placement of the panel in the connected position between the opposing connectors. A preferred method fills the first type connector channel atop the first panel with encasement material before standing the third panel atop the connector. The encasement material may have properties to allow mounding sufficiently above the first type connector channel to facilitate filling the horizontal cavity formed by the edge connection. Reinforcing bar may be placed along the horizontal connection at this step if desired in addition to the existing rebar that was positioned over the top of the first panel or second panel at step  409 . Next at step  420 , the process connects the panels, moving them into final position by placing the first type connector of the first panel in a connected position with the second type connector of the third panel, thereby forming the cavity (cavity  13   b  in  FIG. 3  for example) that encloses the reinforcing bar. This structure is sealed by the adhesive that was applied outside the connector cavity and by the encasement material inside the connector cavity. Additional encasement material may be pushed into the cavity from both lateral sides of the cavity to fill it as completely as possible. It can be understood that vertical and horizontal edge connections have been disclosed which may be used in repeated combination to build larger structures such as building walls. 
     While generally the embodiment of  FIGS. 1-3  provides panels of uniform thickness preferably about  6  feet in length by  2  feet in width in order to be installed manually, other embodiments provide for increasing panel thicknesses when additional strength and stability is required. In these cases, the tongue and groove edge connection design remains consistent. Other embodiments vary the lengths and widths of individual panels. Further, alterations to any fixed mold dimension are accomplished by blocking a portion of the filled mold cavity to accomplish desired structures. This is especially helpful when addressing panels for placing in proximity to windows and doors. 
     The example shown in  FIGS. 1-2A  includes panels with edge connectors formed along each edge to form the desired edge connections. In particular, each panel  10   a - d  includes first type connectors  11  along a first lateral edge and top edge, and second type connectors  12  along a second lateral edge and bottom edge. Panel  20  includes second type connectors along the bottom and second lateral edge, and the first type connector  11  along the first lateral edge and top edge. In some forms of the invention, panels adapted to rest on a foundation (or floor structure) may have a flat bottom edge, or some other edge profile to facilitate a desired connection to the foundation. Similarly, an upper panel such as panel  20  in  FIG. 1  may include a flat or other upper edge rather than an edge connector according to the present invention. Also, the edge connectors may be reversed within the scope of the invention such that the first type connector represents the groove connector of the tongue and groove arrangement and the second type connector represents the tongue connector of the tongue and groove arrangement. 
     It should be noted that the diamond-shaped cavity  13   a  shown in  FIG. 3  represents simply one preferred edge connection cavity profile and the present invention in not limited to this diamond-shaped cavity. An edge connection cavity within the scope of the present invention may be circular or any other shape. Furthermore, an edge connection cavity according to the invention may be larger than shown in  FIG. 3  to accommodate additional reinforcing bar, or smaller to accommodate smaller reinforcing bar. 
     In this disclosure and the following claims, the material used to fill the edge connection cavities such as cavity  13   a  in  FIG. 3  is referred to as “encasement material.” The invention encompasses any suitable encasement material to fill the respective cavity as desired and encase the reinforcing bars. For example, a suitable mortar may be used particularly in edge connection cavities that extend horizontally. A suitable non-shrink grout may be used particularly to fill edge connection cavities that extend vertically. In some cases the same encasement material may be used in all edge connection cavities for a given panel assembly, while in other cases different encasement materials may be used in different cavities in a given panel assembly. The invention is not limited to any particular encasement material encompasses the use of cement-based and other mortars and grouts with or without additives such as polymers. 
       FIGS. 5 and 6  show embodiments which include additional structural elements between adjacent panels in parts of a complete assembly.  FIG. 5  is a perspective view of the top corner of wall panels  50 ,  51 ,  52 , and  53 , showing corner column  52  and cap elements  55  and  56  that tie the wall panels together at a corner according to one embodiment. Wall panels may be panels such as panels  10   a - d  and  20  described above. Corner column  52  may comprise a structural reinforcement member preferably cast in high strength concrete (3000-4000 psi concrete) as discussed below. Cap elements  55  and  56  may also be reinforced, high strength concrete.  FIG. 6  is a perspective view of a post/side column  60 , assembled together with panels  61 ,  62 , and  63 . Panels  61 ,  62 , and  63  may comprise panels such as panels  10   a - d  and  20  described above, while side column  60  comprises a structural element preferably cast in high strength concrete with or without internal reinforcing such as reinforcing bars or cages. 
     As shown in  FIG. 6 , side column  60  includes the same connector arrangement used on the adjacent panels  61 ,  62 , and  63 . In particular, side column  60  includes a first lateral edge having a first type connector  65  and a second lateral edge having a second type connector  66 . These connectors  65  and  66  may correspond to the first and second type connector  11  and  12 , respectively, shown particularly in  FIG. 3 . Adjacent panels  61 ,  62 , and  63  in  FIG. 6  include corresponding edge connectors so that connector  65  of side column  60  may be placed in a connected position with a corresponding second type connector  68  on the opposing edge of panel  61  and connector  66  of the side column may be placed in a connected position with a corresponding first type connector  69  on panel  63  (and a similar second type connector on panel  62  although not shown in the perspective of  FIG. 6 ). Although not shown in the perspective of  FIG. 5 , a similar connector arrangement is used with corner column  52  and cap elements  55  and  56 . Thus corner column  52  may include a first type connector (corresponding to connector  11  in  FIG. 3 ) along edge  58  and a second type connector (corresponding to connector 12  in  FIG. 3 ) along edge  59 . These connectors make a connection with complementary edge connectors on the opposing edges of panels  50 ,  51 ,  52 , and  53  similar to the connection arrangement described above in connection with  FIG. 3  for example. Both cap elements  55  and  56  in  FIG. 5  may include a second type connector  54  (which may be the connector  12  shown in  FIG. 3 ) adapted to mate with a complementary connector on the top edge of panels  50  and  51 . 
     Thus  FIGS. 5 and 6  show how panels may be joined together at the sides, corners, and on the top with structural concrete elements (columns  52  and  60 , and cap elements  55  and  56 ) that are cast with traditional weight, high strength concrete, yet are still light enough to be installed manually because they are much narrower compared to the panels  50 - 53  and  61 - 63 . These structural concrete elements connect to adjacent panels in the same fashion as the connection between panels described above in connection with  FIGS. 1-3 . Thus edge connector reinforcing bars may be included in the connection cavities (corresponding to cavity  13   a  in  FIG. 3  for example) between the high strength concrete elements and adjacent panels and tied in to the other edge connector reinforcing bars to form a high performance building component. 
     The columns and cap elements shown in  FIGS. 5 and 6  are described above as “structural” elements because they may be cast from high strength concrete as described above and thus may be used to improve the structural performance of a panel assembly according to the present invention. However, it should be born in mind that the panels such as example panels  10   a - d  and  20  described in connection with  FIGS. 1-4  are themselves preferably structural, or at least produce a structural assembly in that the resulting assembly may be used to provide structural support for building elements such as roofing structures. Accordingly, although a given element, such as panel  20  may be labelled here as a “panel,” it may function as beam or a column in a given assembly. Also, the column elements, particularly corner  52  need not be structural elements according to this definition (since the wall panels themselves may be structural). 
     Panels such as panels  10   a - d  and  20  shown in  FIGS. 1-3 , and the additional panels and column and cap elements shown in  FIGS. 5 and 6 , may incorporate any suitable reinforcing bars, mesh, or other material in their interior. The reinforcing material may be arranged as straight bar or may be formed into suitable cages for casting in the panel concrete. 
       FIG. 7  is a perspective exploded view of a “window frame” style mold made up of two “L” shaped mold sections  70 . The mold sections  70  may be connected together by suitable means to form a mold for casting concrete panels according to the present invention such as panels  10   a - d  in  FIGS. 1 and 2A . In particular, mold sections  70  include edge structures for forming the first and second type connectors such as connector  11  and  12  shown in  FIG. 3 . Manufacturing panels using the mold shown in  FIG. 7  allows for horizontal casting of the panels and post and cap precast process, offering a variety of surfaces for product differentiation. The pouring surface can be flat and smooth, or it can include a variety of textured surfaces. The top surface can be hand screeded for a relatively smooth surface, or it can be overlaid with a textured surface. This manufacturing system also provides for the rapid recycling of forms, whereby the panel can be stripped from the mold in a diagonal fashion, and yet remain in place for further curing. 
     Another embodiment provides a panel cast with plumbing services in place.  FIG. 8  is a cross sectional view of a panel according to such an embodiment, with the panel  80  cast with a plumbing pipe  81  embedded therein. Other embodiments may provide electrical conduits and other passages and structures precast into the panels in place of or in addition to pipe  81 . One preferred embodiment provides panels with vertical electrical conduits cast therein, and pull lines placed in the conduits to speed electrical wiring on the construction site. In this embodiment, the conduits are precast in designated vertically oriented panels such as panels  10   a - d  in  FIG. 1 , with matching conduits precast in panels  20  in  FIG. 1 . Caps such as  55  and  56  in  FIG. 4  may also include openings cast therein to allow electrical wiring to pass all the way from ceiling level to outlet boxes cast in the panels. 
     Still other embodiments provide panels cast with openings to insert a window. Further embodiments may provide panels cast in such a way to create an opening of a size and shape that when two panels are placed side by side, a window can be inserted in the opening. The same technique provides that a panel can be cast in such a way to create an opening so that when two panels are placed side by side, a door can be framed into the opening. Alternatively, end posts (not shown) may be connected along the free edge of two spaced apart panels (such as panels  10   a - d  in  FIG. 1 ) and the area between the two posts may provide room to frame a door. These end posts would be similar to post  60 , but with a suitable connector (such as connector  11  or  12  shown in  FIG. 3 ) is formed in the concrete on only one lateral side to form the desired connection to the panel. 
       FIGS. 9 and 10  show alternate arrangements for the tongue and groove connection between adjoined panels within the scope of the present invention. Referring first to  FIG. 9 , the first type connector  911  in this embodiment is formed on a panel  910   a  and includes ridges  915  which protrude from a base plane  908  of the first type connector. The portion of the first type connector  911  defining base plane  908  provides a shoulder  921 . As with the previously described embodiments, ridges  915  define a V shaped channel there between.  FIG. 9  also shows a second type connector  912  formed in the concrete making up another panel  910   b.  As in the previously described embodiments, the second type connector  912  includes a groove  917  made up of a shallow groove  918  and a deep groove  916  formed in the shallow groove. Groove  917  is recessed from the base plane  908  of the second type connector, with the portion of the second type connector lying in the base plane providing a shoulder  922  adapted to abut the shoulder  921  of the first type connector when the connectors are in the illustrated connected position. The surfaces of deep groove  916  form a first portion of a cavity  913  in the connection between the first type connector and second type connector, while the channel between ridges  915  forms another portion of the cavity. 
     In the embodiment shown in  FIG. 9 , when the first type connector  911  is placed in the connected position with the second type connector  912 , a first narrow gap  924  is left between a surface of shallow groove  918  and a facing side surface of one of ridges  915 . This first narrow gap  924  is illustrated as being present adjacent the outside surface of each ridge  915 . A second narrow gap  925  resides in the adjoined panels  910   a  and  910   b  between a top surface of each ridge  915  and a facing surface of shallow groove  918 , again on both lateral sides of the connection on either side of cavity  913 . Gaps  924  and  925  in this embodiment provide areas for a defined layer of adhesive (not shown in  FIG. 9 ) in the connection to assist in maintaining the connection between the panels. It will be noted that the abutting shoulders  921  and  922  define the width dimension of gaps  924  and  925 . It should also be appreciated that the dimensions shown in  FIG. 9  are shown only for purposes of example, and are not intended to be limiting. 
     Although no reinforcing bars are shown in  FIG. 9 , cavity  913  provides space for receiving one, two, or perhaps more lengths of reinforcing material such as reinforcing steel bar (rebar). As with the cavity  13   a  illustrated in  FIG. 3 , at least a portion of cavity  913 , and preferably the entire length of the cavity is filled with a suitable encasement material to set the reinforcing bar or bars in place. 
       FIG. 10  shows another embodiment of a first connector type  1011  associated with panel  1010   a  and a second connector type  1012  associated with panel  1010   b.  As with the previously described embodiments, the first type connector includes two ridges  1015  protruding from a base plane  1008   a  of the first type connector and defining a V-shaped channel there between, and the second type connector includes a groove recessed from a base plane  1008   b  of the second type connector. In this particular embodiment, the first type connector base plane  1008   a  is separated slightly from the second type connector base plane  1008   b  when the connectors are in the connected position. Second type connector  1012  has a groove  1017  includes a shallow groove  1018  and a deep groove  1016 . The space between deep groove  1016  and the channel formed between ridges  1015  defines the reinforcing receiving cavity  1013 . As in previously described embodiments, cavity  1013  is adapted to receive a reinforcing bar  1019  and perhaps additional reinforcing bars. 
     In the embodiment shown in  FIG. 10 , it is contact between the outside edges of ridges  1015  and the inside edges of shallow groove  1018  which defines the connected position between the two connector types. That is, contact between the inside edges of shallow groove  1018  and the outside edges of ridges  1015  control how closely the two connector types may be brought together. In the connected position shown in  FIG. 10 , a small gap  1024  is left between the surface of the first type connector lying in base plane  1008   a  and the surface of the second type connector lying in base plane  1008   b.  Gaps  1025  are also left between the distal surfaces of ridges  1015  and the bottom surfaces of shallow groove  1018 . All of these gaps provide areas for adhesive material to help hold the adjoined panels together. 
       FIG. 11  is a perspective view of a wall  1100  constructed using precast panels  1110   a - d  and  1120   a - b,  and reinforcing columns  1160   a - b  according to another embodiment. Panels  1110   a - d  and  1120   a - b  may be similar to panels  10   a - d  and  20  described above. Wall  1100  is assembled in manner described above in connection with  FIGS. 1-4  with reinforcement bars  1119   a - c  employed extending downward in position to extend into a foundation (the foundation not shown in this view). Panels  1120   a - b  are assembled atop panels  1110   a - d  to complete the wall height. In this embodiment, the panels  1120   a - b  may have a first type connector similar to connector  11  shown in  FIG. 3  formed along the panel top edge them facilitate a tongue and groove connection according to the present invention with horizontal beam  1150  which may be similar to beam or cap  56  shown in  FIG. 5  with a second type connector  1112  (similar to connector  12  in  FIG. 3 , for example) formed in the concrete along the bottom edge of the beam. Wall  1100  also includes two columns  1160   a  and  1160   b  which may be similar to the column  60  described above in connection with  FIG. 6 . Column  1160   b  may include a first type connector similar to connector  11  in  FIG. 3  along an edge opposing panel  1110   c,  and a second type connector similar to connector  12  in  FIG. 3  along an edge opposing panel  1110   b.  Column  1160   a  may have a similar edge connector configuration. Of course, these edge connectors on the columns  1160   a - b  are not visible in the perspective of  FIG. 11 . 
       FIG. 11  illustrates one of numerous different configurations of reinforcement bar within the scope of the present invention. Reinforcement bars  1119   a  and  1119   b  may comprise bars that extend from the position exposed in the perspective of  FIG. 11  upwardly in a connection cavity (similar to cavity  13   a  in  FIG. 3 ) formed between the near side of the respective column  1160   a - b  and perhaps all the way up to a bend around the upper left corner of panel  1110   c.  This reinforcement bar arrangement is similar to the arrangement of reinforcing bars  19   a - d  shown in  FIGS. 2A and 2B . Reinforcing bar  1119   c  in  FIG. 11  does not extend vertically through a vertically extending edge connector cavity, but rather includes a 90 degree bend obscured by the lower edge of panel  1110   d  in this view, with a portion  1102  extending in the space provided by an edge connector formed along the bottom edge of panel  1110   d.  This edge connector may comprise a connector similar to second type connector  12  shown in  FIG. 3 . The vertical reinforcement provided along the near lateral edge of panel  1110   d  in  FIG. 11  is provided by C-shaped reinforcement bar  1119   d  which includes 90 degree bends at its upper and lower ends to provide horizontal portions  1103  and  1104 . It should also be noted that reinforcement bar  1119   d  extends vertically from the bottom edge of panel  1110   d  to the top edge of panel  1120   b.  This is in contrast to the embodiment described above in connection with  FIGS. 2A and 2B  in which the vertical reinforcing bars along the panel lateral edges terminated in the respective cavity formed along the top edge of the respective vertically oriented panel. A reinforcing bar similar to  1119   d  may be included in the edge connector cavity formed between the opposing edges of panel  1110   b  and column  1160   b,  and/or between the opposing edges of panel  1110   c  and column  1160   b.  Alternatively to the reinforcing bar  1119   d  spanning both panels  1110   d  and  1120   b  in  FIG. 11 , the reinforcing bar may extend up to and bend around a panel corner at the top edge of panel  1110   d,  and a separate piece of reinforcing bar may extend vertically along the near lateral edge of panel  1120   b.  This or any reinforcing bar used in a panel system according to the present invention may be bent in a C-shape, S-shape (a vertical section with a 90 degree bend one direction at one end and the opposite direction at the opposite end), L-shape, or any other shape to provide the desired reinforcement in the various edge connection cavities formed in the panel system. The edge connector cavity provided by the panel system of the present invention facilitates numerous different reinforcement bar configurations to meet the desired structural needs. Furthermore, some implementations of a panel system according to the present invention may use separate lengths of overlapping reinforcing bar in a given edge connection cavity to provide the desired reinforcement along that edge connection. In some cases where the lengths of different reinforcing bar overlap, it may be possible and desirable to connect the separate bars together by tying with wire, by adhesives, by welding, or by any suitable connection technique. For example, reinforcing bar portions  1102  and  1103  in  FIG. 11  may be connected together prior to adding additional panels or other elements of the desired assembly. 
     It is noted that the edge connector comprising a second type connector  12  ( FIG. 3 ) along the bottom of panels  1110   a - d  as shown forms a cavity between grooves of the connector and the flat foundation underneath. The groove (or dual groove as shown in  FIG. 3 ) inside the base plane of the connector, this second type connector itself forms a cavity large enough to enclose at least two side-by-side lengths of reinforcing bar. In some preferred embodiments the second type edge connector similar to connector  12  in  FIG. 3  is sized in a 4 inch thick panel to allow two side-by-side lengths of #4 rebar to fit in the connector groove facing a flat surface such as the flat surface of a foundation or floor structure. Such a construction presents not only the structural advantage of the tongue and groove connection where it is used, but also the advantage of using the same precast second connector type structure  12  as described above in connection with  FIG. 3  to connect panels to flat surfaces. 
       FIG. 12  is a perspective view of a wall  1100  to which additional concrete panels and columns have been added, and to which a steel frame wall structure  1201  has also been added to produce a hybrid wall  1200 . In particular, the concrete panel portion of wall  1200  includes additional panels  1110   e,    1110   f,  and  1120   c,  along with additional reinforcing bars  1119   e,    1119   f,  and  1119   g.  Frame structure  1201  may comprise any suitable framing structure. Although steel framing elements, including vertical elements or studs  1205  are shown, other hybrid wall implementations may include wood framing elements. Steel or wood framing may be constructed in any suitable fashion. One preferred hybrid wall arrangement including frame structure  1201  may employ framing panels such as those disclosed in U.S. patent application Ser. No. 14/065,288 and U.S. patent application Ser. No. 14/065,303 to produce the frame structure. The entire content of each of these pending applications is incorporated herein by this reference. 
     The steel frame structure  1201  is built at the interior side of a panel wall  1100 , although other implementations may place the framed wall to the exterior of the concrete panel wall. In either case, such hybrid construction provides the advantages of the structural characteristics of each type of wall, the concrete panel assembly according to the present invention, and the framed wall structure. This hybrid wall arrangement may allow the use of precast concrete panels for the exterior or interior walls in areas where framing is required by building codes. The precast panel wall  1100  may be connected to the frame structure  1201  with connectors which are shown  FIGS. 13 and 14 . 
     Referring to  FIGS. 13 and 14 , frame connector  1300  is adapted to cooperate with a panel edge connection according to the present invention to provide a robust structural connection between the frame structure  1201  and the concrete panel wall.  FIGS. 13 and 14  show connector  1300  in a partially installed condition between frame structure  1201  and one of the concrete panels shown in  FIG. 12 , particularly panel  1110   c.  Frame connector  1300  includes a frame attachment part  1301  and a panel attachment part  1302  that includes parts  1303  that are adapted to abut the distal ends of panel connector ridges  1315 , and a V-shaped part  1304  adapted to abut the V-shaped surface formed in the panel connector  1311  between ridges  1315 . Frame connector  1300  may be formed from any suitable material, including a suitable sheet steel similar to that from which the steel framing members are produced. The profile of frame connector  1300  needed to follow the shape of the panel connector  1311  in  FIGS. 13 and 14  may also be formed in any suitable fashion. For example, sheet metal may be stamped to form the desired profile shown best in  FIG. 14 . Any suitable fasteners or fastening technique may be used to connect frame connector  1300  to the frame structure.  FIGS. 13 and 14  show sheet metal screws through attachment part  1301  and into framing member  1205 . Of course, once an additional panel is placed in a connected position with connector  1311  of panel  1110   c,  the panel attachment part  1302  will be securely connected to the panel assembly. It will be appreciated from the view of  FIG. 14  that the V-shaped part  1304  fits in the V-shaped channel between ridges  1315  so that it does not substantially interfere with the function of the cavity ( 13  in  FIG. 3 ) formed partially by the channel. That is, the installed frame connector  1300  does not interfere with the placement of one or more reinforcing bars in the cavity formed in the edge connection. The frame connectors  1300  are preferably installed by constructing the frame wall structure  1201  first, and then assembling the precast panel wall outside the frame structure. As the panels are placed in position with an exposed edge connector, the frame connectors are attached to the frame structure in position in the exposed edge connector (the position shown in  FIGS. 13  and  14  for example) prior to placing the next panel in the connected position with that exposed edge connector. Although  FIGS. 13 and 14  show frame connector  1300  in a horizontal panel connector, the frame connectors may be placed in any connection, horizontal or vertical, whether between panels or columns, or any other element including an edge structure according to the present invention. 
     The present invention encompasses a number of variations in the illustrated frame connector  1300  and its connection to a frame wall. For example, a frame connector may include a panel attachment part that does not extend all the way across the V-shaped or other cavity making up the edge connection cavity. In one alternative embodiment, the panel attachment part corresponding to part  1302  in  FIGS. 13 and 14  may extend only to the top of the first ridge  1315  and may include no portion that follows the edge connection cavity profile of the given edge connection. Also, frame connectors such as connector  1300  in  FIGS. 13 and 14  need not attach to any particular part of the frame wall. For example, rather than attaching to a framing member comprising a stud of the framed wall, the frame connector may be attached to a horizontal or other rail connected to or between studs in the framed wall. 
       FIG. 15  comprises another example wall  1500  produced using concrete panels, posts, columns, and beams with edge connectors as described above. The illustrated structural base panels  1501  may be 46 inches tall by 16 inches wide, while the structural top panels  1502  may be 36 inches tall by 16 inches wide. This panel size arrangement allows two or more of the top panels to be left out of the structure to produce a window rough in  1503 . The base panels  1501  below the window rough in  1503  may be removed to provide a rough in for a door rather than the illustrated window rough in. The wall column  1505 , end column  1506 , and corner column  1507  may or may not be structural. The base beam  1508  and top beam  1509  complete the height of the wall structure. These beams are preferably structural elements. All of these elements preferably include edge connectors as described above to facilitate the assembly with the edge connector cavities reinforcing bar placements as described above. 
     As can be understood from the disclosure herein, the techniques described create a panel construction system that can be employed to create a variety of structures. The most basic are single walls or a fully enclosed cube structure without windows. Other applications can create a structure using the panels to make a fully enclosed cube and having at least one pair of panels making a window receiving area and one pair of panels making a door receiving area. Yet another application is to assemble the pre-cast panels as described using the first and second type connectors when placing the panels as floor material, eliminating the need to cast a floor and much of the time involved. A further application is to use the panels as a second story floor material to build a level on top of an existing structure. 
     Still other techniques may be used to improve structural strength in the context the various applications that use panels as a roof structure and floor structure (grade supported or otherwise). Using the connector techniques described herein to provide reinforcing bars and stability as desired, precast panels may be made with a strength or density taking into account the desired application, but using the same construction techniques, by employing the ability at the precast stage to alter product density through changes in the mix design. Different densities that relate to required strengths can be achieved with ease, creating various product applications from the same mold. 
     The advantages of the present invention include, without limitation, a panelized concrete building method that improves upon concrete block construction by eliminating excessive mortar joints. It improves upon existing large concrete panel systems by utilizing lightweight materials that can create panels which are easy installed by two persons without heavy machinery. It improves upon existing smaller panel systems by eliminating the need for reinforcement cast within the panel itself. Additionally, the invention provides versatility in product configurations in regard to thicknesses, lengths, densities, surface textures and cast-in utilities. 
     As used herein, whether in the above description or the following claims, the terms “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” and the like are to be understood to be open-ended, that is, to mean including but not limited to. Any use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another, or the temporal order in which acts of a method are performed. Rather, unless specifically stated otherwise, such ordinal terms are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term). 
     The term “each” may be used in the following claims for convenience in describing characteristics or features of multiple elements, and any such use of the term “each” is in the inclusive sense unless specifically stated otherwise. For example, if a claim defines two or more elements as “each” having a characteristic or feature, the use of the term “each” is not intended to exclude from the claim scope a situation having a third one of the elements which does not have the defined characteristic or feature. 
     The above described preferred embodiments are intended to illustrate the principles of the invention, but not to limit the scope of the invention. Various other embodiments and modifications to these preferred embodiments may be made by those skilled in the art without departing from the scope of the present invention.