BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a top perspective view of a vertical wall or column, including the crack inducer of the present invention, with the concrete depicted as being transparent to disclose details of the invention;
FIG. 2 is a side perspective view of an embodiment of the invention that is similar to that of FIG. 1;
FIG. 3 is a side elevational view of a modified embodiment of the invention for use at the top of a concrete wall, pier, column or beam;
FIG. 4 is a top plan view of a concrete volume containing another embodiment of the invention; and
FIG. 5 is a view of some cross-sectional shapes for the core plate of the embodiment of FIGS. 1 to 3.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, in which like reference numerals are used to refer to the same or functionally similar elements, FIGS. 1 and 2 illustrate the crack inducer arrangement 10 of the present invention for controlling the propagation of cracks in a volume of concrete or a concrete structure 60 having outer vertical surfaces 62 and 64 defining a volume width W of the structure. The volume 60, which may be a section of wall, pier, column or even a concrete beam, contains reinforcing bars or re-bars 66 and 68 of known placement and design. Only a small section of concrete volume 60 is shown in FIG. 1, with the structure extending vertically, that is, into and out of the plane of FIG. 1, and to the left and right of the figure.
The crack inducer 10 includes an elongated and relatively rigid core plate 12 of steel, plastic or other material of sufficient rigidity, a water-stop 18 of elasomer material, and a plurality of spaced cross-plates 30 of steel, connected to the core plate 12, e.g. by welding or other rigid fastening method.
The core plate 12, which is preferably galvanized, resin or epoxy coated or otherwise corrosion resistant, includes a plate portion 14 of rectangular cross-section, for example, and may also include an enlarged portion 16, such as a flange portion having a width in a direction parallel to the outer surfaces 62 and 64 and perpendicular to the elongation direction of the core plate, that is relatively narrow. The plate portion 14 with the flange portion 16, together may form an L-shape or a T-shape (see FIG. 2) or portion 16 may be a circular or other shaped enlargement so that the plate and flange portions for a bulbous shape (see FIG. 5). The angle between plate and flange portions 14 and 16 may alternatively be other than a right angle, but may be an acute or an obtuse angle. The flange 16 has holes or perforations 20 through which the concrete migrates, minimizing the propagation of cracks traverse to the plate core 12 (C2 in FIG. 2).
The water-stop 18 is a resilient member made, for example, of a GEON (a registered trademark) R1700D brand polymer blend available from Polyone Corporation of Avon Lake Ohio. Polyvinyl chloride or similar semi-flexible polymer or rubber material that resists water can be used for the water-stop, or various other materials can be used to form the water-stop 18 of the crack inducer. The water-stop is preferably an extrusion, and can be made alternatively of polyethylene, urethane, thermoplastic elastomers (TPE) or other suitable materials. Water-stop 18 extends at least partly around the plate portion 14 and includes a solid portion 22, a tapered edge portion 24 ending at a corner 44 facing away from the core plate 12, a pair of side portions 26 connected to the solid portion 22, and projections 28 overhanging the flange portion 16, or both flanges when the T-shaped core member of FIG. 2 is used.
Although a wide variety of polymer blends or other relatively resilient materials is usable as the water stop, the example that has been reduced to practice is a blend of Di(2-ethylhexyl)phthalate with calcium carbonate, carbon black, lead stearate and lead oxide sulfate.
The projections 28 slow down the migration of calcium effervescence and therefore contribute to a clotting of calcium effervescence from the concrete volume near the water-stop member to avoid calcium effervescence from reaching the crack induced by the core plate 12. The projections include a wing portion 32 and a large circular-cross-sectioned bead 34 or other shaped enlargement at the tip end for localizing the calcium effervescence further and therefore keeping it away from the induced cracks, shown for example at C1 and C2 in FIG. 2.
The water-stop 18 is fixed to the core plate 12 by a waterproof material such as epoxy adhesive, wire through aligned holes in the water-stop and plate portion, or both.
As shown in FIG. 1, the crack inducing core of the invention includes either the plate combination 14, 16 with water-stop 18 alone that together have a core width C in the direction of the plane of plate portion 14, or include one or two reveals 72 and 74 that are imbedded at the outer surfaces 62 and 64 and extend parallel to the plates and in the concrete volume by widths R1 and R2.
The inventor has discovered that, unexpectedly, if the core width; that is the total of C plus R1 plus R2 (understanding that R1 and/or R2 may be zero if no reveal is used); if this total core width is at least 20% of the volume width W, and preferable at least ⅓ of the total volume width W, then favorable crack induction and control occurs.
This is contrary the convention thinking in the art which either believes that such incorporated cores only have adverse effects or have no effect at all on controlling cracks in vertically extending concrete structures.
As shown in FIG. 3, the volume of concrete 60 may include an end surface 63, in this case the top of the a concrete wall, pier or beam. End surface 63 extends transversely, e.g. 90 degrees or some other angle, i.e. about 40 to 140 degrees, to at least one of the outer surfaces 64. The elongated, rigid core 12 of the invention will now include the plate portion 14 plus an angle plate 15 lying in the first plane and extending adjacent the end surface and inside the volume, at a non-zero angle to the plate portion 14, for inducing a crack toward the end surface 63 from the angle plate 15. Angle plate 15 also includes a water-stop 19 of the same construction as water-stop 18, and extending partly around plate 15. Angle plate 15 preferably extends at an angle of about 4 degrees to the plate portion 14 and to the end surface, or about 60 to 120 degrees from plate portion 14 and/or to end surface 63, depending on the angle of end surface 63.
The main purpose of the angle plate 15 with its water-stop 19 is to direct the induced crack from the vertical plate 14 and water-stop 18 below, to continue straight across the top of the wall, pier or beam 60, and to provide a water-stop across the top of the concrete structure at the crack. The angle 15 should also extend substantially the entire width of the structure.
As also shown in FIG. 3, the crack inducer of the present invention can be made in modular lengths of about 3 to 8 feet and the ends of each length include either a plate portion extension 14A or a water-stop extension 18A, so that the ends can be spliced and bonded together by epoxy or structural sealant with the plate portion extension 14A of one length extending into the water-stop extension 18A of the next length.
Referring now to FIG. 4, the crack inducer core 12 of the present invention is a hollow polygonal body 80 that is preferably a sheet of stainless steel that is elongated and bent to shape, e.g. with hollow body sides or walls 82 forming the two sides of a triangle in sectional view as shown in FIG. 4, and a pair of flanges 84 that are connected, e.g. by welding to the cross plates 30 at are, in turn, connected, e.g. by wires, to the re-bars 66 or 68. The height of the triangle with the sides 82 can be about 1.5 inches, for example, with flanges that are each about 0.5 inches wide. This height can increase to about 2.75 inches when no reveal is used. An approximately 12 to 24 inch long cross plate 30 of steel is advantageous, that is ⅛″ thick and ¼″ wide or otherwise vary in size and/or shape. The cross plates 30 are placed to form a 1 to 3 inch cover (e.g. 2 inches) from the concrete surface 64, for example. All dimensions are given as examples only, however.
No external elastomeric water-stop is needed in the embodiment of FIG. 4, however, since the V-shaped configuration forms a natural water-stop and crack inducer in one. The hollow interior of the polygon 82 can be partly filled with porous air containing material for creating a void in the core member. This material may be simple expandable foam insulation material that is sprayed into the hollow space inside sides 82 to about half fill it, before the core 12 is installed or at least before the concrete is poured. It does not matter that the foam eventually deteriorates since once the concrete is poured and the void is formed, the void in the concrete will remain for the life of the wall, pier, column or beam, i.e. decades or longer. This void now forms the cite for calcium effervescence so that this white chalky deposit stays near the core member and away from the crack C1 that is controlled by the present invention.
Although a triangular core body 80 is shown the hollow polygon can have a greater number of sides, for example, it may be a trapezoid, a rhombus, a square, a rectangle or any other four sides hollow figure that is preferably open toward the cross plates, or a five, six, seven or higher sided hollow, open figure. Stainless steel is used because of its corrosion resistance. The least expensive grade stainless steel is preferred with gauges from 24 to 18 being advantageous, depending on the size of the concrete structure and the demands that will be put on this wall, pier, column or beam.
While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.
Patent Application
20080072504
