Patent AU-2015100623-A4 (AU)
Title: Method and apparatus for forming a flexible mat defined by interconnected concrete panels
Inventor: WADE DARREN
IPC: E02B3/12
Filed: 2015-05-11
Granted: 2015-06-25
Abstract: Patent Abstract The method and apparatus herein described can be utilised for forming flexible mats that include side-by-side, interconnected concrete panels. Such mats can serve for erosion control, for providing walkways and roadways, and for other purposes. The mats include a plurality of concrete panels that are spaced from each other and are interconnected by thin, flexible connecting elements that extend between and interconnect adjacent concrete panels. Referring now to the drawings, and particularly to FIGS. 1 and 2 thereof, there is shown a portion of flexible mat 10 that includes a plurality of side-by-side concrete panels 12 that are carried on a fibrous base sheet 14. Concrete panels 12 can be of generally pyramid shape, as shown, and can have longitudinal and transverse cross sections that also are generally pyramid style. Although shown in FIG. 1 as of pyramid form, for purposes of illustration, and although described herein as having that form, it should be appreciated that concrete panels 12 can be of any desired outline form. In that regard, the outline of panels 12 can be of any desired polygonal shape including trilateral and quadrilateral, from triangular to as many sides as are desired. Additionally, panels 12 can include curved sides and can be in the form of circles, ellipses, ovals, and the like, or they can be defined by a combination of straight-line and curved peripheral elements. Panels 12 having rectilinear side and end faces can be arranged in a pattern that allows the spacing between adjacent panels to be maintained substantially uniform. Advantageously, panels 12 can be of pyramid form and can be of substantially uniform shape and size. The panels can be spaced from each other a distance of from about 1/2 inch to about 1 inch or more, as desired, to provide gaps or spaces between the opposed end faces and opposed side faces of adjacent panels, and thereby allow the adjacent panels to pivot relative to each other. Thus, spacing of the ends and sides of adjacent panels from each other allows areas of the resulting mat to flex about the mat's longitudinal and transverse axis, and to conform with any irregularities of the surface onto which the mat is to be placed, so that the mat conforms substantially with the form of that surface. Concrete panels 12 can be of any convenient or desired overall size. The uniformly-shaped and uniformly-sized panels 12 of pyramid form as shown in FIGS. 1 and 2, for example, can have a thickness of the order of from about 1 inches to about 3 inches for most uses of the mat. However, even thinner or even thicker panels can be provided in those applications of the mat where the compressive loads expected to be imposed upon the concrete panels when in use will either allow or will require. Thus, where the mat is to be placed in a drainage swale or along the bank of a body of water to reduce surface erosion, the compressive load on the panels will be minimal or non-existent, and the panels can be made thinner. On the other hand, where the mat is to be placed on the ground to provide a roadway for vehicles the compressive load on the panels will be considerably higher and the panels must be made thicker if cracking of the panels is to be avoided. Pyramid panels 12 as shown in FIG. 1 can have a length of the order of from about 3 inches to about 12 inches, and a width also of the order of from about 3 inches, to about 12 inches. Although panels 12 shown in FIG. 1 are positioned so that the respective end faces and side faces of adjacent panels are aligned both longitudinally and transversely, if desired panels 12 can be positioned on base sheet 14 so that the panels in adjacent longitudinally extending rows of panels are offset from each other, in a staggered relationship. Concrete panels 12 can be formed from various concrete compositions that can include various types and sizes of aggregate materials, depending upon the surface texture and surface appearance desired on panels 12, the loads to which the panels will be subjected, and also upon the use to which mat 10 is intended to be put. As previously noted, for waterway and drainage ditch erosion control purposes, the concrete panels need not have great strength, because they will not be subjected to high loads when used in such applications, and therefore the concrete composition can be a conventional, air-entrained concrete that is readily available from concrete suppliers. On the other hand, for roadway and walkway purposes, where panels 12 will be subjected to compressive forces imposed by static or moving loads, the concrete from which the panels are formed can advantageously be a high-strength concrete. For example, a commonly commercially available 5,000 psi, air-entrained, fibre-reinforced concrete can be utilised to form panels intended for mats that provide walkways and roadways, to minimise the tendency for cracking or breaking of the panels under the loads imposed by vehicular traffic. The fibres incorporated in such concrete mixtures can be a plurality of randomly-distributed poly-meric fibres 18 (see FIG. 2) of any desired form, such as monofilaments, thin strips, strings, twisted fibres, or the like. The lengths of such fibres can vary from about 2 inches to as much as 8 inches or more, and their diameter, if of circular cross section, or their width, if in the form of strips, can vary from about 0.001 inch to about 0.100 inch, depending upon the cross-sectional shape and the nature of the material from which the fibres are formed. Concrete panels 12 have a base surface 16 to which fibrous base sheet 14 is bonded. Because panels 12 are each bonded to the upper face of base sheet 14, the sheet also serves to hold concrete panels 12 in the desired spaced relationship relative to each other. Bonding of fibrous sheet 14 to concrete panels 12 can be effected by placing the sheet in contact With freshly-poured concrete and pressing the sheet against the concrete so that the wet concrete penetrates into the spaces between the inter-engaged fibres that define the base sheet. Extending between and interconnecting adjacent concrete panels 12 are a plurality of longitudinally extending connectors 20 and a plurality of transversely-extending connectors 21 that serve to limit the maximum movement of adjacent interconnected panels away from each other. Connectors 20 and 21 can be provided by a pre-formed, open mesh sheet 22 that can be provided in the form as shown in FIG. 3. Such open mesh sheets are sometimes referred to as "geogrids," and they generally include a regular pattern of spaced, side-by-side, generally rectangular openings 24. Such geogrids are available in various polymeric materials and are available with openings of various sizes. A suitable polymeric geogrid for use in mats of the type described herein can be obtained numerous suppliers both globally and nationally throughout Australia. Open mesh sheet 22 can be formed from various poly-meric materials, such as oriented or non-oriented polypropylene, polyethylene, copolymers thereof, and the like. Mesh sheet 22 is bonded to or partially embedded in the respective concrete panels and serves primarily to provide a plurality of interconnection elements that extend between adjacent panels in the form of longitudinally-extending connectors 20 and transversely-extending connectors 21. Instead of polymeric materials, the open mesh sheet can be an open mesh sheet of metallic material, such as a commonly-available wire mesh that can have hexagonal openings. Alternatively, the concrete panels can be interconnected by longitudinally- and transversely-extending metallic Wire strands made from metals that resist corrosion caused by the concrete, such as stainless steel, copper, or other metals that have a protective surface coating that resists corrosion, such as galvanised steel. Flexible mats formed from interconnected, side-by-side concrete panels can be made continuously by apparatus of the type shown in FIG. 4. A conventional concrete mixer truck includes a rotatable mixer drum for providing a supply of mixed concrete into the side trough 54 and distributed evenly upwards with a screw conveyer 58. The concrete is then transferred to a second trough 56 and then distributed across the mould carrying drum 38 by a second screw conveyer 58 housed within the trough 56. The Mat-forming apparatus 34 receives concrete from a concrete mixer before it is able to complete the above description to form mats having side-by side, interconnected concrete panels. Mat-forming apparatus 34 includes a rotatable, mould carrying drum 38 that includes on its periphery a plurality of pyramid shaped moulds having a predetermined, uniform depth. Drum 38 is a hollow structure defined by a cylindrical outer surface 40. Drum 38 is rotatably supported on suitable bearings (not shown) that are carried by a support frame defined by a pair of spaced, parallel support columns 44, only one of which is visible in FIG. 4. Positioned rearwardly of mould drum 38 and rotatably supported by a pair of spaced, parallel support beams 46 that extend rearwardly from respective support columns 44 is a grid roll 48. Roll 48 can be a polymeric geogrid in web form, such as geogrid 22 having a configuration such as that shown in FIG. 3, or it can be a metallic grid, having a configuration such as that of a metallic grid described above. Positioned forwardly of mould drum 38 and rotatably supported by a pair of spaced, parallel support columns 50 is a fabric roll 52. Roll 52 can be a roll of fibrous material in web form to provide the base sheet shown in FIGS. 1 and 2 as base sheet 14. Referring to FIG. 4, a trough 54 that is inclined upwardly which contains a screw conveyor 58 terminates into a trough outlet 56 positioned above the upper periphery of mould drum 38. Trough 54 is adapted to convey the concrete mix from its origination to the respective moulds carried on the periphery of mould d