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1. Field of the Invention
The present invention relates generally to the field of concrete structures of the sort which may often be used in the construction of open topped or domed, ground level or elevated tanks and the like that may generally be used to hold liquids, for example, water. In particular the present invention relates to plastic lined concrete structures and the methodology used in the fabrication of composite plastic lined concrete structures where the plastic lining is securely affixed to a concrete wall. The invention has special utility in connection with plastic lined prestressed/post-tensioned concrete tanks.
2. The Prior Art Background
Concrete tanks have been widely used for decades to hold fresh or waste water, and the like. Generally speaking such tanks are highly commercially valuable properties, and a large construction industry has been established to serve the needs of a variety of activities and enterprises which desire an economical and reliable means for holding a readily available supply of fresh water or for storing waste water during and/or prior to treatment. Such tanks are currently available in sizes ranging from about 50,000 gallons to several million gallons or more.
Prior art concrete tanks, while extremely successful in many regards, have had limited applicability in situations where the liquid to be contained is capable of reacting with or otherwise harming concrete.
To increase the overall applicability of concrete tanks, plastic linings have been proposed to limit the exposure of the interior walls of tanks to the material contained therein. However, it has been a very difficult and expensive operation to attach large sheets of plastic to concrete walls in such a way that the plastic sheets are securely attached to the walls and all of the seams between adjacent sheets have complete integrity.
The present invention provides a solution for many of the problems encountered previously in the construction of plastic lined concrete tanks. That is to say, in accordance with the concepts and principles of the invention, a method is provided for efficiently and economically constructing plastic lined concrete structures wherein the structural integrity of the incorporated plastic linings is greatly enhanced. In this latter regard, the methodology provided by the invention is particularly applicable to all varieties of concrete tanks, including, for example, and without limitation, concrete tanks that are standard cast-in place, wire wound and prestressed, and internally tendoned and post-tensioned. Thus, in one form of the invention, the same provides a method that includes forming first and second plastic lined concrete panels, each panel including a concrete slab having an elongated edge and a surface, and a plastic sheet having a plurality of anchoring projections protruding outwardly from a face thereof. The forming of the panels is conducted in such a way that the face of each plastic sheet is engaged against the surface of a corresponding concrete slab and the anchoring projections are embedded in the concrete of the corresponding slab. In addition, the plastic sheets are each arranged and positioned such that an edge flap portion thereof projects outwardly beyond the edge of the corresponding slab. The formed panels are arranged in adjacent, aligned positions with the elongated edge of the concrete slab of the first panel disposed in opposing spaced relationship relative to the elongated edge of the concrete slab of the second panel so that an elongated gap is presented between the edges. In addition, an outboard segment of the edge flap portion of the plastic sheet of the first panel is disposed in overlapping relationship relative to an outboard segment of the edge flap portion of the plastic sheet of the second panel at said gap. The overlapping segments are then welded together with an upwardly extending seam.
In another adaptation of the invention, a method is provided for constructing a plastic lined concrete structure which comprises providing first and second plastic sheets, each sheet having a face and a plurality of anchoring projections protruding outwardly from the face. In this adaptation, the method further includes forming a first plastic lined concrete panel by causing a first quantity of wet cementitious material to come into contact with a portion of the face of the first plastic sheet, permitting the first quantity of cementitious material to set in the form of a first solid concrete slab having the anchoring projections of the first plastic sheet embedded therein. The first concrete slab desirably has an elongated edge and the first plastic sheet and the first quantity of wet cementitious material are initially arranged relative to one another such that an edge flap portion of the first plastic sheet projects outwardly beyond the edge of the first slab after the cementitious material has become set. Also in this adaptation of the invention, a second plastic lined concrete panel is formed in essentially the same manner as the first plastic lined panel. The formed panels are arranged in adjacent, aligned positions with the elongated edge of the first concrete slab disposed in opposing spaced relationship relative to the elongated edge of the second concrete slab to thereby present an elongated gap between the edges. In addition, an outboard segment of the edge flap portion of the plastic sheet of the first panel is arranged in overlapping relationship relative to an outboard segment of the edge flap portion of the plastic sheet of the second panel at said gap. The overlapping outboard segments are then welded together in situ with an upwardly extending seam.
In yet another aspect of the invention, a method is provided for constructing a plastic lined concrete tank. In accordance with this aspect of the invention, the method includes forming a plurality of plastic lined concrete panels. Each of the panels includes a concrete slab having opposed, laterally spaced, elongated edges and an inner surface, and a plastic sheet having a plurality of anchoring projections protruding outwardly from a face thereof. The forming of the panels is conducted in such a way that the face of each plastic sheet is engaged against the surface of a corresponding concrete slab with the anchoring projections embedded in the concrete of the corresponding slab. The plastic sheets are arranged, configured and positioned such that a respective edge flap portion thereof projects outwardly beyond each edge of the corresponding slab. Each of the edge flap portions has an outboard segment. The formed panels are arranged in adjacent, aligned positions around a periphery of a tank foundation with the inner surfaces of the slabs facing inwardly, with the elongated edges of the slabs extending upwardly, with the respective elongated edges of each slab disposed in opposing spaced relationship relative to the elongated edges of adjacent slabs to thereby present elongated gaps therebetween, with the plastic sheets disposed within the periphery, and with the outboard segments of the edge flap portions of each sheet overlapping the outboard segments of the edge flap portions of the sheets of adjacent panels at said gap. The overlapping outboard segments are welded together in situ with an upwardly extending seam.
Desirably, although not necessarily, a wedge welder may be used for welding the overlapping segments together. When a wedge welder is used, a main body portion of the welder may ideally be located on an opposite side of the plastic sheets from the concrete slabs during the welding. Ideally, a second portion of the wedge welder may be positioned within the gap between the edges during said welding.
In preferred forms of the invention, the edges of the panels may be coextensive in length and the edge flap portions may project outwardly beyond the edges along essentially the entire length thereof. In other preferred forms of the invention, the panels may initially be formed with the edges thereof disposed to extend in an essentially horizontal direction. That is to say, the panels may be formed on the ground and thereafter erected so that the edges extend in an essentially upright direction. When the panels are erect, the welding may ideally be accomplished by causing a welder mechanism to move upwardly along the overlapping segments of the edge flap portions of the plastic sheets. In further accordance with the concepts and principles of the invention, the gap between the edges of the panels may be filled with a grouting material after the welding has been completed. In this latter regard, it is a very desirable feature of the invention for the plastic sheets to be arranged and constructed such that anchoring projections are provided on the edge flap portions so that the same project into the gap. Accordingly, during the grouting operation, a firm bond may be created between the anchoring projections and the grout to hold the plastic sheet firmly against the concrete at all locations including the gaps.
In further accordance with the concepts and principles of the invention, the same provides plastic lined structures and plastic lined tanks that have been built employing the methodology of the invention.
As mentioned above, the present invention relates generally to the field of concrete structures of the sort which may often be used in the construction of ground level or elevated concrete liquid containing storage tanks and the like, and to plastic lined concrete structures and the methodology used in the fabrication of composite plastic lined concrete structures whereby the plastic lining is securely affixed to a concrete wall. In connection with the foregoing, and in further accordance with the invention, the tanks may have no roof or a roof that comprises a dome made from concrete, aluminum, fabric, or a flat panel roof with or without column supports that bear at or beneath the floor of the tank.
In a particularly preferred mode of the invention, the same provides methodology for constructing plastic lined concrete tanks; however, as will be apparent to those of ordinary skill in the concrete construction art, the invention more broadly relates to the construction of any sort of plastic lined concrete structures where it is desirable to prefabricate a plurality of lined concrete panels, cause the panels to be arranged in an aligned, side-by-side relationship, and thereafter weld the separate linings on adjacent panels together in situ to thereby present a continuous sealed barrier.
Broadly, and with particular reference to
Each of the panels 10 also includes a plastic sheet 22 having a plurality of anchoring projections 24 protruding outwardly from a face 26 thereof, and the panels 10 are desirably formed in such a way that the face 26 of each plastic sheet 22 is engaged against the surface 18 of the corresponding concrete slab 12 with the anchoring projections 24 embedded within the concrete of the slab 12. The sheets 22 may be formed from any sort of thermoplastic material which is essentially inert to the substances that it will come into contact with during operation and tough enough to withstand the physical rigors associated with the construction and/or use of the lined structure. Ideally, the sheets 22 may be formed from high density polyethylene, linear low density polyethylene, polypropylene and/or PVC. Desirably the plastic sheets 22 are wider than the concrete slabs 12, and each sheet 22 is arranged and positioned on its corresponding slab 12 in such a way that an edge flap portion 28 thereof projects outwardly beyond the edge 14 of the corresponding slab 12 and an edge flap portion 30 projects outwardly beyond the opposite edge 16 of the corresponding slab 12.
The sheets 22 generally may have a thickness ranging from about 0.5 mm (0.020 inch) to about 7 mm (0.28 inch), and desirably the thickness may be within the range of from about 1.5 to 4 mm. For heavy duty operation under adverse and/or corrosive chemical conditions, it has been found that a high density polyethylene material having a thickness of about 3 mm may be desirable. Conversely, for applications where the tank will contain relatively pure water and be exposed to mild temperature conditions, it may be desirable, for economical reasons, to use a linear low density polyethylene having a thickness of 2 mm.
As can be seen from
A preferred procedure for forming the panels 10 is illustrated in
The sheet 22 is laid out such that the edge flap portions 28 and 30 extend laterally beyond the lateral extremities of the upper form surface 42 on each side thereof. In this regard, edge flap portion 30 can be seen in
As can be appreciated from
As is illustrated in
As described above, the panels 10 are pre-fabricated and arranged in place after the concrete has become set. Alternatively, in accordance with another embodiment of the invention, the panels 10 may be formed in situ in an already erect condition. In accordance with this aspect of the invention, and with specific reference to
In another embodiment of the invention, the panels 10 may be formed using concrete spraying methodology. In accordance with this form of the invention, a form assembly similar to the assembly 140 may be used. However, in this case, the outer form element 144 is not needed. The construction of the panel 10 in this case simply involves constructing the form element 144, placing the plastic sheet over the face 146 of the latter with the ribs projecting outwardly, installing the steel reinforcing material, and spraying concrete onto the exposed surface of plastic sheet 22.
In each of the embodiments described above, the final arrangement of the panels 10 is as illustrated in
Preferably, each gap 34 may vary in width from about 4 inches to about 20 inches, and desirably the width of the gap 34 should be about 6 to 8 inches. Advantageously, each of the flap portions 28, 30 may project laterally and outwardly beyond edges 14, 16 of slab 12 for a distance of from about 4 inches to about 20 inches, and ideally the outboard segments 36, 38 should overlap a minimum of 2 inches and a maximum of 10 inches. Generally, it is preferred for the overlapping segments 36, 38 to be positioned centrally of the gap 34. In a particularly preferred form of the invention, the gap 34 may be about 7 inches wide and the flap portions 28, 30 may project outwardly beyond the edges 14, 16 of slab 12 for a distance of about 5 inches, whereby the overlap is about 3 inches wide.
The overlapping outboard segments 36 and 38 may be welded together in situ using hot air welding, hot gas welding, infrared element welding and/or wedge welding. However, wedge welding may desirably be used in accordance with the preferred aspects of the invention. A typical wedge welder 56 is illustrated in
In further accordance with the concepts and principles of the present invention, the overlapping outboard segments 36, 38 of the edge flap portions 28, 30 are welded together in situ using a wedge welder 56. This operation is best illustrated in
After each seam is completed, the gap 34 may desirably be filled with a grouting material 70 as illustrated schematically in