US2873505A

US2873505A - Method for pouring concrete structures

Info

Publication number: US2873505A
Application number: US471380A
Authority: US
Inventors: Sheldon Arnold
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-11-26
Filing date: 1954-11-26
Publication date: 1959-02-17
Anticipated expiration: 1976-02-17

Description

Feb. 17, 1959 A. SHELDON METHOD FOR POURING CONCRETE STRUCTURES 2 Sheets-Sheet 1 Filed Nov. 26, 1954 a ATTORN Y INVENTOR k/vozo Aka-200w Feb. 17, 1959 A. SHELDON METHOD FOR POURING CONCRETE STRUCTURES 2 Sheets-Sheet 2 Filed Nov. 26, 1954 ATTORNE United States PatentO METHOD FOR POURING CONCRETE STRUCTURES a Arnold Sheldon, Glen Gardner, N. J. Application November 26, 1954, Serial No. 471,380

1 Claim. (Cl. 25-155) The present invention relates to a method for pouring concrete structures.

The invention is described as embodied in flexible forms for pouring concrete walls of various kinds having curves of various radii and tangents to the curves and in methods of making various structures, for example, such as swimming poolshaving vertical or inclined serpentine walls.

Among the advantages of the method of pouring concrete walls. described is that it enables a completely formed floor, wall, and cap to be made in three pouring operations. Or, where the top of the wall is formed without an overhanging cap, a complete footing and wall can be made with two pouring operations.

every case is a precision cast wall. And even for very large walls the method can be performed with only two The result in the method described, two men are enabled to build a-l are those resulting from the fact that they are simple, strong, and rugged and very easy to use, lending themselves readily to use by the average homeowner.

The forms are very easy to fabricate and consequently are these forms can be used over and over again, for many years, their cost per job becomes insignificant. The forms described have concrete supporting faces of smooth flexible sheet material, sheet steel being used in the particular forms described. The particular forms described, withcomparatively low in initial cost, and, moreover, because out modification or adaptation, can be used to build a wall of any length and thickness and of any curvature or combination of curves with a radius of 5 feet or larger.

Sharper bends can be formed by the use of thinner gage sheet material in the forms.

In forming walls opposed sets of flexible sheet forms are used, one set of the forms being bolted to anchors in a previously cast footing (orfloor), and the other firmly held in uniformly spaced relationshipfrom the first set and advantageously being supported and, in some in- For example, in building a pool, the outer forms for the pool wall may be "bolted to the perimeter of the floor with the inner forms stances, suspended from the first set.

coupled to the outer forms and supported from them.

The forms described have smooth faces and are well suited for the use of vibration devices during the pouring.

With these forms the highest quality of poured concrete can be obtained.

The forms described include rows of perforations running parallel to the top and bottom edges of the form.

Where desired, vertical stiflening elements may be secured to the outer surface of the sheets in the forms, either permanently or temporarily. For very gradual curves or straight tangents additional longitudinal stiffening elemerits may be used with the forms.

' the forms in one or two jobs.

ice

In casting a serpentine wall as described, a number of flexible forms in end-to-end relationship isarranged to define the desired curves. These first forms assume the desired wall curves because they are bolted directly, or indirectly, to a previously cast footing (or floor). These first forms have two rows of closely spaced perforations running parallel to and near the top and bottom edges of the sheet, respectively. A second group of similar forms with at least two rows of holes parallel to and near the top and bottom edges of the sheet are used to definethe other face of the wall. The second formsare spaced at uniform distance from and supported fromthe first forms by means of concrete form ties and lag bolts. The holes in the second forms being spaced at distances corresponding'to the desired spacing of the ties.

Because of the close spacing of the holes in the first forms, one of these holes is always substantially opposite a hole in the second forms and thus, regardless of the curving of the forms, it is easy to run concrete form ties between opposite pairs ,ofholes and thus to obtain the desired uniform spacing of the forms. t

Advantageously, when the second forms are removed from the exposed face of one side of the wall, it is found to be as smooth as the surface of the steel sheet material of the forms and requires no further finishing. I have found that there is substantially no leakage of cement from the rows of closely spaced holes in the first forms, even though most of these holes are left open when the forms are set up and the concrete is poured. The rows of small bumps which are formed being readily smoothed off or being covered by earth. For example, inmaking a swimming pool, the first forms with the closely spaced holes are arranged around the outside of the pool. Advantageously, the serpentine wall obtains greatly increased rigidity and resistance to overturning due to its curves. In effect, the concrete is in horizontal arches, and therefore, advantageously is in compression when lateral forces are applied.

Among the many advantages of the curved wall construction described, for example, in the case of building walls or retaining walls, is the fact that the walls have greatly increased strength both due to the arch effect, which iswell suited to withstand side loads such as are exerted by an embankment or by theearth around a swimming pool in pressing it against the wallsfof the pool, and due to the corrugation eifect in producing a better vertical load "bearing wall. The convex portions of the curves act in effect as abutments extending, out from the average position of the centerline of the wall. The result is a great increase in the strength of the concrete. Because of the strength inherent in the design, a minimum percentage of reinforcement is needed; the resultant saving in cost, in many instances, pays for the initial cost of The serpentine concrete wall described herein is capable of sustaining unusually large loads, both in compression from top to bottom and bending and overturning forces, such as those experienced by the wall of an empty swimming pool when the earth is saturated with rain, or during frost. heaves. These large forces would simply buckle in'a flat wall containing the same amount of concrete. t

The curved walls described can be made thinner, resulting in a further saving in material, this also saves in the overall weight of the structure and in the required size of the foundations, thus enabling a two-fold saving, in addition to the saving in reinforcement discussed above. i t

In building a swimming pool with inclined walls,in accordancewith the method described, low flexible forms are used in casting a curbing around the excavation at its lip. The inner form is then suspended by means of cantilevered form ties from the curbing and from the of Figure 1;

top of the inner form. When the concrete is poured between the curbing and the suspended form, the concrete runs down the sloping wall of the excavation and into the bottom to form the sides and bottom of the pool which may then be troweled up to smooth any rough places, completing the pool. When the method of the present invention is used in building retaining walls, the wall is made serpentine so that it alternately curves toward and away from the 'embankment which it is supporting. The footings for the wall are cast so that they all project into the embankment asfar as the nodes of the curves. The result is, in efiect, to. provide cantilevered arms projecting inwardly from the outwardly curving portions of the wall underneath a substantial portion of the embankment so as to resist any overturning forces exerted by the embankment against the retaining wall. The resulting structure is extremely strong and requires only a fraction of the "amount of concrete required in the usual type of battered wall used to retain embankments today.

.The forms described lend themselves most readily to the building of a wide variety of different footing and wall arrangements, including walls with walking strips adjacent the bottom or top of the walls. The method described is well suited for building terraced garden arrangements, or scalloped wall bay arrangements, and is highly advantageous in building tanks.

The various aspects and advantages of the present invention will be more fully understood from the follow- I ing description considered in conjunction with the accompanying drawings, in which:

Figure 1 is a partial perspective view, partially in section, of a concrete swimming pool made with the method and apparatus described herein;

Figure 2 illustrates the first step in the building of the swimming pool shown in Figure 1; I

Figure 3 shows the inner and outer wall forms in place ready for the pouring of the wall of the swimming pool Figure 4 shows the forms in place for the pouring of v the coping, which completes the swimming pool;

Figure 5 is an exploded perspective view of the first and second flexible forms used in supporting the outside and inside surfaces, respectively, of the pool shown;

Figure 6 is a partial perspective view of the flexible form used for casting the coping along the top of the wall of the pool;

Figure 7 is a partial perspective view ofv the flexible form used in making walkways adjacent the tops or bottoms of walls;

Figure 8 illustrates a method of pouring curved sloping pool walls;

v Figure 9 illustrates the way in which abutting edges of the form are disengageably locked together; and

Figure 10 shows a wall tie with a cradle secured thereto for supporting and aligning horizontal reinforcing rods.

As shown in Figure '1, the swimming pool includes a I generally saucer-shaped concrete bottom 10 which curves upwardly around the edges, which edges may be somewhat thicker than the center so as to form a footing portion 12 beneath the wall 14. Because of the inverted arch shape of the bottom 10, the concrete therein is in compression and thus requires only a minimum of reinforcing material as may be required for resisting stresses due to temperature variations. The bottom It may include spaced reinforcing rods but usually a layer of 6 inch square reinforcing wire mesh 15 is sufficient. lengths of rods 16 spaced every few feet are driven into the earth and left standing so as to be included in the footing portion 12 with their ends projecting above the top surface 17 of the footing 12 to provide a good bond at the construction joint with the wall 14 which is poured after the integral bottom and footing ,have set.

Also, the surface 17 is trowelled rough as it hardens to provide better bonding with the wall 14.

Short Also, a key-way may be formed by laying a plast pipe temporarily along the surface 17, the pipe being removed before the wall is poured to have a semi-circular recess extending along the length of the footing 12.

' The wall 14 is serpentine, of uniform thickness, and vertical. A swimming pool with a sloping serpentine wall is described later. The wall 14 may include vertical reinforcing rods 18 spaced along the wall, with the upper ends 20 of these rods 18 projecting above the roughened top surface 21 of the wall 14, so as to provide a good construction joint with a coping portion 22 which may be cast on top of" the wall 14. When the coping 22 is included, the rods 18 are bent outwardly at right angles to the wall 14, as indicated by the dotted arrow, before the coping is poured, to reinforce this coping, which has a generally inverted L-shape, as seen in cross section. The coping 22 is poured after the wall The coping may include a number of longitudinal reinforcing rods 24; for example, four rods are shown running longitudinally along the length of the coping. Three of these rods 24 are spaced at uniform distances beneath the upper surface of the coping 22 and the fourth rod is in the lower portion of the coping 22 which overhangs and projects down along the outer surface of the wall 14. Among the advantages of these forms are their smooth, obstruction-free upper edges which act as guides to facilitate screeding off. These edges may advantageously be used as tracks on which to run a small Weighted truck 25 described in detail later.

Instead of using a coping, the reinforcing rods 18 may be ended below the top surface 20 of the wall and this surface then screeded off smooth on a level with the top of the outer form to finish the pool, as explained in detail below.

Figures 2, 3, and 4 illustrate a method embodying the present invention. Some of the various reinforcement elements shown in Figure l are omitted from Figures 2, 3, and 4 in order to make the various steps of the method more clear, but it will be understood that reinforcing rods and wire mesh are used as described above and would be bent at the various steps in the building of the structure, as explained in connection with Figure 1.

In order to cast the bottom 10 ofthe pool, a low flexible form 30,- as shown in Figures 2 and 6, is staked in position in an excavation by means of iron stakes 32. Each stage projects down through the bight of a U-shaped bracket 36 somewhat above mid-way between the upper and lower edges of the form 30. The stakes 32 are releasably locked to these brackets 36 by metal wedges 33 driven horizontally through transverse holes in these brackets. The inner surface of the form 30 is used to to define the outside face 40 of the footing portion 12.

Each of the forms 30 is of No. 10 gage steel sheet 12 inches high and 8 feet long. As shown in Figure 6, an upper and lower row of

holes

41 and 42, respectively, are provided extending, respectively, along parallel to and 3 inches down from the top and 3 inches up from the bottom edges of the form 30. These holes are hi of an inch in diameter 1 inch apart on centers, and extend the full length of the form 30. The features of the connection means used at the ends of these forms 30 are discussed later. The forms are connected in abutting relation to form a smooth continuous inner surface. Through the lower row of holes 42 are inserted lag bolts 43 which fit snugly and are screwed into concrete bolt anchors 44 so as to support the anchors, which are then cast into the concrete, for purposes described hereinafter. These anchors 44 comprise a helically formed wire with spaced turns, the turns being welded to a pair of diametrically opposed rods extending longitudinally of the helix. Such anchors are available commercially from Superior Concrete Accessories Corporation as Cone-Fast Coil Ties, or from the Dayton Company as RichmondTies. As many as four bolts 43 opposite the corresponding rows in form 48. "lag bolts 56 are then inserted through the holes 54 in and anchors 44may be used for each form 30, spaced evenly along itslength, but usually two bolts and anchors are entirely. adequate.

With these anchors 44, I use spreader cones 46 around the shank of each lag bolt adjacent the surface of the concrete so that after the concrete has set and the lag bolts are unscrewed, these cones 46 can be removed leaving funnel-shaped openings to provide easy access to the anchors 44, which are used in the next step of the process. Moreover, the resulting funnel-shaped openings in the concrete are easy to point up, after the wall is complete, and leave the anchors 44 spaced a distance in from the surface of the concrete in accordance with good practice.

The outside portion of the rough top 17 of the footing comes up to a level about one inch below the bottoms of the upper holes 41. When the bottom and footing 12 have hardened, the flexible forms are removed by removing the wedges 38, pulling up the stakes 32, and unscrewing the lag bolts 43.

As shown in Figure 3, the next step is the bolting in place of the outside flexible wall forms generally indicated at 48 against the outside face of the footing 12. The form 48 (see also Figure 5) is also 10 gage sheet steel. It is 3 feet high and 8 feet long. It includes three I

rows

50, 52, and 54 of closely spaced holes. The upper row of holes extends along three inches from the top edge of the form 48, and the second row 52 extends along nine inches above the bottom edge of the form 48. The third row 54 is three inches above the bottom edge. These holes are all 3 of an inch in diameter and spaced on one inch centers.

Because the holes in the lower row 54.are so closely spaced, fourof these holes in each form 48' line up with the four funnel-mouthed holes and anchors 44 left when the four lagbolts 43 and cones 46 were removed from each of the forms 30. This alignment of the holes in row 54 and of the anchors 44 occurs regardless of the curvature of serpentine .form of the face 40 of the footing 12, and because the holes in row 54 are M of an cally outside of each form. These studs are 3 .feet

high, each with three holes 50', 52, and 54' positioned Longer the studs 55 and through whichever holes in .the row 54 are aligned with the anchors 44, and are tightened;

firmly to hold the forms 48 to the footing.

In order to secure the inner flexible forms 58 (see also Figure 5) in place, the upper and

intermediate rows

50 and 52 of holes in the outer forms 48 are used. The

forms 58 include three rows of 4 inch holes spaced tom edge of the form 58 is rested down on the inneri. .edge of the footing 12 with the bottom row 64 opposite theintermediate row 52 of the form 48. The intermediate row 62 is opposite the top row 50. Four studs 65 may be used with the inner forms 58; These studs are identical with the studs 55 except that the two holes 60 and 62 are at the top to correspond with the rows60 and 62.

Because of the close spacing of the holes in the

rows

50 and 52, one or another of these holes is always located opposite to a corresponding hole in the interme-.

* diate and bottom rows 62 and 64 of the inner form 58, regardless of the curvature being used. However, with 'No. 10 gage steel, I find it preferable to keep all curves at least 5 feet in radius. Where sharper bends are desired, thinner gage steel. is used. Ifind that the. thinner '6 gage forms are entirely satisfactory for supporting concrete with sharper bends because these sharper bends provide a stifiening action, as explained above, which offsets the greater flexibility terial.

Where very gradual bends are being made, I find that it is sometimes desirable, as described in detail later, to provide additional longitudinal stiffening for the

forms

48 and 58 by using one inch thick roofing boards between the outer surfaces of the forms and the

studs

55 and 65, respectively.

Suitable lengths of form coil ties 68 are inserted between the two

forms

48 and 58 and more lag bolts 56 are screwedthrough the holes in the studs 55 and through the aligned holes in forms and into the opposite ends of the form ties 68. These ties 68 are similar to the anchors 44 except that two helically wound wires are used at opposite ends to provide threads for engaging the lag bolts 56, and the rods in the ties are of a length to span between the spaced forms. These rods are preferably arranged one above the other to provide a slight degree of lateral compliance to aid in inserting the lag bolts. The ties 68 are cast. into the concrete. Cones 46 are also used with them, as 'shown. The forms .48 and 58 are uniformly spaced.

,In order to secure the ends of the

form

48 and 58 in abutting relationship with the ends of the respective adjacent forms, as shown in Figure 9, by 2 inch angle of the thinner gage ma- .irons, 2 feet long are welded along parallel to the ends of all of these forms with the longer lag outstanding. In order to interlock the forms, against relative lateral shifting, I find it desirable to have the angle irons at one end of each form spaced back a slight distance from the edge so that the projecting edge forms a lip 73, for

example, as shown in, Figures 6 and 8. At the opposite end the angle iron projects beyond the edge of the form to leave a rabbeted socket for receiving the lip 73. These angle irons leave 6 inches at the top and bottom edges of the forms free for the use of longitudinal stifiening boards, as discussed below. Three inch holes are provided in each angle iron for the use of slotted key bolts 72 and wedges 74, as indicated in Figure 9, to. lock the forms together.

The next step is the pouring of the concrete between the

forms

48 and 58 to form wall 14, as indicated by the arrows in Figure 3. The top 76 of the wall 14 is made rough and on a level with the top of the form 48, leaving the top edge of the inner form projecting 6 inches above the top 76. The upper row of holes 60 in the inner form are used in the construction of the coping, as explained later.

As soon as the wall 14 has set, the outerform 48 is removed by unscrewing the lag bolts. At this point the wall is backfilled up to a level 77 about six inches'below the rough top surface 76. In place of the lag bolts which were .in the outer ends of the upper ties 68, stud bolts 78 are inserted. These stud bolts are then used to support additional form ties 79 (see Figure 4) which are cantilevered out from the stud bolts and connected by short lag bolts 43 to the lower row 42 of holes in the same flexible narrow form 30 which was used for forming the floor and footing. The top row 41 is aligned with corresponding holes in the top row 60 of the inner form 58, and the

forms

58 and 30 are then fastened together by short lag bolts .43 and double length coil ties 88, as shown in Figure 4. The ends of these forms 30 are fastened together by by 2 inch angle irons (see Figure 6) using slotted key bolts similar to those shown in Figure 8. These angle irons are arranged to provide a lip 73 for engagement with a rabbeted socket similar to that described in connection with

forms

48 and 58. The bottom edge of the leg of the angle irons 90 are cut off at an angle and thetop of the angle iron is spaced down from the top edgeof the form 30, as shown, to provide. clearance for longitudinal stiffening elements,

where desired. The coping 22 is then cast in place between the top edge of the inner form and the form 30, resting down on the top 76 of the wall and on the backfilled earth 77. As soon as the coping is dry, the form 30 and the inner wall form 58 are removed, leaving a completed swimming pool.

When it is desired to make the wall 14 without a coping or cap 22, shorter reinforcing rods are used and its top 76 is screeded oil level with the top edge of the outer form 48 at the completion of the step shown in Figure 3. If desired, the wall can be made 6 inches higher by clamping the lower edge of the outer form against the top of the face 40 using clamping pieces held by bolts in the anchors 44 in the footing. Then the top edges of the inner and

outer forms

48 and 58 are at the same height and can be used to guide a weighted screeding truck.

Figure 4, the reinforcing rods 24 are wired to the underside of the double length ties 88 and the lower rod 24 to the tie 79.

In order to minimize the number of forms required to complete larger size swimming pools, I have found it advantageous to cast the entire bottom 10 at once.

- Then I cast one half of the wall 14, and then use the same forms to cast the opposite half. I may use the coping 22 as a means of further tying the two halves of the wall 14 together. This tying action is obtained by stopping the ends of the first half of the coping somewhat short, for instance three or four feet short, of the ends ofthe first half of the wall. Then, the second half of the coping overlaps three or four feet of both ends of the first half of the wall so that the two parts of the wall are firmly united by the overlapped coping.

In order to provide longitudinal stiffening for the

forms

48 and 58 when they are used to build straight walls or walls having a slight curvature, I may stiffen the upper and lower edges of the forms by 12 or 16 foot stringers of ripped pine roofers one inch thick and about 2 /2 inches wide placed immediately above and below the lag bolts through the top and bottom rows of holes in the wall forms. The joints-in these stringers are staggered from each other and from the joints in the forms. In addition, where desired, one by six inch roofing boards 7% feet long may be placed against the outer surfaces of the

forms

48 and 58.

A highly advantageous method for pouring a sloping retaining wall, for example, for making a swimming pool, is illustrated in Figure 8. An excavation is made and the walls of the excavation are pushed out and back by a bulldozer to form sloping earth banks 92. A curbing 94 is then cast around the upper edge of the banks with its inner face at the lip of the bank. The outer forms used for the curbing 94 are the forms 30. The inner forms 96 are similar to the forms 30 but have only four holes in each row 41' and 42 spaced on 2 foot centers. The forms 30 and 96 are removed after the curb has set. The level of the top of the curb is spaced about mid-way between the rows of

holes

41 and 42 in the forms 30 so that one row of coil ties 68 is cast crosswise through the curbing 94. Stud bolts 78 are inserted into the inner'ends of the coil ties 68 in curb 94, and other coil ties are then used to cantilever the forms 96 in position inside of the inner face of the curb a distance corresponding to the desired thickness of the walls 98 of the pool, indicated in phantom. The top rows of holes 41 are connected by longer coil ties 88 to the holes 41, as shown, so that .reinfor'cing rods 100dri-ven in the ground and left standing are cast vertically in the curb and then bent over and down into the center of the wall. Concrete is then poured between the forms 30 and 96 and is allowed to run down the bank 92. A man in the excavation in hip boots trowels up the inner surface of the walls 98. The bottom of a pool with sloping walls 98 may be of poured concrete or may be an impervious dirt layer.

So far only two sizes of forms have been described: these include

forms

30 and 48, which have rows of closely spaced holes and their corresponding opposed forms 96 and 58, respectively, which have rows of holes spaced on 2 foot centers. These forms can be used to make walls with or without caps and of variable radii, as already described. Also, using

forms

48 and 58, walls of any height can be made, as will be apparent from Figure 3. After the wall 14 has set, the

forms

48 and 58 are unbolted, raised up and have their lower rows of holes 54 and 64 bolted to the upper anchors 68. This process is repeated as many times as desired. A coping can be formed at the wall top, if desired.

A third size of form 102, as shown in Figure 7, can be used to, obtain even a wider variety of walls, footings, and walkways can be built. This foim is 6 inches high and 8 feet long with a row of holes on 2 foot centers down the middle, and with stake pockets 36 similar to those on forms 30. When these are staked to the ground adjacent the top or bottom of a wall, a sidewalk can be readily formed. For example, in place of the form 30 in Figure 4 a form 102 is staked along the top 77 of the backfill, which in this case would be level with the surface 76, at a distance from and parallel to the upstanding edge of the inner form 76, to make a walkway around the outside of the top of the wall.

By using the forms 102 spaced in from the lower edge of the forms 58, a walkway or horizontal shelf for swimmers to stand on is formed around the floor of the pool adjacent the wall 14.

Along the unobstructed top edges of the form may advantageously be run a truck, as indicated at 104 in Figure 4. Such a truck may be used to dump or spread the concrete mix, but as illustrated here is a small weighted truck fitted with flanged wheels 106 to run on the form edges. The truck carries a small electric vibrator 108 of the external form type to give lateral side to side vibration. Across the front of the truck is a screed 110 angled so as to plow oif any excess mix and dump it to the outside of the forms. The wheel flanges are spaced to accommodate slight irregularities in the forms.

These flexible forms are highly suited for the use of internal vibrators, for the forms are so unobstructed. Also, external vibrators can be applied to their outside faces, shaking the concrete downsmoothly and densely against the opposed concrete-supporting faces of the forms to yield the highest quality of poured concrete with smooth attractive surfaces.

With these forms, a somewhat drier concrete mix can be used, advantageously increasing the strength of the structure.

I have found that only an insignificant amount of concrete tends to dribble out of the pluralities of open holes in the various rows, described above. The resulting bumps on the outer surface of the walls are easily smoothed oif after the forms are removed.

Where drier mixes are used, substantially no concrete comes out through the V inch holes.

Where curves of shorter radii are formed, the abutting edges of the inner sheets may tend to meet at an angle. I pull these edges into a smooth curve by using coil ties and cones against the concrete-supporting faces of the forms at their joint. A lag bolt passes out from the coil tie through aligned notches in the abutting form edges and through a hole at the center of a 2 by 3 board which is about a foot and a half long. Tightening up the bolt pulls the abutting edges into a smooth curve.

Although the forms have been described as inner 9 and outer forms, their relative positions can be reversed by casting the footing with an upstanding rim to provide a face such as the face 40 of Figure 2, but facing inwardly.

In order to locate and hold reinforcing rods in position, whenever they may be used, the various wall ties may advantageously have chairs or cradles secured thereto. For example, as shown in Figure 3, a U-shaped chair 112 is welded to the lower cross tie 68. This chair 112 is formed by a stilf wire or thin rod bent into a U-shape with its legs straddling the tie and projecting up on either side. The legs of the chair are thus laterally and longitudinally offset so as also to be able to straddle and hold a reinforcing rod 114, which in some instances may be included, extending lengthwise in the bottom portion of the wall 14.

In Figure is shown a dual cradle 116 for supporting two horizontal rods 118 in side by side relationship. The cradle 116 is formed of a stiff wire or thin rod bent into a generally bridge-truss shape with two pockets 120 at the top near either end for supporting the rods. The lower ends of the two legs 122 of the cradle are welded to the cross tie 68" near either end. The tie 68' is similar to the tie '68 but is longer, for forming thicker walls.

A further advantage of these forms is that when the ties are secured in place they help to hold the curvature of the forms in the horizontal plane, and the horizontal curvature holds the forms vertically straight.

From the foregoing description it will be understood that I have provided a method well adapted to yield the many advantages described above. It will be understood that the forms of the present invention are subject to modification and changes as may best fit them for each particular application, and that the scope of the present invention is intended to include such modifications or adaptations, as defined by the following claim, limited only by the prior art.

The subject matter divided from this application is 10 claimed in a copending application Serial No. 686,813, filed September 25, 1957.

What I claim is:

The method of casting a curved concrete wall comprising the steps of casting a footing having at least one vertical face defining the desired curvature of one surface of the completed wall, securing a flexible sheet against said face to conform to the curvature of said face, curving a second flexible sheet to conform to said first sheet and securing said second flexible sheet to said first sheet at a first uniform distance from said first sheet, casting a wall portion therebetween on top of said footing, removing said first sheet, supporting a third flexible sheet at a second greater uniform distance from said second sheet than was said first sheet backfilling adjacent said third sheet, and casting a top portion of said wall between the top of said second sheet and said third sheet.

References Cited in the file of this patent UNITED STATES PATENTS 811,032 Byor Ian. 30, 1906 1,044,862 Crary Nov. 19, 1912 1,141,057 Heltzel May 25, 1915 1,446,681 Wire Feb. 27, 1923 1,517,244 Martin Dec. 2, 1924 1,628,316 Heltzel May 10, 1927 1,922,584 Heltzel Aug. 15, 1933 2,523,131 Martin Sept. 17, 1950 2,506,485 Boudousquie May 2, 1950 2,614,311 Shook Oct. 21, 1952 2,669,000 Seeman Feb. 16, 1954 OTHER REFERENCES Engineering News-Record (1), Feb. 2,. 1950.

Engineering News-Record (2), Mar. 2, 1950. Engineering News-Record (3), Apr. 20, 1950.