US3324207A - Method of placing concrete with a predetermined selected placement of aggregate - Google Patents

Description

June 6, 1967 J, M s Ls o 3,324,207

METHOD OF PLACING CONCRETE WITH A PREDETERMINED SELECTED PLACEMENT 0F AGGREGATE Original Filed July 12, 1963 2 Sheets-Sheet 1 /3 r o l 5] w /6 61 .I O I.

z/ames M S/w/szane INVENTOR.

BY I 7W E W June 6, 1967 J. M. SHILSTONE METHOD OF PLACING CONCRETE WITH A PREDETERMINED SELECTED PLACEMENT OF AGGREGATE Original Filed July 12, 1963 2 Sheets-Sheet 2 INVENTOR.

A 770 IPA/[76' United States Patent 3,324,207 METHOD OF PLACING CONCRETE WITH A PREDETERMINED SELECTED PLACEMENT 0F AGGREGATE James M. Shilstone, R0. Box 13163, Houston, Tex. 77019 Continuation of application Ser. No. 294,600, July 12, 1963. This application June 16, 1965, Ser. No. 471,494 8 Claims. (Cl. 264-35) This application is a continuation of copending application for United States Letters Patent, Ser. No. 294,- 600, filed July 12, 1963.

This invention relates to an improved method of placing concrete and refers more particularly to a method of placing concrete in which different aggregates which are selected for their known properties are placed in predetermined positions in the cast structure.

By way of illustration, but not by way of limitation, the invention will be primarily described in connection with its use in casting concrete structures having an external face or faces formed of exposed aggregate as a means of beautification of the finished product. However, the invention also has application to the casting of structures wherein aggregates having different strength, structural, or weight characteristics are selected and placed in predetermined positions in the finished product so as to contribute their particular characteristics to at least a major extent to the finished product. For example, light weight expanded aggregates (considered objectionable by some structural engineers because of plastic flow that might take place in a structure over a period of years) may be used throughout a major section of a concrete product in which a rigid shell is provided by use of rock aggregate to compensate for the objectionable plastic flow. Thus, a considerable saving in weight may be effected over the use of all rock aggregate.

The use of exposed aggregate as a means of beautifying concrete structures is coming more and more into vogue. However, in placing concrete in accordance with conventional techniques, it has been extremely difiicult to obtain uniformity of distribution of the aggregate over the surface to be exposed so as to prevent a mottled effect. At best the limitation of the amount of coarse aggregate that may be used in pouring concrete provides a rather sparse amount of coarse aggregate at the exposed surface for architectural finishes. Further, where the entire structure is cast with high cost aggregate having a selected special appearance, the cost of the structure is nearly prohibitive. For these reasons, veneers have been resorted to wherein precast panels are hung in place on structural members, but the cost is high and no structural support is provided 'by the panels. Also, a checkerboard appearance is inevitable due to the seams which appear between adjacent panels. Some effort has been made to glue aggregate selected for its appearance to a form prior to the casting of concrete structures; but this has not been entirely satisfactory because of high cost of gluing the aggregate in place, the likelihood of aggregate being dislodge-d during the pouring operation, the difficulty of obtaining uniformity in such a pattern and the special techniques required.

It is an object of this invention to provide a method of casting concrete structures in which a section or layer of predetermined thickness and shape may be provided within the form, filled with an aggregate selected for its known characteristics and retained in place by a perforate barrier while the form is filled with a concrete mix containing a different aggregate and sufiicient mortar to flow through the barrier and into the spaces between the individual particles of the placed aggregate. Once the cast structure has sufficiently cured, the form may be 3,3242%? Patented June 6, 1967 ice removed; and if exposed aggregate is desired, the surface motar may be removed by suitable procedures such as washing, bush hammering, or sand blasting, according to known practices.

Another object is to provide a method of casting ex- 'posed aggregate concrete structures in which the amount of expensive aggregate with good appearance may be minimized and readily available and relatively inexpensive aggregate may be used for the remainder of the structure.

Another object is to provide a more economical method of casting exposed aggregate concrete structures which may be readily cast in place using readily available equipment.

Another object is to provide a method of casting exposed aggregate concrete structures in which the aggregate at the exposed face is uniformly distributed.

Another object is to provide a method of casting exposed aggregate concrete structures in which the exposed faces may be vertical, inclined, or overhead.

Another object is to provide a method of casting exposed aggregate concrete structures which is adapted to the techniques of use of chemicals for retarding hardening of the mortar, thereby permitting washing of mortar from the surface to be exposed.

Another object is to provide a method of casting exposed aggregate concrete structures which is adapted to the use of techniques involving the use of shields to provide designs selectively exposing a portion of the aggregate on the removal of mortar to expose the aggregate on the surface.

Other and further objects will appear from the specification and description of preferred embodiments of the invention.

In accordance with this invention, different aggregates are selected with known characteristics to perform different functions when located in different predetermined sections of the structure to be cast. At least one such aggregate is placed in the form and retained there without any mortar while a mix of the other aggregate and sufficient mortar to provide the mortar for the placed aggregate is placed into the other section of the form. It is preferred to use vibration while placing the concrete mix to force the mortar into the spaces between the placed aggregate.

In the drawings which form a part of the instant specification and in which exemplary methods of this invention are illustrated:

FIG. 1 is a side elevational view illustrating one step in the assembly of a form in the practice of an embodi ment of this invention;

FIG. 2 is a top plan view illustrating a successive step in the assembly of the form of FIG. 1;

FIG. 3 is a plan view of the form of FIG. 2 illustrating -a selected aggregate occupying a predetermined section between the barrier and the form of FIG. 2;

FIG. 4 is a view in vertical section through the ap- Q paratus of FIG. 3 after the center core of concrete mix has been placed; and

FIG. 5 is an isometric view illustrating another embodiment of the method of this invention.

In FIGS. 1 to 4 of the drawings, there is illustrated the stepwise casting of the vertical column in accordance with the method of this invention. FIG. 1 illustrates the mounting of the reinforcement rods 10 on the upper end of a lower column or base 11. The reinforcement will be selected and mounted in accordance with usual practices for the services in which the structures are to be placed. In the interest of simplicity, cross braces between the reinforcement rods have not been shown as they may follow any suitable pattern. In most instances, the reinforcement rod may be used to secure the perforate barrier in place in the form so as to divide the interior of the form into sections or compartments. In the particular embodiment, the barrier is shown as a hardware cloth 12 arranged in overlapping layers. The size of the openings in the barrier will be determined primarily by the size of the aggregate that is retained in the space or compartment provided by the barrier. Usually, square openings having a dimension from A inch to /2 inch have been found to be satisfactory. Briefly, the openings in the barrier should be as large as permissible while still performing the function of retaining the aggregate in the compartment provided by the barrier. While hardware cloth has been shown, this is preferred merely because of its availability and relatively inexpensiveness. Other materials may be used; and, for example, where the barrier is to terminate at or near an exposed face of the concrete structure, it should be of a material which will not corrode or discolor due to weathering. Plastic meshes, fiberglass reinforced plastic, or other suitable materials may be used under such circumstances.

In FIG. 1, the barrier is shown as it is being wrapped about the reinforcement rods, and still another section will be wrapped about the rods until it terminates adjacent the upper ends of the rods.

After the barrier 12 has been secured in place, the form panels 13 are positioned as shown in FIG. 2 to complete the assembly and the casting procedure may be commenced. By reference to FIGS. 2 and 3, it is seen that the barrier 12 has provided an inner or central section 14 and an outer section 15. It is contemplated that the section 15 may be further divided by the use of vertical :panels or barriers 16 as desired which may be either perforate or imperforate. Thus, one aggregate of one characteristic size, appearance or color can be placed in chamber 15 on one side of the panel 16 and a different aggregate having a different characteristic size, appearance or color may be placed on the other side of the panel 16; or the panel 16 may be dispensed with and a single aggregate used to fill the entire space 15. It is obvious that any particular arrangement or placement of panels such as 16 may be used. In most instances, where the panels 16 are used, it is preferred to remove them after the aggregate has been placed in the various compartments of section 15 divided off by the panels. However, where desired, the panels may be left in place during the entire casting process- In the interest of simplicity, the description of the re mainder of the method and of the other figures of the drawings will proceed as though the panels 16 were not used.

FIG. 3 shows the section 15 filtered or packed with an aggregate 17 extending from the bottom of the section 15 to the top. Preferably, the aggregate is usually moistened with water prior to being placed in the section. In order to obtain a uniform and dense aggregate distribution it is not usually necessary to vibrate either the form or the aggregate itself during the filling of the section 15.

Once section 15 has been completely filled with the aggregate but with no mortar being used, section 14 may then be filled with a concrete mix employing a different aggregate and sufficient mortar so that the excess mortar will flow through the barrier and infiltrate the spaces between the individual particles of the aggregate 17. As a pour of the concrete mix rises in section 14, conventional vibrators are used to force the mortar out into the aggregate 17 to fill the spaces or voids therebetween. The form preferably should be leak tight, i.e., imperforate. The core mix should utilize materials selected for their suitability in meeting the structural requirement of the finished product and according to local availability. The core mix may utilize a slump factor which is consistent wit-h normal practice. It has been found, for example, that a core mix having a slump within the range of 3 to inches may be employed; and sufiicient workability exists for the mortar to flow through the barrier and fill the interstices of the aggregate 17.

Where a tall section 15, for example 10 to 20 feet in height, is involved, it may be desirable to fill section 15 in step fashion; that is, place a part of the aggregate 17 in section 15, and then pour the concrete mix into secion 14 to just under the height of the aggregate 17. This will be repeated until the entire structure been cast.

In FIGS. 3 and 4, the aggregate is illustrated as being being rather sparsely spaced within the concrete mix. This is due to the difficulty of illustration on the part of the draftsman, but is to be noted that aggregate 17 should be tightly packed within chamber 15 in order to obtain uniform results and best appearance when the outer surface mortar is removed to expose the aggregate.

Where the finished product is to have the aggregate exposed on one or more faces, this may be done in accordance with usual practices. One method for accomplishing this is to utilize a deterrent for hardening the cement of the concerte and washing the surface mortar from the structure after removal of the form. Another method is to sand blast the surface mortar from the face of the concrete after removal of the form. Also, this is sometimes done by bush hammering the surface mortar from the aggregate. In any event, the aggregate having the desired appearance with uniform distribution will be present and yet the core of the section will have been formed of a relatively inexpensive, readily available, structurally suitable concrete.

The spacing of the barrier relative to the surface of the form should be such as to assure a fully packed layer of aggregate but to reduce the layer to approximately that required, thereby reducing the cost of the relatively expensive aggregate. It is recommended that the spacing of the barrier from the form be approximately 1 /2 times the largest aggregate; but where small aggregate size is used, such as A to /2 inch, it is preferred to use a minimum of about one-inch spacing of the barrier from the form wall. While in the preferred embodiment shown the barrier is illustrated as mounted directly on the reinforcement, it may be suspended from the reinforcement or otherwise mounted in the form. However, usually the reinforcement will be located approximately at the proper distance from the form wall for mounting the barrier; and when this is true, mounting of the barrier is facilitated.

Destructive tests indicate that any parting line or plane imparted by the barrier to structures cast by the method of this invention is substantially negligible from the practical viewpoint. However, if structural requirements dictate it, these may be further reduced either by using a material with a series of alternate depressions and rises whether all in one alignment as in corrugated material or at angular alignment such as two directional corrugations for the barrier, or special barrier material having barblike extensions extending from one or either side;

In the embodiment shown in FIGS. 1 to 4, inclusive, the description has been based on the premise that an exposed aggregate was desired. However, it might well be that this would not be the case or that, if it were the case, still that a desired aggregate having some particular characteristic such as for example lightness would be used for casting the core.

One objection to the use of light weight aggregate such as expanded shales has been that in some uses they have shown a tendency toward plastic flow with time. By the use of stronger non-plastic aggregates in space 15, such light weight, relatively plastic aggregates can be used in core 14, there-by greatly reducing the weight factor of the column and still largely overcoming the deleterious effect of plasticity of expanded shales.

Referring to the embodiment of FIG. 5, there is illustrated a method of casting a horizontal exposed aggregate structure suitable for casting an overhead surface or for casting a flat panel which may be used as a pre-cast structure. The form panel 18 is supported in a substantially horizontal overhead position. It has a side panel 19 which extends upwardly approximately to the height of the thickness of the object to be cast. A selected aggregate 20 is laid on form 19 and barrier 21 is secured over the layer of aggregate 20. The reinforcements 22 are put in place and barrier 21 is preferably secured to the reinforcements. The reinforcements extend upwardly at 23 and a portion of barrier 24 also extends upwardly to about the top of panel 19 and the reinforcements 23. The aggregate 20 fills the section between panel 19 and barrier 24. With this arrangement complete, the core above the reinforcements 22 is filled with the concrete mix made up of a selected aggregate and sufiicient mortar to flow through the barriers 21 and 24*to fill the spaces between the individual particles of the aggregate 20. The upper level of the concrete mix is leveled even with the top edge of panel 19. The structure is permitted to cure at least partially; the form is then stripped; and the exposed surfaces are treated to remove the exposed mortar either by said blasting, washing or other suitable method.

In the foregoing specification and in the claims, reference is made to selection of different aggregates for their known characteristics. This expression is intended to have a broad meaning and when used encompasses not only basically different aggregates such as granite chips and gravel, but also the same type of aggregate, such as gravel for example, but sized differently so as to provide an aggregate of restrictive gradation limits for the surface to be exposed so the individual particles will be more nearly uniform in size. For the non-exposed section, a broader range of gradation is preferred. However, the term aggregate is used herein to refer to what is sometimes called coarse aggregate, and not to include sand and similar fine material used in mortar and grout, sometimes referred to as fine aggregate.

It will be seen that the ends and objects of this invention have been accomplished. There has been provided a method for casting concrete bodies in which the bodies may be cast in place in accordance with standard practices and by use of standard equipment but in which aggregates may be selected in accordance with known characteristics and placed in predetermined sections within the cast bodies. By this means certain characteristics of aggregates may be imparted to the finished product for one purpose and a different aggregate used either for economy or for other desirable characteristics to complete the structure.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the process.

It will be understood that certain features and subcom-binations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1s:

1. The method of pouring of pouring concrete structures with different aggregates selected for their known characteristics occupying different position in the finished stucture comprising the steps of arranging a barrier and a first aggregate within a removable, imperforate form so that the first aggregate is retained in and fills a section of the form, and an aggregate-free section is provided in the form with the barrier between the sections, the barrier having openings smaller than the size of the first aggregate preventing displacement of the first aggregate from its section during the step of placing same; and then placing a mixture of a second aggregate and mortar into the aggregate-free section of the form, the size of the second aggregate being greater than that of the barrier openings, the mortar being in sufiicient quantity for a part thereof to flow through the barrier and into the spaces between the first coarse aggregate, and vibrating the concrete to cause part of the mortar of said mixture to move past the barrier and to the form to fill the spaces between the pieces of the first coarse aggregate.

2. The method of casting in place a structurally sound concrete column comprising the steps of securing reinforcement for the column in an upright position; securing a mesh-like barrier to the reinforcement to enclose a space within the barrier; placing a removable, imperforate form about the reinforcement and barrier leaving a space between the inner wall of the form and the barrier of a dimension great enough to receive a first aggregate therein, said first aggregate being of a size too large to pass through the barrier; packing the space between the form and the barrier with said first aggregate to fill said latter space; then placing uncured concrete in the section within the reinforcement, said concrete having a mortar component and a component of a second aggregate, said second aggregate being of a size too large to pass through the barrier; and vibrating the concrete to cause part of the mortar component of the concrete to flow through the barrier and to the form to fill the voids between the pieces of the first aggregate retained by the barrier.

3. The method of claim 2 wherein said first aggregate next to at least part of the form is ornamental in appearance, and the further steps of at least partially curing the concrete; stripping the form from the structure and removing at least a part of the surface mortar from the outer portion of the first aggregate to give an exposed aggregate effect.

4. The method of casting in place a structural-1y sound exposed coarse aggregate horizontal concrete structure comprising the steps of positioning a lowermost removable, imperforate form with at least one side panel rising at least as high as the desired thickness of the finished horizontal structure; distributing a layer of a first aggregate over the lowermost porton of the form; securing a mesh-like barrier over the layer of first aggegate in contact therewith, said barrier having openings smaller than the size of the first aggregate to retain a full pack of first aggregate between the lowermost portion of the form and the barrier, extending the barrier upwardly with the side panel spaced therefrom a distance to provide a space for receving an additional quantity of said first aggregate, the barrier extending at least as high as the side panel; filling the space between the barrier and the side panel with said additional quantity of said first aggregate; then placing uncured concrete in the interior of the barrier, said concrete having a mortar component and a second aggregate component, said second aggregate being of a size too large to pass through-the barrier openings; and vibrating the concrete to cause part of the mortar component of the concrete to flow through the barrier openings and to the form to fill the voids between the pieces of the first aggregate retained by the barrier; partially curing the concrete; removing the form; and removing at least a portion of the surface mortar from the outer surface of the structure exposed by removal of the form, thereby exposing the surface of part of the first aggregate for aesthetic purposes.

5. The method of casting in place a structurally sound concrete structure utilizing at least first and second aggregates comprising the steps of assembling a removable,

imperforate form for casting the finished structure, said form being partitioned into a plurality of sections by perforate barriers the openings of which are smaller than the size of the first and second aggregates but permit the passage of mortar therethrourgh, introducing at least the first aggregate into at least one but not all of the sections to fill the same; then placing uncured concrete in another section, said concrete having a mortar component and the second aggregate as a component, and vibrating the concrete to cause part of the mortar component to flow through the barrier and to the form to fill the voids between the pieces of the aggregate.

6. The method of claim 4 wherein at least some of said first aggregate introduced into the form prior to the introduction of the concrete has ornamental characteristics and lies adjacent at least one wall of the form, including the further steps of at least partially curing the concrete; stripping the form from the cast structure, and removing at least a portion of the mortar from the outer surface of the structure exposed by removal of the form to expose the surface of part of the ornamental aggregate.

7. The method of casting in place structurally sound structures utilizing at least a first and a second aggregates comprising the steps of arranging a barrier and said first aggregate within a removable, imperforate form with the barrier dividing the form into a plurality of sections with the first aggregate filling at least one of the sections and being retained by the barrier from moving into another one of the sections, said barrier having perforations whereby motar may flow therethrough but the peforations being too small for the first and second aggregates to pass t-herethrough, then placing uncured concrete in another section, said concrete having a mortar component and the second aggregate as a component, and vibrating the concrete to cause part of the mortar to flow through the barrier and to the form to till the voids between the pieces of the first aggregate.

8. The method of casting in place structurally sound concrete structures utilizing at least first and second aggregates comprising the steps of arranging reinforcement material with a perforate barrier secured thereto and a removable, imperforate form with the barrier dividing the form into a plurality of separate sections, placing said first aggregate into all but one of the sections to fill them with the first aggregate, the barrier perforations being smaller than the size of the first and second aggregates to prevent passage of said first and second aggregates through the barrier but being pervious to the flow of mortar; then placing uncured concrete in said one section, said concrete having a mortar component and the second aggregate as a component; and vibrating the concrete to cause part of the mortar to flow through the barrier and to the form to fill the voids between the pieces of the first aggregate.

References Cited UNITED STATES PATENTS 708,248 9/ 1902 Orlikowski 264-112 1,202,341 10/1916 Weisser 264256 XR 1,215,115 2/1917 Connelley 264 2,313,110 3/1943 WertZ 25-131 XR FOREIGN PATENTS 561,231 10/ 1944 Great Britain. 788,985 1/ 1958 Great Britain.

'ROBERT F. WHITE, Primary Examiner.

R. B. MOFFITT, Assistant Examiner.

Claims (1)

1. THE METHOD OF POURING OF POURING CONCRETE STRUCTURES WITH DIFFERENT AGGREGATES SELECTED FOR THEIR KNOWN CHARACTERISTICS OCCUPYING DIFFERENT POSITIONIN THE FINISHED STRUCTURE COMPRISING THE STEPS OF ARRANGING A BARRIER AND A FIRST AGGREGATE WITHIN A REMOVABLE, IMPERFORATE FORM SO THAT THE FIRST AGGREGATE IS RETAINED IN AND FILLS A SECTION OF THE FORM, AND AN AGGREGATE-FREE SECTION IS PROVIDED IN THE FORM WITH THE BARRIER BETWEEN THE SECTIONS, THE BARRIER HAVING OPENINGS SMALLER THAN THE SIZE OF THE FIRST AGGREGATE PREVENTING DISPLACEMENT OF THE FIRST AGGREGATE FROM ITS SECTION DURING THE STEP OF PLACING SAME; AND THEN PLACING A MIXTURE OF A SECOND AGGREGATE AND MORTAR INTO THE AGGREGATE-FREE SECTION OF THE FORM, THE SIZE OF THE SECOND AGGREGATE BEING GREATER THAN THAT OF THE BARRIER

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