US3639555A - Method of making a concrete plug - Google Patents

Abstract

A METHOD OF MAKING A CONCRETE PLUG COMPRISING THE STEPS OF PROVIDING AN ANHYDROUS CEMENT MIX, MOISTURIZING THIS MIX SLIGHTLY TO PARTIALLY HYDRATE THE MIX AND PROVIDE FOR PARTICLE GROWTH, PRESSING THE PARTIALLY HYDRATED MIX INTO A SLUG AND THEN GRINDING THE SLUG TO CREATE A MIX HAVING A PREDETERMINED PARTICLE SIZE LARGER THAN THAT OF THE STARTING MIX, PRESSING THE MIX INTO PLUGS OF FINAL FORM,

WETTING THE PLUGS TO START COMPLETE HYDRATION, AND COMPLETELY HYDRATING THE PLUG UNDER AMBIENT CONDITIONS.

Description

Feb. 1, 1972 w. J. sTEFFAN 3,639,555

METHOD OF MAKING A CONCRETE PLUG Filed Nov. 21, 1969 44 CEMENT QUICK SET ARLY STRENGTH FIG. 3.

CEMENT k PARTIAL HYDRATION EEEN fiE F DRY BLEND I I FOR PARTICLE GROWTH l l I I Y H DRATE QUALITY CONTROL SPECTRO'GRAPHIC I SLUG FORMING COLOR/NT OPERATION COLORANT I GO NO GRANULATE a so SCREEN QUALITY CONTROL I APPEARANCE Fla 2 I LUBRICANT 7 l I I I I A L IP HTIE A FINAL HYDRATION CONFIGURATION INVENTOR. FINAL AIR CURE '|N$pECT|QN W/LL/AMJ .STEFFAN l Md/ M ATTORNEYS United States Patent 3,639,555 METHOD OF MAKING A CONCRETE PLUG William J. Stelfan, Fremont, Calif, assignor to Burke Concrete Accessories, Inc., Burlingame, Calif. Filed Nov. 21, 1969, Ser. No. 878,786 Int. Cl. 1528b 3/00 US. Cl. 264140 9 Claims ABSTRACT OF THE DISCLOSURE A method of making a concrete plug comprising the steps of providing an anhydrous cement mix, moisturizing this mix slightly to partially hydrate the mix and provide for particle growth, pressing the partially hydrated mix into a slug and then grinding the slug to create a mix having a predetermined particle size larger than that of the starting mix, pressing the mix into plugs of final form, wetting the plugs to start complete hydration, and completely hydrating the plug under ambient conditions.

The present invention relates to the art of manufacturing concrete plugs and, more particularly, to the manufacture of concrete plugs to be employed in the construction industry.

In the construction industry, concrete forms are often employed in the formation of concrete walls and the like. Frequently, such forms comprise panels held in opposed relationship by tie rods extending therebetween. Wet concrete is then poured between the panels and allowed to harden in the shape defined by said panels. When the concrete has hardened the panels are removed for subsequent reuse.

It is obvious that in the foregoing operation some means must be provided to provide the proper spacing between the form panels. There are a number of approaches for accomplishing this. According to one prior art arrangement, spacers are mounted on the rods for abutting engagement with the inner surfaces of the panels and waler brackets are employed to force the panels against the spacers. To avoid certain disadvantages inherent with this arrangement other approaches have been devised wherein the rod spacers are eliminated and wherein sealing and grouting cores are disposed about the rods to prevent leakage of fluid concrete around the rods and permit architectural finishing after the panels are removed. 'Reference may be had to commonly assigned copending US. patent application Ser. No. 824,359, filed Apr. 30, 1969, for an arrangement wherein sealing and grouting cores are employed.

This application concerns itself with the manufacture of concrete plugs utilized for architectural finishing purposes after the panels are removed. Plugs are commonly used after removal of the panels to fill in depressions created in the concrete upon removal of the tie rod spacers, sealing and grouting coresand the like along with the panels. It should be understood, however, that the plugs manufactured in accordance with the teachings of the present invention may be used generally to fill in any external void spaces found in a concrete structure.

Finishing plugs of the above described type have been commonly manufactured in the prior art by molding the cement material of the plug in a wet condition. This prior art method of manufacture is quite difficult and produces a plug which is of relatively low compressive strength, thus resulting in a high frequency of plug breakage during use.

It is therefore an object of the present invention to provide a method of manufacturing a concrete plug which results in the formation of a plug having a high degree of durability.

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It is a further object of the present invention to provide a method of manufacutring a cnocrete plug which enables the manufacturer to maintain a high degree of control over the appearance and quality of the finished plug.

These and other objects have been attained according to the teachings of the present invention by providing a method of manufacturing a concrete plug comprising the steps of providing an anhydrous cement mix, moisturizing this mix slightly (i.e. 2 to 3% moisture by weight) to partially hydrate the mix and provide for particle growth, pressing the partially hydrated mix into a slug and then grinding the slug to create a mix having a predetermined particle size larger than that of the starting mix, pressing the mix into plugs of final form, wetting the plugs to start complete hydration, and completely hydrating the plug under ambient conditions.

The above noted and other objects of the present invention will become more apparent when viewed in light of the accompanying drawings, wherein:

FIG. 1 is a perspective view illustrating a concrete wall cross section having a depression in which a plug manufactured according to the method of the present invention is positioned;

FIG. 2 is a diagrammatic flow-sheet presentation depicting the processes of the present invention;

FIG. 3 is a longitudinal cross sectional view illustrating a die cavity and punch arrangement employed during manufacture of a concrete plug in accordance with the teachings of the present invention.

In FIG. 1 a typical construction situation is illustrated calling for use of a concrete plug of the type manufactured according to the teachings of the present invention. More specifically, a portion of a concrete wall 20 is shown which has at least one external architecturally finished surface 22. It may be assumed that wall 20 has been constructed utilizing a form molding process as described above. A portion of the tie rod 24 which was used to hold the form panels (not shown) in position is illustrated. It should be noted that tie rod 24 communicates with a recess 26 formed in the wall and having a cone shaped configuration. If it is desired to provide the wall with an esthetically pleasing appearance a plug 28 generally conforming to the shape of recess 26 is positioned in the wall in the manner illustrated so that the fiat outer surface of the plug is flush with finished surface 22 of the wall.

It is to be understood that the teachings of the present invention may be employed in constructing a concrete plug of any configuration and that it is not limited to formation of a cone-shaped plug. The configurations of plug 28 and recess 26 and the placement and structure of tie rod 24 are shown for purposes of illustration only. The arrangement shown is typical for that found when the apparatus and method disclosed in the aforementioned copending UJS. application Ser. No. 824,359 are utilized. In this instance recess 26 has been created by removal of a cone-shaped grouting core employed in that invention, however, as previously stated, the recess 26 may be of any size and configuration such, for example, as that formed by removal of tie rod spacers utilized in an alternative prior art approach. The plug size and configuration will, of course, be chosen based on the dimensional characteristics of the recess formed in the concrete structure. In addition, it is normally desirable to have the texture and color of the plug conform as nearly as possible to those of the structure with which it is associated. A further desirable characteristic of a plug of this nature is that it be capable of withstanding the stresses encountered when positioning it in its associated recess, as when the plug is pressed thereinto. Generally, the plug is held in place with a suitable adhesive and to accommodate this adhesive the plug is proportioned to be slightly smaller than the recess so that it will seat with its external surface flush with that of the structure in which the recess is formed.

The method of manufacturing a plug according to the present invention will now be described in detail with particular reference to the flow diagram of FIG. 2. The first step to be carried out in the manufacture of a plug is the preparation of an anhydrous cement mix or dry blend. In carrying out the teachings of the present invention it has been found particularly advantageous to provide three principal dry blend components. The three principal components are a cement chosen for its quick set, early strength characteristics, a cement having longterm strength development characteristics and hydrated lime. In addition, color may be added to the anhydrous cement mix where color of the plug to be manufactured is a factor.

One type of quick set cement suitable for use in carrying out the teachings of the present invention is Lumnite cement and a suitable cement having long-term strength characteristics is a type known as white cement. Lumnite cement is calcium aluminate and is sold under the name Lumnite by Universal Atlas Cement Co. of Pittsburgh, Pa. (a division of US. Steel). These materials are well known in the concrete art. The elements of the dry blend are preferably mixed by weight to provide a suitable anhydrous cement mix. Assuming that the cements given as examples above are employed in the mix it has been found that a suitable dry blend is created when the Lumnite cement constitutes in the order of 42.5% by weight of the mix, the white cement in the order of 52.0% by weight of the mix and the hydrated lime in the order of by weight of the mix. Each of these components, however, may vary plus or minus of the base percentages given without harmful effect. Examples of suitable colorants which may be employed in the mix are yellow iron oxide and green iron oxide, although, as stated above, colorants need be added to the mix only where color of the finished product is a necessary factor. When the mix percentages of the major components are those set forth above the desired colorants will add up to 0.5% by weight of the final dry blend.

In carrying out the blending operation any suitable commercial equipment may be utilized. For example, a horizontal ribbon mixer and entoleter arrangement may be utilized to mix the dry blend and to achieve uniform color. Suitable units of this nature are the 3,000 pound capacity horizontal ribbon mixer manufactured by A.E. Paulsen Company, Los Angeles, Calif. and the Model 10 H.P. 3,000 pound capacity unit manufactured by Entoleter Inc., New Haven, Conn.

The blended material preferably is subjected to a spectrographic quality control inspection before the next step in the manufacturing process is carried out. Assuming the blend is properly mixed and the uniform color is achieved, the anhydrous cement mix is partially hydrated by adding 2 to 3% moisture by weight to the mix. This step provides for particle growth and otherwise prepares the mix for the next operation which will be described below. In carrying out this partial hydration step one suitable approach has been to spread the dry blend in a threeeighths inch thick layer. The correct amount of water is then added by spraying the surface of the layer and the mix is allowed to set for hydration of wetted particles. Another suitable approach would be to simply subject the mix to a controlled atmosphere of a relatively high humidity.

After the desired partial hydration of the mix has taken place the material is introduced into a suitable slugging machine such as the Stokes Model R-4 so that it may be formed into slugs having sufficient strength to withstand transit. The formed slugs are then introduced into a grinder mechanism so that the material is reduced to granular form. A piece of equipment suitable for this operation is the Stokes No. 43-C Granulator. This granulated form is desirable for carrying out the final plug press operation which will be described in greater detail below. A granular output density of 1.24 grams per cubic centimeter may be obtained when a one-eighth inch mesh screen is employed with the above noted piece of granulator equipment. A granular density of this order has been found to be quite suitable for proper performance of the following operations.

The next principal step to be carried out in the manufacture of a plug is the press operation in which the plug is pressed into final form. However, before introduction of the granular material into the press equipment it is desirable to add a suitable lubricant to facilitate press die operation. Assuming the one-eighth inch granular size and output density of 1.24 grams per cubic centimeter suitable die lubrication may be provided by adding magnesium stearate to the grinder output within the range of 0.1% to 0.5% by weight.

After addition of the lubricant to the granular material the lubricated granular material is introduced into a suitable die press so that the desired number of plugs may be formed to their final configuration. One suitable piece of equipment for carrying out this operation is the Stokes Model 4 which, as stated above, may also be used in the preliminary slugging operation. A suitable die arrangement for use in this and similar pieces of equipment is shown in FIG. 3. Essentially, the die mechanisms comprises a die block 40, an upper punch 42 and a lower punch 44. In operation, the cavity 46 defined by the die block is first filled with a predetermined quantity of the lubricated granular material. Punches 42 and 44 are then moved toward one another by the press equipment in a well-known manner to compress the graular material contained in the cavity. The formed plug is then ejected from the machine and conveyed to the next step in the operation. A compaction ratio suitable for formation of a plug is 1.7:1 at 12.5 tons.

From the final press operation the formed plugs are introduced to water to start the final hydration process. However, intermediate these two steps the formed plugs are subjected to a quality control operation whereby their apperance may be checked. Imperfect plugs are recirculated back into the system through the granulation and screening equipment while approved plugs are conveyed directly to the hydration site. Hydration is preferably carried out by introducing the formed plugs into a suitable water absorption water tank for a time sufiicient to permit the plugs to absorb water sufiicient to complete the hydration process. Complete hydration will normally be assured when the plugs have absorbed in the order of 11 to 14% of water by weight.

The final major step involved in the manufacture of the plugs is the step of air curing. This may simply be accomplished by leaving the plugs exposed to ambient air for a predetermined period. After the curing process the plugs are subjected to a final inspection at which point they are packed and shipped to a job site or storedfor later use. The final inspection stage may include a quality control check of the ultimate compressive strength of the plugs. As stated above, through utilization of the method according to the present invention, plugs having a compressive strength in the order of 4,000 p.s.i. may be expected to be produced. This contrasts with the relatively low compressive strength in the order of 600 p.s.i. of plugs produced using a wet molding technique.

The exemplary embodiment of the method may be summarized as follows:

Step I.-Starting components (by weight):

Step II.--Mix starting components to blend together.

Step III.Partially hydrate mix by the addition of 2 to 3% moisture by weight to promote particle growth.

Step IV.Slug partially hyrated mix by compacting in a ratio of 1.7 to 1 at 12.5 tons.

Step V.Grind slugged mix to A5 inch mesh screen size to produce a granular mix having a density of 1.24 grams/cm.

Step VI.Add 0.1 to 0.5% by weight of magnesium stearate to ground mix for lubrication purposes.

Step VII.Press lubricated mix to final plug form by compacting in a ratio of 1.7 to 1 at 12.5 tons.

Step VIII.Start final hydration by wetting formed plugs 11 to 14% by weight.

Step IX.Cure formed and wetted plugs in ambient air.

I claim as my invention:

1. A method of making a concrete plug comprising the steps of:

providing an anhydrous cement mix of particulated elements; partially hydrating the mix; forming the partially hydrated mix into a plurality of particles having a size greater than the size of the anhydrous cement mix particulated elements by pressing the mix into slug form and then reducing the pressed slugs to the desired particle size;

compressing the plurality of particles so that they assume the form of a solid plug; and,

hydrating the plug.

2. The method of claim 1 wherein the mix is partially hydrated by adding thereto 2 to 3% moisture by weight.

3. The method of claim 1 wherein the plug is hydrated by setting the plugs and curing the wetted plugs in the ambient atmosphere.

4. The method of claim 1 wherein a mold lubricant is added to the plurality of particles before compression thereof into solid plug form.

5. The mehod of claim 1 wherein the anhydrous cement mix is provided by blending together in dry form at least a quick-set cement, a cement having long term strength development characteristics, and hydrated lime.

6. The method of claim 1 including the additional step of screening the plurality of particles from the rest of the ground slugs prior to compression of said particles into solid plug form.

7. The method of claim 5 wherein said quick-set cement is cement of the calcium aluminate type and wherein said cement having long term strength development characteristics is white cement.

8. The method of claim 5 wherein the anhydrous cement mix further includes particulated colorant materials.

9. A method of making a concrete plug comprising the steps of providing an anhydrous cement mix of particulated elements comprising at least in the order of 42.5 percent cement of the calcium aluminate type, 52.0 percent white cement and 5 percent hydrated lime;

partially hydrating the mix by adding 2 to 3 percent moisture by weight to the mix; forming the partially hydrated mix into a plurality of particles having a density in the order of 1.24 grams per cubic centimeter; adding magnesium stearate to the plurality of particles within the range of 0.1 percent to 0.5 percent by weight; compressing the combined magnesium stearate and plurality of particles so that they assume a solid .plug; and,

hydrating the plug by adding water within the range of 11 to 14 percent by weight thereto.

References Cited UNITED STATES PATENTS 732,674 6/1903 Bell et al. 264'333 2,123,317 7/1938 Schless 264-333 2,572,510 10/1951 OrSini 264-162 ROBERT F. WHITE, Primary Examiner G. AUVILLE, Assistant Examiner US. Cl. X.R.

264232, 294, 333, Dig 43

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