The present invention is generally in the field of solid concrete elements. More particularly, the invention is concerned with centrifuge-cast foundation elements, their manufacture and an apparatus for manufacturing same.
Such elements are often referred to in the art as ‘armor units’ or ‘armor elements’.
The term “foundation element” used hereinafter in the specification and claims is used in its broadest aspect and denotes a variety of foundation/construction elements, e.g. as a bed for marine construction, wave breakers, dams, supportive walls, soil foundation and consolidation, etc.
Use of foundation elements for various construction purposes is well known. At times, large rocks are used for such purposes. However, a disadvantage concerned with using rocks is the availability of such large rocks and the expenses involved with quarrying and transportation of the rocks to the work site.
Rather than using rocks, there is an ever-growing use of molded foundation elements which are relatively cheap and which may also be molded at or adjacent the work site. Even more so, in molding such elements, one may also control the mechanical properties of the elements, e.g. the compressive strength, weight, wear resistance, etc., by controlling different parameters such as type of concrete used, additives used (binders and aggregates), amount of liquid added, entrapped air, etc. Still, one may control the shape and the size of the elements to thereby impart them with various properties so as to meet requirements of a particular construction site.
Presently, foundation elements of the concerned type are molded in a harmonized manner, i.e. the distribution of aggregate material (typically gravel) through a section of the element is essentially equal.
U.S. Pat. Nos. 4,976,291 and 5,035,850 disclose a concrete-type composite pipe produced by rotating a drum mold while casting concrete there into to form a concrete layer of a uniform thickness using a centrifugal force exerted on the cast concrete, casting a corrosion protective layer on an inner surface of the formed concrete layer, scattering aggregates on the inner surface and accelerating the rotation to cause the aggregates or the like to form an intermediate layer between the concrete layer and the corrosion protective layer.
It is an object of the present invention to provide a concrete-molded foundation element formed with a durable crust, enveloping a core consisted of aggregated material indexed in an inverted segregation dispersion. It is a further object of the present invention to provide a method for production of such foundation elements and an apparatus for carrying out such a method.
It is an object of the present invention to provide a construction element formed with a durable concrete crust having an external surface with a relatively high compressive strength, said crust enveloping a core made of aggregate material indexed in inverted segregation dispersion.
According to the present invention there is provided a foundation element, symmetrical about a longitudinal axis thereof, said element formed with a crust made of at least normal-strength concrete, said crust enveloping a core made of aggregate material dispersed such that the size of the aggregate material increases from fine to large about a radial section of the element and where space between larger aggregate material is occupied by smaller sized aggregate material. The construction element is molded in a centrifugal process.
The arrangement is such that large aggregate material is disposed adjacent an outer surface of the crust and small aggregate material is disposed at the center of the element.
In accordance with a particular embodiment of the invention, the core material comprises waste material. Such waste material may consist of fly ash, polymeric waste material, radioactive contaminated material, etc. This is an environmentally friendly method for getting rid of such waste material.
In accordance with an other particular embodiment, the construction element is fitted with at least one hoisting-eye. By a preferred embodiment, the hoisting-eye is received within an indention or depression such that it does not project beyond a top surface of the foundation element.
The construction element in accordance with the present invention may have different cross-sections, e.g. cylindrical, triangular, square, hexagonal, octagonal, etc. According to a particular design, where the cross-section of the construction element is polygonal, the number of faces is at least five, so as to avoid significantly differing distance from the center of the core.
In accordance with a further aspect of the present invention, there is provided a method for manufacturing a foundation element symmetrical about a longitudinal axis thereof, said method comprising:
(viii) drying the element.
According to a modification of the invention, steps (ii) to (v) may be replaced by introducing a mixture comprising cement and a mixture of aggregate material comprising graded material indexed between large size and small sized substance material.
In accordance with still a modification, any time after step (v) liquids may be drained or suctioned from the mold which was drawn liquid may then be replaced by substitute material such as cement.
The invention is further concerned with an apparatus for molding a foundation element, comprising a mold mountable on a rotatable plate member; said mold comprising a base, peripheral side walls extending therefrom and a top cover attachable to the side walls; said top cover comprising an inlet opening.
For better understanding the invention and its different aspects, and to see how it may be carried out in practice, reference will now be made to the accompanying drawings, by way of example only, in which:
Attention is first directed to
Element 20 has a crust 22 typically made of normal to high-strength concrete, having a compressive strength of at least 20 MPa. The crust 22 has an outer surface 24 obtaining its shape and pattern from the mold in which it is molded, as will be discussed hereinafter. The cement slurry/paste used for obtaining the concrete crust is made of a mixture of Portland, or other type of cement, with water and at times some additives, as known per se, imparting the concrete with desired parameters e.g. corrosive-resistance, etc. The ratio of cement to water determines the strength of the concrete, namely its compressive strength, and according to the intended use of the foundation elements one decides which concrete to use.
Dispersed inwardly of the crust layer 22 there is large aggregate material in the form of large stones 26 (crushed rock and large gravel), which during the centrifugal molding process are forcefully urged towards the surface 24 of the crust layer 22. It is apparent that the space between larger aggregate material is occupied by smaller sized aggregate material.
Inward from the large aggregate material 26 and in the voids and gaps therebetween, there is dispersed medium size aggregate material 30, e.g. small stones, gravel, etc., with a low amount of cement therebetween. Further inward there is fine aggregate material 40, e.g. sand, filling the gaps between the small aggregate material and comprising a minimal percent of cement.
The innermost layer of the element 20 comprises, in the molding process, the excessive water. After drying what remains is fine aggregate material 40 e.g. various types of sand, and air voids
As can be further seen in
Reverting now to the aggregate core material, it is apparent that it consists of material indexed in an inverted segregation dispersion such that large aggregate material 26 is disposed adjacent the outer surface 24 of the crust 22 with fine aggregate material 40 disposed at the center of the element 20. This arrangement is obtained during the molding process of the core of the element 20, which is carried out under centrifugal forces, whereby the heavier material is radially urged toward the outer surface 24 of the crust 22.
The core material may comprise waste material in various forms, e.g. granulated or powdered material, fibers, compressed material, crushed material, etc. The waste material may be any environmentally hazardous material of which it is desired to dispose of, e.g. polymeric material, fly ash, radioactive-contaminated material, etc. It is thus advantageous that when a foundation element comprises waste components, e.g. radioactive contaminated material, the crust 22 be made of high-strength concrete, e.g. having a compressive strength of at least 50 MPa, so as to increase safety.
Further attention is now directed to
As can further be noted in
The side walls 102 are fitted at their bottom ends with engagement pins 110 for securing into corresponding openings 112 formed in the rotatable plate 79 (
Cover 88 of the mold 78 comprises a plurality of downwardly extending projections 116 (
It is further noted that the top cover 88 is formed with two depressions 120, each of which is formed with an opening for receiving a hoisting eye-hook 50 to be integrally molded with the foundation element 20 (see
The device of
It is to be appreciated by a versed person that the mold 78 may have different cross-sections and different sizes as previously discussed in connection with the foundation element. Furthermore, the inner surfaces 138 of the walls 102 may be textured to thereby impart the external surface of the foundation element 20 with a corresponding decorative texture. Even more so, the walls 102 of the mold 78 may have a non-parallel cross-section, e.g. a rhombus-like cross-section.
In order to understand the method of manufacturing a foundation element in accordance with the present invention, further attention is now directed to
In a first step, a mold 78 is placed on rotatable plate 78 and is rotatably fixed thereto by means of engagement pins 110 projecting into corresponding openings 112 of the rotating plate 79 (see
A cement slurry/paste is poured through funnel 130 into the mold 78, while the mold 78 is rotating at a relatively high speed, thus imparting the slurry with centrifugal forces urging it against the inner walls 102 of the mold 78. After some time, when the cement is partially solid and retains its position as in
After the rotation of the mold 78 is significantly slowed down, an additional amount of cement slurry is introduced through funnel 130 allowing it to fall to the bottom of the mold 78 and form a bottom crust 141 (
Then an aggregated core material is introduced through funnel 130. The aggregate material comprises a mixture of large stones 142, small stones, e.g. gravel 144 and fine aggregate material, e.g. various types of sand 146. Upon insertion of the aggregate mixture, the speed of rotation of mold 78 is increased thereby urging the aggregate material to disperse in a so-called inverted segregation dispersion whereby the large stones 142 are forced to penetrate into the enveloping crust 140 formed in the previous step (see
The speed of rotation of the mold 78 and the duration of rotation depend on the consistency of the concrete as well as on the size and specific weight of the aggregate material. If desired, waste material may be introduced into the core material, e.g. waste polymeric material, fly ash, radioactive contaminated material, etc. of which it is desired to dispose of in an environmentally friendly manner. For such a purpose, it is desired that the crust layer 140 be of at least normal and preferably high-strength concrete, depending on the intended use of the foundation element 20 and on the ingredients of the core material. For example, for marine use and where radioactive-contaminate material is introduced as waste material, it would be preferable that the crust be of high-strength type and have a compressive strength of at least 50 NPa. Furthermore, it may be advantageous that in the first step, a corrosive-resistant layer be applied on the inner surface 138 of the mold 78 or together with the slurry forming the crust 140 to impart the foundation element 20 with corrosive resistance.
In accordance with a modification of the invention, liquid may be drained from the mold or suctioned by a suitable pump arrangement (not shown) to allow substituting the removed liquid, typically water, by a heavy substance such as, for example, a cement slurry or other reinforcing or adhering agent.
Turning now to
The process then ends by elevating the cover 88 (by means of arm 86) and hoisting away the mold 78 and allowing the molded element to consolidate and heal at a suitable drying site (
As an alternative, rather then first molding the crust 22 and then adding the aggregate material, one may combine these steps by introducing into the mold 78 a mixture comprising the cement and the mixture of aggregate material comprising graded material indexed between large sized and small sized material, whereby the cement and the aggregate material will disperse during rotation of the mold 78 at high speed, under the influence of centrifugal force.
Turning now to
Obviously, foundation elements of different shape and size are used as desired according to various engineering and other considerations.
Number | Date | Country | Kind |
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148877 | Mar 2002 | IL | national |
Filing Document | Filing Date | Country | Kind |
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PCT/IL03/00106 | 2/12/2003 | WO |