CA1318167C - Interlocking slab element and ground surface cover - Google Patents

Abstract

INTERLOCKING SLAB ELEMENT AND
GROUND SURFACE COVER
Abstract of the Disclosure A tile-like integrally molded slab element of ceramic material, and a ground cover made up of repeatable patterns of such elements wherein the slab elements include a hexagonal section having two 90°
and four 135° angles and equal sides and a square section with a side adjoining a side of the hexagon which is adjacent one of the 90° angles.

Description

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INTERLOCKING SLAB ELEMENT AND
GROUND SURFACE COVER
My invention is directed to uniquely shaped slab elements for covering the ground or other like surfaces, and to surface coverings composed of config-urations of such elements. Specifically, my invention is directed to such slab elements which can be com-bined with other like slab elements in a variety of different orientations to form stable load-carrying surfaces in a multiplicity of different patterns.
The present invention is a new and improved slab element and ground surface cover arrangements of such elements. The invention provides many of the advantages of my previous invention entitled INTER-LOCKING SLAB ELEMENT FOR COVERING THE GROUND AND THE
LIKE disclosed in my U.S. Patent No. 4,544,305, and, in addition providing other desirable and unique advantages and characteristics.
Slab elements of differing shapes have been employed in the construction of traffic-carrying surfaces such as roadways, footways, embankments and pool decks. Typically, the slab elements are made of i3~3~

concrete, formed in desired shape in molds, and cured under high pressure where the slab material is com-pacted and hardened into the desired shape in the mold, and removed from the mold and exposed to ambient air to complete the curing cycle. The method by which such slab elements can be made are well known in the art and form no part of my invention. Hence, methods for making slab elements will not be addressed further except to note that the shape of the molds used to form prior art slab elements must be modified so as to conform to the shape of my slab elements.
To construct a surface employing slab elements, an under-surface is prepared in known fashion to provide a smooth flat surface upon which to place the slab elements. The slab elements are placed one at a time such that their vertical or peripheral walls or edge faces come into close contact. The gaps between edge faces may be filled either with mortar, concrete, or other such solidifying spacer element, or, preferably, with sand which is simply poured into the gaps in a known manner. My invention is ideally suited to the latter, less costly method. The traffic load encountered by surfaces constructed in the above manner can vary from as light as pedestrian traffic to as heavy as several ton trucks and forklifts.
Slab elements employed for traffic surfaces have come in a wide variety of shapes from square and 1313~ ~ ~

rectangular to multi-sided and irregular shaped surfaces, but a slab element's shape is known to affect the ground cover's load carrying capacity and durability. When viewed from the top, such slab elements generally fall into one of three basic categories.
The first category is a slab element which has a known and simple geometric shape, such as a rectangle, a square, a hexagon, or an octagon. From an aesthetic point of view, this category of elements is highly desirable and has historically been in great demand. In other respects, this category has hereto-fore been less desirable than other categories herein-after discussed because such shapes preclude an i~terlock joint between adjacent slab elements.
Additionally, proper utilization can require greater material and care than other slab elements and are often not satisfactory in use. For example, if such sla~ elements were placed in the manner expected of my invention, i.e., with sand between them, the surface would not be stable because there is no interlock.
Furthermore, because there is no interlock, long, straight channels are more easily formed between the elements thus permitting rain,- for example, to wash away the sand further reducing the load carrying stability of the ground cover formed with those elements. Hence, such slab elements would typically 13 ~ r~

require mortar or concrete between elements. Mortar or concrete are typically more expensive than sand and are more difficult to work with.
A second category of slab element is one wherein, from a top plan view, khe sla~ element looks substantially rectangular but the edges are deformed in such a manner as to interlock when laid next to an adjacent, identical stone. Examples of second cate-gory slab elements are shown in U.S. Patent No.

2,919,634 and U.S. Patent No. 3,494,266~ Also in-cluded in this category are certain multi-faced irregularly shaped slab elements such as those dis-closed in U.S. Patent No. Des. 82,970. The slab elements disclosed in the aforementioned patents overcome some of the drawbacks of slab elements discussed in the preceding paragraph because they may be interlocked. However, they are less attractive from an aesthetic standpoint. Moreover, the slab elementc in this ca*egory generally may not be inter-mixed with other differently shaped second category slab elements as would be possible wi~h first category slab elements to permit a wide variety of patterns to be created.
A third category of-slab element, and the one with which my invention is concerned, overcomes the drawbacks of both first and second category slab elements. A third category slab element is comprised 13 1 ~

of two or more sections having the shape of flrst category slab elements which are combined into one inteyral slab element. An example of such a slab element is disclosed in U.S. Patent No. 4,128,357.
The slab element of that patent has a main section which is of a known octagonal shape, and a tail section which is of a known square shape, with the main and tail sections being formed as one slab element. The primary advantage of such an integral slab element is that it can interlock for durability and stability. A disadvantage, however, is that it is susceptible of only a few different interlocking patterns.
In my Patent No. 4,544,305, I have disclosed a slab element for use in providing a ground cover particularly suited for use filling the joints with sand. In my prior patent, I have taught that the combined shapes of a square and hexagon could be used to form such a slab element when the hexagon has two pair of minor faces equal to those of the squaxe, each pair joined by a right angle with the pair being joined together by two major faces each twice the length of a minor face, the square being joined at a minor face.
In integrating a paving surface pattern into an architectural or landscaping plan; certain designs call for surfaces with the more classical appearance ~31~

of patterns which are built upon the more regular basic shapes of squares and hexagon~. Such patterns are illustrated iniBritish patents of Crannis et al No. 9640 and Dodgson No. 610, German Patent No.
27-51-536. As I have pointed out in my previous U.S.
Patent No. 4,544,305, slab elements combining these shapes for use in a variety of interlocking patterns cannot be easily selected. Where an objective is, however, to provide an interlocking paving element of brittle ceramic material such as concrete, certain other practical problems are presented~
In the art of roofing, for example, where flexible materials are employed, plural square or hexagon shapes can be joined in an integrated covering element with less concern for the structural problems by joining brittle material~, for exasnple, as shown in Abraham U.S. Patant D75,761. In arts requiring ceramic materia].s, par~icularly for the formation of thinner tile-like rather than thick block-like ele-ments, the avoidance of thin elongated elemants and elements with acute external or internal angles adds to the strength of the element, reduces the incid~nce of element breakage in manufacture, storage, handling, assembly and use, and enhancgs the ease of manufac-ture.
It is a primary objective of the present invention to provide a tile-like interlocking paving ~3~ &~

element utilizing to a maximum extent the nearly regular appearing design shapes of hexagons and squares in an integrated slab element while preserving and extending, to the maximum extent possible, the advantages of my present invention of Patent No.
4,544,305. sy regular, I refer to component shapes having equal sides and equal angles, or at least having sides and angles which are close enough in size so as to be perceived as equal or have the same aesthetic appearance as if they were equal.
It is a more particular objective of the present invention to provide such a paving element which avoids acute angles and elongated shapes, and which is shaped not only to provide the aesthetic requirements set forth above, but to avoid shape characteristics which undermine its strength and resistance to breakage. It is a further objective of the present invention to provide such a paving element which can be arranged in a ground cover pattern which fully covers the surface without the use of irregular pieces and which is suitable for a wide range of designs and patterns using minimal irregular or multiple shaped elements.
These objectives are accomplished by pro-viding a seven sided tile-like paving integrated element having an equi-lateral hexagon portion with a pair of opposed 90 angles separating the lateral ~ 3 ~

sides of the hexagon, and having a square portion adjacent one of the lateral sides.
Another objective of my invention is to provide a slab element which lends itsel~ to forming a large number of different, attractive, interlocking patterns. This objective is accomplished by providing a slab element which has a main hexagonal section and one tail section integral therewith which are oriented substantially in one plane. The main section has a first pair of adjoining lateral peripheral edges or faces and a second pair of adjoining lateral peripher-al edges or faces with the firRt and second pairs of lateral peripheral edges or faces being oppositely disposed in spaced-apart relationship. The main section further has a pair of spaced apart, parallel longitudinal peripheral edges or faces interconnecting the first and second pairs of lateral peripheral faces. The face~ of each pair are joined at right angles~ The tail section has four lateral peripheral faces or edges, with one of the four lateral faces of the tail section being substantially coextensive in size and shape and spacially coincident with one of the lateral faces of the main section. Each of the longitudinal faces is approxi~ately equal to the length of the lateral faces, and the intersection of each longitudinal face with the adjoining lateral face defines an angle of approximately 135. The lateral 13~g~

faces of the tail section define substantially a square. The lateral face ad,acent to the lateral face at which the square tail section is joined lies in the plane of one side of the square and with it forms a single side of the slab element.
sy means of the foregoing angular and length relationships of that peripheral face, adjacent slab elements can be arranged in a wide variety of orien-tations relative to each other to provide many differ-ent interlocking patterns. In addition, and impor-tantly, the elements form a structurally strong design particularly suitable for interlocking paving elements of concrete or other ceramic material and present an appearance of a versatile hexagon and square design.
Brief Descri~tlon of the Drawings Fig. 1 is a front perspective view of a first preferred embodiment of a slab element of my invention for covering the ground and the like.
Fig. 2 is a front elevational view o the slab element of Fig. 1.
Fig. 3 is a top plan view of the slab element of Fig. 1.
Fig. 4 is a bottom plan view of the slab element of Fig. 1.
Fig. 5 is a rear perspective view of the slab element of Fig. 1.

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Fig. 6 is a top plan view similar to Fig. 3 of a mirror image of the slab element of Fig. 1 and is another preferred embodiment of a slab element according to my invention.
Fig. 7 is a top plan view of a repeating first closed pattern with the slab elements of Fig. 1.
Fig. 8 is a top plan view of a repeating second closed pattern wit:h the slab elements of Fig.
1.
Fig. 9 is a top plan view of a repeating third closed pattern with the slab elements of Fig. 1.
Fig. 10 is a top plan view of a xepeating fourth closed pattern with the slab elements of Fig. 1 and Fig. 6.
Fig. 11 is a top plan view of a repeating fifth closed pattern with the slab elements of Fig. 1 and Fig. 6.
Fig. 12 is a top plan view of a repeating first open pattern with the slab elements of Fig. 1 and Fig. 6.
Fig. 13 is a top plan view of a repeating third op~n pattern with the slab elements of Fig. 1.
Fig. 14 is a top plan view of a repeating fourth open pattern of slab elements of Fig. 6.
Detailed Description of the Preferred E~b~
With particular reference to Figs. 1 through 5, there is shown a slab element 1 comprised of a main --10 ~

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hexagonal section 2 and an integral square tail section 3. The main hexagonal section 2 is comprised of four lateral and two l.ongitudinal faces or edges 4 through 9 around the periphery thereof. First longi-tudinal face 4 adjoins a lateral face 5, which is internal, to form an included angle 14 of approxi-mately 135. First lateral face 5 adjoins a second lateral face 6, which is exposed, to define an in-cluded angle 15 of approximately 90. Second lateral face 6 adjoins a second longitudinal face 7, also exposed, to define an included angle 16 of approxi-mately 135. Second longitudinal face 7 adjoins third exposed lateral face 8 to define an included angle 17 of approximately 135. Third lateral face 8 adjoins a fourth exposed lateral face 9 to define an included angle 18 of approximately 90. Fourth lateral face 9 adjoins the first longitudinal face 4 to define an included angle 19 of approximately 135. Each of the lateral faces 5, 6, 8 and 9 are equal in length and preferably about three inches. Major faces g and 7 are equal in length to each equal to the length of the lateral faces 5, 6, 8 and 9, preferably approximately three inches. The faces 4, 5, 6, 7, 8, and 9 lie in planes which are substantial~y perpendicular to the planes containing the upper and lower surface la and lb, respectively, of the slab elements.

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The tail section 3 is comprised of four adjoining faces 10, 11, 12 and 13 around the periphery thereof, each of which is equal in length to that of the faces 4 through 9 of the hexagonal main section 2.
The four tail section faces 10, 11, 12 and 13 pref-erably define substantially a square when viewed from the top as in Fig. 3. Of faces 10, 11, 12 and 13, only face 10 is internal; the others are exposed.
The tail section 3, which is integral to hexagonal main section 2 to form the slab element 1, adjoins at its lateral internal face 10 the hexagonal main section 2 along first lateral internal face 5 thereof. Face 10 and first lateral face 5 are sub-stantially coextensive in size and shape and spatially coincident with each other such that no portion of either of those faces extends beyond the other. The vertical plane along which lateral face 10 and first lateral face 5 spatially coincide is indicated by reference numeral 21. In my preferred embodiments, the upper edge of each face of each main and tail section is chamfered as indicated by reference numerals 20, 20. The chamfer is preferably 6 mm. in height and 4 mm. in depth and, as shown in Fig. 2, starts inwardly from the outeP wall of the face towards the interior of its respective main or tail section 2 or 3. When the slab element 1 is thus provided with chamfers 20, upper edge 21a of plane 21 1 3 1 3 ~ ~ é~

may be viewed as a false joint in which case two identifiable polygons of known shape, namely, a hexagon and a square, are clearly discernible in slab element 1 as ls especial:Ly shown in Fig. 3.
Alternately, s:Lab element 1 need not be provided the chamfers 20 and would then appear as in the bottom plan view of Fig. 4.
As seen in Fig" 2, the slab element 1 is a tile-like slab with a wiclth and length greater than its thickness, its thickness being preferably less than half the largest or longitudinal dimension of the element. This is in contrast to block-like elements as shown in Graham U.S. Patent No. 474,339 and Dodgson British No. 610.
In order to provide an even further variety of design from that available with the slab element 1 shown in Fig. 1 an alternative pre~erred embodiment generally depicted as 1' is provided as shown in top plan view in Fig. 6. Slab element 1' is identical in all respects to slab element 1 except it is a mirror image thereof. Alternatively, slab element 1' could be obtained by providing slab element 1 with chamfers 20 on both the upper edge as shown as well as along the bottom edge ~not depicted~ and turning slab element l over~ Providing a slab element 1 having chamfers 20 along the upper edge and the bottom edge eliminates the need for an alternative slab element ~L3 L81~r~

1', but is not generall~ desirable in that false joint 21 will be created on both the top and the bottom of the slab element creating unnecessary stress concen-trations and leaving less material to maintain the two sections as one integral element. Such weakening at the false joint is not desired in that the slab element could break more easily at the joint 21a under the stress of a heavy load, thereby losing the inter-lock feature sought by my invention. Moreover, having chamfers ~0 along the bottom edge of slab element provides an opportunity for the sand between the slab elements to slowly fill the crevices left by the chamfers on the bottom, causing the slab elements to come loose or have less stability when they are provided in an overall pattern to cover the ground as contemplated by my invention.
As more fully discussed hereinafter, a ground cover may be made by using any substantially L-shaped slab element comprised of two or more differ-ent integral sections of simple geometric shape which meet certain dimensional criteria. When such L-shaped sections are disposed in a common plane, adjacent slab elements are capable of having a wide variety of orientations with respect to each other and can result in a vast number of different interlocking patterns.
However, to satisfy the criteria of my present inven-tion, the slab element must meet the following dimen-sional criteria with respect to included angles and length of faces:
(A) The slab element must be L-shaped and comprised of two integral sections, one a hexagon and one a square;
(s) Each included angle of each section must be either 135 or 90;
(C) The length of each face of each section must be equal;
(D) The internal spatially coincident faces of adjoining sections must be coextensive in size and shape;
(E) The square section must adjoin a side of the hexagonal section which is adjacent a 90 angle of the hexagon.
When these criteria are satisfied, the resulting element 1 will be a seven sided figure, with two faces 4 and 13 having merged into one coplanar surface~
Figs. 7 through 14 show some of the many varied patterns of ground covers which can be obtained by using slab elements 1 and/or 1' of my invention.
The chamfers 20 and dummy jolnts ~la have be~n omitted to facilitate an understanding of the manner in which the patterns may be created, but it is to be under-stood that it is preferred that elements with such chamfers and dummy joints be employed. In the edgers 115 and 116, the main section 2 of a slab element 1 1 3 ~

has been modified to main section 2a or 2b, respec-tively. It should be readily apparent that edger elements may be useful to finish certain patterns and may be created by eliminating any part of a section along a line formed between two confrontin~ face intersections. Also, preformed edges are preferable to breaking a complete slab element 1 as that could lead to frayed edges and weakened elements.
Typically, the slab elements of my invention will be employed to form one of two types of patterns which I refer to as closed or open patterns. Examples of closed patterns are shown in Figs. 7 through 11. I
have used the term closed pattern to mean that there is no opening in the center or in any interior region of the pattern. Conversely, I have used the term open pat~ern to refer to patterns such as are shown in Figs. 12 through 14, in which there is at least one opening in the interior of the patterns. Furthermore, a pattern is repeating where one or more repeaters, as hereinafter described, repeat in similar orientation.
As will be more fully understood by reference to the drawing figllres 9 there are a number of basic "repeaters" which are employed in all of the above patterns whether open or clos~d. These repeaters consist of two of my slab elements 1 and/or 1' in a particular adjoining relationship. For example, a first repeater is indicated generally at 51 in Fig, 7.

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First repeater 51 consists of two slab elements la and lb in a common plane wherein lateral faces lla and llb of tail sections 3a and 3b are located proximate to each other. Similarly, second repeater 52 consists of two slab elements la and lb in a common plane wherein lateral faces 9a and 9b of main sections 2a and 2b are located proximate to each other. As can readily be seen in Fig. 7, using a multiplicity of first repeaters 51 and second repeaters 52 results in the repeating first closed pattern 50. Upon further inspection, a third repeater 57 may be seen in Fig. 7.
Third repeater 57 consists of two slab elements la and lb in a common plane and in which longitudinal face 4a of slab element la is located proximate to longitudi-nal face 7b of slab element lb. Third repeater 57 may be employed as was done in Fig. 7 by making rows of third repeaters 57 which alternate between rightside up and rotated 180. Similarly~ rows of third repeaters 57 may be employed wherein all third repeaters have the same orientation as is shown in Fig. ~ a~ a repeating second closed pattern 55. Also shown in Fig. 8 is a fourth repeater 56 which consists of two slab elements la and lb in which lateral face 9a of main section 2a of slab element la is located proximate to ]ateral face llb of tail section 3b of slab element lb. A fifth repeater 61, shown in Fig.
9, consists of two slab elements la and lb in which longitudinal faces 4a and 4b of slab elements la and lb, respectivel~, are located proximate to each other while their tail sections 3a and 3b are spaced away from each other.
Sixth repeater 66 is shown in Fig. 10 and, when employed in a repeating fourth closed pattern 65, also utilizes fourth repeaters 56 and 56'. Sixth repeater 66 consists of one slab element 1 and one slab element 1' wherein the first longitudinal face 4 of slab element 1 is located proximat~ to second longitudinal face 7 of slab element 1l~ Fourth repeater 56' i5 virtually identical to fourth repeater 56 except that the former is made with slab elements 1' rather than slab elements 1.
As shown in Fig. 11, a fifth closed pattern 70 may consist of alternate repeaters 57 and the mirror image slab elements l' as shown at 71. Other repeaters may be employed with my invention, but I
have chosen to illustrate only some of those repeaters for simplicity.
The varied patterns exemplified in Figs~ 7 through 13 employ a large number of slab elements disposed in a common plane with faces of each of most of those slab elements proxim~tely located relative to faces of at least four other slab elements. That the above relationship is met is borne out by examination of any one of the several slab elements contained in 1 3 ~

the intexior, as opposed to the periphexy, of the above patterns and the proximate relationship had with the neighboring slab elements.
The slab element of the present invention does not lend itself to the same pattern variations of that disclosed in my prior Patent No. 4,544,305, but proviaes an element for Eorming other attractive designs, particularly those of the more classic type which have the appearance of comprising regular hexagons and squares. Even a pattern providing imbeddad regular octagons as shown in Fig. 14 is possible. While actually the hexagon ~egments of my slab elements are not true regular hexagons, it has been found that use of an equilateral hexagon where the angles include 90 and 135 angles creates a perception of regular hexagons to most observers.
Additionally, making an opposed two of the angles of a regular hexagon equal to 90 and the other four equal to 135, with an integral square section adjacent one of the lateral sides forming the 90 angle provides for closed interlocking patterns and for structural enhancement over the prior art, which are among the intended advantages set forth above9 Such a pattern is one which is simple to cos~ of concrete or other such material and is one which is not as prone to breakage as other shapes.

Claims (16)

1. A tile-like slab element for covering the ground or other like surface, said element comprising:
a main hexagonal section having a periphery formed of six faces of equal length, said six faces including four lateral faces and two longitudinal faces, said four lateral faces disposed as two opposing pair of adjacent lateral faces, each pair being joined together at one end thereof at approxi-mately a 90° angle with the other, and at the other ends thereof being joined at approximately a 135°
angle to the end of a respective one of said longi-tudinal faces; and a square section having a periphery of four faces each equal in length to the length of the faces of said hexagonal section, said square section being joined to said hexagonal section at one of said lateral faces, whereby the faces of said square section adjacent the joined face form angles of 135°
and 180° respectively with the next adjacent faces of said hexagonal section;
the hexagonal and square sections of said element being integrally formed of a single piece of ceramic material having a thickness less than half of the longitudinal dimension of said element.

2. The slab element of claim 1, wherein each lateral face and each longitudinal face has an upper edge portion which is chamfered.

3. A ground or similar surface cover comprising a plurality of interlocking ceramic tile-like slab elements, each slab element including:
a main hexagonal section having a periphery formed of six faces of equal length, said six faces including four lateral faces and two longitudinal faces, said four lateral faces disposed as two opposing pair of adjacent lateral faces, each pair being joined together at one end thereof at approxi-mately a 90° angle with the other, and at the other ends thereof being joined at approximately a 135°
angle to the end of a respective one of said longi-tudinal faces; and a square section having a periphery of four faces each equal in length to the length of the faces of said hexagonal section, said square section being joined to said hexagonal section at one of said lateral faces, whereby the faces of said square section adjacent the joined face form angles of 135°
and 180° respectively with the next adjacent faces of said hexagonal section;
the hexagonal and square sections of said element being integrally formed of a single piece of ceramic material having a thickness less than half of the longitudinal dimension of said element;
wherein said slab elements are disposed in a common plane with faces of a substantial number of said slab elements proximately located relative to faces of at least four other of said slab elements.

4. The ground or similar surface cover of claim 3 including a first plurality of said elements arranged in a first repeatable configuration, said first repeatable configuration comprising a first and a second of said interlocking slab elements each shaped substantially identically, and wherein the longitudinal faces of the hexagonal sections of each of said elements include a first longitudinal face adjacent said square section and second longitudinal face, said first longitudinal face of said first slab element being located proximate to said first longi-tudinal face of said second slab element.

5. The ground or similar surface cover of claim 4 wherein a substantial number of said first plural-ities of said first repeatable configuration are arranged such that any face of a slab element located proximate to a longitudinal face of another slab element is a longitudinal face.

6. The ground or similar surface cover of claim 3 including a second plurality of elements arranged in a second repeatable configuration, said second repeat-able configuration comprising a first and a second of said interlocking slab elements each shaped substan-tially identically, and wherein one of said faces of said square section of said first slab element being located proximate to said lateral face of said hex-agonal section of said second slab element next to the lateral faces to which said square section of the second element is joined.

7. The ground or similar surface cover of claim 6 wherein in said second repeatable configuration said first longitudinal face of said first slab element is located proximate to said second longitudinal face of said second slab element.

8. The ground or similar surface cover of claim 7 wherein a substantial number of said second plural-ities of said second repeatable configuration are arranged such that any face of a slab element located proximate to a face of a square section of another slab element is a hexagonal section lateral face.

9. The ground or similar surface cover of claim 7 wherein a substantial number of said second plural-ities of said second repeatable configuration are arranged such that at least one square section face of one of said slab elements is located proximate to one square section lateral face of another of said slab elements.

10. The ground or similar surface cover of claim 3 including a third plurality of a third repeatable configuration, said third repeatable configuration comprising a first and a second of said interlocking slab elements each shaped substantially identically, and wherein one of said faces of said square section of said first slab element is located proximate to said third lateral face of said hexagonal section of said second slab element.

11. The ground or similar surface cover of claim 10 wherein in said third repeatable configuration said first longitudinal face of said first slab element is located proximate to said second longitudinal face of the second slab element.

12. The ground or similar surface cover of claim 3 including a fourth plurality of a fourth repeatable configuration, said fourth repeatable configuration comprising a first and a second of said interlocking slab elements shaped substantially identically, and wherein one of said lateral faces of said square section of said first slab element is located proxi-mate to one of said faces of said square section of said second slab element.

13. The ground cover of claim 3 including a fifth plurality of a fifth repeatable configuration, said fifth repeatable configuration comprising a first and second of said interlocking slab elements each shaped substantially identically, and wherein the lateral faces of the hexagonal sections of said first and second slab elements opposite from the lateral faces to which the square sections of the elements are joined are adjacent.

14. The ground cover of claim 3 including a sixth plurality of a sixth repeatable configuration, said sixth repeatable configuration comprising a first and second of said interlocking slab elements each shaped substantially identically, and wherein the lateral face of the hexagonal section which is oppo-site to the lateral face to which the square section is joined to the first element is adjacent to the face of the square section of the second element which is opposite the face of that square section which is joined to the hexagonal section of that element.

15. An integrally formed tile-like slab element of cast ceramic material having a seven sided top face, a seven sided bottom face identical to but a mirror image of said top face and parallel thereto, and seven side faces each perpendicular to said top and bottom faces and each being rectangular, said seven side faces including first through sixth faces each approximately identical in length and a seventh face equal to twice the length of each other side face, said first face adjoining and forming an in-ternal angle of approximately 135° with said second face, said second face adjoining and forming an internal angle of approximately 90° with said third face, said third face adjoining and forming an in-ternal angle of approximately 135° with said fourth face, said fourth face adjoining and forming an external angle of approximately 135° with said fifth face, said fifth face adjoining and forming an in-ternal angle of approximately 90° with said sixth face, said sixth face adjoining and forming an in-ternal angle of approximately 90° with said seventh face, and said seventh face adjoining and forming an internal angle of approximately 135° with said first face.

16. The slab element of claim 15, wherein each lateral face and each longitudinal face has an upper edge portion which is chamfered.