NL2031530B1

NL2031530B1 - An easily installable porcelain stoneware element for the construction of driveway paving

Info

Publication number: NL2031530B1
Application number: NL2031530A
Authority: NL
Inventors: Borgomeo Francesco
Original assignee: Saxa Grestone S P A
Priority date: 2021-04-09
Filing date: 2022-04-07
Publication date: 2024-06-27
Also published as: FR3121697B3; FR3121697A3; DE202022101889U1; IT202100001820U1; NL2031530A

Abstract

A porcelain stoneware element (1) for the construction of driveway paving is described, comprising a main body (1A) including: 5 -a walking surface (2); -a base surface (3) opposite to the walking surface (2); -a side surface (4) extending perimetrically about the walking surface (2), said side surface (4) being connected to and arranged transversally with respect to 10 the base surface (3) and the walking surface (2). The porcelain stoneware element (1) comprises a plurality of spacers (10) made in one piece with the main body (1A), which protrude laterally from the side surface (4). (Fig. 1)

Description

"An easily installable porcelain stoneware element for the construction of driveway paving" * % *

DESCRIPTION

[0001] The present finding relates to the technical field of porcelain stoneware items for the construction of driveway paving.

[0002] Nowadays, laying porcelain stoneware driveway paving is becoming more and more complicated. Indeed, the introduction of rectified porcelain stoneware tiles on the market has made the life of tilers more complicated than in the past. Unlike conventional tiles, the so- called "sharp-edged" tiles have a right-angled edge which allows them to be placed so closely together during installation as to appear to be a single unit, thus leaving a grout space close to zero. Bearing in mind that the minimum conventional distance for the grout lines should be at least one millimeter to avoid disastrous results, extraordinary effects can be achieved on paving with rectified tiles precisely because of the characteristic of minimizing the grout space and making the surface even flatter. Rectified porcelain stoneware is used with various patterns, such as, by way of non- limiting example, polished marble or faux wood effect with grain that makes it very hard to believe that the walked-on floor is made of porcelain stoneware and is not a traditional wood parquet. However, laying this type of floor correctly requires more experience by the tiler and more attention because the material, especially on the sharp edges, is much more delicate and can chip easily.

Furthermore, a minor laying defect, which would be substantially invisible on traditional floors, is instead amplified with porcelain stoneware floors.

[0003]A proper installation requires almost perfect flatness between the laid tiles, whether they are small or large in size. Often tiles cannot be placed optimally due to substrates which are not perfectly leveled.

Indeed, it frequently happens that they appear perfectly leveled during laying but, once the adhesive has set, show level differences which compromise the aesthetic appearance of the end result. Furthermore, the presence of relatively large and/or irregular grout lines does not allow for the continuity of the desired effect.

[0004] It is an object of the present finding to provide a porcelain stoneware element for the construction of driveway paving which allows avoiding or reducing at least partially the drawbacks discussed above with reference to the prior art.

[0005] In particular, it is an object of the present finding to facilitate the installation of a porcelain stoneware driveway paving so as to reduce the time and cost required for installation, while minimizing possible paving imperfections which may occur when laying the paving.

[0006] These and other objects are achieved by a porcelain stoneware element for the construction of

IO driveway paving as defined in appended claim 1 in the most general form thereof and in the dependent claims in some particular embodiments.

[0007] The finding will be better understood from the following detailed description of the embodiments thereof, given by way of not limiting examples, with reference to the accompanying drawings, in which: - Fig. 1 shows a diagrammatic top perspective view of a porcelain stoneware element for the construction of driveway paving according to a first embodiment of the present finding; - Fig. 2 shows a diagrammatic top plan view of the element for the construction of driveway paving in

Fig. 1; - Fig. 3 shows a diagrammatic side plan view of the element for the construction of driveway paving in

Fig. 1; - Fig. 4 shows a diagrammatic top perspective view of a porcelain stoneware element for the construction of driveway paving according to a second embodiment of the present finding; - Fig. 5 shows a diagrammatic side plan view of the element for the construction of driveway paving in

Fig. 4.

[0008] Similar or equivalent elements in the accompanying

IO figures will be indicated by the same reference numerals.

[0009] It should be noted that for purposes of the present description, the term "rectangular" used to describe a part of an element for the construction of driveway paving according to the present description is to be construed broadly. In other words, for purposes of the present description, the term "rectangular" should be understood to mean rectangular or substantially rectangular. For example and without introducing any limitation, a rectangular element may comprise both an exactly rectangular element and a rectangular element with rounded corners. Once again, it should be noted that for the purposes of the present description the term "rectangular" should be understood to also include the square shape, the latter being considered as a particular case of rectangular shape. Once again, it should be noted that below in the present description the term "truncated pyramid" used to describe an element of the construction of driveway paving according to the present finding is to be understood broadly. In other words, such a term should 5 be construed as a truncated pyramid or a substantially truncated pyramid.

[0010] With reference to Figs. 1-3, in such figures a porcelain stoneware element 1 for the construction of driveway paving according to an embodiment of the present finding is shown. According to an embodiment, in particular, the element 1 is so called “sampietrini” made of porcelain stoneware. As is known, sampietrini are small blocks normally made of leucitite which are traditionally used for the construction of paved roads,

IS e.g., in the historic center of Rome.

[0011] According to an embodiment, the ceramic mixture from which the porcelain stoneware of element 1 is obtained normally comprises or consists of the following components: —one or more alkaline feldspars; these are sodium or potassium feldspars normally found in Italy (Calabria or

Sardinia) or Turkey or the Pyrenees; feldspar is normally introduced into mixture in amounts of at least 40-45%, and such a raw material has the task of conferring fusibility to the mixture itself, so that the melting temperature remains at values below 1200 °C; the dosage of these ingredients, as well as the grinding degree thereof, allows optimizing the firing curve of the product and giving it a porosity-free texture; - one or more plastic clays; they are normally clays with a high percentage of alumina (20-25%) with low iron oxide contents (light firing), or higher iron contents (red- brown firing). They are introduced into the mixture at about 35%; they have the purpose of keeping the non- plastic ingredients together so as to confer malleability and workability to the mixture before firing; the highest quality clays are found in Germany and Ukraine and to a lesser extent in Spain; — inerts or fillers; inerts can be quartz or feldspar sands, pre-baked kaolins; they are normally introduced into the ceramic mixture at about 15-20% and usually are from local quarries and thus are the least expensive part of the mixture.

[0012] It should be noted that a limitation in the production of porcelain stoneware with high thickness is the abnormal amounts of raw materials. Therefore, the present finding also aims at responding to this type of problems.

[0013] The element 1 comprises a main body 1A including a walking surface 2 and a base surface 3 opposite to the walking surface 2. Furthermore, the main body 1A comprises a side surface 4 extending perimetrically about the walking surface 2. The side surface 4 is connected to and arranged transversely with respect to the base surface 3 and the walking surface 2. According to an embodiment, the main body 1A may comprise a connecting surface 5, e.g., a curved connecting surface, which extends perimetrically to the walking surface 2 and connects the side surface 4 to the walking surface 2.

Advantageously, the element 1 comprises a plurality of spacers 10 made in one piece with the main body 1A, which protrude laterally from the side surface 4.

[0014] According to an embodiment, the side surface 4 is quadrangular or substantially quadrangular in shape.

According to an embodiment, the side surface 4 is particularly rectangular or substantially rectangular in shape (the surface 4 generally has sharp-edged corners, although in some cases they may become slightly rounded after grinding and/or firing the element 1, for example).

According to an embodiment, the side surface 4 comprises four faces 4A-4D mutually opposite in pairs. According to an embodiment, the side surface 4 is shaped like the side surface of a truncated pyramid and converges from the walking surface 2 towards the base surface 3. Each face 4A-4D of the side surface 4 comprises a central axis Xl directed in a direction which joins the walking surface 2 and the base surface 3. According to an embodiment, the porcelain stoneware element 1 comprises at least two spacers 10. Furthermore, at least two faces of the faces 4A-4D of the side surface 4 each comprise at least one of the aforementioned spacers 10. According to an embodiment, the element 1 comprises at least four spacers and at least one of said spacers 10 protrudes from each face 4A-4D of the side surface 4. According to an 10 embodiment, the element 1 comprises at least two of said spacers 10 which protrude from the same face 4A-4D of the side surface 4. According to an embodiment, at least two spacers 10 protrude from each face 4A-4D of the side surface 4. With reference to the embodiment shown in

Figs. 1-3, and without introducing any limitation, only two spacers 10 protrude from each face 4A-4D of the side surface 4. In other words, in the embodiment shown in

Figs. 1-3, eight spacers 10 protrude from the side surface 4, two of which protrude from the face 4A, two protrude from the face 4B, two protrude from the face 4C, and two protrude from the face 4D.

[0015] According to an embodiment, the at least two spacers 10 which protrude from the same face 4A-4D of the side surface 4 are off-centered with respect to the central axis X1 of such a face 4A-4D. For example, as can be seen in Fig. 3, the two spacers 10 which protrude from the face 4A are off-centered with respect to the central axis X1. According to an embodiment, at least two spacers 10 protrude from each face 4A-4D of the side surface 4, which are off-centered in the same direction RI1 considering the porcelain stoneware element 1 arranged in a normal installation condition and looking frontally at the face 4A-4D of the side surface 4 from which the at least two spacers 10 protrude. Thereby, it is advantageously possible to place two porcelain stoneware elements 1 side by side without the spacers 10 of one of such elements 1 being at the spacers 10 of the other element 1 placed by the side, thus preventing the distance between the elements 1 from being minimized.

[0016] With reference to Fig. 3, according to an embodiment, two immediately consecutive spacers 10 protruding from the same face 4A-4D of the side surface 4 are spaced apart by a distance Dl generally between 40 mm and 120 mm, and more preferably between 60 mm and 100 mm.

In the embodiment shown in Figs. 1-3, and without introducing any limitation, the distance Dl is 97 mm.

[0017] With reference to Fig. 2, according to an embodiment, each of the spacers 10 has a maximum thickness Wl generally between 1 mm and 3 mm, and more preferably between 1.5 mm and 2.5 mm. In the embodiment shown in Figs. 1-3, and without introducing any limitation, the thickness Wl is 1.5 mm.

[0018] With reference to Fig. 3, according to an embodiment, each of the spacers 10 extends longitudinally in a direction parallel to the central axis X1 of the face 4A-4D from which such a spacer 10 protrudes.

[0019] Again with reference to Fig. 3, according to a convenient embodiment, each spacer 10 has at least one upper spacer face 10A which is proximal to the walking surface 2 and inclined with respect to the walking surface 2 and/or the base surface 3. Furthermore, each spacer 10 comprises at least one spacer side face 10B-10D which is arranged transversely and joined to the upper spacer face 10A. In particular, the side face 10B-10D extends longitudinally along the side surface 4 of the main body 1A. Advantageously, the provision of the inclined upper face 10A allows avoiding possible chipping of the spacer 10 and allows facilitating the laying of the element 1.

[0020] Again with reference to Fig. 3, according to an embodiment, each spacer 10 comprises a lower spacer face 10E opposite to the upper spacer face 10A. The lower face 10E is proximal to the base surface 3 and is arranged transversally with respect to the spacer side surface 10B-10D.

[0021] According to an embodiment, the spacer side face 10B-10D comprises a central flat portion 10B parallel to the face 4A-4D from which such a spacer 10 protrudes.

Furthermore, the side face 10B-10D comprises two inclined flat portions 10C,10D which are connected to and arranged on opposite sides with respect to the central flat portion 10B.

[0022] Again with reference to Fig. 3, according to an embodiment, the element 1 has an average thickness Slm, measured from the base surface 3 to the walking surface 2, which is between 30 mm and 65 mm, and more preferably between 45 mm and 65 mm. In the embodiment shown in Figs. 1-3, and without introducing any limitation, the average thickness Slm is 50 mm. An indication of the average thickness is given, since the walking and/or base surfaces 2,3 may not be perfectly regular (even deliberately, as for surface 2 in particular, to confer a particular appearance to element 1).

[0023] According to an embodiment, the porcelain stoneware from which the element 1 is made comprises bottom ashes resulting from the incineration of municipal solid waste. In particular, according to an embodiment, the porcelain stoneware from which element 1 is made does not include steel mill slag.

[0024] The bottom ashes coming out of the pre-treatment stage preferably have a composition which is either equal or similar to that shown in the following Table 1: < ERLE SOM IEN OM LE BL RANE Lae La se ey

Table 1: Ideal ash composition

[0025] Preferably, a percentage of bottom ashes to be used is from 1% to 40% by volume of the mixture used to

IO produce the porcelain stoneware.

[0026] According to a preferred embodiment, such a percentage of bottom ashes is between 10% and 30%, even more preferably is between 15% and 25%.

[0027] According to an embodiment, if the porcelain stoneware comprises the aforementioned bottom ashes, the alkaline feldspars are removed from the mixture while the amounts of plastic clays and inerts are appropriately increased.

[0028] Conveniently, using the aforementioned ashes as a partial replacement for raw materials results in less consumption of the raw materials themselves. Therefore, there is a saving in production costs, but especially less waste to be sent to landfills (nowadays landfills are becoming saturated} and thus less environmental impact (visual impact of landfills and less land to be used for any new storage sites).

[0029] According to an embodiment, the porcelain stoneware from which the element 1 is obtained from a dry-ground mixture by pressing.

[0030] In this regard, it should be noted that the preparation of the mixture by dry grinding allows for a greater efficiency, in terms of consumption of water and/or additives, and especially a high energy saving, in terms of thermal energy, bringing consumption to about 1/3 compared to that of wet grinding. In addition to economic savings (in terms of maintenance, additives, and consumption of ground bodies), the preparation of the mixture by dry grinding also brings about a huge improvement in terms of environmental impact. Indeed, a decrease in thermal energy of about 2/3 (from 45.04 Sm3/t to 14.29 Sm3/t) means a decrease in CO2 emissions and thus less environmental pollution. Furthermore, the lower water consumption (from 449 1/t to 136 1/t) should also not be underestimated, because it is well known that the lower the water consumption, the less water needs to be treated following use, and therefore the fewer the substances to be removed before the water is sent to the final receptor.

[0031] As for the pressing of the mixture, it should be noted that according to an embodiment the pressing stage is preferably carried out using SACMI PH 690 presses.

[0032] It should be noted that the element 1, being made of porcelain stoneware, has a minimum value of the flexural tensile modulus equal to 35 N/mm2 and a minimum value of the ultimate load equal to 1300 N. These features are important to ensure that the element 1 is not only walkable but also vehicle accessible.

[0033] Once again, it should be noted that according to an embodiment, upon tests carried out according to UNI 1338:2004 and for uniaxial compression UNI EN 1926, the element 1 has the technical features indicated in Table 2 below:

Measured parameter

Slip resistance value (SRV)

Unpolished slip resistance 39 value (USRV)

Water absorption 0.234% 17.23

Indirect traction 11.40 N/mm? 214.43 N/mm?

Flexural tensile modulus 49.53 N/mm?

Table 2

[0034] With reference to Fig. 2, according to an embodiment, the side surface 4 comprises a rectangular perimeter edge 41. In particular, the perimeter edge 41 comprises a first side 411 having a length L1 between 100 mm and 600 mm and a second side 212, orthogonal to the first side 211, which has a length L2 between 100 mm and 600 mm. In the example shown in the accompanying figures, the perimeter edge 41 is particularly square in shape.

[0035] According to an embodiment, the element 1 is constructed so that the perimeter edge 41 has the dimensions indicated in the Table 3 below:

FINAL SIZE UNFIRED SIZE

(mm) {mm) 100 x 100 104.7 x 104.7 100 x 200 104.7 x 209.4 200 x 200 209.4 x 209.4 200 x 400 209.4 x 418.8 400 x 400 418.8 x 418.8 400 x 600 418.8 x 628.2 600 x 600 628.2 x 628.2

Table 3

However, it should be noted that, according to alternative embodiments, the perimeter edge 41 may be a rectangular edge in which each of the sides 411,412 may have any length L1,L2 between 100 mm and 600 mm. In the exemplary embodiment, and without introducing any limitation, both sides 411,412 have the same length L1,

L2 equal to 204 mm.

[0036] As for the process of constructing the element 1, it should be noted that, according to an embodiment, underlying this process solution there is the idea of reusing, in the preparation of the ceramic mixture, recovered materials or rather waste materials from other companies normally intended to be taken to special landfills with precisely the often high costs of disposal, thus developing the circular economy concept.

Specifically, as mentioned above, according to an embodiment it was decided to reuse bottom ashes resulting from the incineration of municipal solid waste. Ashes from incinerators, before being used, must undergo a natural aging process in order to lower the pH thereof through carbonation reactions, and then they undergo a treatment in a special plant, where they are reduced in size, deferrized, and de-metallized with specific machines. Through a sequence of continuously working weighing bins, all the raw materials forming part of the formulation are taken to the grinding department in appropriate proportions. The material to be pressed is uniformly humidified to confer plasticity to the system and thus facilitate the cohesion between the different particles making up the whole. According to the percentage of water, the molding can be performed under different conditions: pressing in the plastic state (water percentage of 20-25%); pressing in the semi-dry state (moisture content of 10-15%); pressing in the dry state (moisture content of 3-73). In the case of the present finding, through a wetting action, the mixture is "granulated", i.e., brought to a moisture content of about 6% and made basically spherical or granular to confer a correct flowability. At this point, the mixture is ready to move on to the next steps. A storage of the mixture allows obtaining a “buffer” for the press department. After storage comes the pressing step.

Pressing consists in taking powders to a hardened steel mold where they undergo a pressing of about 300 kg/cm? which confers the desired shape to the element 1. The pressing cycle begins with the ejection of the product formed in the previous press by lifting the bottom punches from the bottom of the die to the edge of the plane. The advancement of the feeder carriage equipped with the grid pushes the product out of the die and, upon lowering the bottom punches (first drop), completely fills the cavities with powder when the carriage has returned to its rest position. The bottom punch drops by another portion (second drop) and begins the descent of the cross beam. The first compression of the material is not violent because its core functionality is to eject the air present between the powder particles (deaeration). The second compression is that of true shaping, capable of conferring the desired compactness to the material. The cycle then repeats with the ejection of the product and the reloading of the cavities. The pressing step 1s of considerable importance for the specific characteristic desired for the product. Indeed, a pressing imperfection could lead to chipping and/or breakage of spacers 10 both close to the press outlet and in the final product. Therefore, the design layout of the press punch, to confer the required characteristics, and the performance of the pressing itself are both of considerable importance to ensure that the product is optimal, avoiding in particular the possible breakage of spacers.

After leaving the press, the pieces are placed on trolleys built with materials adapted to withstand the high temperatures of the dryer, first, and the kiln, later. The drying step consists in removing the water contained in a solid by evaporation, i.e., by conversion of water from the liquid state to the vapor state.

Therefore, the drying process involves both the transfer of heat from the surrounding environment towards the ceramic body to be dried and the simultaneous transfer of water vapor in the opposite direction. At the beginning of drying (dryer inlet), the internal temperature thereof is low and the diffusion is very slow, thus the evaporation rate should be contained to avoid compacting the surface layer; in this regard, the incoming material is put in contact with warm, but relatively humid air in conventional dryers. The heating rate is adjusted by the alr temperature and speed (flow rate) thereof. For a given material, the time required to achieve uniform heating up to temperatures which allow proper diffusion kinetics essentially depends on the thickness. Correct drying results in limiting shrinkage to contain deformation; giving the object the mechanical strength adapted to withstand the drying tension and to allow handling in successive steps. Upon leaving the dryer, the trolleys enter the firing kiln where the high temperatures (about 1150 °C) will cause the exiting product to have a moisture content of less than 0.5%, according to the specifications of porcelain stoneware, currently dictated by UNI EN 14411 standard. During the firing cycle, the product passes from the pre-heating section to the slow cooling section within 6/8 hours. At the kiln outlet, there is a sorting to eliminate any faulty pieces and packed before being sent to the finished product warehouse.

[0037] Referring now to Figs. 4-5, in such figures a porcelain stoneware element 1F for the construction of driveway paving according to a further embodiment of the present finding is shown. The element 1F shown in Figs. 4-5 essentially differs from the element 1 shown in Figs.

1-3 only in that it includes spacers 10F having a slightly different shape than the shape of the spacers 10 shown in Figs. 1-3. Specifically, as can be seen by comparing the accompanying figures, the spacers 10F of the element shown in Figs. 4-5 differ from the spacers 10 shown in Figs. 1-3 only in that they extend only partially along the respective face 4A of the side surface 4 and in that the side surface 10G of the spacers 10F is shaped so as to converge in the direction from the walking surface 2 towards the base surface 3.

Furthermore, according to an embodiment, the side surface 10G of the spacers 10F may comprise a single curved surface 10G. Besides these differences, everything described above with reference to the element 1 and the spacers 10 remains valid for the element 1F and the spacers 10F as far as applicable. Therefore, for the purposes of brevity of this description, the element 1F will not be described in further detail.

[0038] Based on the foregoing, it can thus be understood how a porcelain stoneware element for the construction of driveway paving according to the present description is capable of achieving the aforesaid purposes.

[0039] Indeed, a porcelain stoneware element for the construction of driveway paving according to the present finding, comprising a plurality of spacers made in one piece with the main body of such an element, advantageously allows solving the problems discussed above with reference to the prior art thus ensuring customers’ satisfaction. This new technology will require less time to install and lower costs than other methods used for laying. The presence of spacers will allow speeding up the installation and ensuring almost perfect coplanarity of the tiles and almost perfect grout lines (of minimum thickness and almost indistinguishable from the rest of the flooring). In particular, during laying, the presence of the spacers allows perfectly matching the tiles thus ensuring the uniformity of the flat surface.

The end result will be an almost perfect flooring without a single "ridge". Furthermore, according to an embodiment of the present finding, by virtue of a process of manufacturing the porcelain stoneware element which includes reusing recovered material from the thermal treatment of urban waste, the objective of carrying out productions with a strong circular economy value is also achieved.

[0040] Without prejudice to the principle of the finding, the embodiments and the constructional details may be broadly varied with respect to the above description disclosed by way of a non-limiting example, without departing from the scope of the finding as defined in the appended claims.

Claims

Claims 1 Porcelain stoneware element (1) for the construction of driveway paving, comprising a main part (1A) comprising: a tread (2); a base surface (3) opposite the tread (2); a side surface (4) extending perimetrically around the tread (2), the side surface (4) being connected to and disposed transversely of the base surface (3) and the tread (2); the porcelain stoneware element (1) comprising a plurality of spacers (10) integral with the main part (1A) extending laterally from the side surface

(4).

2. Porcelain stoneware element (1) according to claim 1, wherein the side surface (4) is quadrangular or substantially quadrangular in shape and comprises four sides (4A - 4D) which are always opposite each other in pairs, the porcelain stoneware element (1) comprising at least two of said spacers (10), and at least two sides (4A - 4D) of the side surface (4) each comprising at least one of said spacers (10), each side (4A-4D) of the side surface (4) comprising a central axis (X1) oriented in a direction connecting the tread (2) and the base surface (3).

3 Porcelain stoneware element (1) according to claim 2, comprising at least four of said spacers (10) and wherein at least one of said spacers (10) projects from each side (4A - 4D) of the side surface (4).

4 Porcelain stoneware element (1) according to claim 2 or 3, comprising at least two of said spacers (10) protruding from the same side (4A - 4D) of the side face (4).

5. Porcelain stoneware element (1) according to claim 4, wherein at least two of said spacers (10) protrude from each side (4A - 4D) of the side surface (4).

6. Porcelain stoneware element (1) according to claim 4 or 5, wherein said at least two spacers (10) protruding from the same side (4A - 4D) of the side face (4) are off-center with respect to the central axis (X1) of such a side (4A - 4D).

7. Porcelain stoneware element (1) according to claim 8, dependent on claim 5, wherein on each side (4A - 4D) of the side face (4) the at least two spacers (10) are located in the same direction (R1) off-centre, given that the porcelain stoneware element (1) is normally positioned, and viewed frontally on the side (4A - 4D) of the side face (4) from which said at least two spacers (10) protrude.

8. Porcelain stoneware element (1) according to any one of claims 4 to 7, wherein two of said immediately successive spacers (10) projecting from the same side (4A - 4D} of the side face (4) are spaced apart, with a distance (D1) generally between 40 and 120 mm, and more preferably between 68 and 100 mm.

9 Porcelain stoneware element (1) according to any of the preceding claims, wherein each of said spacers (10) has a maximum thickness (W1) between 1 and 3 mm, and more preferably between 1.5 and 2.5 mm.

10. Porcelain stoneware element (1) according to any one of claims 2 to 9, wherein each of said spacers (10) extends in the longitudinal direction in accordance with a direction parallel to the central axis (X1) of the edge (4A - 4D) of the side face (4) of the main part (1A) from which such spacer (10) projects.

11. Porcelain stoneware element (1) according to claim 10, wherein each of the spacers (10) has at least one upper spacer surface (10A) proximal to the tread (2) and angled relative to the tread (2) and/or the base plane (3), each of the spacers having at least one spacer side surface

(10B - 10D) comprises that which is transversely disposed and which is connected to the upper spacer surface (104) and extends longitudinally along the side surface (4) of the main part (1A).

12. Porcelain stoneware element (1) according to claim 11, wherein each of said spacers (10) comprises a lower spacer surface (10E) opposite the upper spacer surface (10A), the lower surface (10E) being proximal to the base surface (3) and being arranged transversely to the spacer side surface (10B - 10D).

13. A porcelain stoneware element according to claim 11 or 12, wherein the spacer side surface (10B - 10D) comprises a central flat portion (10B) lying parallel to the side (4A - 4D) of the side face (4) of the main part (1A) from which such spacer (10) projects, the spacer side surface (10B - 10D) comprising two inclined flat portions (10C, 10D) connected to and disposed on opposite sides with respect to the central flat portion (10B).

14 Porcelain stoneware element (1) according to any one of the preceding claims, having an average thickness (S1m) measured from the base surface (3) to the tread surface (2) of between 30 mm and 65 mm.

15. Porcelain stoneware element (1) according to any one of the preceding claims, wherein the porcelain stoneware comprises bottom ash derived from the incineration of municipal solid waste.

16. Porcelain stoneware element (1) according to any one of the preceding claims, wherein the porcelain stoneware is obtained from a dry-ground mixture, by pressing.

17. Porcelain stoneware element (1) according to any one of the preceding claims, wherein the side surface (4) of the main part (1A) comprises a peripheral edge (41) of rectangular shape,

comprising a first side (411) having a length (L1) between 100 mm and 600 mm, and a second side (412), perpendicular to the first side (411), having a length (L2) between 100 mm and 600 mm.