WO2014080368A1

WO2014080368A1 - A cementitious item with elevated surface texture qualities for non-structural applications, and a method for its manufacture

Info

Publication number: WO2014080368A1
Application number: PCT/IB2013/060329
Authority: WO
Inventors: Roberta Alfani; Michele DE LONGIS; Flavio RAMPINELLI
Original assignee: Italcementi S.P.A.
Priority date: 2012-11-23
Filing date: 2013-11-22
Publication date: 2014-05-30
Also published as: EP2922706A1; ITMI20121998A1

Abstract

The object of the present invention is the manufacture of a cementitious item through mold casting of a fluid composition comprising a hydraulic binder, one or more aggregates, an anti- shrinkage agent, a superplasticizer agent and water. The item (1) according to the invention comprises at least a first portion (15) in relief with respect to at least one second portion (25) and wherein the surface roughness of said first portion (15) is less than the surface roughness of said second portion (25). According to the invention, said first portion (15) is obtainable from the solidification of said fluid composition in contact with a polymeric material applied to the surface of a half-mold (10) of said mold, while the second portion (25) is obtainable from the solidification of the fluid composition in contact with a portion of an adhesive film (20) applied to the polymeric material or to the surface of said half-mold (10).

Description

A CEMENTITIOUS ITEM WITH ELEVATED SURFACE TEXTURE QUALITIES FOR NON-STRUCTURAL APPLICATIONS, AND A METHOD FOR ITS MANUFACTURE

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Field of the invention

The present invention relates to the production of cementitious items for nonstructural applications. In particular, the present invention relates to a cementitious item with a particular surface texture for aesthetic purposes and integrated architectural applications. The present invention also relates to a method for making the aforementioned cementitious item.

STATE OF THE ART

In the construction sector, the use of low-thickness cementitious items in sheet form and with a controlled surface roughness, is well known. In a first known form (described for example in patent application PCT/EP/067762) these items are manufactured by calandering followed by compression molding. However, this procedure is not very versatile since it can only be used for the production of an item having limited dimensions and using starting materials with plastic properties, high viscosity and low fluidity even in the fresh state.

The method for manufacturing cementitious items by means of mold casting described in patent application MI2011A001642 has certainly proven to be more satisfactory. This method involves either at least partly or completely coating the inner surface of at least one half-mold with a polymeric material selected from the group consisting of polyethylene terephthalate, polycarbonate, polyamide, polymethylmethacrylate, or other similar material capable of achieving an arithmetic mean surface roughness Ra of not more than 500 nm on the cementitious item during casting.

The items thereby obtained have an elevated surface quality and are used in construction for non-structural applications such as lining elements and coverings, both horizontal and vertical; furthermore, they are particularly suitable for use in the field of building integration photovoltaic (BIPV) to ensure the ideal integration of photovoltaic modules into urban architecture.

In recent years, there has been an increase in the number of requests for "textured" cementitious items, this term being used to indicate a finish in relief, measured in microns, on the surface of the item. These requests derive from the desire of operators in the sector, such as architects and designers, to endow cementitious items with certain desirable aesthetic traits so that they can be used as furnishing and/or design elements.

The aforementioned known processes are clearly unable to meet these requests. The calendering process is completely unsuitable for this purpose due to its lack of versatility in terms of the materials that can be used. Similarly, the mold casting process described in the aforementioned patent application MI2011A001642 only enables the manufacture of an item having uniform surfaces, without any relief features, marked by a maximum surface roughness of less than 500 nm. In fact, these two processes could only be used, although with doubtful effectiveness, to manufacture decorations in relief measuring millimeters or centimeters.

A known method for obtaining a texture on a cementitious item is to apply one of more layers of adhesive film to the surfaces of the item (produced by mold casting, for example) following a predetermined design. The aim of this overlapping is to generate a relief effect (with respect to the surface of the item) or the desired texture. However, this procedure has several disadvantages, the greatest of which involves its duration, which closely depends on the complexity of the desired texture. Indeed, the phase of applying the adhesive film following the manufacture of the item, is the most critical factor in terms of time involved and consequently of manufacturing costs.

In addition to this aspect, note also that the procedure described does not allow a texture to be created in a material of the same type as the cementitious material of which the item is made. Indeed, the texture is created from a different material which is that making up the layers of film. It is apparent that this aspect leads to a low-quality, unreliable product, since the layers of film are more subject to deterioration.

The main object of the present invention is therefore to provide a cementitious item and a method for its manufacture that can resolve the aforementioned technical problem. As part of this object, a first aim of the present invention is to provide a cementitious item with a high-quality texture and elevated reliability. Another aim is to provide a cementitious item with a highly attractive appearance. Yet another aim is to provide a cementitious item in which the desired texture is obtained by means of a procedure involving a single phase (a single production step). A further aim is to provide a cementitious item in which the desired texture is obtained by means of a procedure that is capable of giving the item a high degree of personalization. A last yet no less important aim of the present invention is to provide a cementitious item that can be obtained by means of a manufacturing procedure that is effective, reliable and at a competitive cost.

SUMMARY

The present invention relates, therefore, to a cementitious item with controlled surface texture and roughness, being made starting from a fluid composition comprising:

I. a hydraulic binder

II. one or more aggregates

III. an anti-shrinkage agent

IV. a superplasticizer agent

V. water,

wherein said item comprises at least a first portion in relief with respect to at least one second portion and wherein the arithmetic mean surface roughness Ra of the first portion is less than that of the second surface of said second portion.

The cementitious item according to the invention has portions with differentiated roughness that together give the item an appearance superior to that achieved in traditional cementitious items. In particular, these portions with different roughness are arranged as a function of the desired ornamentation or texture.

For the purposes of the present invention, the term "texture" is used to indicate a cementitious surface in relief having the same cementitious nature as the item, in other words having the same composition as the item on which the relief is created.

The present invention also relates to a method for making a cementitious item with texture, said method comprising the steps of:

- coating the walls of a mold with a polymeric material;

- applying an adhesive film on one or more portions of said half-mold according to a predetermined layout corresponding to said texture;

- pouring a fluid composition into said mold, said fluid composition comprising:

I. a hydraulic binder

II. one or more aggregates

III. an anti-shrinkage agent

IV. a superplasticizer agent

V. water,

- hardening and removing said cementitious item from said mold.

The method according to the invention has proven particularly advantageous since it makes it possible to obtain a cementitious item with texture in a single step, specifically during the production phase of the cementitious item. In other words, the desired texture is created at the same time as the cementitious item. This obviously translates into an advantageous reduction in manufacturing times and costs.

LIST OF FIGURES

Further features and advantages will become more evident from the following detailed description of the method for making the cementitious item according to the present invention, which is illustrated by no way of limitation in the accompanying drawings, in which:

- Figure 1 shows a pair of half-molds for the production of an embodiment of a cementitious item according to the present invention;

- Figure 2 shows the structure of an adhesive film used to make a cementitious item according to the present invention;

- Figure 3 shows one of the half-molds illustrated in Figure 1 to which the adhesive film shown in Figure 2 is applied;

- Figure 4 shows the half-mold illustrated in Figure 3 during its preparation phase;

- Figure 4a shows a detail of Figure 4;

- Figure 5 shows a view of a cementitious item obtainable using the half-mold illustrated in Figures 3 and 4;

- Figure 5a shows a detail of Figure 5. - Figure 6 shows a view of a half-mold used to make a cementitious item according to the invention;

- Figure 7 shows a view of the cementitious item obtainable using the half-mold shown in Figure 6.

The same reference numbers and letters in the figures identify the same element or components.

DETAILED DESCRIPTION

The present invention relates, therefore, to a cementitious item with a texture, or rather with a cementitious surface relief having a personalized form (or design). As mentioned above, according to the invention this cementitious surface relief has the same composition as the item on which the relief is created. This feature gives the texture greater reliability in terms of duration and resistance to deterioration. The item 1 according to the invention is made a starting from a fluid composition comprising:

I. a hydraulic binder;

II. one or more aggregates;

III. an anti-shrinkage agent;

IV. a superplasticizer agent;

V water.

The following description will describe in detail the components from I to IV of the aforementioned fluid composition. Examples of fluid compositions suited to the aims of the present invention will also be described.

Figures 5 and 5a show an example of cementitious item 1 according to the invention. The item 1 comprises at least a first portion 15, 15', 15", 15"' in relief with respect to a second portion 25. These portions have different roughness. More specifically, the roughness of the first portion 15, 15', 15", 15"' is less than the roughness of the second portion 25. As regards the roughness of the surface portions of the item 1 , the relative values will be given later in this description, and for the purposes of the present invention, will be given in terms of the arithmetic mean surface roughness Ra.

According to the present invention, then, at least one surface of the item 1 has predetermined alternating portions of different roughness. This alternating roughness results in a different surface finish for the surfaces, giving the item a highly attractive appearance. This feature is made more appreciable by the position in relief taken by the first portion 15, 15', 15", 15"', with a more precise finish with respect to the second portion 25 with greater roughness. Indeed, when the item 1 is illuminated by a light source, the light concentrating on the edges of the first portion in relief 15, 15', 15", 15"' gives this portion a particular degree of brightness that contrasts with the appearance of the second portion 25, which retains a more matt appearance due to the lower level of surface finish.

Figure 5 shows an item 1 according to the present invention wherein one surface (or first side) of the item comprises a plurality of first portions 15, 15', 15", 15"' in relief with respect to the rest of the surface, which corresponds functionally to the aforementioned second surface 25. In the example shown in Figure 5, the portions with reference numbers 15, 15', 15"' define a particular texture on the surface of the item comprising the letters of the alphabet "D" and Έ" (portions with reference numbers 15 and 15"'), the number "1" (portion with reference number 15') and a star-shape design (portion with reference number 15"). It is evident that the cementitious item 1 according to the invention can have different textures from those shown in the example in Figure 5, i.e. they can be personalized according to needs. In other words, in addition to the alphanumeric characters and/or simple designs such as those shown in Figure 5, the texture can have any conformation or design, as is also evident from the example shown in Figure 7.

Figure 5a shows a detail of the portion in relief in the shape of the letter Έ" and indicated by the reference number 15. In particular, Figure 5a shows the height, indicated with the reference letter h, of the portion 15 with "less roughness" with respect to the second portion 25 having "greater roughness". It has been seen that excellent results in terms of appearance are obtained when the height h is not less than 10 μΐη, preferably not less than 30μιη and more preferably not less than 50 μΠΊ.

It has been seen that the item 1 is particularly appreciable from the point of view of appearance when the roughness of the first portions 5, 15', 15", 5"' in relief is less than that of the second portion 25 by a value at least above 50 nm. It has been seen that with this difference in roughness, the portions 15, 15', 15", 15"' in relief have a mirror-polished effect with respect to the rest of the surface, which has a markedly matt appearance.

It has to be intended that all the preferred and advantageous aspects identified for the cementitious item according to the invention should also be considered preferred and advantageous for the method of its manufacture and its uses as described below.

The present invention also relates to a method for manufacturing a cementitious item 1 , for example in the form of a sheet with the aforementioned properties. With reference to the schematic view shown in figure 1 , the method involves the use of a mold, preferably with vertical walls, formed of two half-molds 10 made of a preferably metallic material. The inner surfaces of the half-molds 10 are coated with a polymeric material preferably selected from the group consisting of polyethylene terephthalate, such as Mylar® and similar materials, polycarbonate, polyamide, polymethylmethacrylate and their mixtures. In particular, for the purposes of the present invention, to coat the surface of the two half-molds 10, a polymeric material with a surface roughness of less than 100 nm is preferably selected.

The method also comprises a phase of applying an adhesive film 20 to one or more portions of at least one of the half-molds, preferably vinylic in nature, according to a predetermined layout defined as a function of the texture one wishes to obtain. Following application of the adhesive film 20, alternating portions "with adhesive" and portions "without adhesive" are generated on the half-mold 10. Following pouring of a fluid composition inside the mold and once this composition solidifies, the portions "with adhesive" define the portions of the cementitious item 1 with "greater roughness" (i.e. the second portion 25), while the portions "without adhesive" define the portions 15, 15', 15", 15"' in relief with "less roughness", i.e. with a better finish. In other words, the alternation of portions "with adhesive" and portions "without adhesive" defines the overall final configuration of the half-mold 10 by means of which, at the end of the hardening phase, the desired texture on the surface of the item 1 is obtained. In substance, the alternation of portions "without adhesive" and portions "with adhesive" is correspondingly transferred to the item during the hardening phase. Figure 2 shows an adhesive film 20 suitable for the purposes of the present invention. This film 20 comprises a protective paper base 21 that is generally silicon-treated on one side, a central part 22 made of vinylic adhesive material and a front film 23 to facilitate application. The adhesive film 20 is selected so that the central part 22 has a thickness of not less than 10 μιτι, preferably not less than 30 μιτΊ, and more preferably not less than 50 μιη. Adhesive films suitable for the purposes of the present invention include films from the Avery range, such as Avery® 900 Super Cast, sold by the company Avery, and films from the 3M™ Scotchcal™ ElectroCut™ Graphic range, sold by the company 3M.

With reference to Figure 3, according to the present invention the adhesive film 20 is made to adhere, preferably completely to one of the half-molds 0, by removing the protective base 21. More specifically, when applied to the half-mold 10, the adhesive is still intact, i.e. it is still covered by the protective film 23. Only once the film 20 has adhered completely to the half-mold 10 and the surface of the half- mold is completely covered by the adhesive, is the protective film 23 removed.

According to a preferred embodiment of the invention, the adhesive film 20 is pre- notched before being applied to the half-mold 10 so as to define removable parts 17 of the adhesive film (see figure 4). In particular, the film 20 is pre-notched in a manner corresponding to the desired texture. To this end, it is preferable to use a numerical control cutting machine, such as a cutting plotter for example, which enables a precise definition of the removable parts 17 to be achieved. Adhesive films that are particularly suitable for being pre-notched are those films of a polyvinylic nature, firstly due to their high degree of adaptability to surfaces, even irregular or uneven surfaces, and secondly due to their durability over time and ease of cutting.

With reference to Figures 4 and 4a, the pre-notched adhesive film 20 is applied to the surface of the half-mold 10. The removable parts 17 of the adhesive are then removed to create the portions 8 of the half-mold 10 "without adhesive" in a manner corresponding to the desired texture. Figure 4 illustrates this phase of the method in detail. The adhesive part 17 is removed so as to free from the adhesive a portion of the half-mold 10 in the shape of an upturned "1" which, following hardening of the item, will create the portion in relief indicated by the reference number 15' in Figure 5.

With particular reference to the detail shown in figure 4a, the portions 8 without adhesive have a first roughness corresponding to that of the surface of the polymeric material (preferably less than 100 nm) coating the half-mold 10, while the portions covered by the adhesive have a roughness corresponding to that of the adhesive itself. At the interface between the adhesive and the portions 8 without adhesive, a difference in thickness (indicated by the reference letter S) is created, which can be accurately measured using known profiling techniques. This difference in thickness S is obviously transferred to the cementitious item 1 following casting of the fluid composition inside the mold. The result is that the aforementioned portions without adhesive create the first portions 15, 15', 15", 15"' of the item 1 "in relief with respect to the rest of the surface (second surface 25). In other words, the thickness S of the adhesive creates the height H of the first portions 15, 15', 15", 15"' with respect to the second surface 25.

It can therefore be seen that these portions "in relief 15, 15', 15", 15"' have a mirror-polished effect created by the hardening of the fluid composition in contact with the surface of the polymeric material coating the half-mold 10. It can also be seen that the rest of the surface of the item 1 , created by the hardening of the fluid composition in contact with the adhesive, has a matt effect deriving from the greater roughness of the vinylic adhesive. The result is that the aesthetic effect deriving from the contrast between the portions with a mirror finish and the rest of the surface depends directly on the degree of roughness of the polymeric material coating the half-mold and the degree of roughness of the adhesive applied to this half-mold.

Figures 3 to 5a refer to a case where the adhesive is applied to only one half- mold. The possibility of coating both half-molds with adhesive in order to obtain, following hardening, a cementitious item having a texture on both surfaces corresponding to the half-molds, naturally falls within the scope of the invention. Components I to V of the composition according to the present invention will now be described in detail.

I. The term hydraulic binder refers to a powdered material in a dry solid state which, when mixed with water, forms plastic pastes capable of setting and hardening like a cement, even underwater. A clinker usable for preparing a binder for the present invention can be any clinker of ordinary cement, as defined according to standard UNI EN 197.1 , that is, a hydraulic material composed of at least two-thirds by mass of calcium silicates (3CaO*SiO2) and (2CaO*SiO₂), the remainder being AI2O3, Fe₂0₃ and other oxides; for example a clinker of Portland cement.

The broad definition of hydraulic binder according to the present invention includes both white, grey or pigmented cements according to the previously cited standard UNI EN 197.1 , and the so-called retaining-wall cements, cementitious agglomerates and hydraulic limes as defined in the Italian law of 26 May 1965 no. 595, and inorganic silicates.

To form an item according to the present invention, binders based on calcium sulfoaluminates may be used, such as the compounds described in the patents and/or patent applications WO2006/18569, EP-A-1306356 and EP-A-0181739, as well as those derived from calcium sulfoa!uminate clinkers described in the Review "Green Chemistry for sustainable cement production and Use" by John W. Phair Green Chem., 2006, 8, 763-780, in particular section 5.3 on page 776, and from calcium su!foaluminate clinkers described in the article "Calcium sulfoaluminates cements-low energy cements, special cements" J.H. Sharp et al., Advances in Cement Research, 1999, 11 , no.1 , pp 3-13. Alternatively, aluminate and sulfo- ferroalluminate cements may also advantageously be used, as described in Advances in Cement Research, 1999, 11 , no.1 Jan., 15-21.

According to the present invention, photocataiytic cements may also be used for manufacturing the items, that is, binders having photocataiytic activity which are obtained by adding to the mixture a photocatalyst capable of oxidizing - in the presence of light, air and moisture - the organic and inorganic contaminants present in the environment.

The photocatalyst may be selected from any compound capable of oxidizing, in the presence of light, oxygen and water, the contaminants which come into contact with the surface of the cementitious compositions in the hardened state, provided that it does not naturally counter-productively affect the physico-mechanical characteristics of the cementitious compositions used in the invention. The preferred photocatalyst according to the present invention is titanium oxide or one of its precursors and more typically titanium oxide at least partly in the anatase form. The expression "titanium oxide at least partly in the anatase form" means that the particles of titanium oxide have an anatase structure of at least 5%, preferably 25%, more preferably at least 50%, and yet more preferably at least 70%, as percentages by weight of the total titanium oxide. Examples of photocatalytic cements are the products in the TX range (Italcementi), such as TX Area®, TX Aria®.

In a preferred embodiment of the invention, the binders used are the sulfoaluminate Alicem® from Italcementi, the Portland cement Ultracem® 52.5R from Italcementi, the cement Italbianco® 52.5 R from Italcementi and the cement TX Area® from Italcementi and blends thereof.

The composition for manufacturing an item according to the present invention may also optionally comprise anhydride or gypsum.

II The aggregates or inert agents, also defined as inert aggregates, according to the present invention may comprise:

- fine aggregates such as fillers, powders and sands defined in the standard UNI EN 206, the term filler according to the present invention being understood as a fine aggregate fraction having a maximum diameter, d_max, equal to 40 microns; - non-fine aggregates having d_max greater than 40 microns.

The aggregates may advantageously be selected from calcareous aggregates, of quartz or silico-calcareous materials, of any shape, or crushed, or spherical, for example pulverized marble, ceramics, and also of types lightened to reduce the final weight of the item.

The relative percentage amount of aggregates of different dimensions optimized so as to obtain the desired roughness values, an indispensible prerequisite for achieving the desired texture; furthermore, this roughness contributes to conferring on the mortar rheological characteristics adapted to mold casting, and in particular: elevated fluidity, prolonged workability for the time necessary for casting, and absence of segregation phenomena prior to hardening. All while safeguarding the final mechanical properties of the hardened item.

Some aggregates, such as in the case of colored pulverized marble, also perform an aesthetic function; more specifically, they are able to confer particular characteristics of color and hue or grain to the item, reproducing the appearance of natural stone.

Optionally, the mixture may also contain one or more auxiliary substances commonly used in the field, such as charges of mineral or pozzolanic origin, organic and/or inorganic pigments or other substances. Mineral or pozzolanic charges are understood to include microsilica, silica fume, slag, fly ash, metakaolin, natural pozzolans, natural limestones, and precipitated calcium carbonates.

III The anti-shrinkage agent or "anti-shrinkage additive" serves to reduce hygrometric shrinkage and can be added in a liquid phase or solid phase. These anti-shrinkage agents, also known as SRAs (Shrinkage Reducing Agents), include a wide variety of glycols, polyols and ethers, and are responsible for reducing shrinkage deformation throughout the operating life of the hardened item. Lime may be added in combination therewith.

In a preferred aspect of the invention, as an anti-shrinkage additive III, Espandex 2000 from Axim in aqueous solution is used, or Shape 920 from Elotex in solid form. Alternatively, the product Cim'antiretrait from Sika-Axim can be used, a liquid additive composed of a blend of synthetic polymers and ethers that, although classified as an anti-foaming product, also possesses anti-shrinkage properties. IV According to the present invention, the cementitious starting composition must contain at least one superplasticizer agent or additive, preferably of a polycarboxylic type, added either in solid phase or in the form of an aqueous solution. In a preferred embodiment of the invention, superplasticizers selected from Melflux 1641 F or 2641 F in solid form, or Driver 72 Axim in liquid form, are used.

Combined use of the superplasticizer components IV and anti-shrinkage agent 111 enables the desired rheological characteristics to be optimized, with a low water- binder ratio, and hygrometric shrinkage measured up to 28 days to be appreciably reduced. The term 'water-binder ratio' refers to the ratio between the total amount of water used in the formulation of the composition and the amount of hydraulic binder I as previously defined. According to a preferred embodiment of the invention, the starting cementitious composition may also contain a waterproofing or water-repellent agent or additive for the purpose of limiting the water absorption of the item by capillary action. These agents include a wide range of organic compounds or organosilicon substances. According to a preferred aspect of the invention, Ligaphob N(T) 90 from Peter Greven or Seal 200 from Elotex, in solid form, are used as the water- repellent additive V.

In addition to the above-mentioned components, the composition in the form of castable mortar used to manufacture the item which is the subject of the present invention may contain various other additives to finely adapt the characteristics of the binder to the required specifications. Examples of these additives may be setting regulators, rheology modifiers or modifiers of physico-mechanical properties, such as for example cellulose or lactic substances, expanders, air entrainers, and air-release agents. Such additives are optional for the purposes of the invention.

The cementitious mixture used to make the cementitious item 1 according to the invention may also comprise the addition of fibers of various nature, such as inorganic fibers like metallic fibers or glass fibers and wollastonite, and organic fibers such as fibers based on polyvinyl alcohol or polypropylene or aramid fibers, selected on the basis of the final application. These fibers, also in the form of sheets or mesh networks, may be added to reduce the fragility of the cementitious item, and are selected according to the final characteristics of the item and its use. To ensure a better understanding of the characteristics and advantages of the invention, there follows a non-limiting example of a method for manufacturing a cementitious item 1 according to the present invention. Initially a metallic mold is prepared, of the type normally used for cementitious applications. The mold, preferably with vertical walls, consists of two paired halves, the internal surface of which is coated with materials such as polyethylene terephthalate, e.g. Mylar® and similar, polycarbonate, polyamide, polymethyl methacrylate and the like. At least one of the two half-molds is coated with an adhesive film 20, preferably vinylic in nature, preferably vectorially cut using a numerical control plotter capable of imparting the desired texture to the cementitious item. Subsequently or in the meantime, a starting fluid composition is created by an intimate mixing of said components from I to IV; water is then added and the mixture is protracted for a variable time depending on the mixer used. The highly fluid mortar (due especially to the presence of the superplasticizer agent) is then poured into the aforementioned mold wherein the adhesive applied to one of the two half-molds, following solidification, will confer to the item the desired decoration or texture.

The cementitious composition can be advantageously obtained using a planetary- type mixer filled with:

- a solid, cementitious-based mixture comprising one or more of the aforementioned components l-IV in the solid phase; this mixture may comprise, for example, a hydraulic binder (e.g. cement), one or more aggregates (e.g. sand, charges of mineral or pozzolanic origin), water-repellent additives and superplasticizers, if in solid form, modifiers, fibers, and pigments,

- water, stored in a liquid dispenser,

- any additives in liquid form.

The solid-phase components are mixed in the planetary-type mixer for a time preferably in the range from 30 seconds to 5 minutes, depending on the characteristics of the mixture and the external temperature, until a homogenous mixture is obtained. The liquid components are then added, including water, and mixing is continued for a period of between 30 seconds and 10 minutes, again depending on the mixer characteristics and the external temperature. The mortar in the cold state thus obtained is poured by means of an appropriate channel into the aforementioned mold. The elevated fluidity enables homogenous filling of the mold, in combination with the application of vibrations to compact the poured mass and promote the release of any trapped mechanical air. After around 24 hours it is possible to demold the item in order to subject it to the seasoning phase, which takes place by maintaining it in a vertical position, preferably in a room air- conditioned to 20 °C and 55% relative humidity.

Using the methodology described above, it is thus possible to manufacture cementitious items varying in shape and thickness and with elevated aesthetic qualities for non-structural applications. In particular, this methodology makes it possible to obtain an item with a particular texture and with an aesthetic and decorative effect making the item easier to personalize, specific and innovative and of a more attractive appearance.

The prefabricated cement products that are the subject of the present invention are intended for use in the construction sector, preferably for non-structural applications such as coating and covering elements with an elevated aesthetic quality, of both the horizontal and vertical type, such as flat slabs and floor tiles, ventilated facades, infill panels, column parts and decorative or cladding elements for both straight and curved internal walls.

In the items according to the present invention, the quality of the texture of the item 1 is assessed by measuring the arithmetic mean surface roughness Ra, by means of a non-contact optical profilometer, such as 3D Talysurf CCI Lite (Taylor- Hobson), equipped with automatic stage and autofocus. The system uses green light scanning interferometry to obtain images and measures of the parts analyzed, providing quantitative information on the structure of surfaces without physical contact with them. The 3D data characterizing the obtainable surface are as follows:

- height parameters: Sq, SSk, Sku, Sp, Sv, Sz, Sa, defined in accordance with the standard ISO 25178;

- parameters of planarity: FLTt, FLTp, FLTv, FLTq defined in accordance with the standard ISO 12781 ;

The 2D data characterizing the surface obtainable using the technique described are as follows:

- height parameters - roughness profile: Rp, Rv, Rz, Rc, Rt, Ra, Rq, Rsk, Rku, defined according to the standard ISO 4287;

- spacing parameters - roughness profile: RSm, Rdq, defined according to the standard ISO 4287;

- peak parameter-roughness profile: RPc, defined according to the standard ISO 4287.

The following examples of composition in preparation of a cementitious item according to the invention illustrate the invention without in any way limiting the scope thereof. In particular, the examples refer to the preparation of the cementitious item, a portion of which is shown in Figure 7.

EXAMPLE 1

The solid components shown in Table 1 below were mixed in a Hobart intensive mixer for 3 minutes.

Table 1

The liquid components were then added, including the water, and mixing was continued for a time equal to 3 minutes, based on the characteristics of the mixer and the external temperature.

The composition in the fresh state thus obtained was poured by means of a suitable channel into a mold in which one half-mold was coated in a vinylic film with the texture shown in Figure 6. The elevated fluidity allowed homogenous filling of the mold, even without the application of vibrations to compact the poured mass. In this case a metallic mold was used, of the type used for cementitious applications, consisting of two paired half-molds.

The surface of the half-molds was coated with polycarbonate having an arithmetic mean surface roughness Ra measured at around 50 nm; an adhesive film, preferably vinylic in nature, was then applied to one of the two half-molds, preferably vectorially cut using a numerical control plotter. In particular, the adhesive film was cut so as to create removable portions of adhesive which were then removed to obtain the desired texture (see Figure 6). The arithmetic mean surface roughness Ra of the adhesive was measured at around 430 nm. At the interface between the polycarbonate coating the half-mold and the adhesive film, a step was observed, the thickness of which was also measured by means of optical profiling at 80 μιη.

After 24 hours the item was removed from the mold and subjected to the seasoning phase, which was done by maintaining it in a vertical position, in a room air-conditioned to 20 °C and 55% relative humidity. An item was thus obtained with dimensions of 40x40 cm and a thickness of 10 mm, with the desired texture (according to how the adhesive film was cut) and shown in Figure 7. At the portions of the item in relief, (i.e. in those portions solidified in contact with the polycarbonate), a surface roughness Ra was measured at 70 nm, while on the rest of the surface (solidified in contact with the adhesive film), the surface roughness Ra was measured at 458 nm.

At the interface between the surfaces with a greater Ra and a lower Ra, a step was measured with a thickness of 91 μιτι.

EXAMPLE 2

Proceeding substantially as described in example 1 , but using the components described in Table 2 below, a panel for a ventilated facade for aesthetic purposes was produced.

Table 2

COMPONENTS % by weight

Ultracem® 52.5R cement (Italcementi) 39.4

Micronized quartz 5.8

Aggregate (0.1 -0.35mm) 43.8

Glass fiber (12 mm) 0.54

Melflux 2641 F 0.2

Cim'antiretrait 0.4

Water 9.9 The thickness of the slab, with surface dimensions of 600 x 600 mm, was 10 mm. Measurement of the surface roughness Ra was 55 nm at the portions of the slab in relief (i.e. in those portions solidified in contact with the polycarbonate), while on the rest of the surface (solidified in contact with the adhesive film) the surface roughness Ra was measured at 495 nm.

At the interface between the surfaces with a greater Ra and a lower Ra, a step was measured with a thickness of 87 μΐη.

EXAMPLE 3 (comparative)

Proceeding substantially as described in example 1 , but using the components described in Table 3 below, a sunshade element was obtained.

Table 3

The sunshade element obtained has dimensions of 20x40 cm and a thickness of 10 mm. Compared to examples 1 and 2, the composition lacks a superplasticizing agent. It was observed that the mortar, due to its poor rheological properties (due to the absence of the superplasticizing agent), unlike those described in examples 1 and 2, did not allow a texture to be obtained that could faithfully reproduce the half-mold, especially in the part with a very low-surface roughness.

By proceeding substantially as described in example 1 , the measurement of the surface roughness Ra of the item obtained was 780 nm at the portions of the slab in relief (i.e. in those portions solidified in contact with the polycarbonate), while on the rest of the surface (solidified in contact with the adhesive film) the surface roughness Ra was measured at 440 nm.

At the interface between the surfaces with a greater Ra and a lower Ra, a step was measured with a thickness of 87 μιτι.

It can be seen therefore that the rheological properties of the mortar, such as its fluidity, the absence of segregation and the low hygrometric shrinkage, are a key factor for obtaining the parts of texture with a low Ra (less than 100 nm). They are, however, a less critical parameter for obtaining a texture with a higher Ra (> 300 nm) and for the interface zone (step) between the two surfaces.

The cementitious item and its manufacturing procedure according to the invention fully achieve the set tasks and aims. In particular, the cementitious item has a texture created by the same cementitious material of which the item is made. The manufacturing procedure according to the invention advantageously makes it possible to define the texture during the manufacturing phase of the cementitious item without requiring any further processing. The procedure is also easily performed at competitive costs and allows for a high degree of personalization of the item.

Claims

1 ) A cementitious item (1 ) with controlled surface texture and roughness, being made starting from a fluid composition comprising:

I. A hydraulic binder;

II. One or more aggregates;

III. An anti-shrinkage agent;

IV. A superplasticizer agent;

V. Water,

wherein said item comprises at least a first portion (15) in relief with respect to at least one second portion (25) and wherein the arithmetic mean surface roughness Ra of said first portion (15) is less than that of said second surface of said second portion (25).

2) A cementitious item (1) according to claim 1 , wherein said arithmetic mean surface roughness Ra of said first portion has a value of less than or equal to 100 nm.

3) A cementitious item according to claim 1 or 2, wherein said arithmetic mean surface roughness Ra of said second portion (25) has a value of more than or equal to 350 nm.

4) A cementitious item according to claim 1 , wherein said arithmetic mean surface roughness Ra of said first portion (15) is less than that of said second portion

(25) by a value of more than 100 nm.

5) A cementitious item according to any one of claims from 1 to 4, wherein said first portion (15) emerges in relief with respect to said second portion (25) by a height of no less than 10 μητι.

6) A cementitious item according to claim 5, wherein said first portion (15) emerges in relief with respect to said second portion (25) by a height of no less than 30 μιτι..

7) A cementitious item according to claim 1 , wherein the percentage by weight of said hydraulic binder in said composition is no more than 60% with respect to said aggregates.

8) A cementitious item according to claim 1 , wherein said aggregates II comprise: fine aggregates such as fillers, powders and sands defined in the UNI EN 206 standard, filler meaning a fine aggregate fraction having a maximum diameter, dmax, equal to 40 micron; non fine aggregates with d_max higher than 40 micron.

9) A cementitious item according to claim 9, wherein the percentage quantity of filler with respect to the aggregates is in the range between 15% and 60% by weight.

10) A cementitious item according to claim 1 , wherein aggregates II have a maximum diameter d_max smaller than one third of the item thickness.

11 ) A cementitious item according to claim 1 , characterized in that said aggregates II together comprise the following fractions: aggregates with a diameter in the range between 0.20 and 0.35 mm, aggregates with a diameter in the range between 0.60 and 0.80 mm, aggregates with a diameter in the range between .00 and 1.50 mm, fillers with a diameter in the range between 0.1 and 40 μητι, powder with a diameter in the range between 0.1 and 0.8 mm, marble granulates with a diameter in the range between 0.1 and 100 μιτι, marble granulates with a diameter in the range between 0.10 and 0.60 mm.

12) A cementitious item according to claim 1 , characterized in that an anti- shrinkage agent III is selected from glycols and polyols, optionally together with lime.

13) A cementitious item according to claim 1 , characterized in that a superplasticizer agent IV is of polycarboxylic type in solid phase or in the form of aqueous solution.

14) A cementitious item according to claim 1 , characterized in that said hydraulic binder I is a photo-catalytic concrete.

15) A method of making a cementitious item shaped as a sheet, said method comprising the steps of:

- coating the walls of a mold with a polymeric material;

- applying an adhesive film on one or more portions of said half-mold according to a predetermined layout;

- pouring a fluid composition into said mold, said fluid composition comprising: I. A hydraulic binder;

II. One or more aggregates;

III. An anti-shrinkage agent; IV. A superplasticizer agent;

V. Water;

- hardening and removing said cementitious item from said mold.

16) A method according to claim 15, wherein said polymeric material is selected from the group consisting of polyethylene terephthalate, polycarbonate, polyamide, polymethylmethacrylate and mixtures thereof.

17) A method according to claim 15 or 16, wherein said polymeric material has an arithmetic mean surface roughness Ra of less than 100 nm.

18) A method according to any one of claims from 15 to 17, wherein said adhesive has a surface roughness Ra of more than 350 nm.

19) A method according to any one of claims from 15 to 18, wherein said adhesive film has a thickness of no less than 10 pm.

20) A method according to any one of claims from 15 to 19, wherein said adhesive film is pre-notched before being applied to said half-mold so as to define removable parts of said adhesive film, said method comprising the step of removing said portions subsequent to the application of said film on said mold, so as to form said predetermined layout.

21 ) A method according to claim 20, wherein said film is pre-notched by a numerical control cutting machine.

22) A cementitious item shaped as a sheet obtainable by the manufacturing method according to any one of claims from 15 to 21 .