FR3101872A1 - Process for making non-structural concrete objects made from secondary raw materials in order to obtain specific effects - Google Patents

Abstract

The invention relates to a method for producing a non-structural concrete object having singularities in the mass or on the surface. The specificity of the invention lies in the enhancement of aesthetic characteristics usually considered as defects in the production of concrete objects. The desired aesthetic characteristics are obtained through the use of concrete made from sorted secondary raw materials, reduced to aggregates/powder and mixed with other constituents. The “imperfections” obtained during the implementation of these recycled concretes can recall the aesthetic characteristics found in “natural” rocks or in artisanal creations of unique pieces: irregularities of surfaces or strata, bubbling effects, segregation, microcracking, heterogeneity and discontinuity of colors, etc. The effects, specific to the use of secondary raw materials, are caused by a series of technical and material measures used during the production process. The desired aesthetic effects do not call into question the structural performance or the integrity of the achievements. Figure to be published with the abstract: Fig.3

Description

Process for producing non-structural concrete objects made from secondary raw materials in order to obtain specific effects

TECHNICAL FIELD OF THE INVENTION

The invention relates to a process for producing a non-structural object (that is to say not intended to take up loads) in concrete from inert and heterogeneous secondary raw materials. The invention thus relates to secondary raw materials from recycling.

Secondary raw materials can be of various origins. They can be materials from the demolition or deconstruction of structures, such as concrete, mortar, breeze block, natural stone, brick, wood, charred wood debris, metals, glass , insulation, rubber and/or PVC, industrial by-products, marine or river sediments, materials from concrete product manufacturing scrap, agro-sourced materials, etc.

The method according to the invention is intended in particular, but not exclusively, for the production of non-structural concrete objects, such as street or garden furniture, roadway elements and decorative floors, low walls, facing elements or decorative.

STATE OF THE ART

The use of demolition waste is an increasingly common approach. Today, standardization authorizes the incorporation of recycled concrete aggregates in concrete, including structural concrete. In non-structural applications, it is possible to integrate up to 100% recycled concrete aggregates as long as the desired performance is maintained.

On the other hand, the use of materials from deconstruction other than recycled concrete requires special attention: the possible variability of the deposits (discontinuity and heterogeneity of the deposits, mixture of materials, mechanical characteristics, etc.), the behavior of these materials (during their crushing, mixing of the mixture incorporating them, etc.) or their potential pollution such as the presence of plaster.

The fresh and hardened properties of the concretes incorporating them, their durability and their aesthetics are all parameters that need to be mastered. In addition, the construction specifications usually impose zero defects. Any product with an aesthetic appearance that deviates from these specifications is usually considered unacceptable.

This level of requirement of the built elements strongly limits the use of secondary raw materials likely to generate defects mainly of aesthetic order.

OBJECT OF THE INVENTION

The invention aims to improve the acceptability of recycled materials by proposing a process for producing a non-structural object from inert and heterogeneous secondary raw materials having a resistance and stability over time in accordance with the use for which the object is intended while presenting singularities.

By "features" are meant distinctive features of the non-structural object traditionally referred to as flaws or irregularities. Among the singularities sought, can be cited a heterogeneity of the color, the texture of the surfaces, segregation, nests of stones, micro-cracks, splinters, bubbling, unevenness, lack of flatness, erosion, vegetation, etc.

The method according to the invention makes it possible to produce non-structural concrete objects which incorporate materials from the demolition/deconstruction of construction sites. The concretes obtained according to the process of the invention have a unique aesthetic character whose composition and implementation, integrating a random dimension, are mastered in terms of aesthetic rendering but also of resistance and stability over time.

The process associated with the invention makes it possible to "transform" voluntarily and in a controlled manner the defects into aesthetic effects on the surface or in the mass, while conferring the resistance and stability over time in accordance with the use for which the non-structural object is intended.

To this end, and according to a first aspect, the invention proposes a method for producing a non-structural concrete object having singularities in the mass or on the surface. The process includes the following steps:

- selection and preparation (crushing, reduction to aggregates and powders) of secondary raw materials to define at least two different “groups” of secondary raw materials. The difference between each group can come from nature (ex: concrete, limestone, bricks, etc.) and/or color (ex: 2 refractory bricks, one dark red the other orange);

- assembly and mixing. Each group makes it possible to produce a specific concrete with its own formulation. The secondary raw materials of each group are therefore associated with the other constituents (cement, other binder, admixtures, sand, water, etc.) so as to obtain, for each group, the desired concrete meeting the defined specifications (workability, general color of the mixture, texture, etc.);

- placement of the concretes produced in the selected mold by applying the principle of assembling layers, each layer being associated with a concrete and therefore with a group of secondary raw materials. The various concretes can be manufactured gradually or simultaneously, their implementation being successive or simultaneous.

More particularly, the invention proposes a method for producing a non-structural concrete object having singularities in the mass or on the surface, from inert and heterogeneous secondary raw materials, the method comprising the steps consisting in selecting the raw materials secondary raw materials and prepare them to define at least two groups of secondary raw materials, assemble and mix the secondary raw materials of each group with a determined concrete composition until a first concrete and a second so-called concrete are obtained. recycling, pouring the first and second recycling concretes obtained into at least one container, producing effects on the surface or in the mass of the first and/or second concrete(s) during the pouring step(s) and/or at the end of it.

Each concrete composition takes into account the physical and chemical specificities of the secondary raw materials and is optimized in order to ensure the durability of the concrete, and more generally of the object. Depending on the secondary raw materials selected and prepared, the composition of the concrete may, if necessary, be different for each of the groups.

The different concretes can be manufactured as and when necessary, allowing alternate strata of different thickness and appearance, singularities (bubbling, texture, etc.) to be obtained, as well as the creation of effects in surface or in the mass. Thus, the casting of the first and second recycling concretes can be carried out alternately so as to form alternating strata of recycling concretes.

Advantageously, the preparation of secondary raw materials includes a mechanical transformation operation by crushing/grinding them in order to obtain particle sizes similar to traditional raw materials (particle size between 0 mm and 32 mm).

A screening operation can also take place when a particular particle size class is targeted (example of 2/4 mm).

Advantageously, each casting of concrete takes place on a previous hardened or unhardened stratum.

Advantageously, the concrete of each stratum has its own rheological properties, ranging from a liquid to firm state. The combination of these different rheologies leads to specific effects on the appearance and confers a singularity on the object.

Advantageously, a reinforcing mesh is placed between each stratum if necessary in view of the specifications.

According to a particular embodiment, the casting of the first and second recycling concretes is carried out simultaneously in the same container.

Advantageously, the various concretes are subjected, during the implementation step and/or at the end of the latter, to a displacement of material by an energy input, this energy input being able to be obtained by simple mass effect, by vibration, by mechanical mixing, by uneven distribution of the concrete with a trowel, by inclination of the mould, etc. The purpose of this operation is to obtain different shapes of layers, inclinations of the layers or more or less pronounced blending between them.

Advantageously, the method may include a surface treatment operation, carried out on the external surfaces, in the fresh state or after hardening of the overall object. This may include, for example, washing, acid application, brushing or mechanical sanding of surfaces, application of a surface hardener, water repellent, pore filler, varnish, chemical deactivation, etc.

Advantageously, the secondary raw material(s) of each group is (are) chosen from the group of materials resulting from the demolition or deconstruction of works, co-products industrial, marine or river sediments, materials from concrete manufacturing scraps/concrete products.

Advantageously, the materials resulting from the demolition or deconstruction of non-structural works comprise concrete, mortar, breeze block, natural stone, advantageously refractory brick, wood, carbonized wood debris, metals, glass, rubber and/or PVC insulation.

Advantageously, the concrete composition comprises one or more hydraulic binders such as a white cement, or a mineral addition, and/or one or more resins, and preferably a binder formed from a white cement, a gray cement and /or a mortar and/or any other form of binder (resins, blast furnace slag, etc.).

Advantageously, a protective layer is applied to the surface of the recycled concrete in the hardened state after a drying step for a period of 7 days under conditions of humidity greater than 80% and a temperature of 20°C.

The implementation of the process according to the invention also presents an ecological interest (by being part of a logic of circular economy, second life of raw materials, recycling), a societal dimension (educational, training, integration, consultation, meetings ) and a creative dimension (design, architecture, art). It takes into account the material, temporal, societal and environmental aspects of urban construction sites by interactively mobilizing professionals, creators, communities, builders, social actors and populations in an original co-construction process.

BRIEF DESCRIPTION OF EXAMPLES OF TYPOLOGIES OF NON-STRUCTURAL OBJECTS MADE ACCORDING TO THE PROCESS OF THE INVENTION

It is decided to present four typologies of objects among all the possibilities of typologies realized by the invention.

Other characteristics and advantages of the invention will emerge from the detailed description of the invention which will follow with reference to the appended figures and in which:

FIG. 1 represents an example of a non-structural work/object characterizing a first typology of objects produced according to the method of the invention;

FIG. 1A represents a detailed view of the work/non-structural object of FIG. 1 and of the rendering obtained;

FIG. 2 represents an example of a non-structural work/object characterizing a second typology of objects produced according to the method of the invention;

FIG. 2A represents a detailed view of the work/non-structural object of FIG. 2 and of the rendering of the strata obtained;

FIG. 3 represents an example of a non-structural work/object characterizing a first typology of objects produced according to the method of the invention;

FIG. 3A represents a detailed view of the structure/non-structural object of FIG. 3 and of the rendering of the strata obtained;

FIG. 4 represents an example of a non-structural work/object characterizing a first typology of objects produced according to the method of the invention;

Figure 4A shows a detailed view of the non-structural work/object of Figure 4 and the rendering obtained.

DETAILED DESCRIPTION OF THE INVENTION

The technical specificity of the invention lies in the enhancement of aesthetic characteristics in concrete objects made from secondary raw materials, which are usually considered as imperfections, defects, poor workmanship. Instead of avoiding them, concealing them, or eliminating them, imperfections and others are on the contrary sought, provoked, designed by setting up a series of technical and material conditions aimed at voluntarily organizing these imperfections, these surface defects.

Sorted by nature and by color, reduced to aggregates and powder (pigments), mixed with a binder (cement, resin, slag, etc.), sand and water, with or without additives then poured in strata or strips on site, in the workshop or in the factory, the secondary raw materials are thus recycled and become noble materials that can be used as materials for the production of non-load-bearing objects with a specific aesthetic appearance, which incorporate "imperfections" that are reminiscent for some those found in "natural" rocks or, in any case, in artisanal creations of unique pieces. For example: irregularities in the boundaries between strata, effects of bubbling, segregation, microcracking, heterogeneity of shades, random patterns, differences in aging over time depending on the strata, etc. These are sought-after aesthetic effects specific to the use of secondary raw materials. These effects do not call into question the required performances relating to the requirements of resistance and stability over time in the field concerned.

In general, the process includes a step of selecting and preparing secondary raw materials to form groups of reduced aggregates to obtain a particle size between 0 mm and 32 mm (gravel, powder, etc.).

The "secondary" aggregates are then mixed with the traditional materials which are sand, a binder (cement, resin, blast furnace slag, etc.), admixture and water to achieve a specific concrete composition. The mixtures obtained will be referred to below as "recycling concretes".

Depending on the desired rheology as well as the color, the proportions of constituents (traditional materials and demolition materials) are determined.

The recycled concretes are then placed in the selected mold by applying the principle of assembling layers, each layer being associated with a concrete and therefore with a group of secondary raw material(s). The different concretes can be manufactured gradually or simultaneously, resulting in their successive or simultaneous implementation. Surface effects (smoothing, textures, etc.) are achieved at the time of implementation by direct or indirect action (use of specific tools, manual processing, etc.).

The type of container will be chosen according to the object to be produced but also according to the intended effects (associated implementation).

It may be a frame on the ground (2D mold) or a formwork or 3D mold, stable (i.e. not mobile) or tiltable with a variable angle of inclination.

As for the casting itself, this can be done in different ways. It can be, for example, a spreading on the ground in the case of a frame or formwork on the ground (2D) or a casting in a formwork in volume. At the time of pouring, several effects can be obtained and depend on the texture of the recycled concretes. Indeed, the pouring of concretes, whose rheological properties differ, can for example be done in strata or marbling, using the techniques of "fresh on fresh", "fresh on dry", marbling by simultaneous mixing of liquid concretes or manual application of layers of concrete in juxtaposed strata.

Depending on the object, different singularities are sought.

It is :

- segregation (phenomenon of separation between constituents of different densities);

- bubbling;

- special topography;

- different aging depending on the areas of the non-structural object (layers, slabs, etc.);

- generation of erosion, cracking, revegetation.

Advantageously, a surface finish is carried out after hardening/drying of the recycling concretes (examples of desired finishes: acidified, waxed, varnished, sanded, ground, screen-printed, brushed, washed, flamed, polished, sawn).

The examples of typologies illustrated and described below relate to works/objects obtained according to the process which is the subject of the invention.

Figures 1 and 1A show a first example of a typology of works/objects produced according to the process. To obtain the effect illustrated, two recycling concretes were produced, one of the concretes constituting a mass concrete deforming little and the other concrete constituting a finishing concrete. Advantageously, the mass concrete is manufactured conventionally using CEM I 42.5 cement, aggregates of different cuts and water. Depending on the desired color, several finishing concretes are produced. The secondary raw materials used are, in this embodiment, demolition materials, and more particularly brick (red colour), charred wood debris (black colour), concrete (grey colour) and rock ( cream color) previously reduced to powder. The cements used are white cement (for light concrete) and self-leveling mortar of commercial reference SikaLevel .

In addition to water, adjuvants are added to overcome rheology problems (a water-reducing plasticizer, for example) and cracking (anti-shrinkage agent). An air entrainer and a cohesive agent have also been added to certain mixtures. It is well understood that the nature and the dosage of the adjuvant(s) incorporated in the finishing concretes are defined according to the desired mixture.

The cracking effects, not visible in the photo, were obtained by using white cement while the efflorescences are obtained by using gray and white cement and curing in the open air.

The slab is made as follows. The first step is to pour the mass concrete. Deforming little, it constitutes the sub-layer of the slab. A fiberglass mesh is then placed on the latter, which is still fresh. The finishing concrete is then poured. This has a higher fluidity than mass concrete. This thus makes it possible to obtain a flowing and harmonious lines and curves on the surface. A matte varnish ( Sikagard Protection Sol commercial reference) was applied to the surface of the finishing concrete after curing for 7 days under controlled humidity (>80%) and temperature (approximately 20°C) conditions.

The whole forms a structure that is sufficiently resistant to bending so as not to crack under the effect of the weight of visitors, nor lead to the appearance of cracks due to the natural dimensional variations of the materials.

The pouring of the recycled concrete is carried out on one frame out of two initially, the rest being poured after dismantling all the frames.

The second typology of structures/objects produced and illustrated in Figures 2 and 2A comes from the pouring of different concretes in volume, in a formwork, strata on strata, with a predominance of liquid concretes, poured fresh on fresh, with fluctuating, undulating, inter-penetrating boundaries between the different layers (liquid aesthetic aspect).

The third typology of structures/objects produced and illustrated in Figures 3 and 3A comes from pouring the various concretes in volume, in a formwork, strata upon strata, with a predominance of dry concrete, poured dry or dry, on fresh on dry, with sharp boundaries, sometimes visible cracks between the different layers and with a grainy aesthetic appearance, the appearance of segregation, nests of gravel, etc.

The fourth type of structures/objects produced and illustrated in Figures 4 and 4A comes from pouring different concretes in strata a few centimeters thick on a structural concrete floor covered with a bonding primer. The concretes of different colors are not mixed together but the bands or pouring zone of the same color adjoin other zones occupied by concrete of another color.

Concrete of a fairly firm plastic consistency is placed on the ground and troweled by hand over the entire area occupied by concrete of one color (a band, an area) for a flat, smooth, the most uniform rendering. possible. Once dry, apply the other areas of color next to it. And so on.

These examples of typologies are described by way of example. It is understood that the person skilled in the art is able to carry out different variant embodiments of the invention without departing from the scope of the invention. Thus, other non-structural objects other than those described above can be made with the process.

It could be:

- landscaping products for public and private spaces not subject to the passage of vehicles (grass slabs, stepping stones, trim steps and risers, tree grates and other grates, etc.);

- markup and safety products (bollards, discontinuous deterrents, bicycle blocks, curbs, studs, posts, etc.);

- information, advertising, signage products and in particular their bases, foundations, anchors (panels, signs, display columns, etc.);

- urban protection products (barriers, bollards, anti-traffic rock, etc.),

- furniture or urban works (benches, seats, tables, pedestals, steles, etc.);

- decorative products (statues, columns, bas-reliefs, decorative rocks, facing slabs for building facades, etc.) for exterior and interior use;

-elements used as containers (flower boxes, baskets, planters, columbariums, urn graves, funeral urns, basins, garbage cans, etc.), elements intended to stabilize the ground at a height (total height of the structure excluding foundation footing), rocks, stackable modular elements or stackable blocks for the formation of low walls;

- stackable retaining wall elements intended to produce retaining walls for applications such as retaining walls for excavation and trenches dug in natural terrain, retaining walls for earth embankments for roads, platforms, etc ;

- facade elements, architecture and construction materials (bricks, slabs, columns, etc.);

Claims (12)

Process for producing a non-structural concrete object having singularities in the mass or on the surface, from inert and heterogeneous secondary raw materials, the process comprising the steps consisting in selecting the secondary raw materials and preparing them to define at least two groups of secondary raw materials, assembling and mixing the secondary raw materials of each group with a determined concrete composition until a first concrete and a second so-called recycling concrete are obtained, pouring the first and second concretes recycling obtained in at least one container, achieve effects on the surface or in the mass of the first and/or second concrete(s) during the casting step(s) and/or at the end thereof. Process for producing a non-structural concrete object according to claim 1, characterized in that the preparation of the secondary raw materials comprises an operation of sorting the materials by nature and by color, then reduction of the secondary raw materials, possible screening, to obtain aggregates. Process for producing a non-structural concrete object according to claim 2, characterized by mixing the aggregates resulting from the transformation of the secondary raw materials with a binder, traditional aggregates, water and potentially adjuvants so as to obtain a concrete. Process for producing a non-structural concrete object according to any one of Claims 1 to 3, characterized in that the casting of the first and second recycling concretes is carried out alternately so as to form alternating strata of recycling concretes. Process for producing a non-structural concrete object according to claim 4, characterized in that the recycling concrete of each stratum has rheological properties different from those of the recycling concrete of the adjacent stratum located above. Process for producing a non-structural concrete object according to any one of Claims 1 to 3, characterized in that the casting of the first and second recycling concretes is carried out simultaneously in the same container. Process for producing a non-structural concrete object according to any one of Claims 4 to 6, characterized in that a reinforcing mesh is placed between each stratum. Process for producing a non-structural concrete object according to any one of the preceding claims, characterized in that the first and/or second recycling concrete(s), during the casting step and/or after of the latter, is subjected to a displacement of material by vibration, by tilting of the container or by mechanical mixing. Process for producing a non-structural concrete object according to any one of the preceding claims, characterized in that it comprises a step of surface treatment of the recycled concretes. Process for producing a non-structural concrete object according to any one of the preceding claims, characterized in that the secondary raw material of each of the groups is chosen from the group of materials resulting from the demolition or deconstruction of structures , industrial co-products, marine or river sediments, materials from concrete product manufacturing scrap. Process for producing a non-structural concrete object according to the preceding claim, characterized in that the materials resulting from the demolition or deconstruction of non-structural works comprise concrete, mortar, breeze block, natural stone, brick, wood, charred wood debris, metals, glass, insulation, rubber and/or PVC. Process for producing a non-structural concrete object according to any one of the preceding claims, characterized in that the concrete composition comprises one or more hydraulic binders such as a white cement, or a mineral addition, and/or a or more resins.