EP3578730A1 - Method for producing concrete staircases and staircase obtained by said method - Google Patents

Abstract

This method for producing one-piece concrete staircases uses a closed mold consisting of a lower mold (2) and an upper mold or cover (3, 4) defining between them a volume intended to be filled. by concrete.

This process consists of:
▪ to fix and install the lower mold (2) in operational position;
Positioning the upper mold or cover (3, 4) facing said lower mold (2) and fixing it on said lower mold;
▪ to inject into the volume defined by the two molds respectively lower (2) and upper (3, 4), and from the lower base of said volume, concrete including self-placing type, to fill the entirety said volume;
▪ after cementing the concrete, remove the upper mold and the lower mold, and thus unmold the stair thus produced.

Description

FIELD OF THE INVENTION

The invention relates, in the first place, to a method for the realization on site or in the factory of concrete staircases, more particularly but not limited to the central drum type.

The invention also relates to concrete stairs obtained by the aforementioned method.

PRIOR STATE OF THE TECHNIQUE

Traditionally, the realization of concrete stairs, including monobloc type, are made on site. However, more and more, these stairs are made in factory, then transported and set up on site.

Thus, in the context of the realization of such concrete stairs directly on site, they are made in the following manner, for example in the case where the staircase comprises a central shaft.

The first step is the establishment of a mold, defining a central column to form the drum. The latter is made by casting concrete through the upper end of the mold defining such a central shaft. Then the concrete is poured on the areas of the mold to define the steps and risers. The concrete thus deposited is vibrated, then the operator equalizes the steps thus made including using a shovel or a trowel, then smooth concrete not yet massed with a trowel.

In fact, conventionally, it is created concomitantly with the pouring of concrete, air bubbles, which rise to the surface when the concrete is hardened. These air bubbles can congeal in the mass of the concrete, but can also burst on the upper surface of each of the steps, causing craters to appear which should be removed. This bubbling phenomenon, well known in the field under consideration, gives rise to the need for a second smoothing operation when the concrete has begun to set.

What is more, it is not uncommon despite this double smoothing operation, a deposit of another coating or coating is implemented on the facing of concrete parts, for the sake of aesthetics including, in order to completely avoid this bubbling phenomenon.

From now on, it will be readily understood that the realization of one-piece concrete staircases, as described above, that these stairs are made on site or in the factory involves significant finishing work, especially time-consuming.

In addition, although some techniques, such as the vibration of concrete, have been developed to reduce this problem, the product nevertheless comes out bubbled and then requires a major finishing work to hide these bubbles.

In addition, the finish must be strong enough to allow repeated passages of users without any wear or burst related to the presence of air bubbles. This explains the need for the presence of at least two layers of plaster, thereby increasing the loss of time.

In addition, the realization of such stairs is accompanied by great difficulty for the operator or operators, to the extent that they must proceed, in addition to pouring concrete, its equalization at each of the steps including the using a shovel, being stressed that this operation is to be carried out even though the concrete is not set in mass, and that the operator is more or less balancing on the buttresses of the mold. In addition to this aspect of arduousness, is added a security problem, precisely because of the positioning of the operator a little as he can, to ensure the operation of equalizing steps and smoothing concrete, the operator to work in the stairs in progress, bent into the mold several meters high, the risk of falling being present.

Finally, because of the use of a relatively firm concrete, it is customary to carry out a vibration operation of the mold or internal with vibrating needles, adding to the aforementioned drawbacks a noise nuisance, further affecting the conditions of the work of the operator.

Solutions have been proposed to overcome these disadvantages. Thus, the document CN 206170284 discloses a method of manufacturing a staircase from a mold. The mold is thus available in several parts, including a bottom giving their shape to different steps and risers, side walls, a top cover closing the mold and constituting the future underside of the stairs. These different parts are then assembled to form a mold in which concrete is poured.

However, the staircase is manufactured not in position, so directly in operational mode for example on the site in question, but upside down. As a result, the air bubbles that rise to the surface of the concrete are then found on the underside of the stairs. They are no longer on the surface of the steps and the passage of users is no longer a problem for the maintenance of the coating layer ensuring the finish. The finishing step turns out to be much less crucial.

On the other hand, although the part affected by the bubbling phenomenon no longer affects the visible surface of the steps, the finishing step remains necessary, the prescribers of this type of staircase claiming a finished product free of any defects, including at the level of the lower face of the staircase, that is to say of the face opposite to that receiving the steps.

But on the other hand and above all, on the one hand the method described does not allow the realization of the staircase in place in its final location, and secondly, it allows the manufacture of a single step height mold, and therefore involves having as many molds as stair types to achieve.

The present invention provides a method for obtaining a stone staircase or balanced barrel, or not, finished out of the mold, and requiring only very minor retouching, reducing the arduousness and dangerousness of work on the mold while allowing the manufacture of several step heights per mold.

SUMMARY DESCRIPTION OF THE INVENTION

For this purpose, the invention is directed to a method for producing on one-piece concrete staircases, in particular but not exclusively of the central drum type, using a closed mold composed of a lower mold and a top mold. or hood, defining between them a volume intended to be filled with concrete.

• ▪ à fixer et installer le moule inférieur en position opérationnelle ;
• ▪ à positionner le moule supérieur ou capot en regard dudit moule inférieur et à le fixer sur ledit moule inférieur ;
• ▪ à injecter dans le volume défini par les deux moules respectivement inférieur et supérieur, et à partir de la base inférieure dudit volume, du béton notamment de type auto-plaçant, jusqu'à combler l'intégralité dudit volume ;
• ▪ après prise en masse du béton, à ôter le moule supérieur et le moule inférieur, et donc à démouler l'escalier ainsi réalisé.

This process consists of:

• ▪ to fix and install the lower mold in operational position;
• Positioning the upper mold or cowl facing said lower mold and fixing it on said lower mold;
• ▪ to inject into the volume defined by the two molds respectively lower and upper, and from the lower base of said volume, concrete including self-placing type, to fill the entirety of said volume;
• ▪ after cementing the concrete, remove the upper mold and the lower mold, and thus unmold the stair thus produced.

In other words, unlike traditional and traditional methods of making concrete stairs, the invention consists first of all in implementing a closed mold, whose shape corresponds to the shape of the staircase to be made, and on the other hand, to inject the concrete with a consistency much more liquid than the traditional concretes used for the stairs, from the bottom end of the mold in an upward movement, in particular by means of a suitable pump, and more particularly a peristaltic pump. Self-placing concrete therefore does not need to be vibrated, usually a very physical and painful operation, and has a greatly reduced number of air bubbles, making it possible to obtain a smoother finished product on the surface.

According to the invention, the various constituent elements of the upper mold or hood, may consist of several sectors, in order to promote, on the one hand, their production, on the other hand their displacement, their storage, their implementation on the site and their demolding.

According to another characteristic of the invention, the internal face of the upper mold or hood, that is to say the surface called to define the shape of the different steps and risers of the future staircase, is coated, in particular by spraying, with a mortar, prior to the injection of the self-placing concrete. This mortar is mainly intended to trap the air resulting from the setting concrete mass between said concrete and mortar. The particular choice of self-placing concrete on the one hand, and the mortar on the other hand, makes it possible to prevent the air bubbles from piercing on the upper surface of the staircase after demolding.

The mortar, which is distinguished from concrete by the absence of gravel in its constitution, comes to form a perfectly smooth layer in contact with the inner wall of the hood. The self-placing concrete is then injected into the mold and comes into contact with the mortar. The last remaining air bubbles are trapped between the top of the concrete and the bottom of the mortar. They no longer appear on the surface of the walk, which appears smooth.

• ▪ entre 5 et 50 % en masse de ciment ;
• ▪ entre 40 et 95 % en masse d'agrégats fins (notamment sables, filler) ;
• ▪ un mélange d'adjuvants choisis dans le groupe comprenant les super-plastifiants, les accélérateurs de prise en masse, les retardateurs de prise en masse, les agents anti-retrait, etc..

In fact and according to the invention, the mortar used comprises:

• ▪ between 5 and 50% by weight of cement;
• ▪ Between 40 and 95% by weight of fine aggregates (especially sand, filler);
• A mixture of adjuvants selected from the group consisting of super-plasticizers, caking accelerators, caking retarders, anti-removal agents, etc.

Advantageously, the inner wall of the cover is covered with mortar before mounting the cover on the lower mold. More advantageously, said mortar is sprayed on this surface, thereby reducing the preparation time of the mold cover.

Furthermore, and according to another characteristic of the invention, the lower and upper molds or bonnet are pre-coated, on their internal face, that is to say on their face intended to receive the self-placing concrete, a component capable of promoting demolding, and in particular demolding oil.

When the cover receives on its internal face the previously mentioned mortar, the demolding oil is previously deposited on said inner face.

In the more specific case of one-block concrete staircases with central casing, the concrete is injected from the base of a column, able to define said central casing, said column communicating with the volume defined by the two molds respectively lower and upper, by means of through lights. In doing so, the concrete being injected at the base or lower end of the column, rises in it and, as and when, fills the volume defined by the two molds, so as to obtain a staircase of character monobloc also integrating the central shaft.

Advantageously, the self-placing concrete used belongs to the SF2 class (spread between 660 mm and 750 mm), or to the SF3 class (spread between 760 mm and 850 mm), these two classes being defined by the NF EN 206 standard, the spreading being a test described by standard NF EN 12350-8.

According to the invention, and when required, stiffeners are integrated and fixed to the lower mold before placing the mold or upper cover.

The invention also relates to monobloc concrete stairs implementing the method described above.

BRIEF DESCRIPTION OF THE FIGURES

• La figure 1 est une vue en éclaté des éléments constitutifs du moule pour obtenir un escalier exempt de fût central conforme au procédé de l'invention.
• La figure 2 est une vue analogue à la figure 1 mais d'un escalier à fût central.
• La figure 3 est une représentation schématique en perspective du moule inférieur pour la réalisation d'un escalier à fût central, dont la figure 4 est une vue de détail et la figure 5 une vue en section sagittale.
• La figure 6 est une représentation schématique en perspective du moule inférieur pour la réalisation de l'escalier à fût central, faisant apparaître les raidisseurs le cas échéant mis en oeuvre dans le cadre du procédé de l'invention.

The way in which the invention can be realized, and the advantages which result therefrom, will emerge more clearly from the following exemplary embodiments, given as an indication and not a limitation to the accompanying figures.

• The figure 1 is an exploded view of the constituent elements of the mold to obtain a staircase free of central shaft according to the method of the invention.
• The figure 2 is a view similar to the figure 1 but of a staircase with central shaft.
• The figure 3 is a schematic representation in perspective of the lower mold for the realization of a staircase with central shaft, whose figure 4 is a detail view and the figure 5 a sagittal section view.
• The figure 6 is a schematic representation in perspective of the lower mold for the realization of the staircase with central shaft, showing the stiffeners where appropriate implemented in the context of the method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The figure 1 therefore represents the fundamental elements for the realization of a monobloc staircase free from any central shaft, and in this case a bench-top staircase.

More specifically, the reference (1) designates the staircase resulting from the implementation of the method according to the invention, reference (2) designates the lower mold and references (3) and (4) designate two sectors of the hood or upper mold, intended to cooperate with the lower mold (2).

As already indicated above, the method of the invention is aimed at producing a one-piece concrete staircase in position. For this purpose, the lower mold is fixed to the ground to prevent lifting during demolding of the staircase. This lower mold, typically made of steel, has in this case a flat and inclined bottom (5), since as well, the underside of the staircase has no specific technical function.

In contrast, the lower mold (2) is intended to receive a hood or upper mold (3) and (4), also steel, whose shape specifically corresponds to the different steps and risers of the staircase to achieve.

The upper cover (3) and (4) is therefore intended to be positioned on the lower mold (2), the latter being provided for this purpose with lateral cutouts (6) able to receive in support of said upper cover (3) and ( 4) of corresponding form, and this, as already said, to define the steps and risers. Typically, the fixation of the upper mold or cover on the lower mold is obtained by means of bolts and centerers distributed along the central shaft on the one hand, and at the outer edges, by means of rods and nuts or bolts. associated with centrers.

Illustrated in this figure, and in particular at the lower mold (2) through holes (7), optionally positioned on or under the riser number 1, or at the inner or outer edge of said mold. It should be remembered that according to the invention, the constituent concrete staircase (1) to be produced is injected from the base, so the lower end of the mold.

This concrete is of the self-placing type of SF2 minimum class, that is to say, having a spreading at Abrham cones greater than 660 mm. The objective of such a relatively liquid concrete is, on the one hand, to allow its rise within the mold, in particular by implementing a peristaltic pump and, on the other hand, to reduce macro-bubbling, a constituent element one of the disadvantages of the methods of the prior art.

By way of example, such a concrete has a grit / sand ratio of between 0.5 and 1.4, typically close to 1. The cement, a key element of the concrete, is dosed between 280 and 500 kg / m ³ of concrete, and typically close to 340 kg / m ³ . The equivalent water / binder ratio in the sense of the EN206 standard is 0.3 to 0.6, typically close to 0.5.

Such a concrete is also likely to receive additives in the sense of standard EN206 of the dairy type, metakaolin, fly ash, calcareous filler, to complete the particle size, optimize the costs or mechanical performance.

Advantageously admixtures are added to the mixture: a super-plasticizer or water reducer with a dosage close to 3 l / m ³ . A superplasticizer thus added may be of the high water reduction type, such as a polycarboxylate.

According to an advantageous characteristic, prior to the injection of concrete into the mold consisting of elements (2), (3) and (4), the internal walls of said mold are coated with a release oil applied for example to the sprayer. Such a demolding oil may consist of a solvent (for example sold under the reference Grace wax E-31), a synthetic oil (for example marketed under the reference Chryso Dem Oléo 64), a vegetable oil or vegetable-based (for example marketed under the reference Grace Decobio S33).

According to yet another advantageous characteristic of the invention, the inner face of the hoods (3) and (4) is coated, in particular by spraying, that is to say, including at the level of what will be the step and the riser of the staircase, a mortar intended as already said to include imprison any bubbles resulting from the concrete between said mortar and concrete, besides promoting the appearance of the steps.

• ▪ entre 5 à 50 % en masse de ciment ;
• ▪ entre 40 et 95 % en masse d'agrégats fins, typiquement inférieurs à 1 millimètre ;
• ▪ et un mélange d'adjuvants comprenant un super-plastifiant et/ou des accélérateurs ou retardateurs de prise en masse du béton et/ou des agents anti-retrait.

This mortar includes:

• ▪ between 5 to 50% by mass of cement;
• ▪ between 40 and 95% by weight of fine aggregates, typically less than 1 millimeter;
• ▪ and a mixture of additives comprising a super-plasticizer and / or accelerators or retarders for setting the concrete and / or anti-shrinkage agents.

In this regard, it is specified that the demolding oil having previously coated the inner face of said covers (3) and (4) is chosen so that the mortar adheres to the fresh state on the hood, but not to the hardened state. It may be an oil of the type previously described. This oil is selected precisely following the completion of various tests, during which we observe the possible detachment of the mortar from the mold and micro-bubbling phenomena or tasks that can appear on the siding. The selection of the oil therefore depends on locally available materials to manufacture the mortar, concrete and equipment used for the application (spraying, scraping or not).

Due to the method of producing a one-piece concrete staircase of the invention, cast in position, it is possible with the same lower mold (2) to be able to make stairs with a walking height slightly different from the mold base, choosing the appropriate covers (3) and (4). These variations with respect to the base height of the mold is generally established with a difference of 2 to 4 millimeters, and this, in order to limit the extra thickness of the trays or the bench of the staircase at the level of his foot or his head. In other words, with the same lower mold, it becomes possible to make stairs with different operating heights, adapting the top cover.

In connection with the figure 2 , an exploded view similar to the figure 1 , but this time for the realization of a monobloc staircase provided with a central shaft (8). In this configuration, the lower mold (2) comprises, in its central position, a column portion, intended to cooperate with the upper covers, each provided with a complementary column portion with that of the lower mold, in order to define a cylinder (in the case of circular base case) adapted to define the shaft or central core.

In addition, in the context of the realization of such a staircase with central shaft, the injection of concrete is always performed at the lower level, but through the column intended to form the central shaft. For this purpose, the elements defining the column are pierced with through-holes (9), allowing the concrete undergoing ascension within the column to be distributed in the volume defined between the upper cover and the lower mold, and thus realize and build the steps and risers of the desired staircase. These lights have been schematized on the Figures 3 to 5 . They are of dimension, and in particular of height substantially lower than risers.

We have illustrated, within the figure 6 , the implementation when required of stiffening elements (10), in this case both horizontal and vertical.

These stiffeners have the main function to resume the thrust of the concrete resulting from the injection, especially at the lower level. This thrust of the concrete is exerted perpendicular to all surfaces, and it may be necessary to block the vertical forces but also horizontal, in particular to avoid rotation of the hoods during the injection of concrete.

These stiffeners may consist of tubular reinforcing bars, in particular of square cross-section, disposed on the top cover, vertically to each of the risers, the diagonals of the square sections being oriented respectively in the horizontal and in the vertical direction. The stiffeners can also result from an assembly of folded and welded sheets. These stiffeners can be fixed with a rod / nut clamping, by means of a profile notched for this purpose, allowing a certain flexibility in the initial positioning of the cover, and the inclination of the profiles at 45 ° allows a good recovery of the horizontal forces and vertical. The tightening then tends to position the hood in the optimum position.

It can also be realized with nut and centraliser, ensuring a better repeatability than the rod / nut system, but on the other hand less tolerant to initial positioning gaps.

The invention relates to monobloc concrete stairs cast in position obtained by the method of the invention. If the mechanical properties of these stairs do not differ or little from the stairs made with the traditional production methods, on the other hand they have a state of finishing very much improved, because of the absence or near-absence of micro-bubbling bursting on the upper surface of the steps, generating a considerable gain in terms of duration of implementation.

Meanwhile, because of the embodiment of these stairs, that is to say, an integral molding (lower face and upper face), the conditions of realization of these stairs are much more comfortable for operators and, above all, allow a Significant increase in safety, since, as well, the operator no longer has to ensure the display of concrete in precarious position or the smoothing thereof. Ultimate finishing operations, when they may be necessary, are done on a staircase whose concrete has hardened so hardened, facilitating considerably these operations.

Claims (12)

Process for the production of one-piece concrete staircases using a closed mold consisting of a lower mold (2) and an upper mold or cover (3, 4) defining between them a volume intended to be filled by concrete, consisting of: ▪ to fix and install the lower mold (2) in operational position; Positioning the upper mold or cover (3, 4) facing said lower mold (2) and fixing it on said lower mold; ▪ to inject into the volume defined by the two molds respectively lower (2) and upper (3, 4), and from the lower base of said volume, concrete including self-placing type, to fill the entirety said volume; ▪ after cementing the concrete, remove the upper mold and the lower mold, and thus unmold the stair thus produced. Process for the production of one-piece concrete staircases with a drum or central core using a closed mold composed of a lower mold (2) and an upper mold or cover (3, 4) defining a volume between them intended to be filled with concrete, consisting of: ▪ to fix and install the lower mold (2) in operational position; Positioning the upper mold or cover (3, 4) facing said lower mold (2) and fixing it on said lower mold; ▪ to inject into the volume defined by the two molds respectively lower (2) and upper (3, 4), and from the lower base of the column intended to form the shaft or central core, concrete including self- placing, said column communicating with the volume defined by the two molds respectively lower and upper, by means of through openings (9), to fill the entirety of said volume; ▪ after cementing the concrete, remove the upper mold and the lower mold, and thus unmold the stair thus produced. Process for producing one-piece concrete staircases according to one of claims 1 and 2, wherein the upper mold or cover consists of several sectors. Process for the production of one-piece concrete staircases according to one of Claims 1 to 3, in which, prior to the injection of the self-placing concrete into the volume defined by the two molds, the coating, in particular by spraying, is coated internal face of the upper mold or hood, that is to say the surface called to define the shape of the various steps and risers of the future staircase, a mortar. A method for producing one-piece concrete stairways according to claim 4, wherein the mortar comprises: ▪ between 5 and 50% by weight of cement; ▪ between 40 and 95% by weight of fine aggregates; A mixture of adjuvants selected from the group consisting of superplasticizers, caking accelerators, setting retarders, anti-shrinkage agents. Method for producing one-piece concrete staircases according to one of claims 4 and 5, wherein the inner wall of the cover (3, 4) is covered with mortar before mounting said cover on the lower mold (2). A method for making one-piece concrete staircases according to one of claims 4 to 6, wherein the mortar is projected onto the inner surface of the hood. Process for the production of one-piece concrete staircases according to one of Claims 1 to 7, in which the lower (2) and upper (3, 4) or bonnet molds are pre-coated on their internal face, ie that is to say on their face intended to receive the self-placing concrete, a component capable of promoting demoulding, and in particular demolding oil. A method for producing one-piece concrete staircases according to claim 8, wherein when the cover receives on its inner face the mortar according to one of claims 4 to 7, the release oil is previously deposited on said inner face. Process for the production of one-piece concrete staircases according to one of Claims 1 to 9, in which the self-placing concrete used is in the class SF2 or in the class SF3. Process for producing one-piece concrete staircases according to one of claims 1 to 10, wherein stiffeners (10) are integrated and fixed to the lower mold before placing the mold or upper cover. Monobloc concrete staircase obtained by implementing the method according to one of claims 1 to 11.

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