FR3110188A1 - PROCESS FOR THE REALIZATION OF A STRUCTURE OR PART OF A THREE-DIMENSIONAL MONOBLOC STRUCTURE IN CONCRETE AND STRUCTURE OR PART OF A THREE-DIMENSIONAL STRUCTURE IN CONCRETE THUS OBTAINED - Google Patents

Abstract

This method uses a closed mold composed of a lower mold (2) and an upper mold or cover (3, 4) defining between them a volume intended to be filled with concrete, consisting of:– installing the mold lower (2) intended, ultimately, to define said at least one flat horizontal surface; - to position the upper mold or cover (3, 4) facing said lower mold (2), and to fix it on said lower mold; - to inject into the volume defined by the two respectively lower and upper moulds, and from the lower base of said volume, self-compacting concrete, until filling the entirety of said volume; - after setting of the concrete, in removing the upper mold and the lower mold, and therefore in unmolding the three-dimensional concrete structure or part of the structure; then in turning over the structure or part of the structure thus obtained, in order to have the at least one flat horizontal surface in the operational position , i.e. in the upper position when said structure is erected in place on site. Figure for the abstract: Fig 5

Description

METHOD FOR MAKING A THREE-DIMENSIONAL CONCRETE STRUCTURE OR PART OF A MONOBLOCK STRUCTURE AND STRUCTURE OR PART OF A THREE-DIMENSIONAL CONCRETE STRUCTURE THUS OBTAINED

Field of invention

The invention relates first of all to a process for the production, in particular in the factory, of structures or parts of one-piece three-dimensional concrete structures, and more particularly, although in a non-limiting manner, of stairs or parts of one-piece stairs in concrete.

The invention also relates to the structures or parts of one-piece three-dimensional concrete structures thus obtained and, more specifically, to stairs or parts of one-piece concrete stairs.

Prior state of the art

Traditionally, concrete stairs, especially of the one-piece type, are made on site. However, increasingly, these stairs are made in the factory and then transported and erected on site.

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

First, a mold is placed, defining a central column intended to form the barrel. The latter is made by pouring concrete through the upper end of the mold defining such a central shaft. Then we proceed to pour the concrete on the areas of the mold intended to define the steps and risers. The concrete thus deposited is vibrated, then the operator levels the steps thus produced, in particular using a shovel or a trowel, then smooths the concrete that has not yet solidified with a trowel.

Indeed, classically, it is created concomitantly with the pouring of the concrete, air bubbles, which rise to the surface during the solidification of the concrete. These air bubbles can freeze in the mass of concrete or on the walls of the formwork, but can also burst on the upper surface of each of the steps, causing craters to appear, which should be eliminated. This phenomenon of bubbling, well known in the field considered, generates the need to carry out a second smoothing operation when the concrete has begun to set.

Moreover, it is not uncommon, notwithstanding this double smoothing operation, for another coating or coating to be deposited on the facing of the concrete parts, for the sake of aesthetics in particular, in order to completely eliminate this phenomenon of bubbling, but also in order to compensate for any flatness defects.

Already, it will be easy to understand that the realization of monobloc concrete stairs, as described above, whether these stairs are made on site or in the factory, entails significant finishing work, which is particularly time-consuming.

Moreover, although certain techniques, such as the vibration of concrete, have been developed to reduce this problem, the product nevertheless comes out bubbled and then requires significant finishing work to hide these bubbles.

In addition, the finish must be strong enough to allow repeated passages of users without showing any wear or bursting due to the presence of air bubbles. This explains the need sometimes for two layers of coating, increasing the loss of time.

In addition, the realization of such stairs is accompanied by great difficulty for the operator or operators, insofar as the latter must proceed, in addition to pouring the concrete, to its equalization at the level of each of the steps, in particular at the using a shovel, it being emphasized that this operation should be carried out even when the concrete has not solidified. In addition to this aspect of arduousness, there is also a safety problem, precisely because of the positioning of the operator as best he can, to ensure this operation of leveling the steps and then smoothing the concrete, the operator having to work in the stairs in progress, the risk of falling from a certain height remaining present.

Finally, due to the implementation of a relatively firm concrete, it is traditionally advisable to carry out an operation of vibration of the mold or internal with vibrating needles, adding to the aforementioned disadvantages a noise nuisance, affecting in an additional way the conditions of operator work.

In order to overcome these difficulties, the Applicant has proposed, for example in document FR 3 081 896, a method for producing such one-piece concrete stairs, implementing a closed mold composed of a lower mold and a mold top or cover, defining between them a volume intended to be filled with concrete, said method consisting of:
– fixing and installing the lower mold in the operational position;
– to position the upper mold or cover opposite said lower mold and to fix it on said lower mold;
– injecting into the volume defined by the two respectively lower and upper moulds, and from the lower base of said volume, concrete in particular of the self-compacting type, until the entirety of said volume is filled;
– then, after the concrete has solidified, to remove the upper mold and the lower mould, and therefore to unmold the staircase thus produced.

In doing so, by virtue of the process thus described, the presence of air bubbles is reduced, in particular at the level of the walking plates, this reduction of air bubbles being able to be optimized, still according to the teachings of this document, by the implementation work at the level of the internal face of the upper mold or cowl, that is to say the face opposite the walking plate, of a mortar, prior to the injection of the self-compacting concrete, the said mortar having mainly intended to trap the air resulting from caking of the concrete between said concrete and the mortar.

If incontestably, the method thus described makes it possible to significantly improve the known techniques of the prior art, and in particular to have the possibility of climbing a staircase directly on site, it nevertheless has a certain number of drawbacks.

Among these, in particular the step of spraying the mortar on the underside of the upper mold or cover, which in fact generates:
– an additional step in the construction of such a staircase,
– an increase in the cost price of such a staircase,
– but also the difficulty of simultaneously stalling the adhesion of the mortar against the lower face, in this case oiled of the upper cover, and its caking.

In summary, if the method thus described in the prior art makes it possible to reduce the phenomenon of bubbling of the concrete, experience demonstrates, first of all, that one does not completely overcome said phenomenon, since in fact, the air bubbles are frequently found enclosed substantially in the vicinity of the upper horizontal faces, that is to say, at the level of the tread plates.

In addition, and as already said, the implementation of a mortar to reduce this phenomenon of bubbling ultimately turns out to be relatively complex to control.

The object of the invention is to overcome these drawbacks.

Brief Disclosure of the Invention

If the method described in the previously mentioned prior art advantageously allows the realization of a staircase on site, therefore directly without requiring transport of said staircase or parts of such a staircase, the present invention is more oriented towards the realization of structures three-dimensional one-piece concrete structures made in the factory, certainly requiring then the displacement of the said structure or part of the structure on the site for its final assembly or its final assembly or erection.

This method for producing a structure or part of a three-dimensional one-piece concrete structure, provided with at least one flat horizontal surface, uses a closed mold composed of a lower mold and an upper mold or cover defining between them a volume intended to be filled with concrete.

This process consists of:
– To install the lower mold intended, ultimately , to define said at least one flat horizontal surface;
– to position the upper mold or cover opposite said lower mold, and to fix it on said lower mold;
– injecting into the volume defined by the two molds respectively lower and upper, and from the lower base of said volume, self-compacting concrete, until filling the entirety of said volume;
– after solidification of the concrete, to remove the upper mold and the lower mold, and therefore to unmold the structure or part of a three-dimensional concrete structure;
- then turning over the structure or part of structure thus obtained, in order to have the at least one flat horizontal surface in the operational position, that is to say in the upper position when said structure is erected in place on site.

In other words, contrary to the teachings of patent FR 3 081 896, the structure, and typically the staircase, is made upside down, without using any mortar, since both, as mentioned in the description of the prior art, the air bubbles resulting from the pouring of the concrete are found enclosed at the level of the upper face of the mould, therefore in this case, due to the production of said structure and in particular of the staircase upside down, at the level of the underside of said staircase once it has been erected. This avoids observing defects at the level of the functional surface of the staircase, that is to say the tread and, moreover, due to the injection of concrete through the lowest point of the volume defined by the mould, said air bubbles, if any formed, tend to form at the upper level of said mold and therefore, once again, at the level of the non-functional lower face of the three-dimensional structure, in particular of the staircase .

According to an advantageous characteristic of the invention, a vent is positioned at the highest point of the volume defined by the two molds, respectively lower and upper. In doing so, the injected concrete not only fills the entirety of said volume, but also overflows said volume in its upper part, that is to say higher than the three-dimensional structure to be produced. This ensures that the mold is completely filled. The concrete core resulting from this overflow, and obviously useless, is broken after the concrete solidifies during demolding.

According to an advantageous characteristic of the invention and, here again, with the aim of avoiding the formation of air bubbles during the solidification of the concrete, once the mold has been produced, that is to say after installation of the lower mold and of the upper mold, the assembly is inclined, typically at an angle of between 3 and 25 degrees relative to the horizontal, during the concrete pouring operation. Due to the inclination of the mold thus formed during this concrete pouring operation, the air bubbles which naturally tend to be trapped at the level of the horizontal faces, de facto no longer have horizontal faces to be trapped, and are capable of escaping at the line of flight created by the inclination of said mould.

In the same spirit, according to another variant of the invention, at least part of the surfaces of said mold intended to define the non-vertical faces of the structure are provided with a draft, again typically inclined from 3 to 25 degrees with respect to horizontally, thus making it possible to avoid any horizontal face during the pouring of the concrete, thus favoring the evacuation of the air bubbles, if any, formed. In doing so, once the structure, and in particular the staircase, has been made, then turned over and erected, the lower face no longer has a rack section with parallel faces as frequently observed, but a lower face presenting an inclined plane with respect to the 'horizontal.

According to yet another variant of the invention, and here again always with the aim of avoiding the formation of bubbling during the solidification of the concrete, the upper face of the mold is no longer in the form of a rack, as in the previous case, but has a continuous curvature, which will become the underside of the staircase, this continuous curvature thus avoiding any horizontal faces likely to allow the imprisonment of air bubbles.

The invention also relates to the three-dimensional one-piece structures and the one-piece concrete stairs obtained by the implementation of this process.

Description of figures

The way in which the invention can be implemented and the resulting advantages will emerge better from the examples of embodiment which follow, given by way of indication and not limitation, in support of the appended figures.

Figure 1 is a schematic representation in perspective of a lower mold according to the invention for the production of a one-piece concrete staircase with a central shaft.

Figure 2 is a schematic side view of the bottom mold of Figure 1.

Figure 3 is a schematic perspective view, according to two different orientations of the lower part of the upper mold according to the invention, and capable of cooperating with the lower mold of Figures 1 and 2.

Figure 4 is a view similar to Figure 3, but of the upper part of said upper mold.

Figure 5 is a schematic exploded view illustrating the different parts of the mold, in addition to the concrete staircase resulting from the implementation of the method of the invention.

FIG. 6 is a schematic view illustrating a staircase resulting from the method of the invention, shown upside down, and having inclined zones at its underside, resulting from undercuts provided within the mold.

Figure 7 is a schematic perspective view of a staircase shown upside down or turned over, highlighting another variant of the invention, in this case a staircase with a smooth lower surface and a continuous curvature with a central shaft.

Figure 8 is a view similar to Figure 7, but of a staircase without a central shaft.

Detailed description of the invention

The following description is made in relation to the manufacture of a one-piece concrete staircase.

It must however be kept in mind that the invention is aimed at the realization of any three-dimensional concrete structure, and that only the shape of the molds is likely to vary to produce said structure, the general principle described below remaining strictly identical.

According to the method of the invention, in order to produce such a one-piece concrete staircase (1), more particularly in the factory and not on site, two molds are used, respectively a lower mold (2) shown in Figures 1 and 2, and an upper mold, in this case consisting of a lower cover (3) and an upper cover (4) shown in Figures 3 and 4.

With regard to the lower mold (2) shown in said Figures 1 and 2, the latter has a succession of vertical (5) and horizontal (6) parts, said horizontal parts (6) being intended to define the tread plates ( 7) of the staircase (1) resulting from the process of the invention, it being recalled that according to said process, the staircase is molded in the inverted or upturned position, as can be seen in particular in Figures 7 and 8 Typically, this mold is made of steel and corresponds to the entire flight of stairs that one wishes to make.

As a corollary, FIGS. 3 and 4 illustrate respectively the lower part or lower cover (3) of the upper mold and the upper part or upper cover (4) of the upper mold, intended, once put in place and fixed on the lower mold (2 ) described in relation to Figures 1 and 2, to define a volume, within which a self-compacting concrete will be injected.

In this embodiment, said lower (3) and upper (4) covers also consist of a succession of horizontal (8) and vertical (9) parts, so that the lower face, also called the underside (13 ) of the staircase resulting from the process of the invention is in the form of a rack, like that represented in FIG. will define, in effect, the underside of the staircase. In the specific case, this lower part therefore has a rack.

However, and as described for example in relation to Figures 7 and 8, this lower surface (13) of the staircase could be smooth and continuous, so that the shape of the upper cover would be adapted accordingly.

There is shown in relation to Figure 5 an exploded view tending to illustrate the assembly of the different parts of the mold and their cooperation with the staircase following its realization. These different parts of the mold are assembled together, in particular by screwing, in order to facilitate the subsequent demoulding of the staircase, once the concrete has set.

This assembly defines a closed volume, within which the self-compacting concrete is injected. According to an essential characteristic of the invention, this injection is carried out at the level of the base of said volume. There is thus materialized in Figures 3 and 5, the injection point (10) of the concrete within this volume, said injection point being in this case carried out within the vertical part (9) the lowest of the upper mould.

This concrete, of a much more liquid consistency than the traditional concrete used for stairs, is therefore injected from the lower end of the mold in an upward movement, in particular by means of a suitable pump, and more particularly of a peristaltic pump. Self-compacting concrete therefore does not need to be vibrated, a usually very physical and painful operation, and has a greatly reduced number of air bubbles, allowing a smoother finished product to be obtained on the surface.

This pumping occurs until the volume defined by the molds, respectively lower and upper, is completely filled.

According to an advantageous characteristic of the invention, the upper end (11) of the mold is provided with a vent (12), allowing the air to escape as the volume defined by the assembly of said molds together, and promoting de facto the elimination of air bubbles themselves, one of the essential pitfalls that the present invention aims to remove.

More specifically, as self-compacting concrete is injected at the level of the lower injection zone (10), the concrete progresses inside said volume towards the top of the mould, inducing complete filling of the volume defined by the mould, until the concrete reaches the top of said volume and escapes at the level of the vent (12). When the concrete actually reaches the vent, the injection of concrete stops.

Once the concrete has solidified, the duration of solidification depends on the nature of the concrete, i.e. once you can unmold the staircase and therefore remove the various elements from the molds illustrated in relation with Figures 1 to 4, the result is the presence of an upper carrot corresponding to the vent, which can be broken at this time.

According to an advantageous embodiment, and illustrated in relation to Figure 6, in which there is shown a staircase (1) provided with a central shaft (14) in the inverted position, the mold is provided with remains, typically inclined 3 to 25 degrees from the horizontal. The implementation of such reliefs, resulting in inclined faces (15) at the level of the underside (13) of the staircase, aims to optimize the objective sought by the present invention, namely to avoid the formation of air bubbles that may remain trapped. Indeed, the presence of these spoils tends, because of the mode of injection of the concrete from the lower base of the volume defined by the two moulds, to chase the concrete progressively at the level of each of the steps in direction of the higher step and, consequently, to expel the air bubbles.

Alternatively, or even cumulatively, it is also possible according to the invention to tilt the entire mold during the concrete injection operation, again typically by a value between 3 and 25 degrees relative to the horizontal. , always with the same objective of chasing air bubbles. Whatever the embodiment of the invention, the priority objective is to avoid the formation of air bubbles between the upper mold and the concrete.

Alternatively, and as mentioned above, it is possible to eliminate any discontinuity at the level of the envelope of the upper mold. In other words, said upper mold is given a smooth and continuous shape, making it possible to produce a staircase as illustrated in FIGS. 7 and 8, respectively with and without a central shaft. We observe that the lower face of the staircase, since it is both represented in an inverted or upturned position, no longer has a rack, but a continuous surface. Due to this continuity of the upper mould, there is therefore no longer a horizontal or substantially horizontal surface likely to allow the imprisonment of air bubbles.

Advantageously, whatever the embodiment chosen, robust self-compacting concrete is used, avoiding saturation in the dosage of adjuvants in order to avoid the risk of microsegregation or surface foaming, likely to be caused by the deflocculating products of the plasticizer or super-plasticizer type. Typically, this self-compacting concrete belongs to class SF2 (spread between 660mm and 750mm), or class SF3 (spread between 760mm and 850mm), these two classes being defined by standard NF EN 206, the spreading being a test described by standard NF EN 12350-8.

The method of the invention results in the possibility of producing a three-dimensional concrete structure, and in particular a one-piece concrete staircase, making it possible to overcome air bubbles at the level of the treads, that is to say of the really functional zone of the staircase, without requiring any prior treatment of the moulds, except for the oiling of the internal face of the molds in order to promote demolding (this demolding oil can consist of a solvent (for example marketed under the reference Grace wax E-31), a synthetic oil (for example marketed under the reference Chryso Dem Oléo 64), a vegetable or vegetable-based oil (for example marketed under the reference Grace Décobio S33)) or the implementation of any additional mortar, thus making it possible to facilitate the production process and to reduce the manufacturing costs thereof.

Claims (7)

Method for producing a structure or part of a three-dimensional one-piece concrete structure, provided with at least one flat horizontal surface (7), said method implementing a closed mold composed of a lower mold (2) and an upper mold (3, 4) or cover defining between them a volume intended to be filled with concrete, consisting of:
– to install the lower mold (2) intended, ultimately , to define said at least one flat horizontal surface;
– to position the upper mold (3, 4) or cover facing said lower mold, and to fix it on said lower mold (2);
– injecting into the volume defined by the two molds respectively lower and upper, and from the lower base of said volume, self-compacting concrete, until filling the entirety of said volume;
– after solidification of the concrete, in removing the upper mold (3, 4) and the lower mold (2), and therefore in unmolding the structure or part of a three-dimensional concrete structure;
- then turning over the structure or part of structure thus obtained, in order to have the at least one flat horizontal surface in the operational position, that is to say in the upper position when said structure is erected in place on site. Method for producing a three-dimensional one-piece structure or part of a concrete structure according to claim 1, in which a vent (12) is also positioned on one or the other of the two molds at the furthest point top of the volume defined by said molds (2, 3, 4), so as to allow the self-compacting concrete injected from the lower base of said volume to fill all of said volume, then to overflow from said volume in its upper part, that is to say higher than the three-dimensional structure to be produced. Method for producing a three-dimensional one-piece structure or part of a concrete structure according to one of Claims 1 and 2, in which, once the mold has been produced, that is to say after installation of the lower mold and the upper mould, the assembly is inclined at an angle of between 3 and 25 degrees with respect to the horizontal during the concrete pouring operation. Process for producing a three-dimensional one-piece structure or part of a concrete structure according to one of Claims 1 to 3, in which the mold has a sagittal section in the form of a rack, capable of defining at the level of the structure three-dimensional to produce vertical faces and non-vertical faces, at least part of the surfaces of said mold intended to define the non-vertical faces being provided with a draft. Process for the production of a three-dimensional one-piece concrete structure or part of a structure according to claim 4, in which the undercuts are inclined from 3 to 25 degrees with respect to the horizontal. Method for producing a structure or part of a three-dimensional one-piece concrete structure according to one of Claims 1 to 3, in which the upper face of the upper mold or cover has a continuous curvature. One-piece concrete staircase or part of a staircase having a series of risers and tread plates obtained according to the process in accordance with one of Claims 1 to 6.