Method for producing a three-dimensional single-piece concrete structure or part thereof and three-dimensional concrete structure or part thereof thus obtained

Abstract

This process employs 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 lower mold (2) intended, ultimately, to define said at least one horizontal flat surface; ▪ positioning the upper mold or cover (3, 4) opposite said lower mold (2), and fixing it onto said lower mold; ▪ injecting self-compacting concrete into the volume defined by the two molds respectively lower and upper, and from the lower base of said volume, until the entire volume is filled; ▪ after the concrete has set, removing the upper mold and the lower mold, and thus demolding the three-dimensional concrete structure or part of a structure;then to turn over the structure or part of the structure thus obtained, in order to have at least one horizontal flat surface in the operational position, that is to say in the upper position when said structure is erected in place on site.;

Description

FIELD OF INVENTION

[0001] The invention relates first of all to a method for the production, in particular in a factory, of three-dimensional monobloc concrete structures or parts of structures, and more particularly, although not limitingly, of monobloc concrete stairs or parts of stairs.

[0002] The invention also relates to the three-dimensional monobloc concrete structures or parts of structures thus obtained and, more specifically, to monobloc concrete stairs or parts of stairs. PRIOR STATE OF TECHNOLOGY

[0003] Traditionally, concrete stairs, especially monolithic ones, are made on site. However, increasingly, these stairs are manufactured in a factory, then transported and erected on site.

[0004] Thus, in the context of the construction 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 column.

[0005] The process begins by creating a mold, defining a central column that will form the shaft. The shaft is then created by pouring concrete through the upper end of the mold. Next, concrete is poured onto the sections of the mold that will define the treads and risers. The poured concrete is vibrated, and then the operator levels the resulting steps, typically using a shovel or trowel, before smoothing the unset concrete with a trowel. Air bubbles typically form during the concrete pour and rise to the surface as the concrete sets. These bubbles can become trapped within the concrete or on the formwork walls, but they can also burst on the upper surface of each step, creating craters that must be removed.This bubbling phenomenon, well known in the field concerned, creates the need to carry out a second smoothing operation when the concrete has begun to set.

[0006] Moreover, notwithstanding this double smoothing operation, it is not uncommon for another coating or plaster to be applied to the facing of the concrete pieces, particularly for aesthetic reasons, in order to completely conceal this bubbling phenomenon, but also to correct any flatness defects.

[0007] It will already be easy to understand that the production of monoblock concrete stairs, as described above, whether these stairs are made on site or in a factory, involves a significant amount of finishing work, which is particularly time-consuming.

[0008] Furthermore, although some techniques, such as concrete vibration, have been developed to reduce this problem, the product still comes out bubbly and therefore requires significant finishing work to hide these bubbles.

[0009] Furthermore, the finish must be sufficiently robust to withstand repeated foot traffic without showing any wear or cracking due to air bubbles. This explains the occasional need for two coats of plaster, thus increasing the time required.

[0010] Furthermore, constructing such staircases is extremely arduous for the operator(s), as they must not only pour the concrete but also level it on each step, often using a shovel. This leveling must be done while the concrete is still wet. In addition to this arduous task, there is a safety issue due to the operator's precarious positioning. While working on the staircase itself, the operator must be in a precarious position to level the steps and smooth the concrete, and the risk of falling from a height remains.

[0011] Finally, due to the implementation of a relatively firm concrete, it is traditionally necessary to carry out a vibration operation of the mold or internally with vibrating needles, adding to the aforementioned disadvantages a noise nuisance, further affecting the working conditions of the operator.

[0012] In order to overcome these difficulties, the Applicant proposed, for example in document FR 3 081 896, a method for producing such monolithic concrete staircases, using 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, said method consisting of: ▪ to fix and install the lower mold in the operational position; ▪ to position the upper mold or hood opposite the said lower mold and fix it on the 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 in particular of the self-placing type, until the entire volume is filled; ▪ then, after the concrete has set, to remove the upper mold and the lower mold, and thus to demold the staircase thus produced.

[0013] By doing so, thanks to the process thus described, the presence of air bubbles is reduced, particularly at the level of the step platforms, this reduction of air bubbles can be optimized, again according to the teachings of this document, by the implementation at the level of the inner face of the upper mold or hood, that is to say the face facing the step platform, of a mortar, prior to the injection of the self-placing concrete, the said mortar having mainly intended to trap the air resulting from the setting of the concrete between the said concrete and the mortar.

[0014] While the process described undoubtedly significantly improves upon known techniques of the prior art, particularly by allowing for the construction of a staircase directly on site, it nevertheless presents a number of drawbacks. Among these is the step of projecting mortar onto the underside of the upper mold or hood, which inevitably leads to: ▪ 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 ensuring the adhesion of the mortar against the lower face, in this case oiled, of the upper cover, and its setting.

[0015] In summary, while the process described in the prior art reduces the phenomenon of concrete bubbling, experience demonstrates, firstly, that it does not completely eliminate this phenomenon, since air bubbles are frequently found trapped in the vicinity of the upper horizontal faces, i.e., at the level of the treads.

[0016] Furthermore, and as already mentioned, the implementation of a mortar to reduce this bubbling phenomenon ultimately proves to be relatively complex to control.

[0017] The object of the invention is to overcome these drawbacks. SUMMARY OF THE INVENTION

[0018] While the process described in the previously mentioned prior art advantageously allows the construction of a staircase on site, therefore directly without requiring the transport of said staircase or parts of such a staircase, the present invention is more oriented towards the production of monobloc three-dimensional concrete structures made in a factory, which certainly then requires the movement of said structure or part of structure on site for its final assembly or final erection.

[0019] The method according to the invention for producing a three-dimensional monobloc concrete structure or part of a structure, equipped with at least one horizontal flat surface, essentially consists of producing said structure "upside down", that is to say, reversing the erection of the mold compared to the method described in document FR 3081 896. This method therefore also employs a closed mold composed of a lower mold and an upper mold or hood defining between them a volume intended to be filled with concrete.

[0020] This process consists of: ▪ to install the intended lower mold, In short,to define said at least one horizontal flat surface, said lower mold having a succession of vertical and horizontal parts, said horizontal parts being intended to define said at least one flat surface; ▪ to position the upper mold or hood opposite said lower mold, and to fix 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, self-compacting concrete, until the entire volume is filled; ▪ after the concrete has set, to remove the upper mold and the lower mold, and thus to demold the three-dimensional concrete structure or part of a structure; ▪ then to turn over the structure or part of a structure thus obtained, in order to have said at least one horizontal flat surface in the operational position, that is to say in the upper position when said structure is erected in place on site.

[0021] In other words, contrary to the teachings of patent FR 3 081 896, the structure, and typically the staircase, is made upside down, without the use of any mortar, since, as mentioned in the description of the prior art, the air bubbles resulting from the pouring of the concrete are trapped at the level of the upper face of the mold, therefore in this case, due to the construction of said structure and in particular the staircase upside down, at the level of the lower face of said staircase once it has been erected.This avoids observing defects at the level of the functional surface of the staircase, i.e. the tread and, moreover, because of the injection of the concrete through the lowest point of the volume defined by the mold, the said air bubbles which may be formed tend to form at the upper level of said mold and therefore, once again, at the level of the lower non-functional face of the three-dimensional structure in particular of the staircase.

[0022] According to an advantageous feature of the invention, a vent is positioned at the highest point of the volume defined by the two molds, one lower and one upper. By doing so, the injected concrete not only fills the entire volume but also overflows at its upper part, i.e., higher than the three-dimensional structure to be created. This ensures complete filling of the mold. The resulting concrete core, which is obviously unnecessary, is broken off after the concrete has set during demolding.

[0023] According to an advantageous feature of the invention, and again with the aim of preventing the formation of air bubbles during the concrete setting process, once the mold is made—that is, after the lower and upper molds are installed—the entire assembly is inclined, typically at an angle of between 3 and 25 degrees to the horizontal, during the concrete pouring operation. Due to this slight inclination of the mold thus formed during this concrete pouring operation, the air bubbles, which naturally tend to be trapped on the horizontal surfaces, do not have access to the mold. de facto more horizontal faces to become trapped, and are likely to escape at the vanishing line created by the inclination of said mold.

[0024] In the same vein, according to another embodiment of the invention, at least some of the surfaces of the mold intended to define the non-vertical faces of the structure are provided with a draft angle, again typically inclined at 3 to 25 degrees to the horizontal, thus avoiding any horizontal face during the concrete pouring and facilitating the evacuation of any air bubbles that may have formed. By doing so, once the structure, and in particular the staircase, is completed, then turned over and erected, the lower face no longer has a parallel-sided, rack-like cross-section as frequently observed, but rather a lower face with a plane inclined to the horizontal.

[0025] According to yet another variant of the invention, and again with the aim of avoiding the formation of bubbles during the setting of the concrete, the upper face of the mold is no longer in the shape of a rack, as in the previous case, but has a continuous curvature, which will become the lower face of the staircase, this continuous curvature thus avoiding any horizontal faces likely to allow the entrapment of air bubbles.

[0026] The invention also relates to three-dimensional monobloc structures and monobloc concrete staircases obtained by implementing this process. DESCRIPTION FIGURES

[0027] The manner in which the invention can be implemented and the resulting advantages will be more clearly shown in the following examples of implementation, given by way of illustration and not limitation, in support of the attached figures. There figure 1is a schematic perspective representation of a lower mold according to the invention for the production of a single-piece concrete staircase with a central column. figure 2 is a schematic side view of the lower mold of the figure 1 . There figure 3 is a schematic perspective view, in two different orientations, of the lower part of the upper mold according to the invention, and adapted to cooperate with the lower mold of the figures 1 and 2 . There figure 4 is a view analogous to the figure 3 , but from the upper part of said upper mold. The 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 process of the invention. figure 6is a schematic view illustrating a staircase resulting from the process of the invention, shown upside down, and exhibiting inclined areas on its underside, resulting from draft angles created within the mold. figure 7 is a schematic perspective view of a staircase shown upside down or reversed, highlighting another variant of the invention, in this case a staircase with a smooth lower surface and continuous curvature with a central column. figure 8 is a view analogous to the figure 7 , but of a staircase without a central column. DETAILED DESCRIPTION OF THE INVENTION

[0028] The following description is made in relation to the manufacture of a one-piece concrete staircase.

[0029] It must be borne in mind, however, that the invention aims at the production of any three-dimensional concrete structure, and that only the shape of the molds may vary in order 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 monolithic concrete staircase (1), more particularly in a factory and not on site, two molds are used, respectively a lower mold (2) shown in the figures 1 and 2 , and an upper mold, in this case consisting of a lower cover (3) and an upper cover (4) shown within the figures 3 and 4 As can be seen in these figures, the mussels are erected vertically.

[0030] Regarding the lower mold (2) shown in the said figures 1 and 2This one has a succession of vertical (5) and horizontal (6) parts, said horizontal parts (6) being intended to define the treads (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 an inverted or upside-down position, as can be observed in particular on the figures 7 and 8 Typically, this mold is made of steel and corresponds to the entire flight of stairs that one wishes to create.

[0031] Consequently, the figures 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 the figures 1 and 2 to define a volume, within which self-compacting concrete will be injected.

[0032] In this embodiment, said lower (3) and upper (4) covers are also made up 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 method of the invention, is rack-shaped, like that shown in the figure 5 It should be noted that, due to the staircase being constructed in an inverted position, this upper mold effectively defines the lower face of the staircase. In this specific case, this lower section therefore features a stringer.

[0033] However, and as described for example in relation to the figures 7 and 8 , this lower surface (13) of the staircase could be smooth and continuous, so that the shape of the upper hood would be adapted accordingly.

[0034] We have represented in relation to the figure 5An exploded view illustrating the assembly of the different parts of the mold and their interaction with the staircase after its construction. These different parts of the mold are assembled together, notably by screwing, to facilitate the subsequent demolding of the staircase, once the concrete has set.

[0035] This assembly defines a closed volume, into which self-compacting concrete is injected. According to an essential feature of the invention, this injection is carried out at the base of said volume. This has thus been materialized on the figures 3 And 5 , the injection point (10) of the concrete within this volume, said injection point being in this case located within the lowest vertical part (9) of the upper mold.

[0036] This concrete, with a significantly more fluid consistency than traditional concretes used for stairs, is injected from the bottom of the mold using an upward motion, typically with the aid of a suitable pump, and more specifically a peristaltic pump. Self-compacting concrete therefore does not require vibration, a typically very physical and arduous task, and exhibits a greatly reduced number of air bubbles, resulting in a smoother finished product.

[0037] This pumping continues until the volume defined by the molds, respectively lower and upper, is completely filled.

[0038] According to an advantageous feature of the invention, the upper end (11) of the mold is provided with a vent (12), allowing air to escape as the volume defined by the assembly of said molds together is filled, and de facto promoting the suppression of air bubbles proper, one of the essential pitfalls that the present invention aims to avoid.

[0039] More specifically, as self-compacting concrete is injected into the lower injection zone (10), the concrete progresses within the volume towards the top of the mold, resulting in the complete filling of the volume defined by the mold, until the concrete reaches the top of the volume and escapes through the vent (12). When the concrete actually reaches the vent, the concrete injection ceases.

[0040] Once the concrete has set, the setting time depending on the type of concrete, that is, once the staircase can be demolded and the various elements of the molds illustrated in relation to the figures 1 to 4 This results in the presence of an upper core corresponding to the vent, which can be broken at that point.

[0041] According to an advantageous embodiment, and illustrated in relation to the figure 6In a diagram representing a staircase (1) with a central column (14) in an inverted position, the mold is fitted with draft angles, typically inclined at 3 to 25 degrees to the horizontal. The implementation of such draft angles, resulting in inclined surfaces (15) on the underside (13) of the staircase, aims to optimize the objective of the present invention, namely, preventing the formation of air bubbles that could remain trapped. Indeed, due to the method of injecting the concrete from the lower base of the volume defined by the two molds, the presence of these draft angles tends to expel the concrete at each step towards the step above, and consequently, to expel the air bubbles.

[0042] Alternatively, or even cumulatively, the invention also allows for slightly tilting the entire mold during the concrete injection operation, again typically by a factor of between 3 and 25 degrees relative to the horizontal, always with the same objective of expelling air bubbles. Regardless of the embodiment of the invention, the primary objective is to prevent the formation of air bubbles between the upper mold and the concrete.

[0043] Alternatively, and as mentioned previously, it is possible to eliminate any discontinuity in the upper mold's outer shell. In other words, the upper mold is given a smooth, continuous shape, allowing for the creation of a staircase as illustrated in the... figures 7 and 8respectively with and without a central column. It can be observed that the underside of the staircase, since it is represented in both inverted and upside-down positions, no longer has a rack, but a continuous surface. Due to this continuity of the upper mold, there is therefore no longer a horizontal or nearly horizontal surface capable of trapping air bubbles.

[0044] Advantageously, regardless of the chosen construction method, robust self-compacting concrete is used, avoiding saturation with admixtures to prevent the risk of micro-segregation or surface foaming, which can be caused by deflocculants such as plasticizers or superplasticizers. Typically, this self-compacting concrete belongs to class SF2 (slump between 660 mm and 750 mm) or class SF3 (slump between 760 mm and 850 mm), both classes being defined by standard NF EN 206, with slump being a test described by standard NF EN 12350-8.

[0045] The process of the invention results in the possibility of producing a three-dimensional concrete structure, and in particular a monobloc concrete staircase, making it possible to eliminate air bubbles at the level of the treads, i.e. the actually functional area of ​​the staircase, without requiring prior treatment of the molds, apart from oiling the inner face of the molds in order to facilitate demolding (this demolding oil can consist of a solvent-based oil (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 facilitating the production process and reducing manufacturing costs.

Claims

1. Method for producing a three-dimensional single-piece structure or part of a structure made of concrete, provided with at least one horizontal planar surface (7), said method implementing a closed mould composed of a lower mould (2) and an upper mould (3, 4) or hood defining between them a volume intended to be filled with concrete, consisting of: • installing the lower mould (2) intended, in fine, to define said at least one horizontal planar surface, said lower mould (2) having a succession of vertical (5) and horizontal (6) parts, said horizontal parts (6) being intended to define said at least one planar surface (7); • positioning the upper mould (3, 4) or hood opposite said lower mould, and fixing it to said lower mould (2); • injecting self-positioning concrete into the volume defined by the two moulds, respectively lower and upper, and from the lower base of said volume, until filling the entirety of said volume; • after setting of the concrete, removing the upper mould (3, 4) and the lower mould (2), and therefore removing the structure or part of a three-dimensional structure made of concrete; • and then inverting the structure or part of structure thus obtained, in order to have the at least one horizontal planar surface in the operational position, that is to say in the upper position when said structure is erected in place on site.

2. Method for producing a three-dimensional single-piece structure or part of a structure made of concrete according to claim 1, wherein a vent (12) is further positioned on either of the two moulds at the highest point of the volume defined by said moulds (2, 3, 4), so as to allow the self-locating concrete injected from the lower base of said volume to fill the entirety of said volume, and then to protrude from said volume at its upper part, i.e. higher than the three-dimensional structure to be produced.

3. Method for producing a three-dimensional single-piece structure or part of a structure made of concrete according to one of claims 1 and 2, wherein, once the mould has been produced, that is to say after installation of the lower mould and the upper mould, the whole is inclined by an angle of between 3 and 25 degrees with respect to the horizontal during the operation of pouring the concrete.

4. Method for producing a three-dimensional one-piece structure or part of a structure made of concrete according to any one of claims 1 to 3, wherein the mould has a sagittal section in the form of a rack, capable of defining vertical faces and non-vertical faces at the level of the three-dimensional structure to be produced, at least part of the surfaces of said mould intended to define the non-vertical faces being provided with a draft.

5. Method for producing a three-dimensional single-piece structure or part of a structure made of concrete according to claim 4, wherein the drafts are inclined by 3 to 25 degrees with respect to the horizontal.

6. Method for producing a three-dimensional single-piece structure or part of a structure made of concrete according to any one of claims 1 to 3, wherein the upper face of the upper mould or hood has a continuous curvature.

7. Single-piece staircase or staircase part made of concrete having a series of risers and step trays obtained according to the method according to any one of claims 1 to 6.

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