Method for producing a cracked concrete sample by controlled cracking and associated device

Abstract

-------- Method for producing a cracked concrete sample by controlled cracking and associated device The invention relates to a method for producing a cracked concrete sample (2) by controlled cracking, comprising: a) setting up a formwork (3) according to desired dimensions for the sample (2); b) arranging at least one vertical support frame (4) transversely to the formwork (3), the at least one vertical support frame (4) extending over all or part of the depth of the formwork (3), a mesh (5) being stretched over each support frame (4) in a corresponding vertical cracking plane; c) pouring concrete into the formwork (3) through the open upper face (3c) to fill the formwork; d) homogenizing the concrete in the formwork (3); e) waiting for a predefined period for the concrete to dry; f) removing the formwork (3) and the at least one support frame (4);and g) initiating controlled cracking in each desired cracking plane of the sample. The invention also relates to an associated device. Figure to be published with the abstract: Figure 1;

Description

Title of the invention: Method for producing a cracked concrete sample by controlled cracking and associated device

[0001] The present invention relates to the technical field of the production of concrete samples for carrying out mechanical tests, and relates more particularly to a method and a device for the production of a concrete sample by controlled cracking allowing the testing of fixings.

[0002] Test guides for fixings anchored in concrete bodies require that the fixings be tested in the most unfavorable situation, i.e. when the fixing is anchored in a cracking plane. It is therefore necessary to be able to obtain concrete samples suitable for carrying out mechanical tests on fixings arranged in cracking planes.

[0003] The current method consists of placing crack initiators, generally by breaking the adhesion on a portion of the longitudinal reinforcements, which act as springs subsequently when the crack opens, in the formwork of a sample and then, after drying of the concrete, to initiate cracking at the crack initiators. Said crack initiators make it possible to ensure the area in which the crack is created, but do not make it possible to ensure a plane in which said crack will propagate. With this technique, it is therefore necessary to check the arrangement of the crack when installing each fixing to be tested, for example using an endoscope to examine the drilling in which the fixing is planned to be installed.Furthermore, it is very difficult to test cast-in-place fasteners because it is not possible to guarantee that these fasteners will be arranged in a cracking plane after cracking.

[0004] Another approach is developed in Japanese patent JP6841416 B2. This document discloses a device and a method for manufacturing a concrete sample in which a crack is simulated. For this, it is planned to pour a first concrete block, wait for the first concrete block to dry, then place a film on the upper face of the latter in order to pour a second concrete block on the first block. The film is intended to simulate a crack in the concrete sample consisting of the first block and the second block. After the two concrete blocks have dried, a hole is made between them in order to install a fixed fastener.

[0005] However, this technique has several disadvantages, such as the fact that the sample may not be homogeneous due to the fact that the first block and the second block are not cast simultaneously, the fact that the first block and the second block are cast one on top of the other and the fact that the film constitutes a barrier which prevents the continuity of the sample between the first block and the second block. Furthermore, this device does not allow the production of a reinforced concrete sample and requires the use of an external frame to carry out tests on the fixings.

[0006] Therefore, the prior art solutions proposed for the production of a cracked concrete sample still have drawbacks and improvements are possible.

[0007] The invention aims in particular to propose a method and a device which make it possible to ensure the propagation of cracking in a desired plane in the manufactured concrete sample.

[0008] Another objective of the invention is to propose a method and a device which make it possible to guarantee that the cracking is indeed carried out in the desired cracking plane, which makes it possible to know precisely the position of the crack without needing to carry out additional examinations or checks as is the case when using “conventional” crack initiators.

[0009] Another objective of the invention is to provide a method and a device which make it possible to produce a concrete sample configured for testing cast-in-place fixings.

[0010] Another objective of the invention is to provide a method and a device which make it possible to produce a concrete sample configured for testing attached fixings.

[0011] Another objective of the invention is to propose a method and a device which make it possible to guarantee the homogeneity of the concrete sample and the continuity, before cracking, of the sample on either side of the cracking plane.

[0012] Another objective of the invention is to provide a method and a device which make it possible to control the crack opening in the concrete sample.

[0013] Thus, the present invention relates to a method for producing a cracked concrete sample by controlled cracking, characterized in that it comprises the following steps: a) placing a formwork according to desired dimensions for the sample, the formwork comprising a horizontal bottom and at least three vertical lateral hips forming with the bottom the formwork with an open upper face; b) arranging at least one vertical support frame transversely to the formwork, the at least one vertical support frame extending over all or part of the depth of the formwork, a mesh being stretched over each support frame in the corresponding vertical cracking plane, each vertical support frame defining a vertical cracking plane, each cracking plane being perpendicular to a selected direction; c) pouring concrete into the formwork through the open upper face to fill the formwork;d) homogenize the concrete in the formwork; e) wait for a predefined period for the concrete to dry; f) remove the formwork and at least one; support frame; and g) initiating controlled cracking in each desired cracking plane of the specimen.

[0014] This method makes it possible to control the propagation of cracks in the concrete sample produced. Indeed, each mesh makes it possible to guide a crack in a respective plane, which makes it possible to ensure that the crack propagates well according to the desired cracking plane.

[0015] Preferably, each mesh is tensioned over the respective support frame before the latter is arranged on the formwork. However, alternatively, each support frame may be arranged on the formwork before each mesh is tensioned over the respective support frame.

[0016] According to one embodiment, the method further comprises an additional step, before step c), consisting of placing at least one vibrating tool at the bottom of the formwork and step d) of homogenizing the concrete consists of vibrating the concrete using the at least one vibrating tool.

[0017] Homogenizing the concrete using a vibrating tool placed at the bottom of the formwork allows any air bubbles introduced into the concrete during pouring to be evacuated and allows a homogeneous sample to be obtained.

[0018] According to one embodiment, the method further comprises an additional step, between steps d) and e), consisting of carrying out surfacing and finishing of the concrete at the level of the open upper face.

[0019] Carrying out surfacing and a concrete finishing step at the level of the open upper face makes it possible to obtain a flat surface representative of real conditions of use, that is to say representative of a slab or a concrete body implemented on a structure such as a bridge or a building for example.

[0020] According to one embodiment, the method further comprises, between steps b) and c), the following additional steps: making at least one set of primary openings in the at least one lattice, the openings of a set of primary openings being aligned along the selected direction, normal to the at least one lattice, when there are several lattices; passing a horizontal reinforcement through each set of primary openings; fixing the at least one horizontal reinforcement using at least one transverse reinforcement; and arranging at least one anti-adhesion element on the at least one horizontal reinforcement at an intersection between the at least one horizontal reinforcement and a plane of a lattice.

[0021] The additional steps described above make it possible to arrange reinforcements in the sample while ensuring the propagation of cracks in the cracking planes, and therefore make it possible to obtain a cracked reinforced concrete sample with controlled cracking.

[0022] According to one embodiment, the method further comprises, between steps b) and c), the following additional steps: making at least one secondary opening in at least one lattice; positioning a cast-in-place fastener to be tested in each secondary opening; securing each cast-in-place fastener to be tested to the support frame on which the lattice in which the respective secondary opening is formed is secured; and

[0023] the method further comprising, following step e), a further step of releasing each cast-in-place fastener to be tested from the respective support frame.

[0024] The additional steps described above make it possible to have so-called cast-in-place fixings in the concrete sample, which subsequently makes it possible to carry out mechanical tests on cast-in-place fixings arranged in a cracking plane as recommended in the test guides.

[0025] According to one embodiment, the secondary openings are made, and the cast-in-place fasteners to be tested are positioned, close to the open upper face.

[0026] According to one embodiment, the method further comprises, before step c), an additional step consisting of placing retaining wires in each opening made in the at least one mesh so as to prevent deformation of the at least one mesh at an opening during step c) of pouring the concrete.

[0027] The use of retaining wires allows for the use of openings of the desired size in the mesh, including sufficiently large openings around the cast-in-place fasteners so that the mesh is not in direct proximity to the fastener and the mechanical tests are representative, while ensuring that the mesh does not deform during the pouring of the concrete.

[0028] According to one embodiment, the method further comprises, following step g), the following additional steps: making at least one hole in at least one external face of the concrete sample, each hole being made perpendicular to the corresponding external face and in a desired cracking plane; and implanting in each hole a fixed fastener to be tested.

[0029] The additional steps described above make it possible to have so-called reported fixings in the concrete sample, which subsequently makes it possible to carry out mechanical tests on reported fixings arranged in a cracking plane as recommended in the test guides.

[0030] According to one embodiment, the drillings are made, and the added fixings to be tested are implanted, in external faces of the sample which are vertical at least up to step e).

[0031] According to this embodiment, the formwork is designed and dimensioned such that the faces of the sample which are vertical during casting are representative and can be used to carry out mechanical tests on fasteners. This makes it possible to maximize the surfaces suitable for receiving fasteners to carry out representative tests, and therefore to maximize the number of fasteners that can be tested with the same sample.

[0032] According to one embodiment, in the final state, at least one lattice extends in the sample over the entire corresponding desired cracking plane over the entire depth of the sample, i.e. external dimensions of the lattice are equal to external dimensions of the sample when viewed in cross-section along said desired cracking plane.

[0033] The arrangement of a lattice over the entire cross-section of the sample makes it possible to guide the crack throughout the sample and ensures propagation in the cracking plane only.

[0034] According to one embodiment, in the final state, at least one lattice extends from an external surface of the sample towards a core thereof by a distance equal to an anchoring depth of a fixing arranged in the plane of said lattice.

[0035] The provision of a mesh over the anchoring depth of the fasteners makes it possible to ensure that the cracking is well within the desired cracking plane over at least the entire anchoring depth of the fasteners, as recommended in the test guides.

[0036] According to one embodiment, the initiation of cracking of step g) comprises, for at least one desired cracking plane, the use of expansion means configured to apply a force between parts of the sample located on either side of said desired cracking plane, so as to put the sample in tension.

[0037] The use of expansion means makes it possible to easily initiate and propagate a crack in a cracking plane, the crack subsequently being guided by the mesh.

[0038] In the case where the sample comprises horizontal reinforcements, these are preferably put in tension to promote the propagation of the crack.

[0039] According to one embodiment, the method further comprises a final step of using the expansion means to control the opening size of at least one crack.

[0040] The use of expansion means to control the crack opening size makes it possible in particular to carry out mechanical tests at a controlled crack opening.

[0041] According to one embodiment, in the final state, the crack opening is in a range from 0 to 1 mm, preferably in a range from 0.1 to 0.8 mm.

[0042] The use of a crack opening of between 0 and 1 mm makes it possible to cover a range representative of real cracking in a concrete body, and the use of a crack opening of between 0.1 and 0.8 mm makes it possible to carry out tests recommended by the test guides.

[0043] According to one embodiment, the pouring of the concrete during step c) is done in a balanced manner on each side of each lattice so as to limit the forces induced by the pouring of the concrete in directions perpendicular to the planes of the lattices.

[0044] This prevents deformation or tearing of a mesh during the pouring of concrete.

[0045] According to one embodiment, the at least one lattice is a lattice of fibers, preferably of glass fibers.

[0046] According to one embodiment, the concrete used to manufacture the sample comprises aggregates and a mesh size of the at least one mesh is greater than a maximum size of the aggregates.

[0047] Using a mesh size larger than the maximum size of the concrete aggregates allows the aggregates to be able to pass through the plane of a mesh when pouring the concrete, thereby ensuring continuity and homogeneity of the sample across the cracking plane before cracking. This allows a representative sample to be produced of an actual concrete slab or body.

[0048] The present invention also relates to a device for producing a cracked concrete sample, comprising a formwork comprising a horizontal bottom and at least three vertical lateral hips to form the formwork with an open upper face, characterized in that it further comprises at least one support frame configured to be arranged vertically, transversely to the formwork and to stretch a mesh thereon, so as to be configured to carry out a method according to one of the embodiments described above.

[0049] The device described above makes it possible to implement the method according to the present invention and allows the production of a sample of cracked concrete by controlled cracking, said sample being configured to allow mechanical tests to be carried out on cast-in-place fixings or added fixings.

[0050] A device according to an embodiment of the present invention and a method according to the present invention will now be described by way of non-limiting example, with reference to the accompanying drawings.

[0051] In these drawings:

[0052] [Fig-1] is a perspective view of a device for producing a cracked concrete sample according to the present invention, with an exploded view of a support frame according to the present invention.

[0053] [Fig.2] is a sectional view of the device according to [Fig.l], according to the plane of the frame of central support, and also presents an enlarged view of the trellis.

[0054] [Fig.3] is a side view of a cracked concrete sample obtained using a method and device according to the present invention.

[0055] If we first refer to [Fig. 1], we can see that a device 1 for producing a cracked concrete sample 2 is shown there. The device 1 comprises a formwork 3 and vertical support frames 4.

[0056] The formwork 3 comprises four side panels 3a arranged vertically and a horizontal bottom 3b, and the formwork 3 is configured so as to leave an upper face 3c open.

[0057] The use of four side panels 3a makes it possible to manufacture a cracked concrete sample 2 in the form of a straight paving stone, of course a different number of panels 3a can be used to obtain samples 2 of different shapes.

[0058] The side panels 3a and the bottom 3b are preferably configured such that concrete does not permanently adhere to their surface in order to allow separation of the cracked concrete sample 2 and the formwork 3 after the concrete has dried. The side panels 3a are preferably made of wood but can also be made of another material such as steel. According to the preferred embodiment, the bottom 3b of the formwork 3 is formed by the ground, on which a non-stick film or coating may possibly have been placed. According to a variant, the bottom 3b can also be made from a wooden element.

[0059] In [Fig. 1] an additional support frame 4 has been shown in an exploded view in order to present its structure more clearly.

[0060] Each vertical support frame 4 comprises an upper transverse element 4a to which a lattice 5 is fixed, and each vertical support frame 4 defines, in use, a vertical plane, called the cracking plane, in which the corresponding lattice 5 extends.

[0061] According to the preferred embodiment of the present invention, the mesh 5 is a fiberglass mesh, but could alternatively be made from another material, such as polyester.

[0062] According to the embodiment shown in Figures 1 and 2, each lattice 5 comprises square meshes 5a. It will however be understood that as a variant the meshes 5a may have different shapes, for example polygonal.

[0063] In use, each vertical support frame 4 is arranged transversely to an interior space 3d of the formwork 3 defined by the side panels 3a, the bottom 3b and the open upper face 3c, such that the mesh 5 which is fixed on said support frame 4 extends transversely to said interior space 3d in the vertical plane called the respective cracking plane, that is to say a plane in which it is desired to be able to guide a crack in the sample 2.

[0064] Preferably, the dimensions of the lattices 5 are chosen such that each lattice 5 extends, in its cracking plane, from one lateral panel 3a to an opposite lateral panel 3a.

[0065] Each support frame 4 is also arranged such that all the frames of support 4 are parallel to each other and perpendicular to a selected direction. Each support frame 4 is fixed to the formwork 3 in order to be held in position in use.

[0066] According to the preferred embodiment, the support frames 4 are made of wood so that the transverse elements 4a can be nailed to the lateral hips 3a. It will be understood, however, that the support frames 4 can be made of other materials, for example metal, and that other fastening solutions, for example welding, gluing or mechanical fastening, can be used to fix the support frames 4 to the formwork 3.

[0067] As shown in [Fig.l], in use, a lattice 5 can extend, from the open upper face 3c, over the total height L1 of the formwork 3, or over a lower height corresponding at least to a distance L2, called the anchoring depth.

[0068] When the trellis 5 extends over the entire height L1 of the formwork 3, the support frame 4 comprises a lower transverse element 4b, arranged at the bottom 3c of the formwork 3, to which a lower end of the trellis 5 is fixed in order to stretch the trellis 5 between the upper transverse element 4a and the lower transverse element 4b.

[0069] The upper transverse element 4a and the lower transverse element 4b can each be designed as a single piece to which the mesh 5 is fixed, for example by nailing, gluing or stapling, or as two pieces which allow the mesh 5 to be clamped to fix it. When the lower transverse element 4b is made as a single piece, the mesh 5 can also be fixed by clamping between the lower transverse element 4b and the bottom 3b of the formwork 3.

[0070] When the trellis 5 extends over a height L2 less than the total height L1 of the formwork 3, the support frame 4 does not include a lower transverse element 4b and the trellis 5 is fixed, so as to remain in the so-called vertical cracking plane, by lateral fixing elements 4c. It will be understood that, in the case where the trellis extends over the entire height L1, lateral fixing elements 4c can also be used in addition to the lower transverse element 4b.

[0071] According to the embodiment shown in [Fig.l], the lateral fixing elements 4c are in the form of staples connected to the lateral hips 3a. However, it will be understood that the lateral fixing elements 4c may, as a variant, take other forms such as for example glue dots, it would also be possible to make vertical grooves in the lateral hips 3a in which rods of corresponding sizes would be received and then blocked in order to pinch the trellis 5 and hold the trellis 5 in position.

[0072] According to a variant of the embodiment shown in the Figures, the support frames 4 could also comprise vertical lateral support elements at the periphery of the lattices 5, in order to facilitate the arrangement of the lattices 5 on the support frames 4, to facilitate the fixing of the lattices 5 to the support frames 4, and to allow a possible arrangement of the lattices 5 on the support frames 4 before an arrangement of the support frames 4 on the formwork 3.

[0073] According to the preferred embodiment shown in Figures 1 and 2, horizontal reinforcements 6 extend from one end to the other of the formwork 3 in the selected direction, and therefore perpendicular to the planes of the trellises 5.

[0074] The horizontal reinforcements 6 are held in position by transverse reinforcements 7, as is already known for the implementation of reinforced concrete. In order to allow the passage of the horizontal reinforcements 6 through the lattices 5, primary openings 5b aligned in the selected direction are made in the lattices 5. According to the embodiment shown in Figures 1 and 2, four horizontal reinforcements 6 are provided. It will be understood, however, that another number of horizontal reinforcements 6 can be selected for the sample 2. It will also be understood that, according to the embodiment shown in [Fig.l], the selected direction corresponds to a length direction of the formwork 3, but that the selected direction could also, as a variant, correspond to another direction of the formwork 3, in particular a width direction.

[0075] As shown in Figures 1 to 3, anti-adhesion elements 8 are arranged on each horizontal reinforcement 6 at the intersections between said horizontal reinforcement 6 and the vertical plane of each mesh 5 in order to prevent adhesion between concrete and said horizontal reinforcement 6 in these areas. Such anti-adhesion elements 8 are already known and will not be described in detail.

[0076] The device 1 allows the placement of cast-in-place fasteners 9 in the sample 2. As can be seen in Figures 1 and 2, secondary openings 5c are made in certain lattices 5. A secondary opening 5c ​​is made in a lattice 5 so as to allow the arrangement of a cast-in-place fastener 9. As can be seen in [Fig.2], the dimensions of a secondary opening 5c ​​are greater than the dimensions of the corresponding cast-in-place fastener 9, so as to be able to arrange the cast-in-place fastener 9 in the plane of the corresponding lattice 5 and so that mechanical tests carried out on the cast-in-place fastener 9, once the sample 2 has been produced, are not distorted by a proximity of the lattice 5 to the cast-in-place fastener 9.

[0077] Each cast-in-place fastener 9 is held in position by means of the corresponding support frame 4 so that in the final state it extends by the length L2, called the anchoring depth, in the sample 2 towards the core of the sample 2. Preferably, a through hole 4d is made in the upper transverse element 4a of the respective support frame 4 and the cast-in-place fastener 9 is passed through the through hole 4d and is held in position by a locking element. The locking element may, for example, take the form of a clamping ring.

[0078] Retaining wires 10 are arranged around each secondary opening 5c ​​and pass through meshes 5a of the mesh 5, so that the mesh 5 does not deform when concrete is poured into the formwork 3. It will be understood that in the same way and for the same reasons, retaining wires 10 can be put in place around each primary opening 5b.

[0079] Two concrete supply pipes 11 are provided for pouring concrete into the formwork 3. Preferably, the concrete is poured in a balanced manner on each side of each lattice 5 so as to limit forces induced by the pouring of the concrete in directions perpendicular to the planes of the lattices 5, in order to limit deformation of the lattices 5 during the pouring of the concrete. It will be understood that a single concrete supply pipe 11 may be used or that the concrete may be supplied in another way, such as for example by shoveling.

[0080] As shown in [Fig.2], a vibrating tool 12 is also provided to homogenize the concrete after pouring and to evacuate any air bubbles introduced into the concrete during pouring. Alternatively, other solutions could also be used, such as for example placing the device 1 on a vibrating table.

[0081] As shown schematically in the enlarged view of [Fig.2], the meshes 5a of the lattices 5 are configured according to the concrete used, so that a dimension of the aggregates 13 of the concrete is smaller than a dimension of the meshes 5a. This allows, during the pouring of the concrete, the aggregates 13 of the concrete to be able to cross the plane of a lattice so as to guarantee the continuity and homogeneity of the sample 2 on either side of the so-called cracking plane, before cracking.

[0082] [Fig. 3] represents a side view of a cracked concrete sample 2 manufactured using a device 1 according to the present invention, the horizontal reinforcements 6 and the anti-adhesion elements 8 are represented by transparency in dotted lines. The first crack F1 represents a crack initiated then guided by a mesh 5 extending over the length L2 in a first vertical cracking plane. The second crack F2 represents a crack initiated then guided by a mesh 5 extending over the length L1 in a second vertical cracking plane. It can be seen that a drilling 14 has been made over a length L2, perpendicular to an external surface 2a and centered on the second vertical cracking plane. This drilling 14 is intended to receive an attached fixing 9 which will be sealed in the sample 2 mechanically or chemically.In the case of mechanical sealing, the connection between the attached fixing 9 and the concrete is ensured by friction or expansion of at least one mechanical element, said at least one mechanical element generally being. made of steel. In the case of chemical sealing, the connection between the attached fixing 9 and the concrete is ensured by adhesion, preferably using a polymer or cement mortar.

[0083] Preferably, the holes 14 are made in external surfaces 2a of the sample 2 which are vertical during the pouring of the concrete, so that added fixings 9 can be put in place successively on two opposite sides of the sample 2 and the mechanical tests carried out on said added fixings 9 can be considered as having been carried out under identical conditions. This makes it possible to maximize the number of fixings 9 tested for the same concrete sample 2.

[0084] The third crack F3 represents a crack which has just been initiated by expansion means 15, which may for example be in the form of a wedge, that is to say a conical expansion element which spreads the edges of the crack when an impact is applied to it.

[0085] Said expansion means 15 can also be used to control a crack opening Lf during a mechanical test carried out on a fastener 9, said fastener 9 being able to be a fastener 9 cast in place or a fixed fastener 9.

[0086] Preferably, the device makes it possible to control the crack opening Lf between 0 and 1 mm, and more preferably between 0.3 and 0.8 mm.

[0087] The fasteners 9 shown in Figures 1 and 2 are fasteners 9 comprising a single anchorage, it will however be understood that all types of fasteners 9 can be used, such as for example fixing rails which comprise several anchorage points.

[0088] A method for manufacturing a cracked concrete sample 2 according to the present invention will now be described. The various elements necessary for implementing the method have been described in detail during the description of the device according to the present invention and their descriptions will therefore not be repeated in detail below.

[0089] The method according to the present invention firstly comprises putting in place a formwork 3 according to the desired dimensions for the sample 2. The formwork 3 comprises a horizontal bottom 3b and at least four vertical lateral hips 3a forming with the bottom 3b, the formwork 3 with an open upper face 3c.

[0090] The method then comprises arranging at least one vertical support frame 4 transversely to the formwork 3, the at least one vertical support frame 4 extending over all or part of the depth of the formwork 3. According to the method, a mesh 5 is stretched over each support frame 4 in the corresponding vertical cracking plane, each vertical support frame 4 defines a vertical cracking plane, and each cracking plane is perpendicular to a selected direction.

[0091] Preferably, the at least one lattice is a fiber lattice, more preferably of glass fibers.

[0092] Preferably, the method comprises placing at least one vibrating tool 12 at the bottom of the formwork 3.

[0093] Optionally, the method comprises placing horizontal reinforcements 6. The method then comprises making at least one set of primary openings 5b in the at least one trellis 5, the openings 5b of a set of primary openings 5b being aligned in the selected direction, normal to the at least one trellis 5, when there are several trellises 5, then passing a horizontal reinforcement 6 through each set of primary openings 5b, then fixing the at least one horizontal reinforcement 6 using at least one transverse reinforcement 7, and finally arranging at least one anti-adhesion element 8 on the at least one horizontal reinforcement 6 at an intersection between the at least one horizontal reinforcement 6 and a plane of a trellis 5.

[0094] It will be understood that the above steps are carried out only in the case where it is desired to produce a sample 2 in reinforced concrete.

[0095] Optionally, the method comprises placing so-called cast-in-place fasteners 9. The method then comprises making at least one secondary opening 5c ​​in at least one lattice 5, then positioning a cast-in-place fastener 9 to be tested in each secondary opening 5c, and finally fixing each cast-in-place fastener 9 to be tested to the support frame 4 on which the lattice 5 is fixed in which the respective secondary opening 5c ​​is formed.

[0096] Preferably, the secondary openings 5c are made, and the cast-in-place fasteners 9 to be tested are positioned, close to the open upper face 3c.

[0097] It will be understood that the above steps are carried out only in the case where it is desired to install cast-in-place fasteners 9 in the sample 2 so as to be able to subsequently carry out mechanical tests on said cast-in-place fasteners 9.

[0098] Preferably, the method comprises a step consisting of placing retaining wires 10 in each opening 5b, 5c made in the at least one trellis 5 so as to prevent deformation of the at least one trellis 5 at an opening 5b, 5c during the future pouring of concrete.

[0099] After which the method comprises pouring concrete into the formwork through the open upper face to fill the formwork.

[0100] Preferably, according to the method, the concrete is poured via the open upper face 3c and in a balanced manner on each side of each lattice 5 so as to limit the forces induced by the pouring of the concrete in directions perpendicular to the planes of the lattices 5.

[0101] After this, the method comprises homogenizing the concrete in the formwork.

[0102] Preferably, the homogenization of the concrete consists of vibrating the concrete using at least one vibrating tool 12.

[0103] More preferably, the method further comprises surfacing and finishing the concrete at the open upper face.

[0104] The method then comprises waiting for a predefined period for the concrete to dry.

[0105] It will be understood that once the concrete has dried, the formwork 3 and the sample 2 can be freely manipulated, moved or rotated as required.

[0106] In the optional case where fixings 9 reported in the sample 2 have been put in place, it will be understood that the method then comprises a step consisting of releasing each fixing 9 cast in place to be tested from the respective support frame 4.

[0107] Then the method comprises removing the formwork and the at least one support frame.

[0108] It will be understood that once the formwork 3 has been removed, the sample 2 can be freely manipulated, moved or rotated as needed.

[0109] Subsequently the method comprises initiating controlled cracking in each desired cracking plane of the sample.

[0110] Preferably, the initiation of cracking comprises, for at least one desired cracking plane, the use of expansion means 15 configured to apply a force between parts of the sample 2 located on either side of said desired cracking plane, so as to put the sample 2 in tension.

[0111] It will be understood that holes may possibly be made in sample 2 to allow the use of said expansion means.

[0112] In the case where the sample comprises horizontal reinforcements, these are preferably put in tension to promote the propagation of the crack.

[0113] Optionally, the method may further comprise installing so-called added fasteners 9. The method then comprises making at least one hole 14 in at least one external face 2a of the concrete sample 2, each hole 14 being made perpendicular to the corresponding external face 2a and in a desired cracking plane, then implanting in each hole 14 an added fastener 9 to be tested.

[0114] Preferably according to the method, the drillings 14 are made, and the fixings 9 to be tested are implanted, in external faces 2a of the sample 2 which are vertical at least until the concrete drying stage.

[0115] It will be understood that the above steps are carried out only in the case where it is desired to put in place fixings 9 added to the sample 2 so as to be able to subsequently carry out mechanical tests on said added fixings 9.

[0116] It will also be understood that, as required, sample 2 may be returned to facilitate the production of the drillings 14 and the installation of the added fixings 9 or even to facilitate the performance of mechanical tests on the fixings 9.

[0117] Preferably, the method then comprises using the expansion means to control the opening size Lf of at least one crack.

[0118] It will be understood that this step makes it possible to control the crack openings Lf of the sample 2 during the mechanical tests carried out on the fasteners 9, whether they are fasteners 9 cast in place or attached fasteners 9.

[0119] Preferably, the method is configured so that in the final state, the crack opening Lf is in a range from 0 to 1 mm, and more preferably in a range from 0.3 to 0.8 mm.

[0120] Preferably, according to the method, the dimensions of the lattices 5 are chosen such that each lattice 5 extends in its cracking plane from one lateral panel 3a to an opposite lateral panel 3a.

[0121] More preferably, according to the method, the concrete used to manufacture the sample 2 comprises aggregates 13 and a mesh size 5a of the at least one lattice 5 is greater than a maximum size of the aggregates 13.

[0122] More preferably, the method is provided such that in the final state, at least one lattice 5 extends in the sample 2 over the entire desired cracking plane corresponding to the entire depth L1 of the sample 2, that is to say that external dimensions of the lattice 5 are equal to external dimensions of the sample 2 when seen in cross-section along said desired cracking plane.

[0123] Alternatively, the method may be provided such that in the final state, at least one lattice 5 extends from an external surface 2a of the sample towards a core thereof by a distance L2 equal to an anchoring depth of a fixing 9 arranged in the plane of said lattice 5.

[0124] It will finally be understood that the method according to the present invention allows the use of different types of fixings for the cast-in-place fixings 9 and for the attached fixings 9, such as for example single anchor fixings or fixings with several anchor points, for example connection plates or anchor rails.

[0125] The method according to the invention therefore makes it possible to obtain a cracked concrete sample 2 by controlled cracking. Said sample 2 may be made of concrete or reinforced concrete and may comprise fixings 9 cast in place or fixings 9 added. Said fixings 9 are arranged, in a precise and guaranteed manner, vertically in cracking planes in order to allow mechanical tests to be carried out on said fixings 9.

Claims

Claims

1. A method for producing a cracked concrete sample (2) by controlled cracking, characterized in that it comprises the following steps: a) placing a formwork (3) according to desired dimensions for the sample (2), the formwork (3) comprising a horizontal bottom (3b) and at least three vertical lateral hips (3a) forming with the bottom (3b) the formwork (3) with an open upper face (3c); b) arranging at least one vertical support frame (4) transversely to the formwork (3), the at least one vertical support frame (4) extending over all or part of the depth of the formwork (3), a mesh (5) being stretched over each support frame (4) in a corresponding vertical cracking plane, each vertical support frame (4) defining a vertical cracking plane, each cracking plane being perpendicular to a selected direction;c) pouring concrete into the formwork (3) through the open upper face (3c) to fill the formwork, the concrete being poured in a balanced manner on each side of each mesh (5) so as to limit forces induced by the pouring of the concrete in directions perpendicular to the planes of the meshes (5), the concrete comprising aggregates (13) and a mesh size (5a) of the at least one mesh (5) being greater than a maximum size of the aggregates (13); d) homogenizing the concrete in the formwork (3); e) waiting for a predefined period for the concrete to dry; f) removing the formwork (3) and the at least one support frame (4); and g) initiating controlled cracking in each desired cracking plane of the sample.;

2. Method according to claim 1, characterized in that it further comprises an additional step, before step c), consisting of placing at least one vibrating tool (12) at the bottom of the formwork (3) and step d) of homogenizing the concrete consists of vibrating the concrete using the at least one vibrating tool (12).

3. Method according to claim 1 or claim 2, characterized in that the method further comprises an additional step, between steps d) and e), consisting of carrying out surfacing and finishing of the concrete at the open upper face (3c).

4. Method according to any one of claims 1 to 3, characterized by the fact that it further comprises, between steps b) and c), the following additional steps: - making at least one set of primary openings (5b) in the at least one lattice (5), the openings (5b) of a set of primary openings (5b) being aligned along the selected direction, normal to the at least one lattice (5), when there are several lattices; - passing a horizontal reinforcement (6) through each set of primary openings (5b); - fixing the at least one horizontal reinforcement (6) using at least one transverse reinforcement (7); and - arranging at least one anti-adhesion element (8) on the at least one horizontal reinforcement (6) at an intersection between the at least one horizontal reinforcement (6) and a plane of a lattice (5).

5. Method according to any one of claims 1 to 4, characterized in that it further comprises, between steps b) and c), the following additional steps: - making at least one secondary opening (5c) in at least one lattice (5); - positioning a cast-in-place fastener (9) to be tested in each secondary opening (5c); - fixing each cast-in-place fastener (9) to be tested to the support frame (4) on which the lattice (5) in which the respective secondary opening (5c) is formed is fixed; and the method further comprising, following step e), an additional step of releasing each cast-in-place fastener (9) to be tested from the respective support frame (4).

6. Method according to claim 5, characterized in that the secondary openings (5c) are made, and the cast-in-place fixings (9) to be tested are positioned, close to the open upper face (3c).

7. Method according to any one of claims 4 to 6, characterized in that it further comprises, before step c), an additional step consisting of placing retaining wires (10) in each opening (5b, 5c) made in the at least one lattice (5) so as to prevent deformation of the at least one lattice (5) at an opening (5b, 5c) during step c) of pouring the concrete.

8. Method according to any one of claims 1 to 7, characterized in that it further comprises, following step g), the supplementary steps- following additional steps: - making at least one hole (14) in at least one external face (2a) of the concrete sample (2), each hole (14) being made perpendicular to the corresponding external face (2a) and in a desired cracking plane; and - installing in each hole (14) a fixing (9) to be tested.

9. Method according to claim 8, characterized in that the holes (14) are made, and the fixings (9) to be tested are implanted, in external faces (2a) of the sample (2) which are vertical at least up to step e).

10. Method according to any one of claims 1 to 9, characterized in that in the final state, at least one lattice (5) extends in the sample (2) over the entire corresponding desired cracking plane over the entire depth (Ll) of the sample (2), that is to say that external dimensions of the lattice (5) are equal to external dimensions of the sample (2) when seen in cross-section along said desired cracking plane.

11. A method according to claim 5 or 8, or any one of claims 6, 7 or 9, when dependent on claim 5 or 8, characterized in that in the final state, at least one lattice (5) extends from an external surface (2a) of the sample (2) towards a core thereof by a distance equal to an anchoring depth (L2) of a fastener (9) arranged in the plane of said lattice (5).

12. Method according to any one of claims 1 to 11, characterized in that the initiation of cracking in step g) comprises, for at least one desired cracking plane, the use of expansion means (15) configured to apply a force between parts of the sample (2) located on either side of said desired cracking plane, so as to put the sample (2) in tension.

13. A method according to claim 12, characterized in that it further comprises a final step of using the expansion means (15) to control the opening size (Lf) of at least one crack.

14. Method according to any one of claims 1 to 13, characterized in that in the final state, the crack opening (Lf) is in a range from 0 to 1 mm, preferably in a range from 0.1 to 0.8 mm.

15. Method according to any one of claims 1 to 14, characterized in that the at least one lattice (5) is a lattice of fibers, preferably glass fibers.

16. Device (1) for producing a cracked concrete sample (2), comprising a formwork (3) comprising a horizontal bottom (3b) and at least three vertical lateral hips (3a) to form the formwork (3) with an open upper face (3c), characterized in that it further comprises at least one support frame (4) configured to be arranged vertically, transversely to the formwork (3) and to stretch a mesh (5) thereon, so as to be configured to carry out a method according to any one of claims 1 to 15.

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