A method and elements for assembling a non-recoverable formwork

Abstract: A method for assembling a non-recoverable formwork made of a ribbed slab comprising base elements (1,2,3,4) manufactured from transformed resins and/or expanded polystyrene, wherein an auxiliary structure is built up upon which, in order to form said formwork, said base elements, comprising each at least one channel part (6) forming a part of a bedding for a beam of concrete, are disposed adjacent to each other. The different base elements (1,2,3,4), which are provided with reinforced walls (7,8) situated on both sides of said channel part (6), are connected by each time linking at least four adjacent base elements (1,2,3,4) with a covering element (5) disposed on the reinforcing walls (9) between two successive channel parts (6) of the connected base elements.

Description: The invention relates to a method for assembling a non-recoverable formwork made of a ribbed slab comprising base elements manufactured from transformed resins and/or expanded polystyrene, wherein an auxiliary structure is built up upon which, in order to form said formwork, said base elements, comprising each at least one channel part forming a part of a bedding for a beam of concrete, are disposed adjacent to each other. Such a method and such means are for example known under the name of isolated roofing DFC-Sipra and described in US-A-4 468 911 or in Cahier du CSTB n° 1450 livraison 180, (june 1977). According to the known method non-recoverable isolating members made for example of expanded polystyrene are disposed on an auxiliary structure. The isolating members are provided with channels wherein concrete is poured for forming a transverse beam supporting the roofing. The channels extend only over a part of the height of the member in such a manner that the bottom plane of the member forms a substantially homogeneous isolation layer for sound and thermal isolation. Once the different elements have been assembled the concrete can be poured thereon in order to form a roofing. Once the concrete has hardened the shuttering is removed and the isolation layer at the underside becomes visible. The isolating members thus remain in the roofing. A drawback of the known method is that the used base elements are generally of a large dimension (4 m in length, 1,20 m in width) and that the concrete is already poured therein before assembling, which signifies that they cannot easily be handled. Further the space between two successive channels is completely filled with isolating material which makes the members also heavy and fragile. The different elements are simply disposed adjacent to each other and there is no rigid linking between the different elements, which causes them to move with respect to each other. It is an object of the invention to realize a method for applying an isolation layer wherein use is made of less fragile and more easily to handle isolating members, and wherein after assembling the displacement of the different elements with respect to each other is hindered. This object is achieved by the method according to claim 1 and the assembly according to any of claims 2-7. The presence of reinforcing walls provides a more rigid structure of the base element with less weight because the base elements are no longer completely filled with material between successive channel parts. Further by making use of base elements the overall dimensions of the elements can be reduced which makes them more easy to handle. The covering element serves to connect adjacent base elements and to cover the reinforcing walls so that no concrete can reach the covered volume. Due to the fact that adjacent base elements are connected, they cannot move with respect to each other which allows the channel parts of the different members to be correctly aligned and hinders displacement of the elements with respect to each other. The carefully planned form of the moulds facilitates their adaptation to any geometric form of building floorplan, whether it be square, rectangular, circular of any polygonal planned. Use is made of base elements having a predetermined dimension, a remaining surface part of the formwork to be assembled between a border of a surface to be covered by said formwork and an end of a base element, which surface part is smaller than a further surface of said base element, being formed by a complementary element connected to the latter base element and continuing at least a bottom plane of said base element. The said base element is provided with reinforcing walls, situated on both sides of said channel part. The use of reinforcing walls lightens the elements and makes them more rigid. A first preferred embodiment of a base element according to the invention is characterized in that said channel part is substantially situated along a central axis of said base element. Such base elements are particularly suitable to be used as unidirectional slabs for substantially parallel aligned transverse beams. A second preferred embodiment of a base element according to the invention is characterized in that a further channel part is provided extending substantially perpendicular to said channel part. Such base elements are particularly suitable to be used for lattice ribbed transverse beams. Preferably said base elements comprise a bottom plane, each border of which being provided with first linking meams for linking with an adjacently disposed base element. The bottom plane borders of adjacently disposed base elements can thus be connected to each other so that they remain immobile with respect to each other. A combination of a base element and a covering element to be used in a method according to the invention is characterized in that said base element respectively said covering element is provided with second respectively third linking means arranged to cooperate with each other. This enables to rigidly fix the covering element to the base element. Preferably said base elements are provided with support means applied in said channel part for supporting reinforcement rods. Preferably said base element and/or said covering element is made of transformed resin or expanded polystyrene. Those materials have excellent sound and thermal isolation properties and are further waterproof. The invention will now be described in more details by means of the drawings, given solely by way of example. It will be clear that the invention is not limited to the illustrated examples and that within the scope of the invention several modifications are possible. In the drawings : Figure 1 illustrates schematically a first preferred embodiment of a method according to the invention and wherein use is made of unidirectional base elements ; Figure 2 illustrates schematically a second preferred embodiment of a method according to the invention and wherein use is made of lattice ribbed base elements ; Figure 3 illustrates schematically said method according to said first preferred embodiment in a phase wherein the assembling is nearly finished ; Figure 4 illustrates schematically said method according to said second preferred embodiment in a phase wherein the assembling is nearly finished ; Figure 5 illustrates a view from above a unidirectional base element ; Figure 6 illustrates a cross section through a unidirectional base element ; Figure 7 shows the bottom surface of a unidirectional base element ; Figure 8 shows a detailed view of a covering element to be used with a unidirectional base element ; Figure 9 shows a cross-section through the covering element illustrated in figure 8 ; Figure 10 illustrates a view from above from a lattice ribbed base element ; Figure 11 shows a cross section through a lattice ribbed base element ; Figures 12 and 13 show cross sections through a covering element for a bidirectional base element ; Figure 14 shows a top view of a covering element to be used by a lattice ribbed base element ; Figure 15 shows a complementary element ; Figure 16 illustrates schematically the construction of a roofing provided with a formwork according to the invention ; Figure 17 shows the placing of a reinforcement in a unidirectional base element ; Figure 18 shows the placing of a reinforcement in a lattice ribbed element ; Figure 19 shows a part of a roofing provided with a formwork according to the invention. Figure 20 illustrates a cross-section through a covering element for a unidirectional base element. In the drawings a same reference number refers to a same or analogous element. A roofing, a ceiling or any other horizontal or inclined structural element extending between two generally vertically disposed, supporting elements of a building, is generally made of concrete. Since concrete is a good thermal conductor and has bad acoustic isolation properties use is made of isolation members which improves the isolation of the roofing. Those isolation members are often included in the formwork used to poor the concrete, thus forming a non-recoverable formwork of isolating material. The advantage of using isolating material for the formwork is that the assembly of the formwork and the application of the isolating layer is realized in one and the same operation step. Figure 1 shows four base elements 1, 2, 3 and 4 of a formwork made of ribbed slabs according to the invention. In the first preferred embodiment each base element is formed by a unidirectional mould provided with a channel part 6 which extends through a central axis of the base element. That channel part is provided for placing therein reinforcements, preferably made of iron rods, and pouring thereafter concrete into that channel part in order to form a transverse beam of the roofing. The channel part thus forms a bedding for a transverse beam. The base elements or base moulds are placed adjacent to each other as is illustrated in figure 1. Base element 4 is moved into the open space shown adjacent the elements 2 and 3 and the channel part 6 of base mould 3 is continued by the channel part 6 of base mould 4, once the latter has been correctly disposed. In order to link adjacent base elements with each other and thus prevent that they could move with respect to each other, use is made of a covering element 5. In the embodiment of figure 1, covering element 5 links the four moulds to each other, which is particularly advantageous since it provides that the four moulds cannot move with respect to each other and this by using only one covering element. Figure 3 illustrates a second phase wherein the assembling of the formwork is nearly achieved. The different base elements fit together in such a way that the heads of the reinforcing walls coincide. A system of convex and concave grooves facilitates this. Each covering element has reinforcing walls 40, 41 similar to those in the base element. The covering elements fit together, thanks to the grooves placed along the sides of the elements. The covering element 14 has a rounded shape and is provided with grooves that permit its assembly with a group of four base elements. Small reinforcing walls strenghten it. The base and covering elements are made of transformed resins and/or expanded polystyrene or any other material having poor thermal conductive characteristics. Transformed resins or expanded polystyrene is particularly suitable since it is a waterproof material and thus will not absorb the water contained in the concrete to be poured on the upper surface of the isolating element. Indeed, since the water of the concrete is not absorbed by the element, which is the case when the concrete is poured on a shuttering made of wood or any other water-absorbing material, the water/cement relation of the concrete will not be modified. Therefore, the hardening of the concrete will be more homogeneous and will faster reach its resistance level. Further transformed resins or expanded polystyrene is a good acoustic isolation. Since concrete has bad acoustic attenuation properties, the acoustic isolation of the roofing made of concrete and the isolating elements will be much improved due to other good acoustic isolation properties of the isolating elements. Finally transformed resins or expanded polystyrene has also good fire resistant properties and is resistant to fire up to 180 minutes. Each base element comprises a bottom plate 12 upon which a grid of reinforcing walls 9 are disposed. The reinforcing walls are substantially perpendicular to the bottom plate and extend between a border of the base element and a wall 7 or 8 delimiting the channel part 6. The reinforcing walls thus extend on both sides of the channel part 6 and an open space is each time left between two successive reinforcing walls. Due to the use of reinforcing walls, the base elements have a rigid structure and a low weight. The reinforcing walls assure the undeformability of the channel which holds the rib of the slab. The rigid structure is particularly important since there must be avoided that due to the relatively high weight of the concrete to be poured in the channel part and upon the covering element, the base element would be deformed or damaged and consequently lost some or all of its properties. When concrete is poured in the channel part, the pressure applied by the concrete against the walls 7 and 8 will be substantially compensated by the reinforcing walls 9, which will also sustain the covering plate and the concrete poured thereon. The different reinforcing walls 9 of a base element form a grid within that element and assure its indeformability while reinforcing the channel walls 7 and 8. Further due to the low weight of the base elements they are easy to handle, which makes their adjacent placement more easy to carry out. The lightness of the elements enables to save in the cost of their loading and transport and avoids the use of heavy machinery for the assembling thereof. The open space between two successive reinforcing walls further improves the thermal and sound isolation properties of the base element. Figures 2 and 4 show a second embodiment of an isolating element according to the invention, wherein the base elements 15, 16, 17 and 18 are provided with two channel parts 6 and 13 which extend substantially perpendicular to each other. Those base elements, called bidirectional moulds, are used for roofings with lattice ribbed transverse beams. The presence of two channel parts in the base elements imposes a different shape of the covering element 14 with respect to the one used in the first embodiment, as can be seen in the drawings. Those elements are used when bidirectional transverse beams are required. The covering element 14 is provided with rounded angles and so are the cross-points of the channel parts in order to reinforce the structure of those elements. These two types of moulds allows all of the constituent elements of the ribbed slabs to be formed, achieving in this way a continuous and monolithic structure. It is possible to adapt the system to any measurements imposed by the design of the ribbed slabs. It is sufficient to construct the formwork with the moulds appropriate in each case. Of all the possible ones, the following have been selected as standard moulds. Unidirectional mould : Ribs : interaxes distances = 70 cm Dimensions of the finished ribs width = 10 cm heights = 15 + 4 cm 20 + 4 cm 25 + 4 cm Thickness 3 cm Slab : Height corresponding to the com-compression layer 4 cm Bidirectional mould : Ribs : Interaxes distance, lattice = 70 x 70 cm Dimensions of the finished ribs width = 10 cm heights = 15 + 4 cm 20 + 4 cm 25 + 4 cm Thickness 3 cm Slab : Height corresponding to the compression layer 4 cm The measurements given above do not mean there is any limitation in the system. The different moulds can adopt any size, form or variation used to execute these types of slabs. The mould of transformed resins and/or expanded polystyrene have the following values as insulation, soundproofing and fire resistant material : Coefficient of heat transmission : (K) = 0'32 (Kcal/m 2 .h oC) Absorption of noise levels (in zones between ribs) : on impact : 77 dBA environmental : 48 dBA It is resistant to fire for 180 minutes. Figures 5 and 10 illustrate a view from above of a base element provided with first linking means 23, 24 in order to link the base element with adjacent base elements. Such first linking means are present on the bottom plane of the base element. Preferably the first linking means comprises a recess 23 and a projection 24. The first linking means are preferably situated at the extremities of the channel part in order to obtain a suitable alignment of the successive channel parts. The walls 7, 8, 19 and 20 (Fig. 5, 10) of the channel parts have an upper border provided with second linking means 21, 22 in order to link the base element with the covering element. The second linking means are formed by a first step-like profile 21 and a second step-like profile 22 as is illustrated in Figure 10. The first step-like profile 21 has its lower part on the side of the channel, while the second step-like profile 22 has its upper part on the side of the channel. The second linking means cooperate with third linking means 23a and 24a, (figures 12 and 13) provided on the covering element and showing a profile which fits with the one of the second linking means. So the step-like profile 23a fits with 21 and 24a with 22. As can be seen from figure 5, the base elements provided with only one channel part are also provided with second linking means showing an analogous profile. However, the second step-like profile 22 is not present on a channel wall but on a reinforcing walls situated substantially in the middle of the element. The presence of a first and a second step-like profile enables a correct positioning of the covering element on the base element and prevents that the covering element could shift once it has been put on the base element. As can be seen from figure 3, the covering element 5 is disposed assymetrically with respect to the structure of the base element which enables a better linkage of the base elements and moreover hinders a relative shift of the different elements. Preferably the base elements are provided with reinforcement spacers 25 as can be seen in figures 5, 6, 10 and 11. Those reinforcement spacers 25 show a substantially U-shaped profile and reinforces the channel part. At the same time those reinforcement spacers 25 serve as a support and guiding means for a reinforcement made of iron rods 39 such as shown in figures 17 and 18. Those reinforcement spacers allow a suitable alignement of the iron rods. The bottom plane of the base element is provided with a grid of small chennels such as illustrated in figure 7 and wherein conduits such as electricity, water or gas conduits can be installed. This has the advantage that, when such a conduit has to be installed, the space and the channel therefore are already provided in the roofing which offers a substantial time and money saving. Besides the fact that the small channels 26 shown in figures 3 and 7 can be used for installing conduits, they also assure the adherence of any ceiling finish, in particular gypsum. As can be seen from figures 1, 3 and 8, the covering element 5 of the first embodiment has inclined border parts 29. The bevel of the covering element favours the pouring of the concrete in the channel parts and gives the finished concrete beam a greater compression head. The covering element further comprises fourth linking means (figures 8 and 9) for example formed by a projection 30 which fits into a recess 31, enabling to link successive covering elements to each other and thus obtaining a tight covering of the space between two successive channel parts of connected base elements. Preferably the covering element is provided with notches 32 situated on the top side and allowing to support reinforcing rods. The notches are preferably situated on the corners of the covering plate as is illustrated in figure 14, thus enabling the reinforcing rod to be carried by nearly the whole surface of the covering element. Since the base elements have standard dimensions and since a roofing or the like can have various dimensions, complementary elements must be provided in order to fill up the remaining surface part left between a border of the surface to be covered and an end of the last base element of a succession of base elements. The complementary element is used in the construction of unidirectional as well as bidirectional elements and serves as an additional mould. Since that remaining surface is of course always smaller than the surface of a base element and since base elements are preferably not cut into pieces in order to maintain their homogeneous structure, a complementary element 33 as shown in figure 15 is used. That complementary element is also provided with linking means 34 which fits with the first linking means of the base elements. This enables the complementary element to be suitably connected to the bottom plane of the base elements. The bottom surface of the complementary element is also provided with one or more recesses 36 as it is the case for base elements. The complementary element is further provided with conical holes 35 which traverse that element and assure its adhesion to the concrete to be poured. By assembling a formwork according to the invention, an auxiliary structure 27 (figure 16) is first build up. The auxiliary structure is for example formed by a scaffold of pillars 28 or telescopic metal stanchions, over which a flat board (of wood or plastic) is placed to serve as a surface for the support of the moulds. Once the auxiliary structure has been build up, the base elements are placed thereupon in the way illustrated in figures 1-4. Depending upon the type of formwork to be assembled either unidirectional or bidirectional moulds are used. The bottom planes of the adjacent base elements are connected by means of the first linking means 23, 24, so that a substantially homogeneous bottom plane is obtained, and that substantially no seams are visible. Thereafter adjacent moulds are connected by means of the covering elements placed on top of the base elements. In order to compensate for remaining parts, use is made of the complementary elements. It must be pointed out that each covering plate connects four units of base plate thus obtaining the interconnection of each and every unit of base plate and covering plate used with all of the other units. The complementary elements are than cut into appropriate pieces in order to compensate for said remaining parts. After that, the formwork for the remaining individual elements of the structure (abaci, perimetral beams, secondary beams, juts, etc.) is constructed using the complementary mould. By linking the base elements by means of the covering elements, there is obtained a formwork that remains immobile. Further, due to the fact that the base elements are connected, there is obtained a uniform structure so that substantially no thermal leakage can occur between the different base elements. Once the formwork has been assembled a reinforcement, for example made of iron rod, is placed into said channel (figures 17, 18). After placing said reinforcement the concrete 38 is poured over said reinforcement and said formwork. Figure 19 shows the roofing with the concrete and the formwork. When the concrete has hardened, for example after 96 hours, the auxiliary structure can be removed. Due to the use of the formwork, the auxiliary structure can be removed earlier, because the waterproof surface of the formwork will enable the concrete to maintain its humidity. The relation water/ cement does not change since substantially no water is absorbed by the formwork. The hardening of the concrete is more homogeneous and therefore the concrete will reach faster its resistance, which enables a faster remove of the auxiliary structure. Further due to the presence of the formwork, the concrete does not come into direct contact with the auxiliary structure, so that it is not necessary to clean that auxiliary structure and remove therefrom remaining concrete. This enables a substantial money saving since it is not necessary to clean the auxiliary structure before using it again. The formwork remains thus permanently in the roofing since it remains fixed to the reinforcement and the concrete. The poor thermal conductive characteristics of the formwork enables a substantial energy saving since the heat can no longer pass from one stage to another due to the presence of the isolating material. The system offers many advantages with respect to the remaining traditional construction systems of ribbed slabs. This circumstance permits the partial removal of the auxiliary structure by 40 %, maintaining that necessary for reasons of security for 28 days. The resulting concrete sections conserve the width and continuity projected and have ribs with exact finishes thanks to the undeformability and self-alignment of the moulds. The interconnection of the moulds that form the surface for the placing of the concrete assure an equal distance between the ribs of the slab and the correct position of the reinforcing bars. The result is a continuous and homogeneous structure. The assembly of the moulds and edges with the grooves assures a perfect watertightness of the whole, that together with the impermeability achieved by incorporating resins between the components of the moulds, means a maximum utilisation of the concrete. One advantage derived from this is the increase in the number of times the auxiliary structure can be used as it does not come into contact with either the water of the mixing or that of the curing process. As this system requires the installation of a prior auxiliary structure 27, 28 to serve as support for the moulds, it facilitates, from the beginning, transit over the entire surface formed by the interconnected moulds, reducing the risk of accidents, falls and materials breakage during the period of execution. Given the lightness of the pieces, with this system there is an economizing in the loading, transport and unloading of the moulds, therefore avoiding the use of heavy machinery. There is a decrease in fatigue due to the manipulation of the moulds, in erecting time and in the possibility of mistakes in the assembling of the moulds, given the simplicity of the preparation of the units, which can only be fitted together one way. As the surface provided by the interconnected moulds has a thickness of 3 cm, it facilitates the opening of ceiling chases and provides a useful thickness to house electrical wiring, water, heating and installations. In the zones between ribs, screens and lighting fixtures can be housed. The moulds incorporate in the structure the insulation and soundproofing necessary in ceilings and floors, both the insulation and soundproofing necessary between the various floors of the building, but also with respect to the exterior. There is, therefore, a reduction in energy costs and an increase in comfort because of the absence of temperature jumps (the system presents an ideal surface, acting as a screen for the installation of heating systems under the floor surface). Finally, the material reacts well in case of fire, as it is self-extinguishable and of low inflammability. This contributes great security, both in the execution of the work and later when the moulds, once incorporated in the slab, act as a barrier against the spread of fire.

Claims: A method for assembling a non-recoverable formwork made of a ribbed slab comprising base elements (1-4, 15-18) manufactured from transformed resins and/or expanded polystyrene, wherein an auxiliary structure (27) is built up upon which, in order to form said formwork, said base elements (1, 2, 3, 4), comprising each at least one channel part (6) forming a part of a bedding for a beam of concrete and provided with reinforced walls (9) situated on both sides of said channel part (6), are disposed adjacent to each other, characterized in that the different base elements (1, 2, 3, 4 ) are connected by each time linking at least four adjacet base elements with a covering element (5,14) disposed on the reinforcing walls (9) between two successive channel parts (6) of adjacent base elements. An assembly of elements for a non-recoverable formwork made of a ribbed slab, the said assembly comprising base elements (1, 2, 3, 4) manufactured from transformed resins and/or expanded polystyrene, said base elements,comprising each at least one channel part (6) forming a part of a bedding for a beam of concrete and provided with reinforced walls (9) situated on both sides of said channel part (6), characterized in that the assembly further comprises covering elements (1, 2, 3, 4) which are disposed adjacent to each other and are connected to the base elements by linking at least four adjacent base elements with a covering element (5,14), said covering element being disposed on the reinforcing walls (9) between two successive channel parts (6) of adjacent base elements. An assembly of elements for a non-recoverable formwork, as claimed in claim 2, characterized in that the base elements (15-18) are provided with two channel parts (6, 13) extending substantially in a perpendicular sense to each other, and the covering element (14) is provided with rounded angles being used to link the base elements. An assembly of elements for a non-recoverable formwork, as claimed in anyone of claims 2 or 3, characterized in that the covering elements (5) are provided with third linking means (23a, 24a) comprising a recess (23a) and a projection (24a) to link the base elements (1, 2, 3 and 4) through second linking means (21 and 22), provided on the base elements formed by a first step-like profile (21) having its lower part on a side of the channel (6) and a second step-like profile (22) having its upper part on a side of the channel (6), the second linking means (21 and 22) cooperating with third linking means (23a and 24a) provided on the covering element (5) such that the recess (23a) fits with said first step-like profile (21) and said projection (24a) fits with said second step-like profile (22). An assembly of elements for a non-recoverable formwork, as claimed in anyone of claims 2-4, characterized in that the covering element (5) is assymetrically arranged in relation to the structure of the base element, the base elements (1-4) being provided with reinforcement spacers (25) having an U-shaped profile and serving to support and guide reinforcement made of iron rods (39), said spacers being positioned on the bottom plane of the base element,and in that the bottom plane of the base element is provided with a grid formed by small channels wherein conduits such as electricity, water or gas conduits can be installed (26). An assembly of elements for a non-recoverable formwork, as claimed in anyone of claims 2-5, characterized in that the covering element (5) has inclined border parts (29), and a fourth linking means (30,31) formed by a projection (30) and a recess (31), said projection (30) of a covering element being suitable to fit in a recess (31) of a successive covering element (5), and having notches (32) situated on the top side of the said covering elements for supporting reinforcing rods preferably located on the corners of the covering elements. An assembly of a non-recoverable formwork, as claimed in anyone of claims 2-6, characterized in that it comprises a complementary element (33) provided with linking means (34) for forming unidirectional as well as bidirectional elements, and serving as an additional mould, having one or more recesses (36) and conical holes (35) which traverse that element.

Inventors: RUBIO HERNANDEZ FRANCISCO, SAINZ DE LA MAZA DEL CASTILLO, RUBIO HERNANDEZ, FRANCISCO, SAINZ DE LA MAZA DEL CASTILLO, JOSE ANTONIO, Sainz de la Maza del Castillo, José Antonio
Applicants: SAINZ DE LA MAZA DEL CASTILLO, SAINZ DE LA MAZA DEL CASTILLO, JOSE ANTONIO
Application year: 1991
Main classification: E04B5
IPC codes: E04B5