METHOD OF MOULDING A FLOOR PLATE OF CONCRETE

Abstract: The invention relates to a method in concreting a floor structure slab (10) wherein the lower side of the floor structure slab is concreted against a heat and sound insulating rigid panel (11) provided as a formwork element, which is allowed to remain at the lower side of the floor structure slab after setting of the concrete. The invention also relates to an intermediate floor structure having a floor structure slab (10) of concrete with underfloor heating elements (13) embedded therein, a heat and sound insulation panel (11) being provided at the lower side of the slab.

Description: Method of moulding a floor plate of concrete The invention relates to a method in concreting a floor slab, preferably a floor slab in an intermediate floor structure underfloor heating elements being embedded into the slab, such as ducts for circulating hot air for supplying heat to the floor slab in order to satisfy the heat requirement of the upper floor. In that case it is required at one hand that the floor slab has a good heat insulation on the lower side thereof and that the floor covering material applied to the upper side of the floor slab is not greatly heat insulating in order that the desired heat transmission to the upper floor will be obtained, and at the other hand that the con¬ crete floor structure is provided with some type of sound insulation at the upper side thereof in order to obtain an acceptable sound reduction between the floors, which is contrary to the requirements for the heat transmission because such sound insulation also provides increased heat insulation. The purpose of the invention is to provide a floor structure preferably an intermediate floor structure with underfloor heating elements, which at low costs combines technical requirements mentioned above regarding heat and sound insulation, and for this purpose it is proposed according to the invention a method of the kind referred to above with the characterizing features of claim 1. The invention also relates to an intermediate floor structure with a concrete floor slab with underfloor heat¬ ing elements embedded therein, with the characterizing fea¬ tures of claim 10. The invention provides the advantage that the floor structure can be manufactured at lower costs and less efforts in relation to the technique now used wherein either a pre-fabricated thin concrete slab (usually having a thickness of 40 mm) is used as formwork element and then is allowed to form part of the floor structure, or conven- tional formwork is used the formwork being stripped and the elements thereof being cleaned after concreting. In both cases the heat insulation must be attached to the floor slab at the lower side thereof special expensive studs being used in order to satisfy existing requirements as to sound insulation. The heat and sound insulating panel used in the method and the intermediate floor structure according to the invention preferably comprises a sandwich element hav¬ ing an intermediate heat and sound insulating layer of foamed plastic or the like, and surface layers of plywood. A special smart feature of the preferred embodiment of the invention is that the sandwich element functioning as formwork element is attached to the floor slab by means of sound absorbing attachments so that the sandwich element after concreting of the floor slab can be lowered from the lower side thereof an air gap being formed between the floor slab and the sandwich element improving the sound absorbing properties of the floor structure. The upper sound insulation then can be reduced and the heat supply to the upper floor be improved. The width of the sound insu¬ lating gap can be determined by calculation or by local tests. A further advantage of the invention is that a sand¬ wich element of the kind referred to above easily can be provided on the lower side thereof with a covering of of any kind e.g. gypsum plaster board. Illustrative embodiments of the invention will be described in more detail below reference being made to the accompanying drawings wherein FIG. 1 is a vertical cross-sectional view illustrat¬ ing concreting of the floor slab, FIG. 2 is a corresponding view as that in FIG. 1 and discloses the finished floor structure with a sandwich ele- ment engaging tightly the lower side of the floor slab, FIG. 3 is a corresponding view as that in FIG. 2 but discloses the sandwich element in a lowered position so that there is a gap between the lower side of the floor slab and the upper side of the sandwich element, FIG. 4 is an enlarged fragmentary vertical cross-sec¬ tional view of a fastening element for adjustably connect¬ ing the floor slab and the sandwich element which engages tightly the lower side of the floor slab, FIG. 5 is a view similar to that in FIG. 4 but with the fastening element adjusted such that there is gap between the sandwich element and the lower side of the floor slab, FIG. 6 is a diagram illustrating the result of impact sound measurement on a floor structure according to the invention with a sandwich element engaging tightly the floor slab and without floor convering on the upper side of the floor structure, FIG. 7 is a corresponding diagram as that in FIG. 6 relating to the same kind of floor structure but with a gap between the floor slab and the sandwich element, FIG. 8 is a diagram disclosing a comparison between the diagrams in FIGS. 6 and 7, and FIGS. 9 and 10 are corresponding diagrams as those in FIGS. 6 and 7 relating to a corresponding floor structure but with a plastic carpet as floor covering on the upper side of the floor slab. In a building there shall be concreted according to FIG. 1 a floor slab 10 on formwork elements 11 which are supported at a correct level by conventional props 12. If Legalett heating system shall be installed ducts 13 should be embedded into the floor structure for circulating hot air as indicated in the drawing, but other floor heating elements can be embedded into the concrete. Also necessary steel reinforcement should be embedded into the concrete though this has not been shown in the drawing, and in order to reduce the weight of the floor structure also foamed plastic bodies can be embedded into the concrete. The formwork elements are of a special embodiment; reference is made also to FIG. 4. They comprise sandwich elements having a core 14 of a suitable heat and sound insulating rigid material such as foamed plastic or cemented mineral wool board. Surface layers 15 are attached (by gluing) to both sides of the core 14. The surface lay¬ ers can comprise plywood panels, gypsum plaster boards, metal sheet, or any other material suitable for the pur¬ pose. In the preferred embodiment the sandwich element has a core 14 of foamed plastic having a thickness of 50 mm, and surface layers of 6.5 mm plywood and is made in conventional modular size of 1.2 x 2.4 m. Such a sandwich element has a weight which allows manual handling thereof, which is of course a substantial advantage from an ergo¬ nomic point of view. Due to the sandwich structure the sandwich element is sufficiently rigid in order to serve as a formwork element at concreting of the slab. In order to secure the sandwich elements in the con¬ crete special fastening means 16 are provided, which shall also be embedded into the concrete. The construction of these fastening elements is disclosed in FIGS. 4 and 5. The fastening element includes a metal socket 17 forming a flange 18 at one end thereof, an anchoring stirrup 19, a cross-shaped element, or an element of another shape which can provide a good anchorage in the concrete being attached to the other end of the socket. The anchorage stirrup is used for anchoring and accurately fixing installations (ducts for air circulation, building installation pipes, electrical wiring pipes etc.) so that they are prevented from floating up or changing position during concreting. For the same purpose the fastening element is provided with flaps 19A having apertures wherein such anchoring can take place. A threaded blind hole 20 extends from the end of the socket 17 where the flange 18 is located nearly to the other end of the socket. A screw bolt 21 is screwed into the blind hole. A metal washer 22 is provided on the bolt between the head thereof and a block 23 of sponge rubber or similar material. The bolt passes with clearance through an aperture 24 in the upper plywood panel 15, the block 23, the washer 22, and the bolt head being received in a wider aperture 25 extending through the lower plywood panel 15 and the insulating layer 14. The bolt 21 is tightened with the flange 18 and the block 23 engaging opposite sides of the upper plywood panel and with the socket 17 projecting from the upper side of the upper plywood panel to be embed¬ ded into the concrete as shown in FIG. 1. When the concreting has been finished and the con- crete has set there is obtained a concrete floor structure according to FIG. 2. The sandwich element has now fulfilled its task as formwork element but is allowed to remain on the concrete slab 10 engaging tightly the lower side thereof and securely anchored in the slab by means of the fastening elements 16 in order now to serve as a heat and sound insulating layer at the lower side of the concrete slab. The attachment in the slab as made sound absorbing by means of the block 23 of sponge rubber or the like. This sound absorption can, however, be provided in another raan- ner than that shown herein by using any of the elements existing on the market for vibration absorbing suspension of machines or the like. It is also possible to replace the fastening elements shown and described by simple wall ties attached to the sandwich element and anchored to the rein- forcement or the ducts in the concrete slab or solely in the concrete itself. The purpose of heat and sound insulating sandwich element at the lower side of the concrete slab is to attenuate the heat transmission at the lower side of the floor structure so that the heat transmitted to the con¬ crete slab by the ducts or other underfloor heating ele¬ ments is directed upwards to the space above the floor structure. The purpose of the sandwich element is also to attenuate the sound transmission through the floor struc¬ ture particularly the transmission of impact sound from the upper floor to the lower floor. The sandwich element can be provided with a suitable ceiling lining at the lower side thereof e.g. gypsum plas- ter boards 26, FIG. 5, which covers the apertures 25. The sound insulation of the floor structure fabri¬ cated as described above can be improved in a very simple manner. By unscrewing the bolts 21 in their respective sockets 17 so that the sandwich element 11 will be lowered from the concrete slab there can be provided a gap 27 between the slab and the sandwich element in the manner disclosed in FIGS. 3 and 5. In order that the sandwich ele¬ ment will not adhere to the slab it should be coated with form oil at the upper side thereof before concreting so that it will be easily released from the concrete slab when it shall be lowered. For the same purpose a plastic foil can instead be provided at the upper side of the sandwich element. The width of the gap has to be determined by cal¬ culations or local measurements. Practical measurements have been made on the floor structure of the invention in order to investigate the sound insulating property thereof. These measurements have referred to the impact sound insulation because it is only with regard to this insulation that specific measures have to be taken; in order that the requirements regarding the air born sound insulation shall be satisfied usually no specific measures are required as far as concrete floor structures are concerned. The results of the measurements are illustrated in FIGS. 6 to 10. FIG. 6 discloses the result of impact sound measure¬ ments according to Swedish standard SIS 02 52 54 within the standardised frequency interval ranging from 100 to 3150 Hz for an intermediate floor structure according to FIG. 2 with heating ducts 13 embedded therein and with a surface weight of the concrete slab of 460 kg/m . The measurements refer to a space volume of 27.5 m . The sandwich element 11 had a core 14 of foamed plastic having a thickness of 50 mm, and the two surface layers 15 consisted of 6.5 mm ply¬ wood. At the lower side on the lower plywood panel there was attached a 13 mm gypsum plaster board as shown at 26 in FIG. 5. The fine graph represents the measured values according to the columns to the right of the diagram while the bold graph is the reference graph for impact sound level inserted in accordance with the standard mentioned above. As will be seen the measured graph is located sub¬ stantially below the reference graph particularly in the lower frequency range which is of special interest in this connection. The value of the weighted impact sound level Lnw calculated in accordance with the standard mentioned was at 73 dB. FIG. 7 discloses the results of a corresponding meas¬ urement with the sandwich panel 11 lowered 40 mm according to FIG. 3. Then, there was obtained a value of Lnw of 72 dB, and also in this case the measured graph is located considerably below the reference graph and moreover also at higher frequencies. FIG. 8 discloses a comparison of the measured graphs in FIGS. 6 and 7 in order to illustrate the improvement of the impact sound insulation obtained by low¬ ering the sandwich element the solid graph corresponding to that in FIG. 6 and the dashed graph corresponding to that in FIG. 7. FIGS. 9 and 10 refer to corresponding measurements as those in FIGS. 6 and 7 but with a plastics floor covering at the upper side of the floor structure, and in this case there is obtained a more accentuated improvement of the impact sound insulation. According to FIG. 9 with the sand¬ wich element engaging tightly the lower side of the floor slab Lnw was 62 dB, and according to FIG. 10 with a 40 mm gap between the floor slab and the sandwich element Lnw was 54 dB. Besides allowing a simplification of the method in concreting a floor structure by using an element of the floor structure, viz. the sandwich element, as a formwork element at concreting the invention also provides an improved sound insulation as compared with conventionally concrete floor structures, combined with the possibility of directing the heat transmission from heating ducts embedded into the floor structure, to the floor space located above the floor structure.

Claims: CLAIMS 1. Method in concreting a floor structure slab (10), c h a r a c t e r i z e d in that the lower side of the floor structure is concreted against a heat and sound insu- lating rigid panel (11) provided as formwork element, which is allowed to remain at the lower side of the floor struc¬ ture slab after setting of the concrete. 2. Method according to claim 1 c h a r a c t e r i z e d in that the panel (11) comprises a sandwich element having a heat and sound insulating layer (14) between surface layers (15) preferably of plywood attached to the heat and sound insulating layer. 3. Method according to claim 1 or 2 c h a r a c t e r i z e d in that fastening elements (16) for the heat- and sound insulating panel (11) are embedded into the floor structure slab (10) by the concreting. 4. Method according to any of claims 1 to 3 c h a r a c t e r i z e d in that the fastening elements (16) are provided with sound absorbing means (23) . 5. Method according to any of claims 1 to 4 c h a r a c t e r i z e d in that the heat and sound insu¬ lating panel (11) is left at the lower side of the floor structure slab (10) engaging tightly the lower side. 6. Method according to any of claims 1 to 4 c h a r a c t e r i z e d in that the heat and sound insu¬ lating panel (11) after setting of the concrete is lowered from the lower side of the floor structure slab (10) a gap (27) being provided between the lower side of the floor structure slab and the upper side of the panel. 7. Method according to claims 3 or 4 and 6 c h a r a c t e r i z e d in that the fastening elements are made adjustable for adjusting the width of the gap between the floor structure slab (10) and the heat and sound insulating panel (11) . 8. Method according to any of claims 1 to 7 c h a r a c t e r i z e d in that underfloor heating ele¬ ments (13) are embedded into the floor structure slab (10) by the concreting. 9. Method according to claim 8 c h a r a c t e r i z e d in that the underfloor heating elements (13) comprise ducts for circulating hot air. 10. Intermediate floor structure having a floor structure slab (10) of concrete with underfloor heating elements (13) embedded therein c h a r a c t e r i z e d in that a heat and sound insu¬ lating rigid panel (11) is provided at the lower side of the floor structure slab. 11. Intermediate floor structure according to claim 10 c h a r a c t e r i z e d in that a gap (27) is pro¬ vided between the lower side of the floor structure slab (10) and the upper side of the heat and sound insulating rigid panel (11) . 12. Intermediate floor structure according to claim 11 c h a r a c t e r i z e d in that adjustable connecting elements (16) are provided between the floor structure slab (10) and the heat and sound insulating panel (11) for adjustment of the width of the gap. 13. Intermediate floor structure according to claim 12 c h a r a c t e r i z e d in that the heat and sound insulating panel (11) comprises a sandwich element with a heat and sound insulating layer (14) between surface layers (15) preferably of plywood, attached to the heat and sound insulating layer.

Inventors: THORSTENSSON SVEN-HUGO, THORSTENSSON, SVEN-HUGO
Applicants: LEGALETT INTERNATIONAL AB, THORSTENSSON SVEN HUGO, THORSTENSSON, SVEN-HUGO
Application year: 1996
Main classification: E04B5
IPC codes: E04B5, E04B9