EP1180563A1

EP1180563A1 - Method for fabricating slabs having polyestyrene arches and prestressed concrete rib and slabs thus fabricated

Info

Publication number: EP1180563A1
Application number: EP00927250A
Authority: EP
Inventors: Jaime Enrique Jimenez Sanchez
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-05-17
Filing date: 2000-05-11
Publication date: 2002-02-20
Anticipated expiration: 2020-05-11
Also published as: AU4568800A; DE60014069D1; PT1180563E; ES2161139A1; ES2161139B1; WO2000070162A1; ATE277241T1; EP1180563B1

Abstract

It relates to a process for fabricating vault type slabs or polystyrene with prestressed concrete buttresses, which employing a modified sliding extruding or moulding machine for continuous production on a pre-stress track, fills in and vibrates the concrete on the polystyrene vaults placed on the track. Said vaults have the shape of the top slab buttress cut out in the vault itself, and simultaneously as it concretes it the machine leaves an alveolus in the centre of each buttress. The prefabricated slab thus obtained is fully self supporting with the same thickness as the traditional forging which it replaces. It comprises two concrete buttresses preferably with a double T shape, and by addition on site of a steel containing compression layer, the building floor joist itself is obtained.

Description

OBJECT OF THE INVENTION

The present invention relates to a buttressed top slab for building structures, which by employing polystyrene or another material as light flooring blocks, embed said structure in the concrete buttresses of the slab, thereby configuring a prefabricated slab in a single body.
The object of this invention is to define the manufacturing process having a sliding extruder or moulder with prestressed joists or alveolar slabs, so that when pouring the concrete into the space left in the vault top slabs, which is normally double-T shaped but may adopt a single -T configuration as well, a vibration ensures that the concrete adheres the top slabs to the concrete buttresses, thus producing a slab with sufficient resistance enabling to manipulate it and walk on it with complete safety.
The system means to replace conventional joists and top slabs with this prefabricated slab in flat structures characteristic of household constructions currently used in Spain and in warm weather countries. Classic joist and vault structures are currently the most inexpensive structures in tropical or Mediterranean climates.

BACKGROUND OF THE INVENTION

Flat joist and top slab structures are those used most widely, due to their efficient use of materials and labour in construction fabrication and assembly. In Nordic and central European countries, where temperatures are low for most of the year, and rainfall is frequent, construction work must be shortened as much as possible to prevent undue labour expenses and reduce the risk of freezing in construction work pouring of concrete. This means that in these Nordic countries prefabricated top slabs are used of the half-slab type, both prestressed and reinforced, or prestressed alveolar slabs, with an absence of classic joist and vault structures.
A further reason for employing prefabricated joist structures is worker safety, as most labour accidents in construction work occur in the structure construction stage, and specifically entail falling of workers due to the vault breaking; this results in wealthier countries dictating standards in which safer systems are demanded, or the floor must be planked entirely in order to prevent the vaults from breaking.
Currently in Spain new safety standards are requiring planks on all floor joists, and therefore the use of joists is diminishing.
Use of prefabricated or alveolar slabs in home construction means that joists must be thicker than slabs, so that false ceilings must be placed which increase the cost of the building compared to the classic plaster whitewash.
Previous to this invention a patent was applied for the same slab with this configuration, although in a static screed or mould, without a moulding machine.
Said invention application is numbered P-9801814 and was filed on 27 August 1998 by the author of the present patent in Spain. Afterwards Chapter I and II of the PCT have been applied for, under registration number PCT/ES99/00273.
The main difference with said invention is the continuous fabrication method, which allows it to be made with less labour and more quickly, in a track 100 to 200 metres long and cut to the desired length with diamond disc.
Connection of the buttress to the support girders is solved by construction placing of a steel connector in the alveolus which bears the slab buttress. Said alveolus is continuous along the entire buttresses. The finished product is further improved as regards end burrs and concrete slurry on the slab, etc.

DESCRIPTION OF THE INVENTION

The invention object of the present memory relates to a type of pre-stressed prefabricated slab with the ensuing time reduction in the construction work as the forging need not be assembled on site, and the absence of a lower planking, as well as providing a solution for support of the prefabricated joists which allows leaving the bottom part of the structure fully flat and ready to receive the inexpensive plaster directly.
The slab may be used with classic unidirectional flat joist floor structures (used to support joists and girders of the forging) as well as for the support of load walls made of brick, and its main advantage is manifested when combining TUL joists consisting of a ferrule cage with a concrete screed. These joists allow to support the structure of said flooring, thus avoiding the expensive construction.
Use of polystyrene top slabs and inferior covering of the concrete buttress with polystyrene provides a great thermal insulation and extra impact sound insulation, while traditional forging cannot provide this on its own.
The slab comprises a prefabrication of width between 0.6 and 2.4 m approximately, with a typical width of 1.2 m as a result of transportation widths and the weight which cranes can lift. The length of the slab can vary depending on the clearance between joists and on the loads, but a typical value is a 19 cm buttresses plus 3 cm polystyrene coating the buttresses on the bottom, which when added to a further 4 cm concrete applied in construction give the 26 cm of traditional top slabs calculated for clearances of 3 to 6 m and typical household loads of 660 kg/m2 of total load.
Each prefabricated slab incorporates two solid concrete or alveolar buttresses of the same width as the slab which stiffen it and prevent planking or support in the construction, so that they are self supporting, as with alveolar slabs. These buttresses may have several shapes, with the most common one being those which have a double -T shape in each buttress, although it may also have a single - T. The double T wings may be rectangular, trapezoidal, triangular, round, etc.
The motive for the top T is that in order to be self supporting a compression head is required for the top concrete wider than the single buttresses; in turn, this greater width by means of the greater contact surface with the poured concrete allows to ensure the transmission of loads through the slope between the two concretes; it also allows the linkage of the lightening material between ribbings, which mainly consists of expanded polystyrene slabs, although ceramic or concrete slabs may also be used. Lastly, because of its greater width it provides greater safety to workers as when walking they will be stepping on concrete areas, not only on the slabs.
The reason for the bottom T is that in the areas where the joist is working in negative torque there is a wider compressed concrete head, thus saving negative steel as compared to traditional narrow bottom buttress floor structures. The bottom wings of the buttresses are further useful in locking the polystyrene or ceramic slabs, preventing them from falling or slipping while the worker walks on them. As the concrete is extruded in factory against them, the adherence between these parts and the buttress concrete is ensured, unlike in traditional joist and slab structures in which the slabs are loose and easily slip from the joists, until the construction concrete is poured.
Naturally, the steel employed to support the positive torques of the joist is incorporated in the bottom part of the buttresses at the time of fabrication. Steel to withstand negative torque is placed on the slab, and confined in place by the compression layer concrete poured in construction. If a compression layer is not incorporated in the construction negative steel may be housed in the open alveolus of the ends.
Steel to be placed on the prefabricate should be prestressed, with the ensuing saving of steel for construction, as the greater elastic limit of these allows to reduce its width considerably as compared to reinforced concrete.
Afterwards in construction, by placing a steel mesh above and pouring 4 or 5 cm more of concrete on all the slabs, the floor joist itself is made. Thus all slabs will operate transversely as well.
Construction of the slab with vaults in-factory entails a further advantage, in that a mould is no longer required to shape the buttresses as the double T shape is achieved with the shape drawn on the polystyrene vaults themselves (or ceramic or concrete), without later removing the framework of the mould required.
Among other advantages of the new slabs is the possibility of reinforcing support areas with cutting steel if calculations so recommend, or further increasing compression heads, both lower and upper, also when required by the calculations. The increased width and reinforcement due to having loads concentrated afterwards on the building is also not a problem as narrower slabs are used to increase the buttresses. The different width of the floor joist is immediately achieved by using thicker or narrower slabs thus adapting to greater or smaller clearances.
The advantage of being self-bearing implies a reduced work in construction assembly, as the classic planking of joists and slabs is not required.
Unlike alveolar slabs, cutting a slab is rather fast as it is only necessary to cut the concrete buttress, and not the two top and bottom slabs of the alveolar slabs, as well as their wider buttresses.
As regards the weight of the finished floor joist, it is lower than the joist and slab floor joist if polystyrene slabs are used, which saves a few kilograms of steel in the calculation. A ceramic slab and joist structure of edge 26 cm weighs 260 kg/m2, while the new structure weighs around 200 kg/m2.
Weight of prefabricated slabs is on the order of 600 kg (for thickness 25 cm, width 1.2 m and length 5 m, typical for homes), which allows current 750 kg cranes to lift these slabs easily. Transport is also much less than for alveolar slabs of the same use, as well as joist and slabs.
Fabrication of angled support slabs can be immediately performed by cutting the required angle on the pre-stress track with a diamond disc.
Plates may be provided with 1, 2, 3 or 4 buttresses, as desired by the designer or the constructor. Buttresses may have several shapes, including rectangular, and thus in order to ensure embedding of the slabs with this type of rectangular buttresses, their walls shall be provided with saw teeth so that the concrete adheres more firmly. On the bottom of the plate the dovetail slots made on the polystyrene slabs every 5 or 10 cm serve to lock the whitewash plaster.
The ends of the support buttresses may have a protruding reinforcement in order to lock the cutting load on the support, according to standards. This connection reinforcement shall be housed in the alveolus which houses the slab buttresses, and the concrete poured in the alveolus ensures the overlapping of this reinforcement with the bottom longitudinal reinforcement of the slab.
Reinforcement of negative torques may be distributed along steel bars of lesser diameter and shared along the entire upper surface of the slabs, not necessarily on top of the buttresses.
The possibility of cutting the polystyrene slab laterally allows in construction to easily adapt to the widths of joists, if these are not multiples of 120 or 60 cm.
As we employ high resistance steel with high resistance concrete, and a considerable thickness, we may place the buttress on the edge of the construction perimeter and serve as an edge band in order to bear the building enclosure; thus saving the traditional edge band.
The main advantage obtained by this novel system shall therefore be economical, as if we evaluate all costs intervening in its fabrication and assembly we obtain the same cost as for a traditional joist and slab structure, which hitherto is considered the cheapest in the market. Despite employing polystyrene slabs, more expensive than those of ceramic or concrete, this is offset by the slab not incorporating any more concrete than a traditional structure, not requiring celosia, reducing the negative torque reinforcement substantially as its compression head is smaller, for a typical thickness of 26 cm it is 60 or 70 kg/cm2 lighter than a traditional reinforced joist structure (if compared to a prestressed joist the weight reduction is greater) thereby saving kilograms of steel in the entire structure, as planking is not required it saves labour, as no special moulds are required investment in manufacturing installations is small, if a prestressed or alveolar joist installation is already available, etc.
A further possibility would be use of extruded or moulded polystyrene slabs (with buttresses) in order to employ less polystyrene and therefore reduce the cost of the slabs.
The general fabrication process for the prestressed slab consists of placing the 1.2 m wide slabs on the track, with the buttresses already formed on the polystyrene.
The moulding machine is provided with two lateral and/or upper traction rollers, which guide the slabs, align them and compress them somewhat against the already moulded slab, achieving greater tightness as well as preventing unwanted floatability of the slabs.
These lateral rollers also serve to prevent the slab from opening due to the concrete pressure and vibrating when passing through the buttresses filler bins.
Rollers may be grooved for a greater grip on the polystyrene. Rollers may also be replaced by endless belts, endless chains or clappers. In addition these guide systems may be powered or not.
A forward filament guide comb will prevent the concrete from overtaking the machine, for which the retainer comb or guillotine shall have the same shape as the buttress (drawn on the polystyrene) and shall slide along the inside of the slabs.
Instead of a comb with the same shape as the buttress and with a clearance of 2 to 10 mm a sliding forward mould can be used, also known as a trumpet, with an approximately rectangular shape and with a clearance with the polystyrene walls of 20 to 30 mm. This forward mould shall be long (between 40 and 100 cm) in order to prevent the concrete from leaving between the former and the slab wall towards the front of the machine. Friction with walls and its permanent forward position with respect to the polystyrene ensure reingestion of any concrete which advances.
A good tightness during filling may be ensured by skids in contact with the polystyrene which slide on it, preventing the lateral exit of the concrete.
In order to configure the inner alveolus of the buttresses we use the same system as for the alveolar slabs, but with a single alveolus. The walls of the slabs will help keep the concrete from deforming, even if it is thin or has a taller than usual Abrans cone.
The slope load between the concrete of the buttress and the compression layer can be ensured by a top striation of the concrete at the end of the machine, leaving an impression, longitudinal canals extruded by the machine itself or by an open alveolus on the top. The alveolus may have zero width (solid buttress), when designing a metal alveolus of the mould with near-zero thickness, but thick enough to ensure an inner vibrating of the buttress.
When resting on prefabricated Tul or concrete screed (approximately 6 cm) with ferrule cage girders, a 6 cm polystyrene layer shall be placed under the buttress, so that in order to rest it is sufficient to cut the polystyrene, whether in shop or better on the construction site, so that the polystyrene edge always touches the edge of the girder screed, preventing gaps when applying the plaster.
Lastly, in order to elevate the slabs they maybe pinched on both sides of the top buttresses wings, even if the slab polystyrene is slightly broken when the clip is applied.
They may also be elevated by laterally pressing on the polystyrene, employing a hook on the ends of the buttresses and housed in the alveolus, leaving steel hooks embedded in the buttresses, etc.
On site stacking or resting on the framework or brick construction shall be performed on short wooden or fibrocement plugs (depending on each case) which shall incrust themselves in the lower polystyrene coating of the buttresses until touching the concrete in the latter.
A solidification may also be performed, by cutting the bottom polystyrene coating of the buttresses before moulding the concrete, marking and measuring the length at which the slab will later be cut. In this way when the moulder is passed pouring concrete, the concrete will descend to the bottom of the track and there will be concrete in sight to rest the framework or load wall of the construction, in this way not spoiling the polystyrene bottom coating of the buttresses.

DESCRIPTION OF THE DRAWINGS

These and further characteristics of the invention will be more clearly understood in view of the accompanying drawings, where for purposes of illustration only the following is shown:
Figure 1 shows a section view of the prefabricated slab for building floor structures in a preferred fabrication. It also shows a cross section of a part of finished forging.
Figure 2 shows a sectional view of the slab with the alveolus open on the top.
Figure 3 shows a sectional view of the slab, with an alveolus and also upper longitudinal grooves.
Figure 4 shows a perspective sectional view of the slab, without the double T shape but with lateral grooves or saw teeth between the concrete buttress and the slab.
Figure 5 shows a perspective view of the emplacement of the slabs on the pre-stress track.
Figure 6 shows a perspective view of a polystyrene slab showing the double T shape of the buttresses cut out on the slab.
Figure 7 shows a perspective view of lateral rollers pressing on a slab.
Figure 8 shows a perspective view of top rollers pressing on the slabs against the track. Also sown is a lateral guide skid.
Figure 9 shows a perspective view of the buttress filling bin, with its front retaining door and its rear fitting mould. Also shown are loose upper sealing skids.
Figure 10 shows a perspective view of a portion of a finished slab with the top buttress cut, the alveolus and a connector housed in it.
Figure 11 shows a perspective view of a slab guide train with lateral rollers, a retention guillotine, fitting mould and rear grooves. Also shown is a section of the finished slab.
Figure 12 shows a perspective view and a front view of a filling bin with a front retention guillotine, and a further filling bin with a front retention pre-mould which by friction prevents the concrete from sliding forward.
Figure 13 shows a sectional view of a Tul or concrete screed type joist and tow slabs bearing on said joist.
Figure 14 shows a sectional view of a slab with one of its buttresses acting as an edge band for a floor joist.
Figure 15 shows a perspective view of raising hooks for the slab.

PREFERRED EMBODIMENT OF THE INVENTION

A preferred embodiment is described with reference to the figures of a slab (1) comprising two concrete buttresses (2) and a polystyrene or other material vault (3). Inside said buttresses is housed reinforcement (4), required to withstand the positive torques of the floor joist.
In order to make floor joist (5) on site the slabs shall be placed parallel to each other, resting on the load girders of the structure, and the floor joist shall be completed by placing reinforcement (6) meant to withstand negative torques and by on-site addition of a steel mesh (7) and a thin concrete compression layer (8).
Slab buttresses (2) may have a double T shape with bottom wings (9) required to support vaults (3) and to act as compressed heads when the floor joist is under negative torques. At the top part of double T shaped buttresses (2), wings (10) will also allow to support vaults (3), also forming a compression head to withstand positive torques of the slab when placed on work, so that they are self bearing, and ensures transmission of loads between buttress (2) and compression layer (8) of the work through rough surface (11) relating the two concretes. Said rough surface (11) is made by scraping the surface or by any other existing means, such as gravure.
Scraping (11) may be replaced by a deep open alveolus (12) or by top longitudinal grooves (13), or by half a top-open shallow alveolus (14). A further alternative is to make grooves (15) on the sides of vaults (3) inside the buttresses, in order to ensure a good attachment between the concrete and the vault.
Double T wings (10) may have various shapes, ranging from triangular to trapezoidal, rectangular or round.
In order to manufacture the part using an extruder or a sliding moulding machine with a prestressed joist or alveolar slab, vaults (16) measuring between 1 and 6 m shall be placed on the pre-stress track. Said vaults will bear a cut-out of the shape (17) of the concrete buttresses.
In order to align, guide and tighten vaults (16) on the pre-stress track, lateral rollers (18) which may be tractioning or not shall be used, pressing on the vault and forcing it to align and compress against the concreted vaults. Whenever a roller is referred to, an endless belt, a chain or a clapper may also be employed. The same can be achieved using top rollers (19) and lateral skids (20).
The concrete is filled by pouring the contents of the moulding machine bin on the buttress space drawn in the vault, using lateral skids (21) which prevent the concrete from exiting between the filling bin (22) and the vault through the contact groove (23).
The concrete is retained on the front of the machine by a retaining guillotine (24) of the type used in these machines, with the shape of the buttress.
Lastly, the concrete is retained on the back using a fitting mould (25) with an inner alveolus, normally used with this type of machine, which by friction and plugging prevents the concrete from puffing at the machine output (26).
A better grip between the compression layer and the slab concrete buttress may be obtained using a top striation (27) of the buttress.
As the cut is perfectly clean using a diamond disc, without the possibility of pre-stress output reinforcement in front and behind the slab, a connector (29) can be housed in alveolus (28) which by means of the concrete provided in the construction site causes the overlap between the connector and slab steel.
Figure 11 shows a full fabrication line comprising a roller (18) guide and alignment area, a retaining gate (24), a filling area with bin and inner alveolus (22), in addition to lateral rollers to offer the concreting pressure (30), a fitting mould with alveolus (25) and lastly a striation area (27). Thus the prefabricated slab (1) with an alveolar (28) buttresses (3) is obtained.
Figure 12 shows separately the retention guillotine (24) which may be replaced by a forward trumpet, pre-mould or friction plug (31), comprising a wide skid (32) which bears on the vault, and a buttress (33) with a rectangular section, separated from the polystyrene walls by 20 to 30 mm.
In this same figure is shown the filling bin for each buttress and the rear fitting mould (25) with its metallic cylinder (34) which shapes the buttress alveolus.
The front view of said set aids in differentiating the two types of forward retainers, the guillotine (24) and friction plug (31). Also remarked is the lateral sealing by skid (23) on the vault.
In order to rest the concrete screed Tul type girder (35) with a ferrule cage (36), it will suffice to have a bottom coating of polystyrene (37) of the same thickness as screed (35), then cutting out excess polystyrene and resting concrete buttress (2) directly on the girder screed. In order to not reduce the calculation width of the girder due to interference with the polystyrene vaults and absorb possible errors, girder screed (35) shall be made 5 or 10 cm wider on each side than obtained from a calculation. By cutting off excess polystyrene on site, groove (38) left between the bottom area of slab (2) and the edge of screed (35) is reduced practically to nothing. Thus the plaster wash will not have to cover too large grooves.
Considering the substantial thickness existing, if the want the joist to have the same thickness as the load girders (normally 26 cm) and as we are using prestressed steel, we can replace the girder of the floor joist edge of work edge closure (39) by a reinforced buttress (40) with cutting reinforcement if required.
Lastly, to raise and handle the prefabricate we may pinch the edges of each buttress (41) with a gravity or hydraulic clamp (42) incrusted in vault (43), searching for the lower area of the top wing of the double T of the concrete buttress. We may also use a hook on the ends of the buttresses and insert it in the alveolus, press on the polystyrene sides of the slab, hooks inserted in the fresh concrete, etc.
This description is not extended with the understanding that any expert in the field will understand the scope of the invention and the advantages derived thereof.
Materials, shapes, size and arrangement of elements are subject to variation as long as the essence of the invention is unaltered.
The terms used in this description are to be understood in a wide and non-limiting sense.

Claims

Fabrication process for polystyrene vault and pre-stressed concrete floor joist top slabs and top slabs obtained thereof; as a continuous production PROCESS: of single T, double T, tubular, inverted ribbed slab or alveolar slab joists; in a long track of 100 to 200 m with pre-stressed steel, using a concrete moulding or extruding machine, with length cut by a diamond disc machine; characterised in that on the fabrication track are placed the vaults of polystyrene or another similar material with the buttresses etched in the vaults, so that they are all aligned on the track; afterwards the pre-stress cables are placed inside the buttresses and stressed; then a moulding type machine is placed above the vaults, resting on the track rails, and the buttresses are continuously filled with concrete, with the machine leaving one or several closed alveoli (28) of the alveolar slab type or tubular joist type, or one or several open top alveoli; thus once the track is concreted the concrete is allowed to set and later cut with a diamond disc to the desired length. On the construction site, inside the alveoli and extending beyond the edges is placed a reinforcement or connector which shall connect the buttresses to the support girder.
Fabrication process for polystyrene vault and pre-stressed concrete floor joist top slabs and top slabs obtained thereof, performed with a moulding or extruding MACHINE of the type employed to manufacture prestressed joists or prestressed alveolar slabs, comprising a screed with wheels on rails, a filling bin, a vibrating mould, a retention guillotine and a rear fitting mould; characterised in that the machine is provided with lateral traction rollers (18) which guide, align and compress the vaults without concrete against those already concreted, and bear the concreting pressure so that the vaults do not open, or it may incorporate top traction rollers (19) in order to also guide, compress and even prevent floatability of the vaults.
Fabrication process for floor joist top slabs as in claim 2, characterised in that the lateral or top rollers may be replaced by endless belts which equally press on the vaults, or by endless chains, or oscillating metal pushers which clap, known as clappers, as they imitate a clapping motion.
Fabrication process for floor joist top slabs as in claims 2 and 3, characterised in that the machine may incorporate top skids (21) or lateral skids (20) which guide and align polystyrene vaults (16).
Fabrication process for floor joist top slabs as in claims 2 to 4, characterised in that the concrete is poured using upper filling bins (22), with sides sealed with corresponding vertical skids (21).
Fabrication process for floor joist top slabs as in claims 2 to 5, characterised in that the concrete may be retained in the forward are of the machine while the buttresses are filled using a retaining guillotine (24) designed with the same shape as the buttress outline but having a clearance of a few millimetres.
Fabrication process for floor joist top slabs as in claims 2 to 5, characterised in that the concrete may be retained in the forward area of the machine while the buttresses are filled using a retaining pre-mould (31) comprising a wide upper skid (32) which grazes the vault and a vertical rectangular core (33) similar in width to the buttress but with a considerable clearance of a few centimetres. This mould shall be long enough to retain by friction and reingest the buttress concrete which tries to advance.
Fabrication process for floor joist top slabs as in claims 2 to 7, characterised in that the concrete may be retained in the forward area of the machine by placing a rear fitting mould (25) of a suitable length which by friction prevents the alveolus from collapsing and/or the swelling of the upper surface of buttress (27) at the output of the machine. Said fitting mould shall be provided with metallic cylinders (34) which conform alveolus (28) inside the buttress, as well as the longitudinal grooves (13) or large groove (14) according to the design.
Fabrication process for polystyrene vault and pre-stressed concrete floor joist top slabs and top slabs obtained thereof of the prefabricated SLAB type comprising ceramic or polystyrene vaults and strong solid buttresses of reinforced or prestressed concrete with a double or single T shape normally, and with the double T wings having a rectangular, trapezoidal, triangular or round shape, concreted before being placed on site, with the buttress edge equal to that of the vaults, as well as with or without a polystyrene coating under the buttresses; characterised in that the slab obtained thus has its ends cut with a diamond disc, without reinforcement extending beyond the concrete buttress ends, nor concrete strut or buttress extending beyond the end; with the section solid or incorporating one or several closed alveoli (28) or alveoli open on the top (12).
Fabrication process for floor joist top slabs as in claim 9, characterised in that connector (29) of the bottom part of the buttresses is housed in alveolus (28) or (12) of the buttress and in its lower area, so that when the construction concrete is poured it enters the alveolus or groove and overlaps the connector and the buttress.
Fabrication process for floor joist top slabs as in claims 9 and 10, characterised in that the upper face of the buttress may have a striation (27) made by the machine itself on passing, or longitudinal grooves (13) made by the fitting mould.
Fabrication process for floor joist top slabs as in claims 9 and 10, characterised in that the buttress may be vertical rectangular in shape, with lateral saw teeth or grooves (15) which place in contact the polystyrene and the concrete, with a top longitudinal groove (14).
Fabrication process for floor joist top slabs as in claims 9 and 10, characterised in that in order to rest the slabs on prefabricated concrete screed girders (35) with a ferrule cage (36), buttress (2) shall be given a bottom polystyrene coating (37) of the same thickness as screed (35) of the girder, so that the polystyrene may be cut on site as much as the slab rests on the girder, leaving a minimum groove (38).
Fabrication process for floor joist top slabs as in claims 9 and 10, characterised in that one of the slab buttresses may be used as an edge girder, which conveniently reinforced shall bear the weight of enclosure (39) of the work. For this the lateral vault shall be cut and the mason work shall be laid on outer buttress (40).
Fabrication process for floor joist top slabs as in claims 9 and 10, characterised in that the slabs are raised and handled using a gravity or hydraulic clamp (42) attached beneath top wings (41) of the buttresses, for which polystyrene (43) is locally trimmed by clamp (42).
Fabrication process for floor joist top slabs as in claims 9 and 10, characterised in that in order to prevent the internal polystyrene coating of the buttresses from being squashed, fibrocement or wooden blocks either triangular or trapezoidal in shape may be provided embedded in the polystyrene until they touch the concrete under the slab buttress.
Fabrication process for floor joist top slabs as in claims 9 and 10, characterised in that in order to prevent the polystyrene from being squashed under the buttresses when supporting weight, they may be filled in underneath by trimming the lower polystyrene before concreting the slab, measuring and indicating the cut length of the slab previously.