FR2618474A1 - Process and device for removal of water from concrete poured into shuttering - Google Patents

Abstract

Before the concrete is poured at least one drain 1 is positioned in the shuttering 8. Concrete is poured into the shuttering 8 around the drain 1. The drain is connected to a vacuum source 40 so that it sucks through the drain 1, at the very heart of the concrete 6, part of the water which is there. Construction of walls or other concrete units.

Description

The present invention relates to a method and a device
spinning concrete poured into a casing.

By formwork we mean any device in the broad sense that
allows to receive poured concrete and to retain it during setting (in
giving it the interior form of the formwork). The invention applies
as well as the manufacturing of concrete elements on a site - for example
full of shuttered concrete walls of a house - only prefabrication in
concrete elements factory, for example concrete walls.

By concrete we mean a mixture of cement, sand,
gravel and hardenable water, common mixture in building.

So that concrete is sufficiently fluid and can be
correctly poured into a formwork, it must contain a quantity
significant water. However, the presence of this abundant water cons
a disadvantage during the subsequent phase of taking is that
ie hardening of the concrete. Indeed, excess water slows sen
if taken, delaying the possibility of stripping and increasing
consequently, the shutdown time of the formwork. The presence
of this water is also a cause of mechanical weakening of the
finished concrete, this concrete being crackable and porous.

It is well known that the spinning of concrete, which consists of
extract a certain amount of water from it before and during the
taken, improves characteristics or concrete. For this purpose
the following techniques have already been proposed
1 - Spinning by centrifugation. This process, which consists
rotate the formwork containing the concrete around an axis of
so as to drive the densest components outwards,
collects water in the central area of the concrete, then evacuates
Unfortunately, this process can only be done when
manufacture of hollow revolution parts, such as pipes or
hollow posts, which considerably limits its interest. Furthermore, it
requires relatively complicated, expensive, and difficult to
enforce.

 2 - Spin by pressure. In this technique, a screen forming a filter is provided on the outside of the concrete (against the walls of the formwork) and an inflatable rubber bladder is placed in the center of the formwork (within the concrete leads). After pouring the concrete, the bladder is inflated using compressed air. This compression draws the excess water out of the concrete, towards the outside, through the screen. Unfortunately this process is very delicate to implement because it requires to be effective the action of high frequency vibrations during spinning, the entire device having to be mounted on a vibrating table. On the other hand, it is only applicable to the production of concrete elements having a central opening (corresponding to the bladder) of relatively large size.

 3 - Spinning by vacuum. According to this technique, after pouring the concrete, a suction bell provided with a filter mat is placed on one of the faces of the poured concrete element. The excess water is sucked out of the concrete and discharged into a tank.

 Unfortunately, this process is also of limited use because the filter mat can only be correctly placed against a flat and free face (excluding formwork), of dimensions adapted to those of the mat, and devoid of any opening or reservation; furthermore, the equipment necessary for implementing the method is extremely expensive, bulky and difficult to maintain. A process of this kind is described, for example, in French patent No. 2,312,624.

 The invention aims to solve these various problems by proposing a method of spinning concrete which is effective, easy to implement by low-skilled personnel, inexpensive, and which can be used for the manufacture of concrete elements having shapes and having various dimensions.

These various results are achieved in the process according to the invention thanks to the fact that the procedure is as follows
a) at least one drain and preferably a series of drains are placed in the formwork, before pouring the concrete
b) the concrete is poured into the formwork, around the drain (s)
c) the drain (s) are connected to a vacuum source so as to draw through the drain (s), within the concrete itself, part of the water therein .

 Spinning is therefore done by means of drains which are embedded in the very heart of the concrete; naturally after hardening, the drains remain in place in the concrete.

 In a preferred embodiment of the invention there is provided a series of drains which are placed in the formwork parallel to each other, all of these drains being connected to a common vacuum source.

 Preferably, to avoid voids remaining inside the concrete, which could harm its solidity, the drains are filled at the end of the spinning operation with a cement grout or a similar hardenable material.

 In this case, the filling of the drains with the cement slurry can advantageously be done by suction by means of the vacuum source which has been used for spinning; this filling takes place after the drains have been placed in communication with a tank containing the wax grout (or the similar material).

When you want to make a vertical concrete wall,
especially on a site, there are preferably vertica drains
in the formwork, and these drains are cleared when they enter
low mite in a common pipe which is connected to the vacuum source
in this hypothesis, it is advantageous to communicate the
drains by their opposite end (high end) with a conduit
common this being connected, via a valve, to a tank containing
cement grout or the like.

Thus, vacuum spinning is done while the valve is
vermée; at the end of the spin, the valve is opened, so as to suck
the cement grout inside the drains.

The drains preferably have a slightly frustoconical shape
whose large base is arranged at the bottom.

Because the drains remain in place in the concrete after
manufacturing, these drains can naturally contribute to strengthening
concrete mechanics; when a reinforcement is provided before casting, for
example a trellis, inside the formwork, it is possible to fix
simply the drains to this frame, which facilitates the installation
and retaining the assembly in the formwork.

The invention also relates to a device for wringing the
concrete, the latter being characterized in that it comprises a series of
drains which communicate via a hose with a suction source such as a vacuum pump.

 Other characteristics and advantages of the invention will appear from the description and the appended drawings which show a preferred embodiment thereof.

On the drawings
- Figure 1 shows in cross section corresponding to the plane (l) - (l) of Figure 2, a device according to the invention implemented in a formwork in which one has just poured concrete for the manufacture of 'a vertical wall
- Figure 2 is a side view seen by the plane (ll) - (ll) of the device of Figure 1, before pouring the concrete
- Figure 3 shows on an enlarged scale a cross section of a drain fitted to the device of Figures 1 and 2.

 In the figures is shown a wringing device according to the invention, which is used in the construction of a vertical concrete wall. Traditionally, a formwork 8 is provided consisting of two wooden plates - or formwork - which are held vertically at a certain distance from one another by means of suitable connecting members, these members comprising by example of the struts 80.

 According to the invention, a wringing device is placed in the formwork, before pouring the concrete. This includes a series of drains, referenced 1, arranged vertically. As seen in FIG. 3, each of the drains 1 is composed of an outer tube 10 having a multitude of small holes 11, an inner tube 13 also having orifices 14, and a filter lining 12 trapped between the two tubes 10 and 13; the outer tube 10 is for example a metal tube or a mechanically resistant plastic material; the inner tube 13 can be of construction similar to that of the outer tube 10 or in a variant be constituted by a simple metal mesh.

 The lining 12 is for example a filtering metallic wool wound around the inner tube 13; the winding is advantageously made more tightly at the upper part of the drain, for example over a length of 80 centimeters.

In the example shown, the forms 8 have a height L which
is for example 2.40 meters and they are spaced from each other
with a width 1 of the order of 0.2 meters. Drains have a height of
2.30 meters and are spaced from each other by a distance d of the order of 30 centimeters.

Although only two drains have been depicted in the figure
re 2, it is understood that a series of regularly spaced drains
is provided in the formwork, over the entire length thereof.

According to an important characteristic of the invention, the
drains 1 are slightly frustoconical, their large base being located in
low. The outside diameter D1 of each drain is for example 13
millimeters at its upper end and 17 millimeters at its end
low, while the inside diameter D2 is 8 millimeters at the top
and 13 millimeters below.

In Figures 1 and 2, the diameter dimension of the drains has
therefore represented proportionally larger than the dimension
to improve the clarity of the drawings.

The drains 1 are fixed, parallel to each other, on
a frame 2 such as a trellis intended to reinforce the concrete wall;
the fixing is done by any suitable means, for example by attacks
wire frames (not shown).

At their lower part the drains 1 penetrate, so
substantially waterproof, in a horizontal pipe 3 which extends over the entire
length of formwork, short distance above ground S.

The pipe 3 comes out from one of its ends of the formwork 8
and is connected by another pipe 4 to a vacuum pump 40; this one
is advantageously fitted with a pressure gauge 41. The other end of the
hose 3 is closed.

At their upper part lb the drains 1 are connected, by the in
tubing 50, to a horizontal conduit 5 which is located
the outside of the formwork 8; the pipes 50 are for example fitted together
on the ends lb of the drains. The conduit 5 is connected, via a valve
7, to a tank 9 which contains a cement grout (liquid cement) or
a similar fluid and curable material.

 The device which has just been described is used in the following manner.

 The formwork 8 is erected on the ground S at the desired location. The operator sets up the assembly constituted by the frame 2, the drains 1, and the pipe 3, in the central region of the formwork. This assembly is kept in the correct position by suitable means, not shown, such as spacers.

 Then the operator sets up the pipes 50 on the upper ends lb of the drains 1, and pours the concrete 6 inside the formwork.

 As soon as the concrete 6 is poured, the valve 7 being closed, it starts the vacuum pump 40. A suction is therefore created in the pipe 3 and in each of the drains 1, suction which causes the extraction of the water. in excess in the concrete, which leads to a core spin from the concrete.

 Experience has shown that it is advantageous, in order to obtain a regular spin, to apply a constant depression, that is to say one which does not vary over time, in the drains; the pressure gauge 41 makes it possible to control the vacuum.

 For a wall width 1 of 20 centimeters, a vacuum of - 0.8 kgf / cm2 will be applied for example below atmospheric pressure; the spin time will be approximately 15 minutes.

 It goes without saying that the duration of the spin will be greater the lower the vacuum in the drains.

 The water is drawn in symmetrically with respect to the axis of the drains, the zone of influence corresponding to a radius of approximately 15 centimeters around each drain.

 Thanks to the slightly frustoconical shape of the drains, the spin is faster at the base of the concrete; the mass of the concrete located at the top remaining more plastic, it can flow downwards by gravity, and thus compensate for the faster withdrawal of the concrete at the base; this arrangement makes it possible to limit the surface deformations resulting from the spin.

 The rigid outer tube 10 of the drains prevents sagging of the drains, absorbing the mechanical forces which result from the suction; The metallic wool lining 12 prevents the cement from passing while allowing the passage of water.

 When the spin is finished, the excess water having been removed from the drains by the pump 40, the valve V is opened, so that the suction generated by the pump lowers the cement slurry 90 in each of the drains, via the conduit 5 and the pipes 50. It is also possible to make the cement grout enter the pipe 3. As soon as the cement grout reaches the pipe 4, the pump 40 is stopped, the pipe 4 is removed from the pipe 3 and the pipes 50 of the drains 1.

 The operation is finished; a drained concrete wall was produced, containing a reinforcement which comprises the trellis 2 as well as the drains 1 and the pipe 3 filled with cement grout.

 It is therefore possible to remove the concrete very quickly, by removing the formwork 8.

 This same process can naturally be used for wringing out concrete elements which are not poured vertically, for example prefabricated cement sheets formed by pouring cement into horizontal molds. In this case, a series of horizontal drains are laid flat in the mold, before casting; these can be simple cylindrical drains, which are connected to a vacuum source.

 From the foregoing explanation, it is easily understood that the method according to the invention is very easy to implement; it saves a great deal of time in the use of formwork on construction sites (very quick formwork); the equipment is compact, light, inexpensive, and very simple to use; moreover the sources of aspiration generally exist on building sites (compressors). The process allows a significant saving of cement for equivalent resistance of the concrete; the increased compactness of the wrung concrete element increases its mechanical resistance, its resistance to corrosion and its sealing.

 The method can be applied to elements of various shapes and sizes; it suffices for this to provide in the formwork drains sized and positioned correspondingly. The pre set: this in the hole element or other reservations does not prevent the use of the process.

 It goes without saying that the invention is not limited to the preferred embodiment which has just been described by way of example; on the contrary, it encompasses all variants.

 Thus, for example, in the type of drain represented (FIG. 3) it would be possible in certain cases to provide elements forming spacers intended to ensure correct mutual positioning of the inner 13 and outer 10 tubes, and to avoid an offset which would be due to the crushing of the lining 12, which would be harmful for the uniformity of the suction.

 In a variant, it is the internal reinforcement which could be designed to serve as a drain, for example in the form of a trellis composed of filter elements which fit into each other.

Claims (10)

 1. Process for wringing out concrete poured into a formwork according to  which  a) at least one drain (1) is placed in the formwork (8), before pouring the concrete;  b) the concrete (6) is poured into the formwork (8), around the drain (1)  c) the drain (1) is connected to a vacuum source (40) so as to  suck through the drain (1), within the concrete (6), part of  the water there.  2. Method according to claim 1, characterized in that a  series of drains (1) which are placed in the formwork (8) parallel  to each other and plugged into a common vacuum source  (40).  3. Method according to one of the preceding claims, character  laughed at the fact that at the end of the spinning operation, the (or  the) drain (s) of a cement grout (90) or of a hardenable material  similar.  4. Method according to claim 3, characterized in that  filling the drain (s) with a cement grout (90) or  by a similar material is done by aspiration by means of the source  vacuum (40), after the drain (s) (1) have been put into com  munication with a tank (9) containing the cement slurry (90) or  the like material.  5. Method - according to one of the preceding claims, for the  manufacture of a vertical concrete wall, characterized in that one uses  reads a series of drains (1) which are arranged vertically in the  formwork (8).  6. Method according to claim 5, characterized in that the  drains- (1) open at their lower end (la) in a common pipe  (3) which is connected to a vacuum source.  7. Method according to claim 5 or 6, characterized in that  the drains (1) communicate, by their high end (lob) with a con  common hose (5) which is connected, via a valve (7), to a reservoir (9)  containing cement grout (90) or the like.  8. Method according to one of claims 5 to 7, characterized in that drains (1) of slightly frustoconical shape are used, the large base of which is arranged at the bottom.  9. Method according to one of the preceding claims, characterized in that - before pouring the concrete - the drain (s) is fixed to a frame, for example to a trellis, intended to reinforce the poured concrete.  10. wringing device for poured concrete, for implementing the method according to one of claims 1 to 9, characterized in that it comprises a series of drains (1) which communicate via 'a pipe (3) with a suction source such as a vacuum pump (40).