EP1456476A1

EP1456476A1 - Method and device for filling a cavity with mortar

Info

Publication number: EP1456476A1
Application number: EP02796911A
Authority: EP
Inventors: Pierre Boulanger; Eric Charpentier; Dominique Guinot; François SAUCIER; Thierry Gasnier; Jacques Carabin; Luc Nerot
Original assignee: GROUPE MARAIS; Lafarge Aluminates SA
Current assignee: GROUPE MARAIS; Imerys Aluminates SA
Priority date: 2001-12-19
Filing date: 2002-12-12
Publication date: 2004-09-15
Also published as: FR2833627B1; FR2833627A1; CA2469834A1; AU2002361442A1; US20050031414A1; WO2003054304A1

Abstract

The invention concerns a method which consists in mixing the mortar and a setting and hardening accelerator in a screw conveyor (13) and in pouring into the cavity (8) by gravity the resulting mixture through a chute (14, 28, 30).

Description

Method and device for filling a cavity with a mortar,

The present invention relates to a method and a device for filling cavities, such as holes or trenches, in particular in infrastructure works, such as street or road pavement, sidewalks, etc. It is known that the work of 'maintenance of such infrastructure works or maintenance and construction of networks of electric cables, gas or water pipes, etc ... buried under these works, require the digging of cavities, troublesome for the users of these works. Also, it is essential to quickly fill these cavities, so that said works can be returned to service as quickly as possible after the completion of said work.

To this end, we have already thought of filling these cavities with an ultra-fast setting mortar allowing, for example, to put a street pavement back into service at most two hours after the end of this work. To do this, a cement-based mortar, ready to use and manufactured in a specialized factory, generally called a concrete plant, is brought in by transport vehicles of the truck-router type, and is added to the said router , an accelerator for setting and hardening said mortar, in the form of a powder and generally based on calcium aluminates, before using said mortar to fill said cavities. However, this process has many disadvantages:

- from the point of view of work safety: an operator must climb at the rear of the router / to the mouth of said router, carrying bags of accelerating and hardening product, weighing 25 kg or even 50 kg, he must open the bags and empty the contents in the router. This results in a risk of falling and exposure to accelerator dust;

- from the point of view of the uniformity of the mortar: the setting and hardening accelerator added to a full load of mortar filling the top cannot mix satisfactorily with the latter during the rotation of said top, so that the setting acceleration and hardening effect is not uniform over the entire mortar load. To remedy such a defect, it is possible not to fill the router with a full load of mortar, but then this results in a significant logistical overhead;

- from the point of view of the rapidity of setting and hardening of the mortar: the setting and hardening of a cement mortar, accelerated by a calcium aluminate, are very rapid and are a function of the proportions, of the nature of the cement and temperature. Consequently, if the emptying of the router cannot be carried out immediately and quickly, the mortar risks hardening in said router, rendering it unusable. In addition, if the emptying of the router is immediate and rapid, but if the use of the mortar cannot be instantaneous, for example due to the nature of the filling process, the mortar hardens before it can be used to fill the cavities. This latter case occurs in particular, when a plurality of small individual cavities or else narrow cavities, such as a narrow trench, have to be filled;

- from the point of view of fouling of the router: after emptying the router, there is always a layer of mortar which adheres to the inside blades of the router. This layer of mortar hardens before the router truck is returned to the plant and can be cleaned and a new layer will be added during the next delivery. Fouling of the router can become excessive in a single day of delivery and require cleaning with a jackhammer; - from the point of view of contamination of the router load: if the router truck is not thoroughly cleaned before being loaded again, the remaining mortar can have an undesirable accelerating effect on the new mortar load; and - from the point of view of the execution of a site: since the setting and hardening of the mortar are very fast after the addition of the accelerator, it can only be introduced into the router, when the truck is in place, ready to unload. But then, as the introduction of the accelerator into the router and the mixing of the mortar and the accelerator by the rotation of said router takes several minutes, this results in an incompressible waiting time for all operators, with interruption momentary site.

The object of the present invention is to remedy all these drawbacks. To this end, according to the invention, the method for filling a cavity by means of a mortar capable of setting, said mortar having to be added with at least one setting and hardening accelerator and being available to the discharge port of a transport vehicle bringing it in the vicinity of said cavity, is remarkable in that: - a first flow is formed, consisting of said mortar and moving in the direction of said cavity;

- A second flow is formed, consisting of said setting and hardening accelerator and moving in the direction of said first flow;

- Merging, by mixing, said first and second stream into a third stream; and

- Said third flow is introduced by gravity into said cavity.

Thus, thanks to the present invention, the continuous addition and mixing of the setting and hardening accelerator to the mortar can be carried out outside the router of the transport vehicle, after loading of ready-to-use mortar and just before accelerated setting and hardening mortar is placed in said cavity. This avoids all the drawbacks of the prior art mentioned above. Preferably, in order to obtain a setting time and a curing speed desired for the accelerated mortar filling the cavity, the flow rate of said second flow is adjusted as a function of the flow rate of said first flow to adjust the proportion of setting accelerator and hardening in said third stream.

Excellent results have been obtained when said mortar is based on Portland cement, while the setting and hardening accelerator is based on calcium aluminates. You can also obtain the desired acceleration with other types of accelerators.

Advantageously, the Portland cement is of the CEM1 type and its formula does not include any mineral additions such as fly ash or filler. It is however possible to obtain an acceptable result with cements of other types and in the presence of mineral additions.

The efficiency of the setting and hardening accelerator depends on its mineralogy and it has been observed that a reduced content of C12A7 (less than 1%) is preferable. The aluminous cement commercially known under the reference LSR 5000 constitutes an excellent setting and hardening accelerator.

This setting and hardening accelerator can be in the form of either a powder or a liquid, for example a grout. In such a grout, the calcium aluminate particles are suspended in water, with calcium aluminate setting inhibitors and, optionally, dispersants. The inhibitors can be zinc borate, boric acid or citric acid and they are incorporated into calcium aluminates in proportions varying between 0.1% and 3% by weight of calcium aluminates. Dispersants can be one or the other of those known commercially under the references SPE 9413, PE 56-1 or Premia 1 50 and used in proportions varying from 0.1% to 3% by weight of calcium aluminates. The setting inhibitors, with or without dispersant, have, in this case, the particularity of giving very stable suspensions over time allowing their storage and their transport over a fairly long period which can reach several months with the appropriate dosages. The dispersants, which are not essential, provide additional stability and a viscosity facilitating handling, in particular by pumping. This type of grout has the advantage, when the grout is mixed with a ready-to-use mortar, to accelerate the setting and hardening of the mixture, the acceleration inhibitor being deactivated by simple contact with the mortar to Portland cement base which completely deactivates it and allows the desired setting and hardening acceleration. For the quality of the mixture and the speed of implementation, it is often preferable that the setting and hardening accelerator is in the form of grout, rather than in the form of powder.

In the case where it is desirable that, after complete filling and hardening of the mortar, said cavity can possibly be opened again (for example to carry out maintenance operations on cables or pipes which it contains), it is advantageous that said mortar has low compressive strength so that it can be easily removed. To do this, a limited cement dosage can be used, for example of the order of 100 kg / m ³ , a water / cement ratio of the order of 2, only sand (maximum particle size 4 mm), and a powerful air entraining adjuvant making it possible to obtain an air content of the order of 1 5% -25% of the total volume.

Furthermore, it is advantageous for the fluidity of said third flow to be sufficiently high - which is achieved with the formulation above. above - so that the mixture of mortar and setting and hardening accelerator of which it is made is self-placing, that is to say that it flows freely in said cavity by completely coating the walls - and any objects therein - and filling the entire volume of said cavity without leaving large voids.

Optionally, colored pigments can be added to at least one of said streams to color the accelerated mortar in the mass. It is thus possible to signal the proximity of an object buried in said cavity. For the implementation of the method described above, the present invention further relates to a device which is remarkable in that it comprises:

a first receptacle for receiving the mortar leaving said discharge port of said transport vehicle; - first advance means, supplied with mortar from said first receptacle and forming said first flow;

- a second receptacle for receiving said setting and hardening accelerator;

- second advance means, supplied with setting and hardening accelerator from said second receptacle and forming said second flow;

- means for melting and mixing said first and second streams; and

- Third advance means, supplied from said melting and mixing means and forming said third flow of mortar and setting and hardening accelerator, resulting from the melting and mixing of said first and second flow.

In an advantageous embodiment, said first and second advancing means, said melting and mixing means and said third advance means consist of a single worm conveyor. This worm conveyor can be inclined relative to the horizontal, its lower end being supplied with mortar from said first receptacle, its intermediate part being supplied with setting and hardening accelerator from said second receptacle and said third flow. mortar and setting and hardening accelerator coming out from the side of the upper part of said worm conveyor.

It may be advantageous that the device of the invention comprises a third receptacle disposed under the upper part of said worm conveyor and intended to receive said third flow of mortar and setting and hardening accelerator and that the lower part of said third receptacle is shaped into a trough capable of introducing said third flow of mortar and setting and hardening accelerator into said cavity.

In order to facilitate the movement of the device of the invention from one cavity to another or along an elongated cavity, the first, second and third receptacles and said worm conveyor can be carried by a chassis provided with wheels . A cavity filling cart is thus obtained.

Advantageously, in the case where the cavity to be filled is a trench, said wheels are able to bear on the ground on either side of said trench, so that then the device according to the invention is arranged astride the latter. The device may, in this case, include guide means cooperating with said trench and intended to guide it along the latter.

In addition, it is possible to provide a plate integral with said chassis, capable of acting as a trowel for the mortar with accelerated setting and hardening having just been introduced into said trench. Such a trowel can be used puyer on the ground on either side of the trench to level the level of said mortar with that of the ground. It can also, as a variant, penetrate inside the trench to communicate to said mortar a smooth surface recessed from the ground level. For filling the trench, the wheeled device can be moved along said trench, said first receptacle being continuously supplied with mortar by said mortar transport vehicle along a route parallel to said trench. In this case, it is advantageous that said wheeled device and said transport vehicle are coupled to a common tractor.

The figures of the appended drawing will make it clear how the invention can be implemented. In these figures, identical references designate similar elements.

Figure 1 is a perspective view of an exemplary embodiment of the device according to the present invention, specially designed to fill trenches of small width.

FIG. 2 is a side elevation view, partially broken away, of the device of FIG. 1.

FIG. 3 is an elevation view of the rear of the device of FIGS. 1 and 2, along the line III-III of FIG. 2.

FIG. 4 is a top view of the device of FIGS. 1, 2 and 3.

FIG. 5 shows, in an enlarged perspective from above, a detail of the device of FIGS. 1 to 4. FIG. 6 schematically illustrates an alternative embodiment for the device of FIGS. 1 to 4.

FIG. 7 schematically illustrates, in top view, an example of implementation of the method according to the present invention, for filling a trench with the device of FIGS. 1 to 4. The device, according to the present invention and shown in Figures 1 to 4 and 7, is in the form of a carriage 1 comprising an elongated frame 2, provided with a pair of front wheels 3 and a pair of rear wheels 4. In the embodiment shown, the two front wheels 3 are mounted in free yokes 5 rotating around vertical axes, so that said front wheels 3 are spontaneously steerable (which is particularly advantageous in the application illustrated in Figure 7). On the other hand, the two rear wheels 4 are wedged on their shaft 6, without the possibility of orientation. In addition, as illustrated in dashed lines in Figure 2, the front wheels 3 and / or the rear wheels 4 are mounted adjustable in height under the action of jacks, such as that designated by the reference 7 in Figures 1 and 2, so that said carriage can occupy either a high displacement position or a low working position. The carriage 1 is specially designed for filling trenches 8 made in the ground 9 and the spacing of the pairs of wheels 3 and 4 is provided so that one wheel of each of the pairs can bear on said ground 9, of a side of said trench 8, the other wheel of each pair being supported on the other side of said trench, so that the carriage 1 can be disposed astride it, as shown in Figures 1, 3, 4 and 7. At its front part, the carriage 1 is provided with coupling means 10.

On the chassis 2 of the carriage 1 are mounted a hopper 1 1, a tank 12, a worm conveyor 13 and a hopper 14. The worm conveyor 1 3 is inclined relative to the horizontal, with its part lower than its rear part. The screw of this conveyor 13 is driven by a motor 15 disposed in the upper rear part. The hopper 1 1 is arranged above the lower front part of the worm conveyor 13. It can communicate with the latter by through an opening 16 made in its lower part, in correspondence with an opening 17 provided in the casing 18 of the worm conveyor 13. The opening 1 6 ^′ of the hopper 1 1 can be closed by a door 19, actuated by a mechanism 20. The reservoir 12 includes a hopper 21, at the base of which is disposed a screw extractor 22, driven by a motor 23. The extractor 22 is provided with an outlet conduit 24 opening out in a receptacle 25, placed above said worm conveyor 13 and in communication with the intermediate part of the latter by an opening 26, formed in said envelope 18.

At its upper part, the worm conveyor 13 comprises a discharge mouth 27, directed downwards and disposed above the hopper 14.

The bottom of the hopper 14 is pierced with an oblong opening 28, delimited laterally by two longitudinal plates 29 and 30, capable of entering said trench 8.

The electrical, hydraulic and / or pneumatic energy necessary for the operation of the devices of the carriage 1 is supplied to the latter by cables or conduits 31, only shown in FIG. 1. The operation of the devices of the carriage 1 is controlled from the control panel 32.

The motors 1 5 and 23 are connected to each other by a servo device, represented schematically by a link 33 in FIG. 2. The carriage 1 further comprises, at its front part, a lug 34 capable of penetrate said trench 8 to guide said carriage when it moves along the latter and, at its rear part, a plate 35 covering said trench. When the carriage 1 is in the high position (see the position in mixed dashes in FIG. 2), the lug 34 is released from the trench 8.

In FIG. 7, a diagrammatic view from above is shown, the application of the carriage 1 to the continuous filling of the trench 8. To do this, the carriage 1 is coupled with lateral offset, by a chain 36 attached to its means coupling 10, at the rear of a tractor 37, which moves in the direction of arrow F parallel to the trench 8 and which is, for example, capable of depositing a cable 38 inside the trench 8. A ready-to-use mortar transport truck 39 is also coupled to the tractor 37 by a drawbar 40. During the advance of the tractor 37, the router 41 of the truck 39 continuously unloads the mortar which it contains in the hopper 11, by means of a chute 42. As a result, said mortar passes through the openings 16 and 17 and is driven by the worm conveyor 13 in the form of a mortar stream.

Simultaneously, setting and hardening accelerator for said mortar, kept in reserve in the hopper 21, is extracted therefrom by the extractor 22 and falls into said receptacle 25. It passes through the opening 26 and it is driven by the worm conveyor 13 in a second stream, which is mixed and fused to said first stream, to form a third stream of mortar with accelerated setting and hardening, which leaves the mouth 27 of the worm conveyor 13 and falls into the hopper 14. From there, it passes into the trench 8 through the oblong funnel formed by the opening 28 and the plates 29 and 30. The mortar with accelerated setting and hardening introduced into the trench 8 is trowel by the plate 35, in order to obtain a smooth surface 8C for said mortar.

Of course, the speed of rotation of the worm conveyor 13 is adapted to the speed of advance of the tractor 37 so that the trench 8 is correctly filled with accelerated mortar. Thanks to the servo control 33, the content of setting and hardening accelerator is kept constant at the desired value, whatever the speed of advance.

In an experimental embodiment in which the router 41 had a capacity of 6m ³ of mortar, it was possible to continuously fill trenches 8, 10 to 20 cm in width and 30 to 50 cm in depth, at the speed of 40 m per minute.

In the above description, it has been implicitly assumed that the setting and hardening accelerator is in powder form. In the case where said accelerator is a grout, the hopper 21 and the extractor 22, 23 of the reservoir 1 2 are replaced by a container 43, containing said grout, and by a positive displacement pump 44, controlled by said servo control 33 and supplying said outlet duct 24 in grout (see Figure 6).

Claims

CLAIMS 1. Method for filling a cavity (8) by means of a mortar capable of setting, said mortar to be added with at least one setting and hardening accelerator and being available at the discharge orifice of a vehicle transport (39) bringing it in the vicinity of said cavity (8), characterized in that:

- A first flow is formed, consisting of said mortar and moving in the direction of said cavity (8); - A second flow is formed, consisting of said setting and hardening accelerator and moving in the direction of said first flow;

- adding said second stream to said first stream and mixing said streams to merge them into a third stream; and

- Introducing said third flow by gravity into said cavity (8).

2. Method according to claim 1, characterized in that the flow rate of said second flow is adjusted as a function of the flow rate of said first flow to adjust the proportion of setting and hardening accelerator in said third flow.

3. Method according to one of claims 1 or 2, characterized in that said mortar is based on Portland cement, while the setting and hardening accelerator is based on calcium aluminates.

4. Method according to claim 3, characterized in that said Portland cement does not include mineral additions, such as fly ash or filler.

5. Method according to one of claims 3 or 4, characterized in that said setting and hardening accelerator has a C12A7 content at most equal to 1%.

6. Method according to one of claims 1 to 5, characterized in that said setting and hardening accelerator is in the form of a powder.

7. Method according to one of claims 1 to 5, characterized in that said setting and hardening accelerator has the liquid form of a grout, comprising setting inhibitors of said accelerator and, optionally, dispersants.

8. Method according to one of claims 3 to 7, characterized in that said mortar comprises approximately 1 00 kg / m ³ of cement, a water / cement ratio of the order of 2, only sand with a particle size at most equal to 4 mm and an air entraining adjuvant making it possible to obtain an air content of the order of 1 5% to 25% of the total volume.

9. Method according to one of claims 1 to 8, characterized in that the fluidity of said third flow is sufficiently high so that the mixture of mortar and setting and hardening accelerator of which it consists is self-placing , that is to say that it flows freely in said cavity by completely coating the walls and filling the entire volume of said cavity without leaving large voids.

10. Device for implementing the process specified under any one of claims 1 to 9, characterized in that it comprises:

- A first receptacle (1 1) for receiving the mortar leaving said discharge port of said transport vehicle (39); - First advance means (1 3), supplied with mortar from said first receptacle (1 1) and forming said first flow;

- a second receptacle (25) for receiving said setting and hardening accelerator; - second advance means (1 3), supplied with setting and hardening accelerator from said second receptacle (25) and forming said second flow;

- Means (1 3) for adding said second stream to said first stream and for mixing said streams by merging them; and

- third advance means (1 3), supplied from said means (1 3) for melting and mixing and forming said third flow of mortar and setting and hardening accelerator, resulting from melting and mixing said first and second streams.

1 1. Device according to claim 1 0, characterized in that said first and second advancing means, said melting and mixing means and said third advancing means are constituted by a single worm conveyor (13).

1 2. Device according to claim 1 1, characterized in that said worm conveyor (1 3) is inclined relative to the horizontal, in that its lower end is supplied with mortar from said first receptacle (1 1), in that its intermediate part is supplied with setting and hardening accelerator from said second receptacle (25) and in that said third flow of mortar and setting and hardening accelerator comes out from the side of the part upper of said worm conveyor (1 3).

13. Device according to claim 1 2, characterized in that it comprises a third receptacle (14) disposed under the upper part of said worm conveyor (13) and intended to receive said third flow of mortar and setting and hardening accelerator and in that the lower part of said third receptacle is shaped as a chute (28, 29, 30) capable of introducing said third flow of mortar and setting and hardening accelerator into said cavity (8) .

14. Device according to one of claims 1 0 to 1 3, characterized in that the first, second and possible third receptacles, as well as said first, second and third means of advance and said means of melting and mixing are carried by a chassis (2) provided with wheels (3, 4).

1 5. Device according to claim 14, intended for filling a trench (8) formed in the ground (9), characterized in that said wheels (3, 4) are capable of bearing on the ground on both sides and d 'other of said trench (8).

1 6. Device according to claim 1 5, characterized in that it comprises means (34) for guiding along said trench.

1 7. Device according to one of claims 1 5 or 1 6, characterized in that it comprises a plate (35) integral with said frame (2) and adapted to act as trowel.

1 8. Method according to one of claims 1 to 9, for the filling of a cavity in the form of a trench (8) formed in the ground (9), said filling being achieved by the device (1 ) of one of claims 14 to 1 7, characterized in that said device (1) is moved along said trench (8) and in that said first receptacle (1 1) is continuously supplied with mortar by said transport vehicle (39) following a route parallel to said trench.

1 9. Method according to claim 18, characterized in that said device (1) and said transport vehicle (39) are coupled to a common tractor (37).