FR2612533A1 - DEVICE FOR SPREADING BITUMEN IN THE STATE OF FOAM, METHOD FOR IMPLEMENTING THE SAME, AND METHOD FOR PRODUCING SURFACE COATINGS - Google Patents

Abstract

The apparatus comprises: a chamber (10) having a face (11) open on the side towards which the spreading is effected, the said face being equipped with at least one grid (12); equipment for simultaneously spraying bitumen and water towards the said grid (12) in order to ensure, in the vicinity of the latter, dispersion of the water in the bitumen, and means for producing, inside the said chamber (10), a current of air passing through the latter and being discharged via the said grid (12). The invention also relates to a process for implementing this apparatus and to a process for producing surface coatings.

Description

The present invention relates to a device for spreading bitumen to

  the state of foam, its method of implementation and a

  process for producing superficial coatings.

  The foaming of bitumen is a known technique which

  is to inject a given amount of water into bitumen heated to high temperature. The vaporization of the water produces foaming that will be more or less important depending on the quality of the bitumen, the amount of water, the presence or absence of foaming products, and many

  - surrounding factors (temperature, humidity, wind, ...).

  The essential property of the foaming is to give the bitumen a low apparent viscosity, due to the presence of a dispersed gas phase in the form of fine bubbles, and especially a high apparent volume which can reach up to twenty times that of the bitumen to the liquid state. A very expanded foam will have a short life,

  that is to say that his deflation will be fast. A little foam

  trimmed but very thin will have a much slower deflation.

  The realization of superficial coatings consists in depositing a layer of bitumen on the support to cover, spreading chippings

  on the bitumen and to compact the chippings.

  This process is a seductive solution to the problem of

  your coatings. However, it is necessary to fix the chippings in the bitumen layer so that the coating does not degrade at the passage of vehicles. Thus, the most critical problem in the production of surface coatings lies in the choice of the viscosity of the binder, which must satisfy two contradictory requirements: on the one hand, the binder must have a relatively low viscosity at the time of grinding. to ensure effective wetting of the aggregates - on the other hand, so that the aggregates are not torn off by

  circulation, the binder must have sufficient viscosity

  after cooling, so as to ensure that the

  granular / soil bond, a cohesion appropriate to the traffic.

  It is thus a question of finding the best compromise of viscosity of the binder, which reconciles the requirement of an effective wetting of the aggregates with that of the solidity of their attachment to the ground, this supposing of course that the other parameters conditioning the result coating (fines and water content of the chippings, state of the support,

  binder, binding-granular affinity, implementation) are approximately

  's degrees. Until now, to ensure the wetting of the chippings, the viscosity of the binders is adjusted to different values by means of fluxing agents (coal oils) or fluidifiers (kerosene), depending on the circulation and climate conditions, which makes it possible to to minimize the rejects of chippings during the more or less long period of evaporation of

  solvents, where the fixing of gravel on the pavement becomes stronger.

  This technique has the disadvantage of evaporating in

  the atmosphere some 50,000 tons of solvents a year. In addition, the use

  These solvents increase the cost of coating

superficial.

  Bitumen foam can make an improvement

  determining in the realization of surface coatings, in solution-

  the problem of wetting chippings with viscous binders capable of supporting directly after

intense, heavy and fast.

  Patent FR-A-2,370,126 relates to a process for producing surface coatings in which a binder in the form of a foam is used. The aggregates are then spread over a layer of bitumen in the state of foam. The foam is made either by injection

  a gas in the binder raised to a temperature above

  condensation, either by vaporization of a liquid in a binder.

  In this technique, the foam develops at the outlet of the bitumen jets and continues to form on the application support. Under these conditions, many factors, atmospheric and other, are

  likely to influence the formation process of the foam.

  The object of the present invention is to provide a solution to the problems mentioned above and aims in particular at improving the characteristics of the bitumen foams (lifetime ...) so that they are fine and stable, and that their handling is facilitated. The present invention provides a bitumen spraying device and method for developing a bitumen foam within an enclosure and spreading it into a continuous web, said foam exhibiting improved characteristics compared to the foams. the prior art. It also relates to a production method

superficial coatings.

  The bitumen spreading device according to the invention is characterized in that it comprises:

  an enclosure of substantially parallelepipedic shape presenting

  an open face on the side towards which the

  said face being equipped with at least one gate, - equipment for simultaneous spraying of bitumen and water towards said grid making it possible to ensure in the vicinity of the latter, the dispersion of the water in the bitumen, - means for producing an air flow inside said enclosure, said air flow passing through said enclosure

and evacuating by said grid.

  According to a secondary characteristic, the jets of pulverized bitumen and the jets of water spray completely overlap at least in the immediate vicinity of said grid, practically without impact.

  on the side walls of the enclosure.

  The spreading method according to the invention is characterized in

  inside an enclosure of substantially parallelepiped shape

  pedicure having an open face on the side towards which the spraying is carried out, said face being equipped with at least one gate, the simultaneous spraying of bitumen and water is carried out towards said gate, so as to ensure, close to the latter the dispersion of the water in the bitumen and in that a stream of air is produced inside said enclosure, said air stream passing through said enclosure and

evacuating by said grid.

  Finally, the process for producing surface coatings is of the type comprising a step of depositing bitumen foam on the support to be covered, a step of spreading grit on said foam and a step of compacting said grit; it is characterized in that said foam deposit is implemented according to the method

previously described.

  In the entire text of this description and the

  the word "bitumen" also means bitumen containing

  These additives are well known to those skilled in the art, they are essentially surfactants promoting the formation of foam and imparting to the bitumen a better adhesiveness. Of course, these additives do not include the fluidifiers and fluxes, which

  one seeks precisely to discard.

  Other features and advantages of the present invention

  will appear on reading the description which will follow, made in

  FIG. 1 is a cross-sectional view of a device according to the present invention; FIG. 2 is a very schematic representation in longitudinal and transverse sections of an exemplary embodiment of a device. FIG. variant of the device of the present invention, - Figure 3 illustrates a second embodiment of a variant of the device of the present invention, in longitudinal and transverse sections, - Figure 4 illustrates a preferred embodiment of the device of this invention, in longitudinal and transverse sections, and - Figure 5 is a top view of the device of Figure 4. Referring to Figure 1, there is shown a view in

  transverse section of a device according to the present invention.

  This device comprises an enclosure 10 which can be fixed

  by any conventional means to a vehicle intended for the spreading of

  you ... me. This enclosure, of substantially parallelepipedal shape

  has an open face 11. This face, oriented towards the side to which will be carried out, is equipped with two grids 12 and 12 '. In the diagram shown here, the device has two grids but could include either one or more than two. The enclosure 10 is equipped with a plurality of bitumen spray nozzles 13, only one of which is visible here. This nozzle 13 is oriented along the axis 14 of the enclosure, perpendicularly to the planes of the grids 12 and 12 '. These nozzles are connected to a liquid bitumen feed circuit of known type which is not shown here. The enclosure 10 further comprises water spray nozzles 15 coupled to a circuit independent of the bitumen supply circuit. The axis 16 of the water spray nozzle 13 may be angularly offset from the axis of the

  Bitumen spraying nozzle of an angle less than or equal to 15.

  In the example described here, this angle is of the order of 15. The bitumen spray nozzles 13 and water 15 are adjustable and can create conical or lamelliform jets. In the case illustrated here, the

  nozzles give rise to corner jets at the top respectively otet.

  It can be seen that near the grid, the jets of bitumen and water overlap completely. The enclosure 10 further comprises means (not shown here) that produce an air stream to

  the interior of which, for example, consists of an equi-

  channel of heating means connected to a conduit which opens on a side face of the enclosure 10; the air flow passes through the enclosure and

  is evacuated by the grids 12 and 12 '.

  Still with reference to Figure 1, the operation of the device can be the following. While the enclosure 10 is mounted by known fastening means on a bitumen spraying vehicle, bitumen and water are simultaneously sprayed through the nozzles 13 and 15 to the grids 12 and 12 '. For example, the bitumen used is heated to high temperature while the water is used at room temperature. Appropriate jet pressures make it possible to disperse the water in the bitumen and to form at the level of the grids 12 and 12 'a foam of bitumen. The projection on the grids facilitates the formation of a fine and stable foam. The air flow then causes the foam formed beyond the grids to the support to be covered. The formation of this foam, combined with the movement of the vehicle gives rise to a strip of foam. It is desirable that the adjustment of the bitumen and water nozzles is such that there is no projection on the lateral faces

  of the enclosure, because the projection of bitumen on such surfaces indi-

  adversely influences the formation of foam.

  At the end of use of the device, it is desirable to circulate the hot air inside the enclosure while the feed bitumen and water circuits are closed. Indeed, during the production of the bitumen foam, bitumen has accumulated at the grids. The air expels the bitumen from the enclosure and cleans it. Tables I and II below give technical characteristics of the foams produced by means of a device such as that described with reference to FIG. 1. The tests were carried out with a

  Bitumen spray nozzle equipped with a GIESLER @ jet.

  The characteristics of the enclosure are the following: - Distance bitumen spray nozzle / first grid 73 mm - Angle d at the top of the jet of bitumen under 4.6x105 Pa: = 50 - Grids transversal dimension: 68 mm - Opening of mesh 2 and 3 mm

T A B L E A U I

With additive water and pure bitumen

bitumen flow 30 l / min.

  - water flow 36 l / h - air flow 16 m3 / h - bitumen pressure: 4.6.105 Pa Opening Distance Weight Ex-Rate N of Inter-Predepansion E * of life ** Test meshes grid of mm mm bitumen kg

I 2 15 1,270 6.50 40

2 2 10 1.385 6.81 42

3 2 0 1,375 7,03 44

4 3 15 2.090 3.16 100

3 10 1,460 5.52 74

6 3 0 1.787 4.9 80

  * The expansion rate is the ratio of the volume occupied by the foam

  bitumen to the volume of the bitumen before foaming.

  ** the life of the bitumen foam is the period of time between the time the foam is formed and the

  when the bitumen has returned to the liquid state again.

T A B L E A U I I

  With additive bitumen and added water

bitumen flow rate: 12 l / min.

  - water flow: 14.4 l / h - air flow: 6.4 m3 / h - bitumen pressure: 5.6. 105 Pa Opening Distance Weight Ex-Duration N of Inter-Predepansion E * of life ** Test meshes grid of (s) mm mm bitumen kg

7 2 15 2,267 5,09 140

8 2 10 2.524 4.29 214

9 2 0 1.475 7.19 124

3 15 2.100 5.95 170

11 3 10 1,792 6.45 154

12 3 0 1.653 7.27 130

  13 - 0 1.769 no foam without water j - I * The expansion ratio is the ratio of the volume occupied by the foam

  bitumen to the volume of the bitumen before foaming.

  ** the life of the bitumen foam is the period of time between the time the foam is formed and the

  when the bitumen has returned to the liquid state again.

  On reading Tables I and II, it appears that the spray pressure of 5.6 × 10 5 Pa is more favorable than the spray at 4.6. 105 Pa and gives rise to a thinner foam and more homogeneous structure; this observation is however valid only for conical jets. In operation at 5.6 × 10 5 Pa, it is notable that the grids having a mesh size of 3 millimeters give a

  better expansion rate than other grids.

  The closer we get to the two grids (to make them one more), the more we increase the rate of expansion of the foam

  but at the same time, it decreases its life.

  In practice, it appears that the foam made with a grid system having a mesh size of 3 millimeters

  is very thin, very homogeneous and free of big bubbles.

  Figure 2 illustrates, very schematically, in longitudinal sections

  tudinal and transverse, an embodiment of a variant of the device according to the invention. The enclosure 20 has 8 conical jets of

  spraying bitumen 21 arranged equidistant from each other.

  The water spray nozzles 22 are arranged between the nozzles 21 for spraying the bitumen so that at the level of the grid 23, the jets of bitumen 24 and water 25 overlap each other. A side entrance 26 of hot air drives the foam formed through the grid 23. The enclosure is equipped, in addition to a convergent double deflector 27 which

  channel the foam pushed beyond the grid 25 by the stream of air.

  Another exemplary embodiment is illustrated in FIG.

  The enclosure 30 comprises 8 conical sprays of asphalt spray 31.

  However, the water spray nozzles 32 are oriented in the same direction as the bitumen spray nozzles 31. The adjustment of the nozzles 32 is such that a jet of bitumen 33, in the vicinity of the grid 34, is covered by the two water jets 35 and 35 'located on each side of the jet of bitumen 33. The chamber 30 is furthermore equipped with a

  air intake 36 and a convergent double deflector 37.

  Finally, a third particularly preferred embodiment is illustrated in FIGS. 4 and 5, respectively, in sections

  longitudinal, transverse and seen from above.

2 6 1 2533

  The enclosure 40 has a plurality of bitumen spray nozzles 41 facing the grid 46. Water spray nozzles 43

  disposed on the lateral face 44 of the enclosure opposite to the con-

  air duct 45, and just behind the nozzles 41 in the direction of displacement.

  the device illustrated by two arrows in solid lines. The jets of bitumen 41 are flat jets parallel to each other. These jets can be advantageously inclined at an angle of 15 to 20 with respect to

to the major axis of the device.

  In this case, the outlet pressure of the bitumen may

  bind, advantageously be between 2.105 and 4.105 Pa.

  In order to allow spreading of bitumen foam on

  variable width, the device of the present invention may

  wear spray equipment that consists of a central part and two "extenders" unfoldable. The preferred dimensions of

  these elements are, respectively, about 2.40 m and 1.00 m.

  The enclosure then has three elements that juxtapose. The interface

  between two consecutive elements consists of two vertical partitions

  wedges that have no effect on the continuity of the foam carpet.

  The spreading width can also be adjusted by completely stopping one or more jets of bitumen and water. The enclosure is then

  equipped with vertical shutters. Hydropneumatic or electric control

  that closing and opening jets acts simultaneously on the flaps that move and isolate the spraying area of the rest of the device.

26 1 2533

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Claims (13)

R E V E N D I C AT O N S   1. Device for spreading bitumen in the state of foam, characterized in that it comprises: - an enclosure (10, 20, 30, 40) of substantially parallelepipedal shape having a face (11) open on the worm side which is carried out spreading, said face being equipped with at least one grid (12,23,34,46), - equipment for simultaneously spraying bitumen and water 1.0 to said grid (12,23,34,46 ) to ensure near the latter, the dispersion of water in the bitumen, and means for producing a stream of air inside said enclosure, said air flow passing through said enclosure   (10, 20, 30, 40) and evacuating through said grid (12, 23, 34, 46).   Bitumen spraying device according to claim 1, characterized in that the jets of sprayed bitumen and the jets of spray water completely overlap at least in the immediate vicinity of said grid and, practically without any impact on the side walls of the liner. 'pregnant. Bitumen spreading device according to claim 2, characterized in that said spraying equipment consists of a bitumen feed ramp and an independent circuit.   each of which is provided with at least one spray nozzle. to said grid.   4. A bitumen spraying device according to claim 3, characterized in that said bitumen spraying nozzle (13,21, 31, 41) extends substantially perpendicularly to the plane of said grid. Bitumen spreading device according to claim 4, characterized in that the axis of said water spray nozzle   (5.22,43) is angularly shifted with respect to said spray nozzle   bitumen (13,21,41) at an angle less than or equal to 15. 2 6 1 2533   6. Asphalt spreading device according to one of the claims   cations I to 5, characterized in that the outlet pressures of the bitumen and water jets at the outlet of said nozzles (13,21,31,41) and (5,22,32,43) are controllable.   7. bitumen spreading device according to one of claims I to 6, characterized in that the means for producing said air stream consist of a blower connected to at least one duct which leads to at least one one of the lateral faces of said enclosure.   Asphalt spreading device according to one of the claims   cations 1 to 7, characterized in that it comprises two parallel grids (12,12 ') adjacent to each other preferably spaced apart from each other   a distance of less than or equal to 15 mm.   9. Asphalt spreading device according to one of the   1 to 8, characterized in that water is generally used in ambient temperature.   10. Asphalt spreading device according to one of the claims   3 to 9, characterized in that the pressure at the outlet of said   Bitumen spray nozzle is at least 2.105 Pa.   11. Device for spreading bitumen according to one of the   1 to 10, characterized in that at least one of the large faces   side of said enclosure is extended by a deflector.   12. Method for spreading bitumen in the state of foam, characterized in that, inside a chamber (10, 20, 30, 40) of substantially parallelepiped shape having a face (11) open on the worm side which is carried out spreading, said face being equipped   at least one grate (12,23,34,46), simul-   pouring bitumen and water towards said grid, so as to ensure, in the vicinity of the latter, the dispersion of the water in the bitumen and in that a stream of air is produced inside said enclosure, said flow of air passing through said enclosure (10, 20, 30, 40) and evacuating by said grid (12,23,34,46). 26 1 2533   13. Process for producing surface coatings of the type comprising a step of depositing bitumen foam on the support to be covered, a step of spreading grit on said foam and a step of compacting said grit, characterized in that said deposit of foam is used according to the method of claiming 12.