EP0440562B1 - Multilayered roadway anti-cracking covering - Google Patents

Abstract

The subject of the invention is a multi-layered roadway covering, in particular for roadways whose foundations are cracked, and a method for producing this covering. <??>The covering according to the invention, constituted by a bituminous membrane applied to the foundation of the roadway and by a running layer or a connecting layer, is characterised in that it comprises, between the bituminous membrane and the running or connecting layer, at least one layer of cold moulded cladding. <??>The method consists in successively applying to the roadway foundation, possibly coated with a surfacing layer:   - a layer of bituminous binder,   - in the cold condition, a layer of a compound containing a bituminous binder and an aggregate,   - a running or connecting layer. <??>These coatings are particularly effective for slowing down the rising through the running layer of cracks forming in the roadway support.

Description

The present invention belongs to the field of road surfaces, in particular road surfaces whose seats crack.

The cracking of the withdrawal of semi-rigid pavements constitutes a handicap to the development of this type of structure, the technical and economic interest of which is also certain. This undesirable phenomenon occurs in particular for roadways comprising foundations treated with hydraulic binders and a wearing course constituted by hot mixes.

Different solutions have been considered to delay or prevent the rise in the upper layers of the roadway, of the cracking caused by the thermal shrinkage of the foundations.

A first improvement consists in interposing a bituminous membrane, having a thickness of 2 to 3 mm, between the wearing course and the support. In the case of a new roadway, the support consists of gravel treated with hydraulic binders. In the case of an existing cracked roadway comprising gravel treated with hydraulic binders, the support consists of the existing coating as described for example by EP-A-0 216 148.
The bitumens used for the bituminous membrane can be pure bitumens or bitumens modified by the addition of macromolecular substances.

A disadvantage of this type of process is that, during the laying of the first hot mix mat on the bituminous membrane, even sandblasted, it melts and percolates from bottom to top at the base of this mat, so that its thickness greatly decreases until it disappears almost completely if the temperature of the mix is excessive. The ability to slow the rise of cracks is then considerably reduced, because a coating of asphalt, even highly enriched with bituminous binder at its base, is obviously less deformable than a layer of pure binder.

An additional improvement was then brought by the application, between the aforementioned bituminous membrane and the wearing course or a layer of connection, of a membrane carried out by unwinding of a nonwoven or by entanglement on site of very strongly synthetic threads. dosed. This process has made it possible to slow the rise of cracks, but its implementation is delicate and consequently expensive.

The present inventors have now discovered a new means for preventing reverse percolation of the binder constituting the bituminous membrane during the application of the hot mix forming the wearing course.

The present invention relates to a new multilayer coating for a roadway, which is intended to slow down or suppress the rise of cracks that may appear in the seat of said roadway.

The invention also relates to a process for producing this coating.

The multilayer coating according to the invention comprises a bituminous membrane applied to the seat of the roadway, and a wearing course or a bonding layer. It is characterized in that it also comprises at least one layer of cold-cast mix, between the bituminous membrane and the wearing course or a bonding layer. Of course, if the surface condition of the support requires it, a surfacing layer will be applied to said support, before applying the bituminous membrane.

The cold-poured asphalt layer consists of a bituminous binder and an aggregate, the maximum particle size of which remains less than approximately 10 mm.

The aggregate is preferably a crushed sand and more particularly a 0/6, 0/4 or 0/2 sand. The thickness of the cold-cast mix layer is between 3 and 12 mm. It is essentially a function of the grain size of the sand. Thus, for a 0/2 sand, the thickness is of the order of 3 to 5 mm; for 0/4 sand, it is 5 to 7 mm; for 0/6 sand, it is 7 to 10 mm.

The cold poured asphalt layer can be a single layer. It can also be a double layer.

The bituminous binder essentially contains a bitumen.

The bitumen is chosen from pure bitumens, preferably from grades 60/70, 80/100, and 180/220.

The bitumen used can be a bitumen modified by the addition of thermoplastic copolymers, either by direct hot mixing of pure bitumen and of copolymer, or by indirect cold mixing of pure bitumen emulsion and of aqueous dispersion of copolymer at the time of manufacture. of the mix to be poured.

Preferably, ethylene vinyl acetate (EVA) or styrene butadiene styrene styrene (SBS) or ethylene methacrylate (EMA) copolymers will be used.

However, it is also possible to use the styrene butadiene rubber block copolymers (SBR) and the acrylic copolymers as well as various mixtures of these copolymers.

The content of copolymer is at most equal to about 5% by weight. The addition of such copolymers has the effect of a less rejection on commissioning, a better binder-aggregate bond, increased brine resistance, a reduction in sensitivity to heat and cold, greater cohesion as well as '' better deformability.

A mineral filler can optionally supplement the particle size of the aggregates such as for example a crushed rock powder, preferably limestone, cement, natural or artificial rock fibers. The mineral filler content is less than 10%.

In a variant of the invention, the bituminous binder also contains synthetic fibers. The fibers used are ultra-fine synthetic fibers (a few decitex) and relatively long (4 to 8 mm).
They are chosen according to the elastic modulus of the material of which they are made, in order to obtain a fibrous mix whose deformability is compatible with that of the support on which it will be applied. Low fiber low modulus will be used for the most deformable pavements.
The proportion of fibers is advantageously between 0.05 and 3% by weight. This proportion may be very low, but given the extreme fineness of these fibers, their number per square meter of asphalt poured is considerable, as well as the length of the network that they constitute.

bitume 80/100 environ

80 % (en poids)

copolymère EVA

< 20 % (en poids)

dope

0 - 3 %.(en poids)

L'épaisseur de la membrane bitumineuse est avantageusement comprise entre 1 et 5 mm.The bituminous membrane applied to the support can be a simple membrane consisting essentially of pure bitumen.
Preferably, this membrane consists of a bitumen modified by the addition of a macromolecular compound, for example an ethylene-vinyl acetate copolymer (EVA) or a styrene-butadiene-styrene copolymer (SBS). Such membranes are described, for example, in patent FR 2,183,618 and its certificate of addition 2,268,113.
The maximum content of copolymer is imposed by the viscosity limit of the modified bitumen to which it flows by a heating and heat-insulated spreading ramp while remaining at a temperature below the degradation temperature of the copolymer.
As an example of a composition which can be used to prepare a bituminous membrane, the following composition may be mentioned:

bitumen about 80/100

80% (by weight)

EVA copolymer

<20% (by weight)

dope

0 - 3%. (By weight)

The thickness of the bituminous membrane is advantageously between 1 and 5 mm.

It should be recalled at this stage that the precise composition of the bituminous membrane, as well as its mode of application are in no way critical in the context of the present invention. Thus, said bituminous membrane can be applied hot, or spread cold when in the form of a bituminous emulsion.

The bituminous membrane can advantageously be coated, in a conventional manner, during a sanding operation, with fine particles, for example with ardoisine or with sandstone.

However, it should be observed that such a sanding or graveling operation is not compulsory. in fact, it is entirely possible to circulate the truck for spreading the cold-poured asphalt directly on said membrane, provided that the tires of the truck are permanently moistened to prevent them from sticking to the membrane.

The exact nature of the wearing courses or link layers is not critical. They are produced in a manner known per se, for example in the form of a surface coating, a hot mix or a cold cast mix. In the particular case of an overlying hot mix, the cold-poured asphalt layer constitutes a thermal and mechanical screen opposing the reverse percolation of the membrane in this asphalt.
The wearing course or bonding layer can also consist of a cold-cast mix containing a modified bitumen to which synthetic fibers have optionally been added.

The coating according to the present invention can be applied to any pavement support. It is particularly useful for pavements whose support undergoes cracking, whatever the origin of the cracking. These may include active cracks originating from a thermal shrinkage phenomenon. The support can, for example, consist of concrete slabs separated by expansion joints. The coating is particularly useful for semi-rigid pavements treated with hydraulic binders and for cement concrete pavements.

The method for producing a multilayer coating according to the invention is characterized in that it consists in applying successively to the roadway, a layer of a bituminous binder spread hot or else cold in the form of an emulsion, a layer of cold-poured asphalt, then a wearing course or a binder course. Each of these layers is applied by conventional methods.

The present invention is illustrated in a nonlimiting manner by the following examples.

Examples 1 and 2 are examples of preparation of compositions intended to constitute the layer of cold-cast mix.

EXAMPLE 1

The bituminous binder used was Mobilplast® sold by the applicant, containing 95% by weight of 80/100 emulsifiable bitumen, and 5% by weight of an EVA 33/45 copolymer.

liant Mobilplast ®

600

agent émulsifiant

9

HCl (d-1,19)

2,15

Eau

400

An emulsion was prepared having the following composition, expressed in kg:

Mobilplast ® binder

600

emulsifying agent

9

HCl (d-1,19)

2.15

Water

400

• pH   2 à 3,5
• viscosité Engler   2 à 6 degrés
• refus sur tamis de
  • 0,630 mm   < 0,1%
  • 0,160 mm   < 0,25%
• indice de rupture LCPC   > 160
• diamètre médian   2 à 4 µm
• sédimentation à 7 jours   < 5%

The characteristics of this emulsion are as follows:

• pH 2 to 3.5
• Engler viscosity 2 to 6 degrees
• rejection on sieve of
  • 0.630 mm <0.1%
  • 0.160 mm <0.25%
• LCPC rupture index> 160
• median diameter 2 to 4 µm
• sedimentation at 7 days <5%

• mélange initial   100
  
• eau de mouillage   7,5
• émulsion à 60%   25
• dope pur   0,2
• fibres polyester   0,2
• liant résiduel   15

The composition intended to form the layer of cold-cast mix was prepared by kneading the following mixture, in which the proportions are expressed in parts by weight:

• initial mix 100
  
• dampening water 7.5
• 60% emulsion 25
• 0.2 pure dope
• 0.2 polyester fibers
• residual binder 15

EXAMPLE 2

• mélange minéral   100
  
• eau de mouillage   8
• émulsion à 60%   20
• dope pur   0,2
• fibres polyester   0,2
• liant résiduel   12

The emulsion prepared in Example 1 was used and the following composition was prepared, in the same manner as in Example 1:

• mineral mixture 100
  
• dampening water 8
• 60% emulsion 20
• 0.2 pure dope
• 0.2 polyester fibers
• residual binder 12

EXAMPLE 3 Shrinkage-bending tests

Shrinkage-bending tests were carried out on a test piece reproducing a multi-layer coating of the invention and on test pieces reproducing control coatings.

The test consists in monitoring the rate of ascent of a crack through the various coatings.

• une traction longitudinale continue lente, simulant le retrait thermique.
• une flexion verticale cyclique, à la fréquence de 1 Hz, simulant le trafic.

Each specimen representative of the support + coating complex is subjected, under constant temperature conditions (5 ° C), to two stresses, simultaneously:

• slow continuous longitudinal traction, simulating thermal shrinkage.
• a cyclic vertical bending, at the frequency of 1 Hz, simulating the traffic.

The progress of the crack is followed by a network of conductive wires.

The test makes it possible to estimate, under these conditions, different characteristics linked to the efficiency of the complex studied (appearance of the crack, speed of propagation, complete cracking time of the complex).

A diagram of the machine used is shown in fig. 1.

(1)

représente le bâti de la machine.

(2)

représente les axes de pivotement des plaques en L (3).

(4)

représente des lames souples.

(5)

représente la traverse supérieure de réaction du vérin pneumatique à course règlable (6).

(7)

représente les galets.

(8)

représente les plaques d'appui.

(9)

représente le réglage de la course du vérin pneumatique(6).

(10)

représente les biellettes de transmission de flèche aux plaques en L (3).

(11)

représente le vérin de traction à vis et la circulation de bille.

(12)

représente les plaques de base boulonnées sur les plaques en L (3) (épaisseurs variables suivant l'épaisseur des éprouvettes).

(13)

représente le collage de l'éprouvette sur les plaques de base (12).

(14)

représente la couche de 1,5 cm de béton bitumineux au soufre préfissurée simulant l'ancienne chaussée fissurée.

(15)

représente la préfissure (feuille carton).

(16)

représente l'interface éventuelle (géotextile, membrane, pontage).

(17)

représente le corps d'éprouvette, c'est-à-dire la couche de roulement.

(18)

représente le clinquant collé interdisant les mouvements verticaux des extrêmités de l'éprouvette tout en permettant un mouvement horizontal (par rapport aux plaques de base).

(19)

représente le réseau de détection de fissure.

In Figure 1,

(1)

represents the machine frame.

(2)

represents the pivot axes of the L-shaped plates (3).

(4)

represents flexible blades.

(5)

represents the upper reaction cross member of the pneumatic cylinder with adjustable stroke (6).

(7)

represents the pebbles.

(8)

represents the support plates.

(9)

represents the adjustment of the stroke of the pneumatic cylinder (6).

(10)

represents the arrow transmission links to the L-shaped plates (3).

(11)

represents the screw traction cylinder and ball circulation.

(12)

represents the base plates bolted to the L-shaped plates (3) (thicknesses varying according to the thickness of the test pieces).

(13)

shows the bonding of the test piece on the base plates (12).

(14)

represents the 1.5 cm layer of pre-cracked sulfur bituminous concrete simulating the old cracked pavement.

(15)

represents the prefissure (cardboard sheet).

(16)

represents the possible interface (geotextile, membrane, bridging).

(17)

represents the body of the test piece, that is to say the wearing course.

(18)

represents the glued foil preventing vertical movements of the ends of the specimen while allowing a horizontal movement (compared to the base plates).

(19)

represents the crack detection network.

• a - Couche support préfissurée en sable bitume soufre d'une épaisseur de 15 mm;
• b - éventuellement système à étudier;
• c - Couche de roulement étalon en béton bitumineux témoin 0/10, désigné ci-après par BB 0/10, généralement en 6 cm d'épaisseur répondant à la formule suivante :

The test specimens were prepared at the compacting table in 400 x 600 xe (mm) plates, e being the thickness. They consist of the following layers:

• a - Pre-cracked support layer in sulfur bitumen sand with a thickness of 15 mm;
• b - possibly the system to be studied;
• c - Standard test layer of 0/10 bituminous concrete, designated below by BB 0/10, generally 6 cm thick, corresponding to the following formula:

Each plate is sawn to provide three test specimens of dimensions 560 x 110 x e. Each test piece receives a network of conductive wires forming part of the crack monitoring system. The test piece is then bonded to two half-plates (made of aluminum) and fixed to the machine according to the diagram in Figure 1.

For a more detailed description of the measurement process and device used, see: "Reflective Cracking in Pavement, Assessment and Control" published for the Conference held in Liège, Belgium on May 8, 9 and 10, 1989, relating the conference by JH Vecoven, LRPC d'Autun, entitled: "Method for studying systems limiting the rise of cracks in pavements".

A support + complex coating complex according to the invention was studied in the context of this experiment, by comparison with three control complexes. Their constitutions are indicated in Table I below.

• Période sans fissure (de l'origine à l'instant amorçage);
• Apparition de la fissure en fond de couche (instant amorçage);
• Période de remontée de la fissure;
• Rupture rapide du système (instant de fissuration totale).

The behavior under test of the systems to be tested can be broken down as follows:

• Period without cracking (from the origin to the moment of priming);
• Appearance of the crack at the bottom of the layer (instant initiation);
• Crack recovery period;
• Rapid breakdown of the system (instant of total cracking).

The results for each studied system, are represented on the graph of figure 2 which provides the progression of crack as a function of time. The cracked thickness E, in mm, is plotted on the ordinate. The cracking time T, in minutes, is plotted on the abscissa.

Each curve corresponds to the average behavior of two test pieces. The number assigned to each curve is the number of the corresponding sample.

The test, although simulating the stresses to which the road is subjected, can only be interpreted by making comparisons with known control systems. The controls used in this study are bituminous concretes at 60/70 directly bonded to their cracked support (samples and curves n ° 1 and 2) and a bituminous concrete system at 60/70 + rich bitumen sand 80/100 itself bonded. on its support (sample and curve n ° 3).

When we observe the curves in Figure 2, we note that the ignition times are quite similar. The witnesses and the system according to the invention seem to have fairly similar behavior during this phase.

• Procédé bicouche :   6 mm/h
• Procédé membrane-coulis :   4 mm/h

On the other hand, when one considers the first phase of propagation of the crack (the first two centimeters), the average speeds of cracking are notably different:

• Two-layer process: 6 mm / h
• Membrane-grout process: 4 mm / h

By comparing the system according to the invention and the control systems, it appears that the systems according to the invention have better resistance to the propagation of cracking.

Claims (11)

1. A multicourse surfacing for a pavement, intended to slow or supress the ascent of the cracks liable to appear in the base course of the pavement, made of an asphaltic membrane applied to the base course and of a wearing or binder course, characterized in that it comprises at least one layer of cold mix between the asphaltic membrane and the wearing or binder course.
2. The multicourse surfacing as claimed in claim 1, wherein the asphaltic membrane is formed of pure asphalt or of asphalt modified with thermoplastic copolymers.
3. The multicourse surfacing as claimed in either of claims 1 and 2, wherein the layer of cold mix contains an asphaltic binder and a granular material whose maximum particle size is less than about 10 mm.
4. The multicourse surfacing as claimed in claim 3, wherein the granular material is selected from among crushed sands.
5. The surfacing as claimed in either of claims 3 and 4, wherein the asphaltic binder contains a pure asphalt.
6. The surfacing as claimed in any one of claims 3 to 5, wherein the asphaltic binder contains an asphalt modified by the addition of at least one copolymer.
7. The surfacing as claimed in claim 6, wherein the copolymer is selected from among ethylene/vinyl acetate copolymers, triblock styrene/butadiene/styrene copolymers, diblock styrene/butadiene rubber copolymers (SBR), acrylic copolymers and mixtures thereof.
8. The surfacing as claimed in any one of claims 1 to 7, wherein the layer of cold mix contains synthetic fibers.
9. The surfacing as claimed in any one of claims 1 to 8, wherein it comprises a primer layer between the base and the asphaltic membrane.
10. A method of producing a pavement surfacing as claimed in any one of claims 1 to 9, intended to slow down the propagation of cracks from the base courses through the surfacing, wherein it comprises applying successively to the base course of the pavement, optionally covered with a primer layer:

    - a layer of asphaltic binder,

    - by cold pouring, a layer of a composition containing an asphaltic binder and a granular material,

    - a wearing course or binder course.
11. The method as claimed in claim 10, wherein the wearing course or binder course is applied hot.

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