EP0603369B1 - Advanced rising crack prevention system between the structural and wearing courses of a roadway, and method for producing same - Google Patents

Abstract

PCT No. PCT/FR93/00690 Sec. 371 Date Apr. 25, 1994 Sec. 102(e) Date Apr. 25, 1994 PCT Filed Jul. 5, 1993 PCT Pub. No. WO94/01623 PCT Pub. Date Jan. 20, 1994.A rising crack prevention system between the structural and wearing courses of a roadway is provided which includes a geotextile layer impregnated with a first asphalt binder, and further includes a layer of roadstones coated with a second asphalt binder adjacent to the geotextile layer impregnated with the first asphalt binder. The unique double-layer construction of the rising crack prevention system is efficient in preventing or at least greatly slowing down the spread of cracks from the structural course to the wearing course of the road.

Description

The invention relates to an improved anti-lift system of cracks inserted between the structure layer and the wearing course of a roadway. It relates still to a method for the realization of such a system.

Road or airport roads are generally formed of several layers, namely a upper layer, called wearing course, based on a material of the surface coated type or even of the concrete type bituminous and one or more lower layers forming the structural layer of the pavement, based on materials treated with hydraulic binders such as cements, dairy blast furnace, pozzolan, fly ash, binders bituminous.

For structures with hydraulic binders, the various mechanical and thermal stresses of a nature static, for example plug withdrawal and thermal withdrawal materials, or of a dynamic nature, namely constraints related to traffic, to which roadways are subject cause the structure layer to crack, the generated cracks transmitting more or less quickly to the wearing course and then appear on the surface of the latter. The presence of cracks on the surface of the pavement allows water to enter the body of said pavement, which causes rapid degradation and important of the latter.

• création d'une interface consistant en une membrane en bitume/caoutchouc coulée sur la couche de structure pour découpler les mouvements de cette dernière et ceux de la couche de roulement qui la surmonte,
• renforcement en traction des couches de béton bitumineux de surface par des grilles de polyester présentant des caractéristiques mécaniques suffisantes, ou encore
• dépôt d'un non tissé de polyester sur la couche de structure fissurée, puis recouvrement du non tissé par une couche d'environ cinq centimètres d'un béton bitumineux qui constitue la couche de roulement.

To prevent or at least delay the appearance of cracks in the wearing course of a roadway, the structural layer of which is subject to cracking, various solutions have been proposed, such as:

• creation of an interface consisting of a bitumen / rubber membrane poured onto the structural layer to decouple the movements of the latter and those of the wearing course which overcomes it,
• tensile reinforcement of the bituminous concrete surface layers by polyester grids having sufficient mechanical characteristics, or
• depositing a polyester nonwoven on the cracked structure layer, then covering the nonwoven with a layer of about five centimeters of bituminous concrete which constitutes the wearing course.

Such solutions have not led to satisfactory results, the cracks reappearing more or less quickly on the surface.

A more efficient solution, proposed in the quote FR-A-2592411, consists of interposing, between the structural layer and the wearing course, an interface in non-woven geotextile impregnated with a bituminous binder consisting of a bitumen modified, for example, by a copolymer of styrene and a conjugated diene such as butadiene.

In an article called “Geogrids in reinforcing asphaltic pavements ”and published in Highways, Vol. 58 (January 1990), no. 1957, Croydon GB, pages 12 to 14, D.S. BUIST and P.R. INESON describe, among other things, the use a polypropylene geotextile mesh (Netlon Tensar Grid AR), to reduce cracking of pavements. More in particular, in the paragraph “Hot Mix Pad Coat” (page 12, column 4), the authors indicate that on the trellis geotextile, kept in tension on the structure layer by fixings and possibly by using a bonding layer, there is manually a layer of hot mixes that are compacted, before carrying out the pavement wearing course.

In the citation EP-A-0469222, a pavement covering with a geotextile sheet bonded, using a layer of bituminous adhesive, to the bituminous concrete base layer of a pavement, by example old road surface, said ply being covered with a porous wearing course at bituminous mix base. If necessary, a layer can be arranged on the base layer in bituminous concrete to eliminate surface irregularities of said layer before laying the geotextile sheet.

We have now found that we could improve the performance of anti-rising crack systems in type of that described in the citation FR-A-2592411, in adjoining a layer of aggregates coated with a quantity specific of a bituminous binder to the geotextile layer itself impregnated with a bituminous binder.

The anti-crack recovery system according to the invention, which is sandwiched between the structural layer and the wearing course of a pavement, is of the type comprising a layer of a geotextile impregnated with a first bituminous binder and a layer of aggregates coated with a second bituminous binder, which is attached to the layer of geotextile impregnated with the first bituminous binder, and it characterized in that the second bituminous binder associated with aggregates, to form the asphalt layer, are used in an amount between 3% and 20% of the weight of aggregates.

According to a first embodiment, the system anti-crack recovery is arranged so between the structural layer and the wearing course of the pavement that the geotextile layer impregnated with the first bituminous binder rests on the structural layer of the pavement, while the layer of aggregates coated with second bituminous binder is coated with the layer of rolling.

According to a second embodiment, the system anti-crack recovery is arranged so between the structural layer and the wearing course of the pavement as the layer of aggregates coated with the second binder bituminous rests on the structure layer of the roadway, while the geotextile layer impregnated with the first bituminous binder is coated with the wearing course.

The layer of aggregates coated with the second binder bituminous can advantageously be a layer of sand coated with said binder. We can also build the layer of aggregates coated with the second bituminous binder by a layer of a cold poured mix or with a layer draining mix.

By geotextile is meant according to the invention any tight texture textile tablecloth, which is produced at from natural or synthetic yarns or fibers and that we usually use in the operations of road construction and land stabilization. Advantageously, the geotextile used according to the invention consists of a nonwoven web formed of filaments continuous based on a polymer such as polyester, isotactic polypropylene, polyamide, polyacrylonitrile, cellulose acetate, polyvinyl chloride, polychloride vinylidene. Especially suitable for a geotextile consisting of a tightly woven nonwoven tablecloth formed of continuous polypropylene-based filaments isotactic, or a polyester, in particular polyalkylene glycol terephthalate such as polyterephthalate ethylene glycol, or a polyamide, in particular polycaproamide or polyhexamethylene adipamide. The tablecloth no woven formed of continuous filaments based on a polymer can be in particular the tablecloth described in one or the other of the citations FR-A-1601049, FR-A-2108145 and FR-A-2592411, said citations indicating the general method of production of such a tablecloth.

The surface mass of the textile sheet constituting the geotextile can vary quite widely and is advantageously between 50 and 500 g / m ² . For example, when the textile web has the structure of the web described in the FR-A-2592411 quote, the surface mass of said textile web is preferably between 100 and 300 g / m ² .

The first bituminous binder, which permeates the geotextile to form the impregnated geotextile layer of the anti-crack rise system, is used advantageously in an amount between 200 g and 1500 g and preferably between 300 g and 1000 g per square meter of geotextile sheet.

The second bituminous binder associated with aggregates, to form the layer of coated aggregates of the anti-lift system of cracks, is more particularly used in quantity included between 4 and 12% of the weight of the aggregates.

In the variant "sand coated with the second binder bituminous ", the aggregate component can be chosen from the various sands that are used on construction sites and whose 6 mm sieve pass is greater than 80% and preferably equal to 100%.

In the "cold cast mix" variant, the aggregate component, selected from sands which are used on road construction sites and whose passer-by 6 mm sieve is greater than 80%, is coated with the second bituminous binder, used in aqueous emulsion, after have been previously contacted with a solution surfactant and possibly with a quantity of cement less than 3% of the weight of the sand forming the component aggregate.

In the "asphalt draining" variant, the component aggregate, chosen from the gravel that is used on road works and including the passer by a 20 mm sieve is greater than 90%, is hot-coated with the second binder bituminous so as to provide, after compaction, a vacuum content in the mix between 15% and 35% and preferably between 20% and 30%.

The first bituminous binder, which permeates the geotextile, as well as the second bituminous binder, which coats the aggregates, can be of identical natures or different and are chosen from bitumens and bitumens modified by polymers, which have a viscosity dynamic at 100 ° C between 0.4 Pa.s and 25 Pa.s and from preferably between 0.7 Pa.s and 20 Pa.s. The first and second bituminous binders can be chosen in particular from bitumens modified with copolymers of styrene and a conjugated diene and especially among bitumens modified with block copolymers of styrene and a diene conjugate such as butadiene, isoprene, carboxylated butadiene, the preparation of which is described in the citations FR-A-2376188, FR-A-2429241, FR-A-2528439 and FR-A-2636340.

To impregnate the geotextile or coating the granules with the chosen bituminous binder, this the latter can be used either in the molten state or under the form of an aqueous emulsion, for example emulsion described in one or other of the citations FR-A-2517317, FR-A-2577545 and FR-A-2577546.

A method for producing an anti-rising crack system according to the invention, sandwiched between the structure layer and the wearing course of a roadway, said system comprising a layer of a geotextile impregnated with a first bituminous binder and attached to a layer of aggregates coated with a second bituminous binder, is of the type in which one of the layers of the crack prevention system on the layer of pavement structure, then we coat the layer as well formed using the other layer of the anti-lift system cracks and apply the wearing course on the assembly thus formed and it is characterized in that, in the layer of aggregates coated with the second bituminous binder, the amount of said binder is between 3% and 20% and more particularly between 4% and 12% of the weight of the aggregates.

According to a first form of implementation, one first apply the geotextile layer impregnated with first bituminous binder on the structure layer of the pavement, then we cover said geotextile layer with layer of aggregates coated with the second bituminous binder and on this last layer we apply the wearing course of the roadway.

According to a second form of implementation, we first apply the layer of aggregates coated with second bituminous binder on the structure layer of the pavement, then coating said layer of coated aggregates by the geotextile layer impregnated with the first binder bituminous and on this last layer we apply the pavement wearing course.

The road surface, which rests on the anti-rising crack system, can be anything type known in the art, the binder used for this layer of bearing being a pure bitumen or a modified bitumen by a polymer and in particular by a copolymer of styrene and a conjugated diene such as butadiene, isoprene or butadiene carboxylated.

When the pavement structure layer is cracked, it is useful to plug the most wide, for example cracks wider than 2 mm, at using a bridging agent consisting of a putty bituminous before applying, on said layer of structure, the first layer, namely impregnated geotextile or aggregates coated, as appropriate, with the anti-lift system cracks.

The layer of aggregates coated with the second binder bituminous which constitutes one of the two layers of the system anti-crack recovery according to the invention has a thickness can be between 1 cm and 6 cm.

The invention is illustrated by the following examples given without limitation.

EXAMPLES 1 TO 3:

In these examples, we study the propagation of cracks in test pieces simulating a structure of roadway with or without an anti-lift system cracks.

The test pieces used each consisted of a multilayer rectangular plate, said plate having a length of 560mm and a width of 110mm and comprising a pre-cracked support layer along its transverse axis simulating the cracked structural layer of a roadway and an apparent layer simulating the wearing course of the pavement, this last layer resting directly on the pre-cracked support layer or being separated from this layer support by an anti-rising crack system.

By using said test tubes, tests to determine the ascent rate of the support layer crack in the test layer simulating the wearing course.

These tests were carried out on a testing machine shrinkage-bending comprising a fixed flat support element and a plane movable support element in translation, defining together a horizontal support plane. The test piece submitted to the test was mounted on the test machine so that that one of the halves of the free face of the support layer transversely prefissured of the test piece was glued on one of the flat support elements and that the other of said halves was glued to the other of said support elements plans.

• une traction longitudinale continue lente, avec une vitesse de 5 µm par minute, simulant le retrait thermique, et
• une flexion verticale cyclique, à la fréquence de 1Hz, simulant le trafic.

Each test piece mounted on the testing machine was subjected, under constant temperature conditions (operation at a temperature of 5 ° C.), simultaneously to two types of stress, namely

• slow continuous longitudinal traction, with a speed of 5 μm per minute, simulating thermal shrinkage, and
• a cyclical vertical bending, at the frequency of 1Hz, simulating the traffic.

The progression of the crack in the layer of the test specimen simulating the wearing course was followed at by means of a network of electrically conductive wires bonded to different heights on the edge of said layer in the area of this song where the crack of such must develop so that the rise in the crack in the layer causes a successive cut of these wires, the position of the wires cut being recorded as a function of time solicitation of the test piece.

On the curve thus obtained, representative of the propagation of the crack as a function of time, the time t _R2 was determined at the end of which the crack had risen by 2 cm in the wearing course.

The test pieces used during the tests had the following structures:
EXAMPLE 1 : two-layer test pieces not comprising an anti-rising crack system, said test pieces being formed from a prefissured support layer 15 mm thick directly surmounted by a wearing layer 50 mm thick.
EXAMPLE 2 : test pieces comprising a pre-cracked support layer 15 mm thick and a wearing layer 30 mm thick between which was interposed a witness system anti-crack recovery consisting of a geotextile sheet impregnated with a bituminous binder of bitumen / polymer type.
EXAMPLE 3 test pieces comprising a pre-cracked support layer 15 mm thick and a wearing layer 30 mm thick between which was interposed an anti-crack recovery system according to the invention, said system being formed of a layer consisting of a geotextile sheet impregnated with a bituminous binder of the bitumen / polymer type resting on the support layer and surmounted by a layer of 20 mm thick of sand coated with a bitumen / polymer binder, this layer of coated sand being surmounted by the wearing course.

The transverse pre-cracked support layer of various test pieces were made from the same concrete bituminous based on sand, bitumen and sulfur.

The wearing course of the various test pieces consisted of a discontinuous 0/10 bituminous concrete formed of 6 parts by weight of a bitumen / polymer composition vulcanized with sulfur and 100 parts by weight of a mixture made by weight of 60% gravel 6 / 10mm, 10% sand 0 / 4mm, 27.5% 0 / 2mm sand and 2.5% filler fines (80% said fines passing the 80 µm sieve and 100% passing the 315µm sieve).

The bitumen / polymer composition used for the realization of the wearing course of the test specimens was prepared as follows. We mixed at 170 ° C and below stirring, 100 parts by weight of a bitumen 180/220 of penetration equal to 200 with 3 parts by weight of a butadiene / styrene block copolymer having a mass molecular viscosimetric mean equal to 75000 and a styrene content by weight equal to 25%, then after 3.5 hours of mixing was added 0.1 part by weight of sulfur to the mass obtained and stirring was continued at the temperature of 170 ° C for another 30 minutes.

The bitumen / polymer composition obtained had a dynamic viscosity at 100 ° C equal to 8.5 Pa.s.

The geotextile sheet impregnated with bituminous bitumen / polymer binder, used in the test pieces of Examples 2 and 3, consisted of a sheet of a nonwoven of isotactic polypropylene yarns having a grammage of 170 g / m ² impregnated with 900 g / m ² d 'a bitumen / polymer binder having a dynamic viscosity at 100 ° C equal to 1 Pa.s, said binder being applied to the web in the form of an aqueous emulsion.

This bitumen / polymer binder was prepared as follows. We first formed a stock solution by incorporating, 100 ° C and with stirring, 2.4 parts by weight of sulfur orthorhombic crystallized and 62 parts by weight of styrene / butadiene block copolymer defined above at 230 parts by weight of a character oil cut naphtheno-paraffinic having an initial point and a point final distillation ASTM (ASTM standard D8 667) equal respectively at 162 ° C and 233 ° C, said incorporation being completed in 1 hour. The stock solution thus obtained was then incorporated into 1950 parts by weight of a bitumen of penetration equal to 82, maintained at 170 ° C. with stirring, after which the mixture thus produced was still maintained with stirring at 170 ° C for 30 minutes.

Bitumen / fluidized polymer binder (viscosity dynamic at 100 ° C equal to 1 Pa.s) thus obtained was then put into an aqueous emulsion as indicated in Example 3 of the FR-A-2577546 to produce the binder emulsion bitumen / polymer used to impregnate the geotextile sheet.

The layer of sand coated with bitumen / polymer binder present in the test tubes of Example 3 was formed of 9 parts by weight of bitumen / polymer binder consisting of same bitumen / polymer composition as that used in the constitution of the wearing course and 100 parts in weight of a mixture consisting, by weight, of 44% of gravette 2/6 mm, 53% 0 / 2mm sand and 3% of the same filler fines nature than those used to produce the layer of rolling.

The results of the control tests and according to the invention are collated in the table below. Examples Crack prevention system t _R2 (min) 1 No 360 2 Geotextile impregnated with bituminous binder of the bitumen / polymer type 450 3 Geotextile impregnated with bituminous binder of the bitumen / polymer type + Sand coated with bitumen / polymer binder 730

The comparison of the results recorded in the table clearly brings out the effectiveness strongly improved anti-crack recovery system according to the invention (example 3) compared to an anti-lift system cracks according to the state of the art (example 2).

Claims (30)

1. System for preventing the upward migration of fissures, which system is sandwiched between the structure layer and the surface layer of a road and is of the type comprising a geotextile layer impregnated with a first bituminous binder and a layer of aggregate coated in a second bituminous binder, which layer is placed next to the geotextile layer impregnated with the first bituminous binder, the system being characterised in that the second bituminous binder, associated with the aggregate to form the layer of coated materials, is used in an amount of between 3% and 20% of the aggregate's weight.
2. System according to Claim 1, characterised in that it is arranged between the road's structure layer and surface layer in such a manner that the geotextile layer impregnated with the first bituminous binder rests upon the structure layer of the road, whilst the layer of aggregate coated in the second bituminous binder is covered by the surface layer.
3. System according to Claim 1, characterised in that it is arranged between the road's structure layer and surface layer in such a manner that the layer of aggregate coated in the second bituminous binder rests upon the structure layer of the road, whilst the geotextile layer impregnated with the first bituminous binder is covered by the surface layer.
4. System according to any one of Claims 1 to 3, characterised in that the geotextile comprises a high density textile sheet having a surface mass of between 50 and 500 g/m².
5. System according to Claim 4, characterised in that the textile sheet comprises a non-woven formed by polymer-based continuous filaments.
6. System according to Claim 5, characterised in that the filaments forming the non-woven sheet are based on a polyester, for example polyalkylene glycol terephthalate, such as polyethylene glycol terephthalate, or on a polyamide, for example polycaproamide or polyhexamethylene adipamide, or on an isotactic polypropylene.
7. System according to any one of Claims 1 to 6, characterised in that the first bituminous binder which impregnates the geotextile is used in an amount of between 200 g and 1500 g, and preferably between 300 g and 1000 g, per m² of geotextile sheet.
8. System according to any one of Claims 1 to 7, characterised in that the second bituminous binder is used in an amount of between 4% and 12% of the weight of the aggregate.
9. System according to any one of Claims 1 to 8, characterised in that the layer of aggregate coated in the second bituminous binder comprises a layer of sand coated in said binder.
10. System according to Claim 9, characterised in that the sand used to form the layer of coated sand is chosen from among the sands which are used for road works and of which more than 80% of the grains, and preferably 100%, pass through a 6 mm mesh sieve.
11. System according to any one of Claims 1 to 8, characterised in that the layer of aggregate coated in the second bituminous binder comprises a cold-formed mix.
12. System according to Claim 11, characterised in that the cold-formed mix comprises an aggregate component, selected from among the sands which are used for road works and of which more than 80% of the grains pass through a 6 mm mesh sieve, coated in the second bituminous binder, applied in the form of an aqueous emulsion, having previously been placed in contact with a surfactant solution and, optionally, with an amount of cement totalling less than 3% of the weight of the sand forming the aggregate component.
13. System according to any one of Claims 1 to 8, characterised in that the layer of aggregate coated in the second bituminous binder comprises a draining mix.
14. System according to Claim 13, characterised in that the draining mix comprises an aggregate component, selected from among the chippings which are used for road works and of which more than 90% pass through a 20 mm mesh sieve, hot-mixed with the second bituminous binder in order to produce, after compaction, cavities in the mix totalling between 15% and 35%, and preferably between 20% and 30%.
15. System according to any one of Claims 1 to 14, characterised in that the first bituminous binder, which impregnates the geotextile, and the second bituminous binder, which coats the aggregate, are of different or identical types and are selected from among pure bitumens and bitumens modified by polymers which have a dynamic viscosity at 100°C of between 0.4 Pa/s and 25 Pa/s, and preferably between 0.7 Pa/s and 20 Pa/s.
16. System according to Claim 15, characterised in that the first and the second bituminous binders are selected from among the bitumens modified by copolymers of styrene and a conjugated diene and, especially, from among the bitumens modified by block copolymers of styrene and a conjugated diene, such as butadiene, isoprene or carboxylated butadiene.
17. System according to any one of Claims 1 to 16, characterised in that the bituminous binder is used in the molten state or in the form of an aqueous emulsion in order to impregnate the geotextile and coat the aggregate.
18. Process for producing a system for preventing the upward migration of fissures, which system is sandwiched between the structure layer and the surface layer of a road, the system comprising a geotextile layer impregnated with a first bituminous binder and placed next to a layer of aggregate coated in a second bituminous binder, the process being of the type where one of the layers of the system for preventing the upward migration of fissures is applied to the structure layer of the road, then the layer so formed is covered by the other layer of the system for preventing the upward migration of fissures and the surface layer is applied to the whole so formed, and it is characterised in that, within the layer of aggregate coated in the second bituminous binder, the amount of said binder lies between 3% and 20% of the weight of the aggregate.
19. Process according to Claim 18, characterised in that first the geotextile layer impregnated with the first bituminous binder is applied to the structure layer of the road, then the geotextile layer is covered by the layer of aggregate coated in the second bituminous binder, and the surface layer of the road is applied to this last layer.
20. Process according to Claim 18, characterised in that first the layer of aggregate coated in the second bituminous binder is applied to the structure layer of the road, then the layer of coated aggregate is covered by the geotextile layer impregnated with the first bituminous binder, and the surface layer of the road is applied to this last layer.
21. Process according to any one of Claims 18 to 20, characterised in that the geotextile comprises a high-density textile sheet having a surface mass of between 50 and 500 g/m².
22. Process according to Claim 21, characterised in that the textile sheet comprises a non-woven formed by polymer-based continuous filaments.
23. Process according to Claim 22, characterised in that the filaments forming the non-woven sheet are based on a polyester, for example polyalkylene glycol terephthalate, such as polyethylene glycol terephthalate, or on a polyamide, for example polycaproamide or polyhexamethylene adipamide, or on an isotactic polypropylene.
24. Process according to any one of Claims 18 to 23, characterised in that the amount of the first bituminous binder which impregnates the geotextile is between 200 g and 1500 g, and preferably between 300 g and 1000 g, per m² of geotextile sheet.
25. Process according to any one of Claims 18 to 24, characterised in that the amount of the second bituminous binder which coats the aggregate is between 4% and 12% of the weight of said aggregate.
26. Process according to any one of Claims 18 to 25, characterised in that the layer of aggregate coated in the second bituminous binder comprises a layer of sand coated in said binder, a cold-formed mix or a draining mix.
27. Process according to any one of Claims 18 to 26, characterised in that the first and second bituminous binders are selected from among pure bitumens and bitumens modified by polymers which have a dynamic viscosity at 100°C of between 0.4 Pa/s and 25 Pa/s, and preferably between 0.7 Pa/s and 20 Pa/s, the bituminous binders being, more especially, bitumens modified by copolymers of styrene and a conjugated diene, the copolymers being more especially block copolymers of styrene and a conjugated diene, such as butadiene, isoprene or carboxylated butadiene.
28. Process according to any one of Claims 18 to 27, characterised in that the bituminous binder is used in the molten state or in the form of an aqueous emulsion in order to impregnate the geotextile and coat the aggregate.
29. Process according to any one of Claims 18 to 28, characterised in that the surface layer contains a binder comprising a pure bitumen or a bitumen modified by a polymer and, in particular, by a block copolymer of styrene and a conjugated diene, such as butadiene, isoprene or carboxylated butadiene.
30. Process according to any one of Claims 18 to 29, characterised in that, if the structure layer of the road contains fissures, the widest fissures, especially those wider than 2 mm, are plugged using a bituminous mastic before applying to the structure layer the impregnated geotextile layer or the layer of coated aggregate of the system for preventing the upward migration of fissures.