EP1838924A1

EP1838924A1 - Low-grip track for driving vehicles

Info

Publication number: EP1838924A1
Application number: EP05700322A
Authority: EP
Inventors: Jean-Claude Zucker; Franz Hummel
Original assignee: Individual
Current assignee: HUMMEL, FRANZ; Zucker Jean-Claude
Priority date: 2005-01-19
Filing date: 2005-01-19
Publication date: 2007-10-03
Also published as: WO2006076816A1

Abstract

The invention relates to a track for driving road motor vehicles in low-grip conditions with a road surface comprising a bituminous concrete coating, wherein said coating comprises a running layer consisting of a non-draining coated material and a finishing film formed by means of a bitumen-based hardenable liquid composition

Description

Low grip track for driving vehicles

The present invention relates to a track for driving land vehicles with motor in low adhesion conditions, with a pavement comprising a coating of asphalt concrete. The present invention also relates to a mix intended for the production of such a track.

The vehicles concerned by the present invention are both passenger cars and competition vehicles, the latter including both modified road vehicles according to various sport categories and specific vehicles such as cars and karts. The invention also relates to two - wheeled vehicles such as motorcycles and motorcycles, road or competition.

A bituminous concrete road surface includes one or more support layers, located over a foundation layer or other suitable support. The support layer (s) provide (s) the bearing capacity of the coating. Above the (or) layer (s) of support is laid a wearing course, which is the top layer of the coating. It ensures road safety and comfort of traffic. Both the support layers and the wearing courses are coated with mineral aggregates and bituminous binders and any additives. Asphalt specifications include:

- the designation of the type of asphalt mix;

- granulometry of aggregates;

- the proportions of sand, chippings and / or crushed and / or rolled stones;

- the type of binder;

the dosage of the binder;

- the nature and quantity of any additives;

- the contents in voids;

- indicative values of stability and creep. For the construction of public roads, these specifications meet many national standards, in particular residual voids and filled voids, as well as stability, rigidity and creep, commonly referred to as Marshall features.

An extremely important feature of a public roadway is its slip resistance. This is variable in time, depending on its wear and weather conditions. Improving the anti-skid quality of the wearing course, i.e., increasing the adhesion of tires to the surface of the coating, is a constant concern of those skilled in the art. Many proposals have been made to this effect. By way of example, WO 99/19566 proposes to make the upper surface of the wearing course rougher by enriching it with crushed, sharp-edged granules so as to increase the frictional forces. To improve the adhesion on wet pavement, it has been proposed the realization of draining mixes: these are characterized by the presence of a significant percentage of voids, of the order of 20%, corresponding to at least about 12% communicating empty voids, providing drainage of the wearing course. These mixes are obtained by combining a large fraction of coarse aggregates (> 2 mm) with a fine fraction and limiting the proportion of bituminous binder / coating generally to 6%, exceptionally 7.5% at most. Examples of such mixes that may be mentioned are those described in document FR 2674548 or in DE 29615276 U.

Whatever the composition of these mixes, the adhesion capacity of a vehicle on a roadway is greatly reduced when the roadway is wet, snowy, or covered with dead leaves, chippings or mud, or even residues. oil or a thin film of sand. Compared to optimal conditions, vehicle in perfect condition on good quality pavement and dry, the adhesion can be reduced by half on a wet pavement, and even up to the tenth in conditions of icy road or in the presence of puddles generating a phenomenon of aquaplaning.

Some driving education organizations organize specific courses in winter conditions. Since these courses are weather dependent, they can only be delivered a few days a year when the pavement is covered with snow or ice. Some sports organizations, such as the IRSI (Ice Race Series International), organize snow-covered and / or ice track races. These races are of increasing interest to the public, because of their spectacular nature, but can only be organized in mountain areas and during the limited period of winter when the low temperatures necessary for the maintenance of a track snow and ice are assured.

To teach drivers to control their vehicles in these difficult conditions, it is known to arrange runway segments or annular tracks by coating a concrete substrate or road surface with several layers of synthetic material based on epoxy or polyester resins. reinforced with fibers. An example of such coatings is described in DE 3314505. The adhesion of a vehicle to this type of track is greatly reduced when watering them with water. These installations therefore make it possible to teach the basics of driving in conditions of low adhesion, but have several defects.

The resins used are expensive and the development of this type of track consumes 2 - 5 kg / m ² . Because of the differences in physical properties between resins and road mix or underlying concrete, the resin layers tend to crack and separate from the substrate. then With braking and skidding, the layers of resin are gradually pulled out, so that they must be replaced frequently: in a teaching center operating in a regular manner, these layers of synthetic coatings must be replaced at least twice a year. For this reason, and because it is also necessary to constantly water these tracks, the length thereof is limited in practice to lengths of the order of one hundred meters. It is not conceivable, for reasons of cost, to make road-type sections or tracks of the automobile circuit of a length of several kilometers. The variety of practicable exercises on these very short tracks is therefore necessarily limited. In addition, these tracks coated with resin require the use of smooth tires. For practical reasons of organization, these tracks are always used with the same school vehicles; the student driver can not exercise with his own vehicle.

The use of these resins can not in practice be envisaged to cover an automobile racing circuit to simulate a race on ice, because of the extremely high powers developed by the racing vehicles, which would cause the almost immediate tearing of the layers of racing. resin.

To produce test tracks for car manufacturers and having a calibrated roughness, the document DE 10116625 proposes to treat a traditional coating, in particular in concrete coating, by a process consisting of a preliminary milling followed by a calibrated polishing and clogging of the pores of the surface with a synthetic resin or cement. The polishing operation must be repeated frequently, ie after a few braking test sessions, to restore the initial specified roughness coefficient. The cost of such maintenance operations is prohibitive for teaching or competition tracks open to the public. The document US Pat. No. 5,352,062 proposes to make a slippery track, the wearing course of which uses an asphalt concrete having a coarse grain size fraction, about 5-20 mm, majority, associated with a fine fraction of sand. The coated asphalt is subjected to a first sanding or dissolving operation to remove the bituminous binder at the surface, and then the coarse aggregates thus exposed are subjected to a polishing operation. The slipperiness of this coating is similar to that of a used road surface. However, this coating has defects for use in a teaching or competition center: by its composition, this asphalt is draining and therefore requires significant watering to achieve and maintain conditions of low adhesion. On the other hand, the operation exposing the coarse aggregates simultaneously causes their partial loosening relative to the binder which surrounds them, so that they are easily torn off during violent braking.

The patent application WO 2004/055271 of the applicants describes a low adhesion track of the defined type of entry, where the coating comprises a wearing course consisting of a non-draining bituminous mix. In this mix, the mineral aggregates consist of more than 90% of 0/4 granular class materials, and the binder / asphalt content is 8.5 ± 1% by mass. The surface of this track has in the dry state the same conditions of adhesion as a normal wet road. If wet, its grip characteristics become close to those of a snowy road. But moreover, its Marshall characteristics are substantially those of a pavement with road standards. This track allows to teach throughout the year the specific driving technique adapted to this kind of weather, even with heavy vehicles.

However, some driving education centers and race organizers may wish have tracks with even lower grip. In addition, some organizers may wish to have a low grip track that does not require watering, particularly in the case where a track must be installed inside a pre-existing hall that does not have a drainage system. water.

A first object of the present invention is to provide a track for driving motor vehicles reproducing conditions of low adhesion in the dry state and very low wet adhesion.

A second object of the present invention is to provide such a track with an installation cost that does not substantially exceed that of a road section having the same arrangement.

A third object of the invention is to provide such a track whose maintenance cost is low, in particular which does not need frequent replacement of a surface layer.

A fourth object of the invention is to provide a track whose structure withstands without unacceptable deformations violent mechanical stresses such as those caused by very powerful competition vehicles or heavy vehicles such as trucks.

These objects are achieved according to a first aspect of the invention by means of a track of the defined type of entry, where said bituminous coating comprises a wearing course consisting of a non-draining mix and a finishing film formed by means of curable liquid composition based on bitumen.

The undrained mix of the track according to the invention may have a binder / coating content of 7-13.5% by weight, the mineral aggregates consisting of more than 90% of materials. of granular class 0/4. This wearing course in itself has higher slipperiness than a normal road surface course. •

The slipperiness of the runway surface is furthermore adjustable to the user 's desires by modulating the amount of curable liquid bitumen composition applied per unit area. This amount is of the order of 80-500 g / m ² , generally 100-300 g / m ² , preferably 150-200 g / m ² . The application of this composition closes the superficial pores of the wearing course and generates a thin film whose average total thickness is preferably of the order of 100 .mu.m. We can proceed with a first application ~ 80-120 g / m ² generating a film ~ 50-70μm and a second application ~ 40 - 80 g / m ² generating a film ~ 30-50μm. As needed, the application may be repeated several times to further thicken and / or equalize the film. Without being bound by the theory, it appears that because of the presence of solvent / diluent for bitumen in the curable liquid composition before drying, there is interaction and bonding with the surface portion of the bituminous binder of the wearing course already at asked. The wearing course can therefore be assimilated at the level of the finishing film, with regard to its surface properties, to a very closed mix with a very high binder content, whereas in its entire volume, its composition confers on it Marshall stability characteristics, sufficient for use, teaching or competition, for which it is intended. Since the curable composition is based on bitumen, it exhibits, after drying, physical properties close to those of the bituminous binder of the wearing course, particularly as regards the coefficient of thermal expansion. The finishing film does not tend to fade from the wearing course due to temperature variations of the track.

The choice of a non-draining asphalt mix, in particular a mix with a residual voids content of 4 ± 2%, and / or a filled voids content of 90 ± 8%, combined with a Finishing film formed by, for example, a bitumen - based paint gives this dry runway the properties of an ordinary road which has been subjected to heavy rain, and the adhesion of an icy road after being subjected to a light watering.

Used in dry conditions, this track allows to provide the education corresponding to the driving on slippery road on a relatively long stretch, not watered. It also allows such teaching inside a hall without evacuation of water. It can also be used to organize multi - skid races indoor or in areas where it is too problematic to spread water regularly on a roadway.

In addition, if the track according to the invention is wet by a rain or a watering system, its adhesion characteristics are equivalent to those of a pavement covered with ice. The track according to the invention thus makes it possible to teach throughout the year the extremely specific driving technique adapted to such conditions, which naturally occur only a few days per year.

The track according to the invention has many advantages over low adhesion driving training courses covered with a resin coating:

- the realization of the track implements the technology of the road construction, as well at the level of the equipments, that is to say, central of coating, transport vehicles, laying machines and rollers of compaction that procedures of manufacture and laying of asphalt. Therefore, the installation can be carried out by a public works company without the need for special training;

- The implementation of the finishing film is easy to achieve; the track according to the invention may have the configuration of a section of an ordinary road or a motor circuit of several kilometers in length with all the topographical variants that may be encountered there, such as hairpin curves at hair, large curved curves, sloping, portions of course more or less steep, etc.

Preferably, the undrained asphalt of the wearing course has a Marshall stability greater than 10kN and Marshall creep less than 3.5 mm. The wearing course then has stability and resistance to deformation sufficient for the track to accommodate endurance racing vehicles or trucks without exhibiting deterioration phenomena such as rutting, pulling, etc. , superior to those of a classic racetrack track.

The inventors have found that the finishing film is not torn from the wearing course by the passage of high power vehicles during the acceleration or braking phase. This is quite surprising. In fact, not only do such vehicles tear off the resin layers deposited on a concrete substrate or an ordinary road surface, as was explained above, but these vehicles also tear off a layer of a finishing product of the type of those used in the context of the present invention, deposited on these same concrete substrates or ordinary road surfaces.

Such a track therefore allows the organization of competitions in which the vehicles necessarily perform spectacular slippages popular with the public, and already at speeds much lower than those achieved on a conventionally structured track having the same configuration. According to the invention, the wearing course may be carried out using a non - draining mix with mineral aggregates consisting of more than 90% 0/4 granular material and in which the binder content coated is 7% to 13.5% by weight.

The bituminous binder can be chosen from the binders known in the state of the art for producing wearing courses. It can also be chosen from bitumens modified with polymers. In the case of a track intended to host automobile competitions, a bituminous binder of the type used to produce road surface layers of AB-S or AB-H type will preferably be chosen. To make tracks in dry and hot climates, B20 / 30 or B30 / 50 bitumens are preferably used. The bituminous binder and the aggregates are qualitatively and quantitatively adapted to one another so as to obtain sufficient stability characteristics.

Preferably, granules and binder are chosen so that the wearing course itself has a high slip even in the absence of finishing film, while being mechanically stable. According to a preferred embodiment, the mineral aggregates may consist of crushed sand of 0/2 particle size, the binder is a bitumen selected from bitumen B20 / 30, B35 / 50 or B50 / 60, and the binder content / coated is 11.5 ± 2% by weight. The fraction of fines is important and is opposed to creep. The user can then choose to use his track with a wearing course that has or has not received a finishing film, or a wearing course that has not received a film making it extremely slippery than in certain areas. Thus, changing winter road conditions can be simulated with relatively slippery areas, simply snow-covered areas and ice-covered areas. The invention will be better understood by those skilled in the art by examining the characteristics of an embodiment of a mix according to the invention and the accompanying drawing, in which

- Figure 1 shows the particle size curve of an example of asphalt.

Example 1

A wearing course in the form of an 8 x 30 m test plate is made on a pre-existing support layer. Mineral aggregates used include 99 'crushed sand from Chailloue gravel pit (France) 0/2 and 1' filler from Picketty supplier. 93% of this mixture pass through the 2 mm sieve and 100% pass through the 4 mm sieve. Table 1 gives the particle size, which is also shown in FIG.

Table 1:

Those skilled in the art will recognize that the values of the particle size of Table 1 are surprising compared to the values usually accepted for the production of road surface wearing courses.

We can observe an inflection of the particle size curve due to the presence of a small quantity of gravel fraction 2.0 / 4.0.

The binder used is a B35 / 50 bitumen. The amount of binder used, of the order of 11.3% relative to the mass of aggregates, was significantly greater than the amounts usually accepted for AB road layers.

The implementation equipment includes:

- Crawler Finisher with hydraulic vibratory table extensible to 5 meters, mark ABG and type TITAN; the table is heated to gas at a temperature of 150 °;

- 1 ball compactor, weight: 16 tons;

- 1 combined roller and tire compactor, weight: 12 tons.

After analysis, the asphalt has the following characteristics:

Binder content (% by mass): 11, 3 Density (t / m ³ ): 2, 4

Filler / Bitumen ratio: ~ 1

Surprisingly, despite the high binder content, the mix is not fluent and has excellent stability and rigidity: in this aspect, the wearing course would have the properties of a layer AB-N or AB-S type of road bearing, whereas on the contrary, with regard to the anti-slip qualities, the wearing course would be perfectly unfit for road use, since it has a much too low adhesion. This wearing course is therefore, without any additional surface treatment, it is ready for use as a teaching track or as a track for the organization of a sports competition, in a condition of low adhesion.

If extremely low adhesion conditions are desired, the wearing course may be finished to apply a small amount of bitumen paint. The mono-component paint based on bitumen with mineral fillers, marketed by Sika AG under the name Inertol® W49 Dick, can be used for this purpose. It is spread with a rubber rake in two successive layers at a rate of about 100 g / m ² , then about 60 g / m ² , producing a film which, after drying, has a thickness varying locally because of the roughness of the wearing course, but which is generally between 40 .mu.m and 80 .mu.m. The initial presence of bitumen solvents, when the paint has not yet dried, contributes to intimately bonding the bituminous binder of the wearing course to the deposited paint film material.

Braking and acceleration tests on the plate are conducted by means of a Peugeot 206 WRC type race car, equipped with rally - to - earth type tires. The track according to the invention, with finishing film and wet, has adhesion values close to those of a road covered with ice. At the end of the test session, there is no evidence of tearing or deterioration of the finishing film.

Claims

claims

Track for driving land vehicles with low adhesion, with a pavement comprising a bituminous concrete pavement, characterized in that said pavement comprises a wearing course consisting of a non-draining asphalt, the mineral aggregates of which are made up of more than 90% 0/4 granular material and having a binder / mix content of 7-13.5% by weight, and a finishing film formed from a liquid curable composition based on bitumen.

2. Track according to claim 1, characterized in that said non-draining coating of the wearing course has a residual voids content of 4 ± 2%.

3. Track according to claim 1 or 2, characterized in that said non-draining coating of the wearing course has a filled voids content of 90 ± 8%.

4. Track according to one of claims 1-3, characterized in that said non-draining coating of the wearing course has a Marshall stability greater than 10 kN and Marshall creep less than 3.5 mm.

Track according to any one of the preceding claims comprising one or more support layers under said wearing course, characterized in that the thickness of said wearing course is between 7 and 35 mm, and in particular between 15 and 35 mm. and 30 mm.

Track according to one of the preceding claims, characterized in that the mineral aggregates of the asphaltic concrete consist of materials of granular class 0/2 and that the content of binder / asphalt is 11.5 ± 2% by weight. mass .

7. Track according to claim 6, characterized in that said mineral aggregates consist of crushed sand.

8. Non-draining bituminous asphalt forming the wearing course of a track for driving land vehicles under conditions of low adhesion, characterized in that the mineral aggregates of said mix consist of crushed sand of particle size 0/2 and that the binder / asphalt content is 11.5 + 2% by weight.

9. Coating according to claim 8, characterized in that said inorganic aggregates comprise more than 10% by weight of fines.

10. Coating according to one of claims 8 or 9, characterized in that said aggregates have grain size values within the following limits:

11. Coating according to one of claims 8 to 10, characterized in that said bituminous binder is selected from bitumens B20 / 30, B35 / 50 and B50 / 60.

12. Tread of a track for driving land motor vehicles consisting of an asphalt mix according to one of claims 8-11.