EP1579074A1

EP1579074A1 - Low-grip track for vehicles

Info

Publication number: EP1579074A1
Application number: EP02782605A
Authority: EP
Inventors: Jean-Claude Zucker; Franz Hummel
Original assignee: Individual
Current assignee: HUMMEL, FRANZ; Zucker Jean-Claude
Priority date: 2002-12-13
Filing date: 2002-12-13
Publication date: 2005-09-28
Anticipated expiration: 2022-12-13
Also published as: AU2002347184A1; WO2004055271A1; EP1579074B1

Abstract

The invention concerns a track for driving road motor vehicles in low-grip conditions, with a road surface comprising a bituminous concrete surface coating, said surface coating comprising a running surface layer consisting of a non-draining coated material whereof the slipperiness ranges between 55 and 68 SRT units.

Description

LOW ADHESION TRACK FOR VEHICLES

The present invention relates to a track for driving land motor vehicles in poor grip conditions, with a road surface comprising a coating of bituminous 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 four-wheeled passenger cars and competition vehicles, the latter including road vehicles modified according to various sporting categories as well as specific vehicles such as single-seaters, including karts. The invention also relates to two-wheeled vehicles such as motorcycles and motorcycles, road or competition.

Although we still frequently meet, especially in less industrialized countries, roads and paths made of beaten earth, laterite or even covered with layers of loose gravel or concrete slabs, the pavements comprising a coating of bituminous concrete tend to to generalize. In industrialized countries, they have become the rule. In general, a bituminous concrete covering comprises one or more support layer (s), located above the foundation layer of another suitable support. The support layer (s) provide the bearing capacity of the coating. Above the support layer or layers is arranged a wearing course, which is there. top layer of the coating. It ensures road safety and traffic comfort. Both the support layers and the wearing course are produced using mixes composed of mineral aggregates and bituminous binders and any additives. Asphalt specifications include

designation of the type of asphalt mix the proportions of sand, gravel and / or crushed and / or rolled stones the type of binder the dosage of the binder the nature and quantity of any additives the empty contents the indicative values of stability and creep.

For the construction of public roads, these specifications obey many national standards. For example, in Switzerland, the design of bituminous concrete coverings obeys the standard SN640 431b, the requirements for mineral aggregates generally obey the standard SN670 130 and several more specific standards, concerning for example fillers or measurement methods. Bitumens can comply with standard SN671 110. The contents of residual voids and filled voids, stability, rigidity and creep, commonly called Marshall characteristics, are measured on the basis of standards SN671 969c and SN671 967a.

An extremely important characteristic of a wearing course on a public roadway is its non-slip quality. The slipperiness of the surface of a pavement is variable over time, depending on wear and the surrounding conditions. It is usefully measured and quantified in particular by means of a standard oscillating pendulum known as a "skid resistance tester", and expressed in so-called SRT units. The measurement method is the subject of standards SN640 510b and SN640 511b in Switzerland.

Improving the anti-slip quality of the wearing course, ie increasing the adhesion of tires to the surface of the coating, is a constant concern of those skilled in the art. This seeks to obtain SRT values greater than 70 and preferably greater than 75. Many proposals have been made in this direction. For example, document WO 99/19566 proposes to make the upper surface of the wearing course rougher by enriching it with crushed type aggregates, with sharp edges, so as to increase the friction forces. Many other documents describe the production of draining mixes: these are characterized by the presence of a large percentage of voids, of the order of 20%, corresponding to at least about 12% of communicating unfilled voids, carrying out the drainage of the wearing course. We can cite by way of example of such a coated one that described in document FR 2 674548.

The difficulties in controlling vehicles traveling on pavements comprising a coating of bituminous concrete, which is the case for the majority of motor vehicles, are considerably amplified when the pavement is wet, snowy, or even covered with dead leaves, gravel or mud, or even oil residues or fine films of sand, all these circumstances having a common denominator, namely that the grip capacity of the vehicle on the road surface is greatly reduced. We know that compared to optimal conditions, vehicle in perfect condition on good quality and dry pavement, grip can be reduced by half on wet pavement, by two thirds if the tires are worn, and even up to a tenth in icy road conditions or in the presence of puddles generating an aquaplaning phenomenon.

Some driving education organizations organize specific courses in winter conditions. These courses being dependent on weather conditions, can usually only be given a few days a year, when the road surface is covered with snow or ice.

To teach drivers to control their vehicles under these difficult conditions, it has already been proposed to arrange track segments or annular tracks carrying a sliding synthetic coating, produced by means of resins, varnishes or paints. adhesion vehicles on these track segments or on these rings is greatly reduced by spraying them constantly with water.

These facilities teach the basics of driving under poor grip, but have several shortcomings.

The resins and paints used are expensive and, during braking and skidding, are gradually blackened and even torn off, so that they must be replaced frequently. In a regularly operating educational center, these synthetic coating films must be replaced at least twice a year. For this reason, and because it is moreover necessary to constantly water the track, the length thereof is necessarily limited to lengths less than, or on the order of a hundred meters. It is not in practice conceivable to produce sections of the road type or of the car circuit type with a length of several kilometers. The variety of exercises practicable on these very short tracks is therefore necessarily very limited.

In addition, these plasticized or coated with paint or resin tracks require the use of smooth tires. For practical reasons, these tracks are therefore always used with the same school vehicles; the student driver cannot exercise with his vehicle which he otherwise uses.

Some sports organizations, such as IRSI (Ice Race Series International), organize races on snowy and / or icy tracks. These races meet a growing interest with the public, because of their spectacular character, but can not be organized, because of the meteorological vagaries, that in mountain area and during the period of winter when the snow cover and / or the low temperatures necessary for the maintenance of a snow and ice track are ensured. The use of resins or paints cannot in practice be envisaged to cover a motor 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 film. paint or resin.

A first object of the present invention is to provide a track for driving motor vehicles reproducing conditions of low grip, and this with a long and varied layout of the road course.

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

A third object of the invention is to produce such a track, the maintenance cost of which is low, in particular which does not require frequent replacement of a surface coating.

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

These aims are achieved by means of a track of the defined type of entry, where the said bituminous coating comprises a wearing course consisting of a non-draining asphalt whose slipperiness, measured with the "skid resistance tester" is between 55 and 68 SRT units.

The SRT value of a wearing course can be lowered in particular by operating the pause at high ambient temperature, by increasing the proportion of the binder, by increasing the proportion of the filler and / or by reducing the thickness of the layer. It has appeared to the inventors that a range of 60-67 SRT units is optimal for application to a competition circuit.

The surface of the track according to the invention has in the dry state the same grip conditions as an ordinary wet road. The choice of a non-draining mix, in particular a mix with a residual void content of 4 ± 2%, a filled void content of 85 ± 6%, gives it the properties of an ordinary road having undergone a very high rain, and this after having simply suffered a light rain or having been subjected to a light watering.

It therefore allows the teaching of driving on wet roads in pleasant climatic conditions. It allows in particular to provide such education in regions where for several months in the year, or even throughout the year, it hardly rains, and where water is too precious a commodity to be spread regularly on a roadway .

In addition, if the track according to the invention is heavily wetted by heavy rain or by a sprinkler system, its grip characteristics are very close to those of an icy road surface. The track according to the invention therefore makes it possible to teach throughout the year the extremely specific driving technique adapted to this kind of conditions, which naturally occur only a few days a year.

The track according to the invention has numerous advantages compared to the tracks for learning to drive under poor grip conditions known in the prior art, that is to say the tracks covered with a layer of resin or paint.

the realization of the track exclusively implements the technology of road construction, as well in terms of equipment, ie coating plant, transport vehicles, laying machines and rollers for compacting the support and rolling layers.

- The installation procedures are exactly the same as for a public road. Consequently, the installation can be carried out by a public works company without the staff needing specific training.

the track according to the invention can have the configuration of an ordinary section of road several kilometers in length with all the topographical variants that can be encountered on a road, such as hairpin turns, large curves, raised, on slopes, sections of more or less steep slopes, etc.

Preferably, the track according to the invention can be produced in the form of a closed circuit, along a line identical or similar to a circuit for motor racing, with the usual safety equipment of this type of installation such as clearance zones. , sandboxes, slides, tire stacks, camera track monitoring systems and security lights.

Preferably, the non-draining mix of the wearing course has a Marshall stability greater than lOkN and a Marshall creep less than 3.5 mm, measured according to standards SN 671 967a and SN 671 969b.

The wearing course then has sufficient stability and resistance to deformation so that the track can accommodate endurance racing vehicles or even single-seaters without presenting deterioration phenomena such as rutting, uprooting, etc., greater than that of a classic racing track. Such a track therefore allows the organization of competitions during which the vehicles necessarily perform spectacular skids prized by the public and this already at speeds clearly lower than those reached on a track of conventional structure having the same configuration.

According to the invention, the wearing course can be produced using a non-draining asphalt, the mineral aggregates of which consist of more than 90% of materials of granular class 0/4 and in which the content of binder / coated is 8.5 ± 1% by mass.

Preferably, the mineral aggregates used comprise a high proportion of rolled sands, for example from 30 to 50%, and have a pass greater than 95% in the 2.8 mm analysis sieve.

In particular, the mineral aggregates can be chosen so as to present particle size values comprised within the following limits:

The bituminous binder can be chosen from the binders known in the state of the art for producing layers of rolling. It can in particular be chosen from bitumens satisfying standard SN 671 110. It can also be chosen from bitumens modified with polymers satisfying standard SN 671 400. In the case of a track intended to host automobile competitions, a bituminous binder of the type used to make road wearing courses of the AB-S or AB-H type is preferably chosen. To make tracks in dry and hot climatic zones, bitumen type B55 / 70 or B50 / 70S is preferably used.

The invention will be better understood by those skilled in the art by examining the characteristics of three embodiments of a mix according to the invention and the accompanying figures, in which

FIG. 1 represents the particle size curve of a first embodiment example; FIG. 2 represents the particle size curve of a second embodiment example FIG. 3 represents the particle size curve of a third embodiment example

Example 1

The mineral aggregates used included 97.3% sand passing through the 2.8 mm analysis sieve. The percentage of crushed sand in the sand fraction was 60%. The mineral aggregates also included 2.7% gravel of classes 4/11. Table 1 gives the particle size according to SN 670 810c.

Table 1:

Those skilled in the art will recognize that the grain size values in Table 1 are surprising compared to the values usually accepted for the production of road surface wearing courses. By way of comparison, these particle size values have been represented in the form of the curve (1) in FIG. 1, opposite the limits of the nominal particle size values allowed according to SN 640 431b for a wearing course of type AB3L, shown in dotted lines. It can be seen that, even if the granulometric curve of the mix according to the invention overlaps the lower nominal limit, for the sieves 0.09 to 0.25, this granulometric curve is essentially outside the standard, in particular for the sieve of 0.5 where the pass is greater than 44% for the sieve of 1 where the pass is greater than 65% for the sieve of 2 where the pass is greater than 85%

We can see an inflection of the grain size curve due to the presence of a small quantity of gravel of the fraction 2.8 / 11.2.

The binder used was a bitumen B50 / 70S from PETROPLUS (Cressier refinery). It is a doped bitumen containing an additive preventing the coating on slightly wet grains. The amount of binder used, of the order of 8.8% relative to the mass of aggregates, was significantly larger than the quantities usually used for road AB layers.

Processing equipment includes.

Tracked finisher with hydraulic vibrating table extendable to 5 meters, ABG brand and TITAN type.

The table is heated with gas to a temperature of

130 °.

1 ball compactor, weight 16 tonnes

1 mixed ball and tire compactor, weight 12 tonnes

The asphalt mixing temperature was 168 °.

After analysis, the asphalt has the following general characteristics:

Binder / Asphalt content (mass%): 8.07 Density (t / m ³ ): 2,375

Filler / Bitumen ratio: 1.4

Wealth module: 4.81

The Marshall features are:

Residual void content (% vol.): 4.9

Content of filled voids (% vol.): 7.4

Bulk density (t / m ³ ): 2,260

Stability (kN): 11.8

Creep (mm): 3.1

Rigidity (kN / mm): 3.8

Those skilled in the art will note that, surprisingly, despite the high content of binder, the mix is not fluid and has excellent values of stability and rigidity: in this aspect, the wearing course would have the ability to '' a road layer of type AB-N or AB-S, whereas on the contrary, as regards the non-slip qualities, the wearing course would be perfectly unfit for normal road use - since the SRT values show that the dry track according to the invention has SRT values similar to those of a normal wet road surface and that the wet track according to the invention grip values close to that of a road covered with ice.

Example 2

The mineral aggregates used included 97.9% sand passing through the 2.8 mm analysis sieve. The percentage of crushed sand in the sand fraction was 60%. The mineral aggregates also included 2.7% gravel of classes 4/11. Table 2 gives the particle size according to SN 670 810c.

Table 2:

Those skilled in the art will recognize that the particle size values in Table 2 are also surprising compared to the values usually accepted for the production of road surface wearing courses. As Comparative, these particle size values have been represented in the form of a curve (2) in FIG. 2, opposite the limits of the nominal particle size values allowed according to SN 640 431b for a wearing course of type AB3L. It is noted that, even if the particle size distribution curve according to the invention intersects the nominal limit lower than the level of the sieve 0.5, this particle size distribution curve is essentially outside the standard, in particular

for the sieve of 1 where the pass is ~ 65% for the sieve of 2 where the pass is ~ 90%.

We will also note the inflection of the grain size curve due to the presence of a small gravel fraction 2.8 / 11.2.

The binder used was the bitumen B50 / 70S of Example 1. The amount of binder used, of the order of 8.4% relative to the mass of aggregates, was clearly greater than the amounts usually used. works for road AB layers. The asphalt mixing temperature was 170 degrees.

The processing equipment is the same as that of Example 1.

After analysis, the asphalt has the following general characteristics:

Binder / Asphalt content (mass%): 7.76 Density (t / m ³ ): 2.386

Filler / Bitumen ratio: 1.4

Wealth module: 4.68

The Marshall features are:

Residual void content (% vol.): 6.0 Filled void content (% vol.): 77.3 Bulk density (t / m ³ ) 2.256 Stability (kN): 10.8 Creep (mm): 2.7 Rigidity (kN / mm): 4.1

A person skilled in the art will also note for this example that, surprisingly, in spite of the high content of binder, the mix is not fluid and has excellent values of stability and rigidity, whereas on the contrary, in Regarding the non-slip qualities, the wearing course would be perfectly unsuitable for normal road use.

Example 3

The mineral aggregates used comprised 99.4% of sand passing through the 2.8 mm analysis sieve and practically did not include gravel with a particle size greater than 4. The percentage of crushed sand in the sand fraction was 60%.

Table 3:

The particle size values in Table 3 have been shown in the form of a curve (3) in FIG. 3. Those skilled in the art will recognize that these values coincide in substance with the lower nominal particle size limit accepted according to SN 640 431b for a wearing course of type AB3L.

The binder used was also the bitumen B50 / 70S of Example 1. The amount of binder used was 9.16% relative to the mass of aggregates.

The asphalt mixing temperature was 171 ° C; the equipment and the conditions of implementation were, moreover, identical to those of Examples 1 and 2

After analysis, the asphalt has the following general characteristics:

Binder / Asphalt content (% mass): 8.39 Density (t / m ³ ): 2.365

Filler / Bitumen ratio: 1.6

Wealth module: 4.90

The Marshall features are:

Number (s) of reheating: 1

Compaction temperature: 153 Residual void content (% vol.): 2.5

Content of filled voids (% vol.): 88.3

Bulk density (t / m ³ ): 2.306

Stability (kN): 7.9

Creep (mm): 4.4

Rigidity (kN / mm): 1,8

Those skilled in the art will recognize that this example of asphalt having a very high content of binder has values of stability, rigidity and creep lower than the two previous examples.

This coating has the following slip values: SRT measurement according to standard SN 640 510b: 66 SRT units measurement in the "dry resistance test" of the dry coating: 75 SRT units

Although the second measurement is carried out under non-standard conditions, it shows that this coating has the same slip characteristics when dry as an ordinary wet road surface.

Example 4: Driving tests with a kart

The asphalt used for producing the wearing course is that of Example 3. The test track carried out is a rectangular segment 35m long by 12m wide. The wearing course of 20mm thick on average is put in place by means of a tack coat of bitumen lacquer on a pre-existing HMT 25 support layer. An equivalent surface consisting of the support layer, located next to the test track serves as a comparison track. A 3 ^rd surface, located upstream of the two previous ones, serves as a momentum zone to launch the test vehicle. The tests were carried out by a professional racing driver with a 100 cm ^{3 single} speed competition kart.

at. Braking tests

Both the test track and the comparison track are slightly wetted by a little rain. The pilot launches the kart, first at low speed, of the order of 40km / h, then at higher speed, of the order of 60km / h, on the momentum zone successively opposite the runway. test and the comparison track and, after having covered a distance of approximately two meters on these tracks, materialized by studs on each of the two tracks, brakes to the maximum until the stop.

Braking distance at low speed (40Km / h):

- test track: 15m

- comparison track: 10-11m Braking at medium speed (60Km / h):

- test track: 32-35m

- comparison track: 18-20m

b. Slalom

Five studs are aligned 5m from each other. The pilot uses the same momentum in front of the test track and in front of the comparison track. The pilot passes without problem between the five studs, without overturning them, on the comparison track.

On the contrary, on the test track, with the same momentum, the pilot can only pass three studs and overturn the other two.

vs. Circular path

The pilot seeks to describe a circular trajectory around a fixed stud, the kart being in skid, the front of the kart being turned towards the center of the circle, by, a radius of approximately 4 m: on the track test the kart is clearly in permanent oversteer on the comparison track, the kart is clearly in permanent understeer

d. Subjective tests

The track is completely wet. Two pilots successively carry out the movements and maneuvers of their choice over the entire surface of the test track and the comparison track. At the end of these driving tests, the two drivers believe that they experience the usual sensations of driving on wet surfaces on the comparison track. However, they feel they have very similar to those experienced when driving on ice on the wet test track.

Example 5: Braking tests with a passenger vehicle

The vehicle used is a Porsche 911 Carrera equipped with summer tires in perfect condition. The vehicle is fitted with all the electronic driving assistance devices fitted in series by the manufacturer.

The pilot successively brings the vehicle to 50 km / h then to 60 km / h in the momentum area and brakes as much as possible from a mark placed respectively on the test track and on the comparison track, up to l 'stop.

The braking distance of the Porsche is approximately lm to 50Km / hr and about 2m to 60Km / hr on the test track.

The results set out in the examples above allow the following conclusions to be drawn:

the three asphalts tested have slip values such that a wearing course produced by means of these offers a much weaker grip than that of a road wearing course. On the other hand, the Marshall characteristics of creep and stability of coated materials 1 and 2 show that wearing courses produced by means of these can withstand without rutting or significant deterioration the maximum stresses exerted by road vehicles, or even by racing cars weighing several hundred kilos and several hundred horsepower.

Asphalt 3 has an even higher slip rate. Its stability is slightly lower than that of the previous two, making it more suitable for making go-kart tracks or tracks intended for driving instruction. Regarding the latter application, it should particular to observe that the cost of a coating comprising a traditional HMT layer and a wearing course according to the invention can be estimated at 18 Swiss francs / square meter respectively for the support layer and 17 Swiss francs / square meter for the wearing course, for a total of approximately 35 francs / square meter of covering. By way of comparison, a slippery driving track produced by means of a concrete support layer with a synthetic resin coating amounts to approximately 80 Swiss francs / square meter for the concrete support and approximately 30 francs / meter square for resin coating, for a total of 110 Swiss francs per square meter. In addition, the coating according to the invention requires practically no maintenance for several years, while in the case of the track coated with a synthetic resin coating, the latter must be changed at least once a year and even more if the use of the installation is permanent.

Claims

claims

1. Track for driving land motor vehicles in poor grip conditions, with a road surface comprising a coating of bituminous concrete, characterized in that said coating comprises a wearing course consisting of a non-draining asphalt whose slipperiness is between 55 and 68 SRT units.

2. Track according to claim 1, characterized in that the slipperiness is between 60 and 67 SRT units.

3. A track according to claim 1 or 2 characterized in that the said non-draining asphalt of the wearing course has a residual void content of 4 ± 2% and a filled void content of 85 ± 6%.

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

5. Track according to any one of the preceding claims comprising one or more support layers under the said wearing course, characterized in that

1 thickness of said wearing course is between 7 and 35mm, and in particular between 15 and 30mm.

6. Track according to one of the preceding claims, arranged in circuit, in particular so as to form a racing circuit.

7. A non-draining mix, for producing the wearing course of a track according to one of the preceding claims comprising mineral aggregates and at least one bituminous binder, characterized in that said mineral aggregates are made up of more than 90% of class materials granular 0/4 and in that the content of binder / coated is 8.5 ± 1% by mass.

8. A mix according to claim 7 characterized in that said mineral aggregates consist of up to 50% of rolled sand and that they have a pass greater than or equal to 95% in the 2.8 mm analysis sieve.

9. A coating according to one of claims 7 or 8 characterized in that said mineral aggregates comprise more than 10% by mass of fines.

10. Asphalt mix according to one of claims 7-9, characterized in that said aggregates have particle size values comprised within the following limits:

11. A mix according to claim 10, characterized in that said aggregates have the following particle size values:

12. Asphalt mix according to one of claims 7 to 11, characterized in that said bituminous binder comprises a 50 / 70S bitumen or a 55/70 bitumen.