FR2818273A1 - PROCESS FOR IMPROVING RESISTANCE TO CHEMICAL AGRESSIONS OF A BITUMINOUS SPRAY - Google Patents

Abstract

The invention concerns a method for enhancing the resistance of a road surfacing bituminous mix to chemical attacks, comprising a bituminous binder and aggregates. The method is characterised in that it consists in adding to the bituminous mix 1 to 5 wt. % of at least a polyolefin, preferably 1 to 2 wt. % relative to the weight of the aggregates to obtain a modified bituminous mix having a compactness rate not less than 97 %.

Description

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 The invention relates to a method for improving the resistance to chemical attack of a bituminous mix intended for the production of the different layers of a road surface, in particular the wearing course, in particular aeronautical road surfaces or any other road surface subject to chemical attack. .

 Under the aggressive action of traffic and bad weather, the surface and the body of roadways are likely to deteriorate. In addition, environmental conditions other than traffic and weather conditions may also affect the condition of the roadway. These include environmental conditions related to pollution. In particular, leaks, or even spills of petroleum liquids on the roadway can degrade the pavement by dissolving the bitumen. The chemicals of the fluxing type or petrochemical solvent are known to be particularly aggressive with respect to this type of material.

 An improvement has been obtained by using, for the manufacture of these pavements, asphalt mixes known for their ability to withstand chemical attack.

However, such mixes have the disadvantages of not only being toxic, but also containing carcinogenic substances.

 The subject of the present invention is therefore a process for improving the resistance to chemical attack of bituminous mixes for the manufacture of pavements and which overcomes the drawbacks of the prior art.

 More particularly, the present invention relates to a process for increasing the resistance to chemical attack of bituminous mixes, in particular those related to leaks or spills of petroleum liquids, and which leads to mixes that are neither toxic nor susceptible to contain carcinogenic substances.

 The person skilled in the art knows the use of polymer type additives for improving the mechanical properties of binders

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 bituminous or bituminous mixes. Thus, the French patent application FR-2753210 describes a pavement bituminous pavement based on bitumen modified by polymers and in which polyethylene has been added. Thanks to such an asphalt, it has been possible to improve the resistance to water and frost, resistance to puncture and rutting, rigidity and resistance to fatigue.

 Furthermore, the European patent EP-0605377 describes asphaltic compositions for the preparation of draining mixes, comprising a first modifier selected from styrene-butadiene or styrene-isoprene copolymers, their mixtures and recycled tires, and a second modifier chosen from polyolefins, polyethylene terephthalate and mixtures thereof. These additives make it possible to increase the resistance to fatigue, the resistance to permanent deformation, as well as the adhesive and cohesive properties.

 As illustrative documents of the prior art, one can also cite the standard NF EN 12591 and the document "Technical Guide: use of modified binders, special bitumens and bitumens with additives in road techniques", published by the Central Laboratory of Bridges and Roads LCPC (ISSN 1151-1516 ISBN 2-7208-7140-4), hereinafter designated by reference 1.

 According to this document, these bitumens can be modified with terpolymers, for example the compound of an ethylenic chain with functional groups of butyl acrylate and methyl glycidyl acrylate which ensures good stability of the bitumen / polymer mixture. as well as elastomers and plastomers allowing a significant improvement in resistance to cracking and rutting.

 In addition to the polymers described above and according to reference 1 Technical Guide: use of modified binders, special bitumens and bitumens with additives in road techniques mentioned above, it is also possible to modify the bitumens by polyvinyl chloride (PVC), other

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 copolymers based on styrene and butadiene, or ethylene and vinyl acetate (EVA).

 It has now been found that it is possible to improve the resistance to chemical attack of bituminous mixes, without risk of pollution, by adding to a bituminous mix a predetermined quantity of polyolefins.

 The object of the invention therefore relates to a process for improving the resistance to chemical attack of a bituminous coating for pavement comprising a bituminous binder and aggregates, characterized in that it consists in adding to the bituminous mix 1 to 5 % of at least one polyolefin and preferably 1 to 2% by weight relative to the weight of the aggregates, to obtain a modified bituminous mix having a degree of compactness greater than or equal to 97%.

 Preferably, the chemicals of the fluxing type or petrochemical solvent are particularly aggressive with respect to bituminous mixes. Anti-kerosene or anti-K is the ability of the asphalt to resist these attacks. The antiK character will be more or less marked depending on the composition of the mix.

 Generally, the bitumen of the composition according to the invention is a bitumen modified with polymers, the bitumens modified with polymers being defined in the sense of the document "Technical Guide: use of modified binders, special bitumens and bitumens with additives in techniques. "mentioned above.

The polymers are advantageously chosen from styrene-butadiene or styrene-isoprene copolymers and their mixtures or terpolymers.

 Advantageously, the bituminous mix comprises 3 to 11, preferably 5 to 11% by weight of bituminous binder with respect to the weight of the aggregates.

 According to another characteristic, the granulometry of the aggregates is chosen from the range O / Dmax, where Dmax is the maximum diameter of the aggregate as defined according to the standard XP P 18-540, and ranging from 4 to 25 mm.

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 The polyolefin is advantageously a polyethylene, a polypropylene or a mixture of both. The polyolefin may be virgin, that is to say, coming directly from industrial manufacture, or recovery, that is to say obtained by recycling used objects or manufacturing waste comprising polyolefins.

 In a particular embodiment, the polyolefin, the bituminous binder and the aggregates are kneaded to form the modified bituminous mix.

 Advantageously, the kneading is carried out at a temperature of 140 to 190OC, and preferably 160 to 190OC.

 The bituminous mixes obtained according to the present invention have a hydrocarbon / hydrocarbon ratio of greater than or equal to 0.70, where the hydrocarbon is the compressive strength at 18 ° C. after immersion for one week in a hydrocarbon bath at 18 ° C. C and Rcair, 8. c compressive strength at 18 C in air.

 In addition, the compactness rate of the bituminous mixes according to the invention, or modified bituminous mixes, measured according to standard NF P 98 250-6 is greater than or equal to 97%.

 The bituminous mix, manufactured using the process according to the invention, can be used on pavements with a high potential to receive an accidental spill of hydrocarbons, road pavements, aeronautical pavements, tank tracks and military roads. , as well as on platforms and industrial roads and also on bus lanes and tramways on tires.

 Its main advantage is a better resistance to chemical attack, especially those created by petroleum liquids (fluxing type or petrochemical solvent).

 The following examples illustrate the invention without, however, limiting its scope.

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1. Raw materials Sample preparation Binders for bituminous mixes - bitumen 50/70, or - bitumen 70/100, or - bitumen 180/220 Binders for bituminous mixes (binder of the prior art) - tar of coal STAVOJET &commat; Aggregates - aggregates from La Noubleau selected for the following granulometric recovery: - class 0/2: from 40 to 46 parts - class 2/4: from 10 to 15 parts - class 4/6: from 15 to 25 parts - class 6/10: from 15 to 25 parts - calcareous filler: from 1 to 3 parts Polyolefin: low density polyethylene, presented in the form of 0/4 mm lenses Hydrocarbon bath. Exxsol oil D80 from the company EXXON 2. Measuring methods Resistance to compression in the air
The resistance to air compression is determined by performing compression tests according to the DURIEZ NF P 98-251-1 standard: - in air after seven days at 18 C and 50% humidity: Rcair, 8. c - in air at 50 ° C after seven days at 50 ° C to 50% humidity: Rcair5o. c Compressive strength after immersion in a hydrocarbon bath at 18 ° C
The compressive strength after immersion in the Exxsol D80 oil bath at 180 ° C, referred to as Rchydrocarburei®, is also determined by carrying out compression tests.

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 according to standard NF P 98-251-1. For this determination, the DURIEZ test specimens are first subjected to the mechanical characterization test, immersed completely for one week in a petroleum bath at a temperature of 18OC.

 From the values of compressive strengths Rcair18'c and R6hydrocarbureig8 measured, we calculate the ratio Rckerosene18 C / Rcairig. c to estimate the degree of conservation of the compressive strength of a bituminous mix after complete immersion in an aggressive agent such as Exxsol oil D80.

 The ratio of 18 Chydrocarbide to C 18 C 18 is representative of the anti-K character of the bituminous mix. The closer the value of this ratio is to 1, the higher the anti-K character of the mix will be marked, or the higher the resistance to chemical aggression caused by the oil.

compactness
The compactness is measured according to standard NF P 98 250-6. It is a measure of the bulk density of a test piece by hydrostatic weighing.

 In the examples, unless otherwise indicated, all amounts are expressed in parts by weight per 100 parts by weight of aggregates.

Examples
A first asphalt mix according to the invention (EB1) was prepared by mixing, with 100 parts of aggregates, 6 parts of a 70/100 bitumen for 4 minutes at 180 ° C. 1.5 parts of a polyethylene are then added to the mixture obtained and kneaded for 8 minutes to homogenize well.

 A second asphalt mix according to the invention (EB2) was prepared by mixing, with 100 parts of aggregates, 6 parts of a 180/220 bitumen for 4 minutes at 150 ° C. Then, 1.2 parts of a polyethylene are added to the mixture obtained and kneaded for 8 minutes to homogenize well.

 A third bituminous mix according to the invention (EB3) was prepared by mixing, with 100 parts of aggregates, 6

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 parts of a 50/70 modified bitumen based on polymers or terpolymers, and 1.5 parts of a polyethylene in the form of wax, and kneaded for 4 minutes at 180OC to homogenize well.

 T1 and T2 bituminous mixes containing no polyethylene or polymers were also prepared as controls: - the bituminous mix T1 was obtained, adding 6 parts by weight of a 50/70 bitumen to 100 parts by weight of aggregates, then kneading for 4 minutes at 150 ° C., the bituminous mix T2 was obtained, adding 7.5 parts of coal tar STAVOJET &commat; to 100 parts of aggregates, then kneading for 4 minutes at 150OC.

- la résistance à la compression à l'air à 50 C Rcairgo. c sur une seconde partie des échantillons, - la résistance à la compression après immersion dans un bain de pétrole Exxsol D80 Rchydrocarbureig. c sur) a partie restante des échantillons, - la compacité hydrostatique mesurée par la méthode hydrostatique décrite dans les normes NF P 98-251-1 et NF P 98-250-6. For each bituminous concrete, T1 and T2 on the one hand, and EB1 to EB3 on the other hand, we measure: - resistance to air compression at 18 C Rcair, 8. c on a part of the samples,

- resistance to air compression at 50 C Rcairgo. c on a second part of the samples; - compressive strength after immersion in an oil bath Exxsol D80 Rchydrocarbureig. c on) the remaining part of the samples, - the hydrostatic compactness measured by the hydrostatic method described in standards NF P 98-251-1 and NF P 98-250-6.

 The results are presented below in Table 1.

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TABLEAU 1

TABLE 1

<Tb>
<tb> T1 <SEP> T2 <SEP> EB1 <SEP> EB2 <SEP> EB3
<tb> Content <SEP> in
<tb> binder <SEP> (%) <SEP> 6 <SEP> 7.5 <SEP> 6 <SEP> 6 <SEP> 6
<tb>Rcair18'C<SEP> [MPa] <SEP> 10.6 <SEP> 33.8 <SEP> 16, <SEP> 9 <SEP> 8, <SEP> 3 <SEP> 9, <SEP> 3
<tb> Rcair50C <SEP> [MPa] <SEP> 1, <SEP> 7 <SEP> 1.7 <SEP> 4, <SEP> 4
<tb> Hydrocarbon 18 C [MPa] <SEP> 1, <SEP> 9 <SEP> 30.3 <SEP> 13.1 <SEP> 6.2 <SEP> 7.2
<tb> Hydrocarbon 18-c / Rcairig. <SEP> c <SEP> 0.18 <SEP> 0, <SEP> 9 <SEP> 0.78 <SEP> 0.75 <SEP> 0, <SEP> 77
<tb> Hydrostatic <SEP> Compactness <SEP> [%] <SEP> 94, <SEP> 1-98, <SEP> 3 <SEP> 97, <SEP> 6 <SEP> 98.3
<Tb>

The mechanical performance of the bituminous mixes, manufactured using the method according to the invention (EB1, EB2 and EB3) and having undergone a chemical attack, are better than those of the mix T1 containing neither polyethylene nor polymers.

 In fact, bituminous mixes EB1, EB2 and EB3 retain more than 75% of their compressive strength after a complete immersion of one week in an oil bath (Exxsol D80 &commat;), whereas the bituminous mix T1 does not canned only 18%.

 Rcairig mechanical performance. c and the hydrocarbon C 18 EB1 to EB3 mixes are lower than those of the asphalt T2, for which the binder is coal tar but of the same order of magnitude as the T1 control. The values of 18 Chydrocarbide C / Rcair18 C show that the bituminous mixes EB1, EB2 and EB3 have an anti-K character relatively close to that of the asphalt T2, with a very significant improvement of the resistance at 50 C in air.

Claims (7)

 1. A method for improving the resistance to chemical attack of a bituminous coating for road surfacing, comprising a bituminous binder and aggregates, characterized in that it consists in adding to the bituminous mix 1 to 5% of at least a polyolefin, preferably 1 to 2% by weight relative to the weight of the aggregates to obtain a modified bituminous mix having a degree of compactness greater than or equal to 97%.  2. Method according to claim 1, characterized in that the polyolefin is a polyethylene, a polypropylene or a mixture of both, virgin or recycling.  3. Process according to any one of the preceding claims, characterized in that the bituminous binder is a bitumen modified with polymers, as defined according to standard NF EN 12491 and the "Technical Guide: use of modified binders, special bitumens. and bitumens with additives in road engineering ", published by the Central Laboratory of Roads and Bridges LCPC (ISSN 1151-1516 ISBN 2-7208-7140-4).  4. Process according to claim 3, characterized in that the polymers are chosen from styrene-butadiene or styrene-isoprene copolymers, terpolymers and their mixtures.  5. Method according to any one of the preceding claims, characterized in that the bituminous mix comprises 3 to 11%, preferably 5 to 11% by weight of bituminous binder based on the weight of the aggregates.  6. Method according to any one of the preceding claims, characterized in that the kneading is carried out at a temperature between 140 and 190OC, and preferably between 160 and 190 C.  7. Process according to any one of the preceding claims, characterized in that the modified bituminous mix has a ratio of hydrocarbyl carbon / Rcairloc greater than or equal to 0.70, wherein the hydrocarbon is the compression resistance at 18 C after immersion. for a week in a hydrocarbon bath <Desc / Clms Page number 10>  at 18 C and Rcair18 C the compressive strength at 18 C in air.