EP0507037A1 - Mixtures based on aggregates and thermofusible binders for roadsurfaces and production process - Google Patents

Abstract

In an embodiment of the process, a hot bituminous mixture with translucent hydrocarbonated binder is prepared, it is separated into fragments on a vibrating metal sheet (1) and these fragments trickle down into a vessel (2) full of cold water, to obtain a non-cohesive bituminous mixture capable of being preserved over a long period of time and regaining its initial properties after reheating. <IMAGE>

Description

The invention relates to mixtures suitable for producing floor coverings for the development of roads, comprising at least aggregates and a hot-melt binder.

This type of mixture includes in particular hot bituminous mixes in which the hot-melt binder is a bituminous binder, and which are obtained by kneading together the aggregates and the binder at a temperature sufficient for the binder to be fluid, then stored, transported and placed hot work. These bituminous mixes are used on a large scale, in particular for road construction, and are prepared in numerous coating plants spread over the territory so that an application site is always at a distance from the installation. nearest coating allowing the transport of the asphalt by trucks, if necessary insulated, without solidification by cooling.

Asphalts with translucent hydrocarbon binders have appeared in recent years, which differ from the bituminous mixes mentioned above by replacing the bituminous binders with binders which are also of petroleum origin but which do not contain the carbon-rich constituents responsible for the black color of bitumens. These mixes with translucent binders are used in lower quantities than the mixes with bituminous binders, in particular for the creation of sidewalks, squares, garden paths, school yards, central blocks of traffic lanes, and generally of all kinds of decorative surfaces with or without circulation. Pigments are frequently introduced to obtain attractive colors which cannot be produced in the presence of bitumen.

The relatively low production volume of mixes with translucent binders does not justify reserving a network of installations for them. similar to that used for bituminous mixes. The same installations are therefore used for the production of these two types of asphalt. If the actual manufacture of asphalt mixes with translucent binders only occupies these installations for short periods of time, to avoid them being stained with traces of bitumen, very important preparation and adaptation of the installation are necessary. before each manufacturing operation. Indeed, it is necessary to clean all the organs having been in contact with the bituminous binder (mixer, storage hopper, transfer carriage) and adapt a special dosing and injection circuit for the translucent hydrocarbon binder, the duration of use of this special circuit being further reduced.

The need for prior cleaning also applies to all transport or application equipment used for both types of asphalt.

• la fabrication de ces derniers doit être rigoureusement planifiée;
• le fonctionnement normal du poste d'enrobage est perturbé, toutes les autres fabrications devant être arrêtées;
• le rendement journalier de l'installation est abaissé.

The use of the same installations for asphalt mixes with bituminous binders and for mixes with translucent binders have the following consequences:

• the manufacture of these must be rigorously planned;
• the normal operation of the coating plant is disrupted, all other manufacturing to be stopped;
• the daily output of the installation is lowered.

In addition, the production, as needed, of small quantities of mixes with translucent binders does not always make it possible to achieve stable operating conditions of the station, which implies a fluctuating quality of the mixes.

The object of the invention is to remedy these drawbacks.

The invention relates to a method of manufacturing a mixture suitable for producing a floor covering for the development of roads, comprising at least aggregates and a hot-melt binder, in which the binder is brought to a sufficiently high temperature. to make it fluid, and it is brought into contact with the aggregates, characterized in that it comprises a step during which the binder is rapidly cooled by forming discrete fragments which do not stick together.

The mixture can be made in advance, in large quantities, stored for a long time and transported over long distances in the particulate state, and reheated at the time and at the place of its use to form a mix very similar to hot mixes prepared according to the conventional process.

The method according to the invention is particularly advantageous when the binder is a translucent hydrocarbon binder, the increase in cost which results from cooling and reheating having a moderate impact on the cost price of the mixture which is already relatively high elsewhere. This makes it possible to have simpler installations, permanently reserved or assigned for long periods to the manufacture of mixtures containing translucent hydrocarbon binders.

Moreover, the process is technically applicable, and may be of interest in appropriate circumstances, with any type of hot-melt binder used for the development of roads and the like.

Likewise, the method is not limited as regards the nature of the aggregates used, which can include in particular conventional mineral aggregates, glass, wood or metals.

According to one embodiment of the method according to the invention, the binder is poured onto the cold aggregates, the cooling of the binder occurring during its contact with the aggregates and leading to the formation of pellets of binder juxtaposed with the aggregates and of which at least the essential part does not adhere to them.

Where appropriate, the binder pellets include fine particles of aggregates, and / or pigments mixed with the aggregates.

When using the mixture of aggregates and pellets, it is heated by kneading it in order to thin the binder and to bind the aggregates, and the asphalt obtained is spread on a substrate to make a coating.

According to another embodiment of the method, a hot mix is prepared by bringing the hot binder into contact with the aggregates also heated, this mix is separated by mechanical treatment into fragments each comprising at least one particle of aggregates coated with the binder, and these fragments are quickly cooled so as to prevent them from sticking together.

Advantageously, the mix is separated into fragments by depositing it on a vibrating support, and the fragments are cooled by dropping them in a cold liquid or in a stream of cold gas.

When using the mixture obtained according to this second embodiment, the fragments are reheated in order to bond them to each other by the fluidized binder, and the continuous asphalt obtained is spread over a substrate to produce a coating, or else it is spread the fragments on a substrate and they are heated to bind them together by the fluidized binder by forming a continuous coating.

The invention also relates to a mixture comprising at least unbound aggregates and a hot-melt binder in the form of discrete pellets, as can be obtained according to the first embodiment of the method according to the invention, as well as a coated non-cohesive when cold, and becoming cohesive by temperature rise, formed of fragments each comprising at least one particle of aggregates coated with a hot-melt binder, as can be obtained according to the second embodiment of the method.

Other characteristics and advantages of the invention will emerge from the exemplary embodiments described below without any limiting character, and from the appended single figure which schematically represents a device for implementing the method according to the invention in its second mode. of achievement.

EXAMPLE 1

A conventional asphalt mixing plant is used, such as those used for the manufacture of hot or cold asphalt mixes, equipped with special piping for the supply of translucent hydrocarbon binders. If the station was previously used for the production of bituminous mixes, it is properly cleaned. The installation of cold crushed mineral aggregates is loaded, onto which a translucent hydrocarbon binder brought to a temperature of 150 to 160 ° C is poured, at a rate of 4 to 8 parts by weight of binder per 100 parts by weight of aggregates . If necessary, these are mixed with 0.5 to 2 parts by weight of pigments.

On contact with cold aggregates, the binder cools quickly and therefore undergoes quenching, forming pellets which, if necessary, contain fine particles of aggregates and / or pigments. A mixture formed of these pellets and of discrete particles of aggregates and, where appropriate, of pigments, is therefore obtained, including residual fine particles, the pellets not sticking to each other or to the discrete particles.

This intimate mixture can be stored for a prolonged period, in bulk or conditioned, for example in bags, without there being any gain in mass, nor segregation of the components, or aging of the binder comparable to that which would be observed in the event of conservation of 'a hot mix.

When the time comes, the product is picked up and transported to the site by dump truck. It is then heated and kneaded by a site heater to be spread in the form of a coating. Pigments can optionally be added during mixing, especially if the mixture does not already have one, which makes it possible to obtain different colors on demand from the same production batch.

The final hot mixture and the coating formed from it are quite similar to a conventionally manufactured hot mix and to the corresponding coating, both in appearance and in the mechanical characteristics determined in the laboratory.

EXAMPLE 2

A hot mix with translucent hydrocarbon binders is prepared by the traditional process.

This asphalt is poured onto a vibrating sheet inclined about 35o with respect to the horizontal. Due to this vibration and this inclination, the aggregate particles roll individually on the sheet, each remaining coated with binder. Arrived at the lower edge of the sheet, the coated particles fall in rain and are received in a tank 2 filled with cold water. On contact with cold water, the binder is suddenly cooled and solidified, forming a gangue around each particle of aggregates. This gives a non-cohesive mix formed of fragments each comprising at least one particle of aggregates coated with translucent binder. These fragments fall onto a conveyor belt 3 immersed in the lower part of the tank 2, which transfers them to a partially submerged bucket elevator 4. This rises them out of the water and pours them onto a discharge mat 5. The tank 2 is shared by a vertical partition 6, interrupted at the bottom to let the conveyor 3 pass, into two compartments 7 and 8 , the lower edge of the sheet 1 being above compartment 7 and the elevator 4 plunging into compartment 8. Cold water is continuously introduced by an inlet 9 at the bottom of the compartment 7, and the same amount of water is discharged through an outlet 10 at the top of this same compartment. There is therefore a circulation of cold water from bottom to top in compartment 7, against the flow of the fragments of the mixture falling.

This mixture can be stored and transported under the same conditions as that of Example 1. After reheating, there is a coated material having the same properties as the starting product. This reheating can be carried out before or after placing the mixture on the substrate to be coated, a new kneading is not necessary.

The mixtures according to the invention can in particular be produced in winter, a period of low occupancy of the installations, to be used in other seasons.

Claims (12)

Method of manufacturing a mixture suitable for producing a floor covering for the development of roads, comprising at least aggregates and a hot-melt binder, process in which the binder is brought to a temperature high enough to make it fluid , and it is brought into contact with the aggregates, characterized in that it comprises a step during which the binder is rapidly cooled by forming discrete fragments which do not stick together. Method according to claim 1, characterized in that the binder is a translucent hydrocarbon binder. Method according to one of claims 1 and 2, characterized in that the binder is poured onto the cold aggregates, the cooling of the binder occurring during its contact with the aggregates and leading to the formation of binder pellets juxtaposed with the aggregates and at least the essential part of which does not adhere to them. Method according to claim 3, characterized in that the binder pellets include fine particles of aggregates and / or pigments mixed with the aggregates. Process according to either of Claims 3 and 4, characterized in that the mixture of aggregates and pellets is heated by kneading it in order to fluidize the binder and to bind the aggregates, and that the asphalt obtained is spread over a substrate for making a coating. Method according to one of claims 1 and 2, characterized in that a hot mix is prepared by bringing the hot binder into contact with the aggregates also heated, which this mix is separated by mechanical treatment into fragments each comprising at minus one particle of aggregates coated by the binder, and that these fragments are suddenly cooled so as to prevent them from sticking together. Process according to claim 6, characterized in that the asphalt is separated into fragments by depositing it on a vibrating support. Method according to one of claims 6 and 7, characterized in that the fragments are cooled by dropping them in a cold liquid or in a stream of cold gas. Method according to one of claims 6 to 8, characterized in that the fragments are heated in order to bond them to each other by the fluidized binder, and that the continuous asphalt obtained is spread on a substrate to produce a coating. Method according to one of claims 6 to 8, characterized in that the fragments are spread on a substrate and that they are heated to bind them together by the fluidized binder by forming a continuous coating. Mixture comprising at least unbound aggregates and a hot-melt binder in the form of discrete pellets, as can be obtained by the process according to either of Claims 3 and 4. Coated non-cohesive cold and becoming cohesive by temperature rise, formed of fragments each comprising at least one particle of aggregates coated with a hot-melt binder, as can be obtained by the process according to one of claims 6 at 8.

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