FR2554140A1 - Thin surfacing for road maintenance and its method of manufacture and application - Google Patents

Abstract

This surfacing consists of an inorganic mixture of continuous particle size coated with a cationic emulsion of a road-type bitumen to which has been added a synthetic elastomer and a product of a cationic nature. The weight percentage of elastomer in the bitumen is between 1 and 5 % and lies preferably between 1.5 and 3 %. This method consists in mixing, at 1, the components of the surfacing, on the actual site of application, then in spreading the mixture obtained over the road with the aid of a distributor sledge 2 and, finally, in allowing the coated material to harden at ambient temperature, over a period of between 15 and 45 minutes.

Description

THIN COATING FOR THE MAINTENANCE OF PAVEMENTS AND
ITS MANUFACTURING AND APPLICATION PROCESS
The present invention relates to a thin coating for pavement maintenance as well as its manufacturing and application process.

Thin pavements can be divided into two main groups
- those called "coated", constituted by the hot application of various combinations of aggregates and hydrocarbon binders which are manufactured in coating plants;
- And those called "surface plasters" made directly on the roadway by successive spreading of layers of hydrocarbon binders and gravel.

 The coated coatings are fairly easy to set up, little dependent on atmospheric conditions; but they also have the disadvantage of becoming quite often slippery in rainy weather. In addition, due to their fairly high price, their distribution is relatively limited.

 Coatings of the "coated" type are economical coatings. They are not slippery, even in heavy rain. However, they have other drawbacks; they are noisy and cause a rolling noise level and their implementation depends on atmospheric conditions since it is practically impossible to apply them when it rains. On the other hand, the gravel which constitutes the plaster and whose primitive quantity is almost always greater than the theoretically necessary quantity is found on the pavement in excess, in little or poorly bonded form and causes, on passing vehicles, numerous broken windshields.

 The object of the present invention is to overcome these drawbacks by proposing a so-called "intermediate" coating, that is to say lying between the coated coatings and the coated coatings. This coating is intermediate in terms of cost price and characteristics. In particular, it incorporates the advantages of those mentioned above of the "plaster" type without having the disadvantages.

 The coating according to the invention is constituted, in combination, by a mixture of sand and gravel coated with a hydrocarbon binder which is a cationic emulsion of bitumen in battens; in an electrophoresis test (action of an electric field), the bitumen particles will tend to move towards the cathode.

This emulsion should have good stability, that is to say a slow rate of rupture with respect to the material so that the aforementioned granular mixture is suitably coated and spread before the water-bitumen separation begins to occur.

 The mineral mixture is generally of continuous particle size, that is to say that all the sizes of the gravel are represented.

In addition, the percentage of fines (elements less than 0.08 mm) is between 7 and 12%.

 An essential component of the coating and, consequently, of the invention is the hydrocarbon binder whose role is to agglutinate between them the mineral constituents - sand and gravel - of the coating.

It is an emulsion in water of a bitumen of road type whose characteristics are improved by adding a synthetic elastomer and treatment of this elastomer after its introduction into the bitumen by addition of a cationic product. .

 The percentage by weight of elastomer in the bitumen is between 1 and 5% and is preferably between 1.5 and 3%.

The preparation of elastomeric bitumen and its emulsion are the subject of precise formulations and special manufacturing which take place in the factory. The elastomer and the bitumen must be chosen to have good compatibility between them. The treatment following the addition of the elastomer in the bitumen has a triple purpose
- ensuring the fine dispersion of the elastomer in the bitumen,
- subsequently oppose decantation and regrouping of the elastomer micelles,
- Increase certain properties provided by the elastomer to the binder, in particular in terms of cohesiveness, elasticity and susceptibility to temperature.

 The process according to the invention consists in mixing the components of the coating at the site of the application by kneading, then spreading the mixture obtained on the road using a distributor sled and finally allowing the mix to harden. room temperature for a period of between I 5 and 45 minutes.

 The coating can therefore be compared to a "mix" manufactured and cold poured. The hardening of this asphalt does not require any subsequent operation but occurs by drying and tightening the coating under the action of vehicle tires. The coating can be returned to traffic within 15 to 45 minutes of its application on the road.

 The present invention will be better understood moreover and its advantages will emerge clearly from the description which follows, with reference to the appended schematic drawing, the single figure of which is a very simplified diagram of the method according to the invention.

 In the figure, the mixer is shown in (I), the distributor sled in (2) and the road surface in (3); the bitumen-elastomer emulsion, water, sand, gravel and additive emulsion supply stations being represented in (4), - (5), (6) and (7) respectively.

 All of this equipment intended to carry out the manufacture and spreading of the mixture directly on the roadway is mounted on a semi-trailer truck.

A 0-10 mm porphyry material obtained in the quarry is reconstituted by mixing 0-2 mm crushed sand, 0-2 mm crushed sand, 2-6 mm gravel and 6-10 mm gravel in the following proportions
.sands 45 to 60%
gravel 55 to 40%.

 This material is stored in (6).

 Is added successively to this material, in the mixer (1) wetting water (stored in (5)), an additive of cationic nature intended to regulate the setting of the mix (stored in (7)) and bitumen-elastomer in the form of an emulsion (stored in (4)).

The proportion by weight of the components is as follows
material 0/10 mm 100
. dampening water 10 to 15
. cationic additive l to 2
60% emulsion of
elastomeric bitumen Il to 14
The mixture is kneaded in the kneader (1) which is a device with two horizontal shafts, with a capacity of around 100 Tons / hour.

Said mixture is then poured into the sledge-distributor (2), towed by the semi-trailer truck (not shown).

 This sled is equipped with paddle shafts intended to distribute in the transverse direction, the mixture spilled by the mixer and at its rear with rubber flaps intended to adjust the thickness of the coating.

 The mixture is spread on the roadway in a layer of continuous thickness of 12 to 15 mm, which leads after drying and circulation to a coating (3) of thickness from 10 to 12 mm for a weight of 14 to 18 kg / m2. The coated hardening does not require any additional operation and occurs by simple drying and tightening of the coating under the action of vehicle tires.

It can be returned to traffic within 15 to 45 minutes of its application on the roadway.

The advantages of such a pavement are numerous and among them, it is worth mentioning in particular those below
- the coating has excellent qualities for the handling of vehicles, even in rainy weather, because the protruding gravel are effective elements for attaching tires while allowing water drainage,
- in spite of the gravel which forms asperities on its surface, the coating is less sound than the "coated" type coatings due to the presence between the gravel of fine elements which absorb and dampen the vibrations generated by the passage of vehicle tires ,
- It significantly reduces the risk of breakage of windshields under the effect of traffic because, unlike coatings of the "coated" type, the gravel of the coating are bonded laterally and are not put in excess. They are therefore much less likely to be eliminated during the period of placement and consolidation of the coating,
- the implementation of the coating can occur in the back of the season and in wet weather with a reduced risk because unlike coatings of the "coated" type whose gravel fixed on the roadway by one side and discontinuously can be peeled off by the action of rainwater arriving at the base of the gravel, the grains of the coating are linked together and form a continuous and impermeable layer so that the rainwater runs over the surface without reaching the base of the layer fixed to the roadway.

Claims (4)

 1- Thin coating for pavement maintenance characterized in that it consists of a mineral mixture with continuous particle size coated with a cationic emulsion of a bitumen of road type added with a synthetic elastomer, and a cationic product.  2- thin coating according to claim I characterized in that the percentage by weight of elastomer in the bitumen is between 1 and 5 96 and is preferably between 1.5 and 3%.  3- thin coating according to claim 1 and claim 2 characterized in that the cationic additive is added to the mixture in an amount of I to 2 parts by weight per 100 parts of mineral mixture and 10 to 15 parts of 60 % of bitumen-elastomer.  4- A method of manufacturing and applying the thin coating according to any one of claims 1 to 3, characterized in that it consists of mixing the components of the coating on the site of the application, then spreading the mixture obtained on the roadway using a distributor sled and finally allowing the mix to harden at room temperature for a period of between 15 and 45 minutes.