FR2813619A1 - Procedure and machine for making cold bitumen-bound materials for road surfacing uses initial phase with water added to mixed components - Google Patents

Abstract

The procedure is carried out in two phases: a first in which two granular materials are mixed together and water is added to them, and a second phase in which a bitumen emulsion is added to the pre-mix and mixed prior to use. The amount of added water is determined by laboratory tests to control the performance of the bitumen-bound product. The mixture is produced in a machine with a feed section (1) comprising a tractor unit hopper (3) and conveyor (5), and a coating section (2) with a loading hopper, mixer (21), and a tank with reservoirs for water (11), emulsion (12) and additive (13).

Description

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The invention relates to a process for obtaining cold bituminous mixes intended for road construction, from a mixture of aggregates and a bituminous emulsion. The invention also relates to a device for implementing this method.

The present invention relates more particularly to bituminous mixes, obtained by cold coating of aggregates using a bituminous emulsion and characterized by a short rupture time of the emulsion.

According to the invention, they have the advantage of remaining easy to handle when they are placed on the road. Even when the breaking time is short, they are not sensitive to variations in atmospheric conditions, the time required for implementation on the road, the nature of the aggregate / emulsion couple, etc.

In addition, the materials obtained according to the invention limit the risks of premature fatigue and tearing generally caused during the ripening period of traditional mixtures when the material is not yet structured.

The term "traditional" here refers to cold-coated materials whose rupture time is sensitive to the above parameters. It is known that ripening, which intervenes last in the rupture of the emulsion, is a phenomenon sensitive to variations in temperature and hygrometry. This sensitivity plays an important role and limits the possibilities of reducing the breaking time of the emulsion.

Indeed, cold mixes, characterized by a short emulsion breaking time, are very sensitive to variations in consistency which can lead to the formation of lumps after transporting the product from the manufacturing center to the place of use. . In fact, these mixes are generally manufactured in a plant located at a distance from the road site, and during transport, under the effect of vibrations linked to the condition of the roadway, the material consolidates under its own weight in the lower part of the load. Then there is a

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 migration of water to the surface of the load, causing exudation.

These variations in consistency have harmful effects on the implementation of the material on the road, in particular on the control of the profile to be respected. Consequently, these variations in consistency have damaging effects on the uniformity of the coating, and therefore on the comfort of the roadway.

In the case of traditional mixtures of cold mixes used by hand or with a grader, the variability of their consistency is not important since the material is taken up several times.

On the other hand, when the implementation on the roadway is carried out using a finisher or an F.I.R. (Rapid Intervention Finisher), this is necessarily carried out in a single step. The installation of cold bituminous concrete is more delicate, especially during the spreading and compacting phases.

In order to avoid these difficulties, it has been envisaged to manufacture bituminous mixes in the cold at the very place of their implementation. Manufacturing then includes, on site, the steps of dosing, kneading the granular reconstitution with the binder.

The term granular reconstitution "explicitly designates the mixture of the different aggregates fractions selected during the assay.

This solution is satisfactory, as far as the spreading conditions are concerned, but taking into account environmental constraints such as noise and dust means limiting their application to the sites of classified installations.

The problem thus posed therefore consists in devising a method and a device allowing the control of the evolution of the coated materials over the time included between the coating of the aggregates by the emulsion and the spreading.

More particularly, the object of the invention is to alleviate the drawbacks of the previous solutions by proposing to combine the coating and implementation steps at the place of implementation.

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 work, the granular reconstitution step being carried out independently of the preceding on the places of production or storage of aggregates.

The invention relates to a process for the cold production of bituminous mixes intended for the construction of a pavement from a mixture of aggregates and bituminous emulsion.

According to the invention, these stages are grouped into two successive phases separated by a transport stage.

The first phase is a bass reconstitution phase comprising the following stages: # supply of at least two granular fractions in a mixer to obtain a premix, # mixing of the premix, # supply of water to the premix.

The second phase is a phase carried out on site and comprising the following stages: # addition of bitumen emulsion to the premix, # mixing of the emulsion / premix mixture to obtain a mix, # optionally addition of water, # optionally addition of an additive.

Finally, there is a third phase succeeding the two previous phases and comprising the following stages: # spreading of the asphalt on the pavement, # compaction.

In a preferred embodiment, the amount of water supplied to the premix during the first phase is determined beforehand in the laboratory so as to control the workability of the mixture after coating.

The invention also relates to a mobile device for spreading asphalt comprising a supply unit for reconstituted aggregates and a coating unit.

The feed assembly includes a tractor, a receiving hopper and a conveyor.

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 The coating assembly includes a loading hopper, an emulsion tank and a mixer.

In different embodiments, each with their own advantages: # the feed assembly comprises a weight flow indicator, # the coating assembly comprises a water tank, an emulsion tank and an additive tank, # the coating assembly comprises metering pumps respectively for the emulsion, for the water and for the additive, # the mobile device comprises control means making it possible to control the supplies of water, emulsion and additive during coating, and # the control means are connected to a weight flow indicator placed at the level of the feed conveyor.

The main advantages of the invention are as follows # the maneuverability of the mix does not depend on the transport times, the climatic conditions or the implementation times on the roadway because the process makes it possible, if necessary, to carry out the transport of materials when they are in the form of aggregates, # the separation of the stages of production of aggregates and coating of these same aggregates makes it possible to take into account environmental constraints (noise, dust).

Various advantages and characteristics of the present invention will emerge from the detailed description below, given with reference to the appended figures, in which: FIG. 1 schematically represents, in side view, an exemplary embodiment of the device according to the invention, - Figure 2 is a top view of the same device.

The device for the cold production of bituminous mixes, shown schematically in the Figures, is a mobile power station (CM), which includes a self-propelled machine 1 for receiving and supplying aggregates, and a trailer 2 towed by the machine self-propelled 1 and supporting the mixer 21. The assembly

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 is controlled 7from a seat 26. The self-propelled machine 1 and the trailer 2 are connected by an articulated link.

The self-propelled machine 1 fulfills the traction and feeding functions of the mixer 21. It is set in motion by the track assembly 8 and it is equipped with an aggregate receiving hopper 3 and a conveyor belt 5 or conveyor input intended for feeding the aggregates into the mixer 21.

The hopper 3, projecting from the front of the tractor 1, is provided with an adjustment hatch 41 intended to regulate the feed rate of the belt 5 in aggregates coming from the hopper 3. The speed of the belt d power 5 is adjustable. The conveyor belt 5 is equipped with a weight flow indicator 6 which makes it possible to measure, permanently, the quantity of aggregates supplied to the mixer 21.

A heat engine 7 is intended to drive the hydraulic pumps (not shown) which serve to set the towing machine 1 in motion.

A generator 9 supplies the belt motor 5 and the various elements carried by the trailer 2.

The trailer 2, on its wheels 25 carries the mixer 21 and respectively reservoirs of water 11, emulsion 12 and additive (or dope) 13. These reservoirs 11, 12, 13 are advantageously constituted by a compartmentalized tank placed under the carpet 5.

The mixer 21 is a conventional mixer, with two horizontal shafts 23, 24, it is placed cantilevered, at the rear of the trailer 2.

The mixer 21 is associated with supply ramps, respectively in water 18, in emulsion 19 and in additive 20 which are each connected by a water pump 14, in emulsion 15 and in additive 16 to the corresponding tank, respectively the tanks 11 , 12 and 13.

Advantageously, a discharge device 22, for example a helmet, can be placed at the rear end of the mixer 3 in order to avoid any loss of homogeneity of the product.

_ A device for regulating and controlling the emulsion supply flow rate (not shown) is used,

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 and a flow controller (not shown) in aggregate, connected to the flow rate weight indicator 6 makes it possible to vary the overall flow rate by 50%.

We will now describe the process of the invention. In a first phase outside the road construction site, the aggregates, made up of gravel and sand, are dosed in predetermined proportions so as to select, for mixing with the emulsion, fractions of aggregates whose particle sizes are each respectively included in a given range. The mixture of different selected fractions is carried out, during a granular reconstitution step, in a so-called white materials power station or using a reconstitution chain of a quarry installation. Preferably, a quantity of water previously determined in the laboratory from the Proctor test is added to the aggregate mixture.

The material is then transported by trucks, possibly covered, to the place of implementation. From the lifted bucket of the trucks, the materials are then dumped from the trucks directly into the hopper of the mobile power station (CM).

During the second phase, on the road site and through the use of the mobile plant described above, the aggregates are conveyed by the feed belt 5 to the mixer 21, in the "upward" direction.

The water contained in the reservoir 11 is metered with the pump 14 and brought into the mixer by means of the ramp 18. The emulsion stored in the reservoir 12 is metered by means of the pump 15 and is introduced into the mixer 21 at Through the diffusion ramp 19, in the mixer 21, the humidified aggregates are powerfully mixed, by the rotation of the paddle, with the emulsion.

Likewise, the additive (or dope) contained in the reservoir 13 is dosed, with the pump 16, and supplied by means of the ramp 20.

At the outlet of the mixer, the coated materials are received by a distribution and adjustment type

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 finisher; quick intervention leveler or finisher (F.I.R.), which spreads the bituminous mix cold on the pavement.

Thus, according to the invention, the time elapsing between the coating and the spreading has been reduced while precisely controlling the conditions of the coating. Covering the trucks prevents the moisture content of the aggregates from varying substantially between the first and second phases. Small variations can be compensated for by the provision of water provided in the mixer 21. This eliminates the effect of the shakes inevitably produced during the transport of the mix and the invention does not have the environmental constraints presented in the introduction can be implemented on any site.

The invention is not limited to the embodiments described in detail, and various modifications can also be made without departing from its scope, in particular any other device for cold production of bituminous mixes making it possible to implement the method. according to the invention.

The reference signs, inserted after the technical characteristics mentioned in the claims, have the sole purpose of facilitating understanding and in no way limit their scope.

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Claims (8)

CLAIMS 1. Process for the cold production of bituminous mixes intended for the construction of a pavement from a mixture of aggregates and bituminous emulsion, characterized in that the stages of the process are grouped in two separate successive phases by a transport step, the first phase being a bass reconstitution phase comprising the following steps: # supply of at least two granular fractions in a mixer to obtain a premix, # kneading of the premix, # supply of water to the premix, the second phase being a phase carried out on site and comprising the following stages: # supply of bitumen emulsion to the premix, # mixing of the emulsion / premix mixture to obtain a mix. 2. Method according to claim 1, characterized in that the quantity of water supplied to the premix during the first phase is determined beforehand in the laboratory so as to control the workability of the mixture after coating. 3. Mobile asphalt spreading device comprising a supply assembly (1) of reconstituted aggregates and a coating assembly (2), the supply assembly (1) comprising a tractor, a receiving hopper (3 ) and a feed conveyor (5), and the coating assembly (2) comprising a loading hopper, a tank and a mixer (21). 4. Device according to claim 3, characterized in that the supply assembly (1) comprises a weight flow indicator (6), 5. Device according to any one of claims 3 and 4, characterized in that the tank comprises water tanks (11), emulsion (12) and additive (13). <Desc / Clms Page number 9>  6. Device according to claim 5, characterized in that the coating assembly (2) comprises metering pumps respectively for water (14), for the emulsion (15) and for the additive (16) for the water. 7. Device according to any one of claims 3 to 6, characterized in that it comprises control means making it possible to control the additions of water, emulsion and additive during the coating. 8. Device according to claim 7, characterized in that said control means are connected to the weight flow indicator (6) placed at the level of the feed conveyor (5).