ROLLER COMPACTOR INTEGRATED TO A WHEEL TRACK MACHINE FOR LABORATORY TESTS ON BITUMINOUS MIXES

Abstract

An integrated machine for making, in laboratory, slabs made of a controlled-compaction bituminous mix in a mould and for making wheel tracking tests on the same, the compaction is performed by two idle disks which slide and press the side extensions of an array of vertical plates overlapping the mix, the wheel tracking test is performed by a wheel located between the disks; after having removed the array of plates, the wheel can be presented to the mix, since the disks are located at a distance greater than the mould width.

Description

FIELD OF THE INVENTION

The present invention refers to the experimental field of the bituminous mixes for road paving, and, more specifically, to the machines adapted to the laboratory manufacturing of controlled compaction slabs for executing on them wheel tracking tests or to be cut in elements adapted to advanced tests.

The viscoelastic and thermoplastic behaviour of the bituminous mixes exposes the outer layers of the road flexible paving to the risk of being permanently deformed (wheel trackings) due to the action of the heavy transport in the areas which are more subjected to the tyres rolling, this effect is augmented by an environment temperature rise.

Such deformations impair the smoothness of a road, and therefore the safety of the vehicles running on it.

For characterising the deterioration, the phenomenon of the permanent deformations is studied by road simulators or wheel track machines, capable of reproducing on a reduced scale and under predetermined test conditions, the action of the vehicle load (rolling wheel).

The specimen under test can be directly taken from the road or can be manufactured, in a laboratory, with a slab shape.

For obtaining this slab with the same mechanical characteristics of the paving to be designed, it is necessary another machine, known as “roller compactor”, simulating the rolling made in a construction site on the spreaded bituminous mix.

The manufactured slab is also used for other objects: by suitably trimming it, it is possible to obtain specimens adapted to dynamic tests for determining the constitution properties of the material and its fatigue resistance.

The experimental laboratory dedicated to the study of road pavings requires two separate machines: one dedicated to the manufacture of the mix slab for the different tests, the other dedicated to the wheel tracking test on the slab itself.

DISCLOSURE AND ADVANTAGES OF THE INVENTION

The object of the present invention consists of unifying the above mentioned machines.

In brief, the invention consists of an architecture adapted to obtain a single machine having two operations.

The invention refers to a way for integrating two separate machines used in an experimental laboratory which studies bituminous mixes for road paving. Such machines are known respectively as “roller compactor” and “wheel track machine”; the first is for manufacturing controlled-compaction mix slabs, the second for simulating, on a reduced scale, the deforming effect generated by tyres rolling on a road. The reference regulations are EN 12697-33 and EN 12697-22 respectively.

A regulated variant of the roller compactor provides a suitably loaded idle metal cylinder alternatively sliding on a row of slabs freely reciprocally translating in a vertical direction, guided by a container containing the mix. These slabs form a flexible interface adapted to transmit shearing stresses to the mixture contained in the mould.

A regulated variant of the wheel track machine comprises a suitably loaded idle wheel horizontally reciprocally sliding on the mix surface for forming a tracking on it, whose depth is the measure to be studied.

The invention comprises the substitution of the conventional cylinder of the compactor with two facing disks located at a distance greater than the size of the mould and the application of two side projecting extensions to the slabs, in order to form sliding tracks of said disks. This arrangement consists of housing between the two disks the wheel dedicated to the wheel tracking. This wheel can be driven to the mix surface once the slabs have been removed, since the distance between the disks is greater than the mould width. In this way, all the handling, loading, control, and measuring devices are available both for the compaction and the wheel tracking.

The advantage brings about a substantial cost reduction for a laboratory. The measuring and control devices necessary for the wheel tracking operation are also available for the roller compactor, which can also be controlled for performing specific experimental procedures which are not expressively anticipated in the reference regulation.

Said object and advantages are all met by the machine object of the present invention, which is characterized for what it is claims in the attached claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The attached drawings, as an exemplifying non limiting example, are the reference for the following description; in particular:

FIGS. 1, 2 and 3 show examples of the prior art;

FIG. 4 shows the machine of the invention.

PRIOR ART

Referring to the wheel track machine, the EN 12697-22 regulation describes the different possible arrangements and the associated test modes. The more common arrangement, as shown in FIG. 1, provides a test room at a controlled temperature, receiving a device (A) generating a constant load on a freely rotating tired wheel (B) around its horizontal axis. Said wheel abuts on the sample (C) which in turn is subjected to cyclical movements along a rectilinear and horizontal path (D). The depth of the tracking formed by the specimen surface after a predetermined number of passes provides the expected measurement (E).

Regarding the roller compactor, the reference regulation EN 12697-33 lists different approaches; the more simple approach, FIG. 2, provides the mix (A) inside a mould (B) upwardly closed by a sector of a cylinder (C), on the cylinder rotation axis acts the load device (D). The sector is moved with a pendular motion dragged by the alternative rectilinear motion (E) received by the mould.

The compacting action on the mix is the same as the one performed by a road roller moving backwards and forwards on the spreaded bituminous mix.

The problems of this arrangement are different.

First of all, the cylinder sector does not need to move along the whole mouth of the mould, so it leaves at the ends of the travel a space sufficient for the grains possibly ejected by the mixture; the result is a slab having two edges which are not suitably compacted. Secondly, the cold surface of the cylinder sector lowers the mix temperature and, consequently, lowers the mobility of the binder inside the contact layer, in this way it increases the non homogeneity in the product. The regulation itself offers a valid alternative for avoiding said disadvantages, by outlining a flexible interface between the roller and the mix (as shown in FIG. 3).

There is a pack of metal slabs (A) vertically arranged to close the mould (B) and which can freely reciprocally translate guided by the walls of the latter.

Such system avoids the ejection of the mix grains (C), by allowing the roller (D) to follow the whole path on the slab series when it is performed the movement (E) and, therefore, to subject the whole sample to the effect of the load produced by a jack (F).

The slabs pack can then be pre-heated with the mould to the temperature of the mix, in order to have a closed container at a high heat inertia for making negligible the cooling of the bitumen during the compaction.

DESCRIPTION OF THE INVENTION

FIG. 4 shows a schematic view of the machine of the invention and substantially illustrates the invention, which consists in an arrangement adapted to obtain a single machine having two operations.

The cylindrical roller characterizing the machines of the prior art is formed by two coaxial facing idle disks A; two side projecting extensions B are added to the rectangular-shaped slabs equipping said machines for obtaining the C shape.

The distance between the disks is such to be greater than the side of the mould D, so that, after the removal of the slabs series and after the mix has been taken to the surface in the container, the jack E can cause the central wheel F to contact the mix surface G, while the disks freely lower besides the upper edge of the mould.

The remaining references indicate the dynamometer H, the vertically sliding guides I, the horizontally sliding guides L and the associated motor M.

The figure does not comprise the vertical displacement sensor, the power, control and driving devices, the tough frame and the thermostatically-controlled protective covering.

In brief, the slab extensions B form the sliding tracks of the disks A and therefore enable the use of the cited devices for compacting the mix slab; by removing the slabs C, it is possible to obtain the central wheel F which, with the loading, control and measuring devices, allows the wheel tracking test.

Claims

1. Integrated machine for making, in laboratory, slabs made of a controlled-compaction bituminous mix in a mould and for making wheel tracking tests on the same, the compaction step is performed by two idle disks which slide and press the side extensions of a vertical plates array overlapping the mix, the wheel tracking test is performed by a wheel located between said disks; after having removed the plates array, the wheel can be presented to the mix since the disks are located at a distance greater than the mould width.

2. Machine according to claim 1, wherein the assembly formed by the facing discs and intermediate wheel is in charge of the reciprocating translating motion, instead of the assembly formed by the mould and plates array.

3. Machine according to claim 1, wherein the plates and disks have different configurations, however they reproduce the operation principle object of the invention.