Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
1998-12-29
2001-02-13
Pezzuto, Helen L. (Department: 1713)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C428S304400, C428S308400, C428S317100, C428S317900
Reexamination Certificate
active
06187428
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a wheel rut-resistant carriageway as well as to a process for obtaining such a carriageway.
2. Description of Background and Relevant Information
A carriageway comprises generally a foundation layer, a base layer, a binding layer and an upper layer. All these layers consist of materials treated with either hydraulic or tar binders. The materials and the binders are determined in relation to the type of traffic that the carriageway has to sustain or, in other words, in relation to the type of wear and deformation to which the carriageway will be subjected when in use. One of these phenomena to which the carriageway is thus exposed, is the formation of wheel ruts.
The ruts, generally defined as deep tracks or marks left by the wheels of a vehicle on a path, result from the load of the vehicles circulating over the carriageway and from the temperature rise of the said carriageway.
Indeed, the formation of wheel ruts in a carriageway comprising bituminous concrete layers is boosted when the temperature of the carriageway or of one of the layers, exceeds the softening temperature of the bitumen of the layer. The carriageway temperature results mainly from the ground temperature on which the carriageway lies and from its exposure to the sun. Moreover, a carriageway designed to sustain the traffic of heavy vehicles undergoes greater stresses in areas such as an approach to a highway toll where the carriageway must sustain the braking of the vehicles or the storage of the trucks in the waiting queues than in the driving zones of the highway lanes.
To remedy this particular fragility of the carriageways, it may be contemplated to build the highly stressed zones of the latter essentially as concrete slabs. However, this solution is solely retained for the new construction of zones of this nature since, in such a case, the time required by concrete to set is acceptable. On the other hand, when repairing the carriageway, this time for the concrete to set is too long and implies traffic prohibitions for trucks for an unacceptable duration.
Wheel ruts in carriageways are dangerous since they channel rainwater and make the carriageway slippery; the more so for trucks when they have to brake when approaching zones such as toll stations. Various technologies have been used to avoid the formation of wheel ruts. Thus, a method consists in mixing the bituminous binder with a mixed load of mineral granulates and waste flakes of plastic material (FR-2.742.174). Another technique consists in using a road coating compound comprising a tar concrete and acrylonitrile fibres, preferably kidney-shaped ones (FR-2.647.822).
Besides, tests have been conducted with ‘white’ coated materials to benefit from the fact that this color absorbs heat less than the usual black tone of bitumen. However, the resistance of such coated materials to the formation of wheel ruts is very poor.
The various techniques described hereabove can be summarized as some kind of replacement technique: part of the agregate is replaced by voids, these voids being obtained by an appropriate choice of the particulate grade of the agregate.
Whatever the resistance to the formation of wheel ruts in the bituminous layers prepared according to these various techniques, none of the latter gives complete satisfaction.
SUMMARY OF THE INVENTION
The purpose of the invention is to provide a wheel rut-resistant carriageway which is constituted in order to improve its resistance to the formation of wheel ruts.
It must be possible to build such a carriageway from scratch as well as to repair an existing one.
The purpose of the invention is met by a wheel rut-resistant carriageway comprising at least one base layer and one upper layer as well as at least one high void rate intermediate layer allowing for evacuation of part of the heat that is introduced into the intermediate layer, by ventilation, thanks to the high void rate.
We call “void rate” the ratio of the volume of voids in respect to the volume of the intermediate layer. This void rate is also called void percentage when expressed in percent.
To interpose an insulation layer between the base layer and the upper layer first enables to associate bituminous products whose formulation is suited, for each layer forming the carriage, to the specific loads encountered during the use of the carriageway and which exhibit good wheel rut resistance. At the same time, it enables, while insulating the lower layers of the carriageway from the upper layers, to avoid any significant rise in their temperatures. This is obtained both by a reduction of the amount of heat transmitted and by ventilation of the intermediate layer resulting in a partial evacuation of heat thanks to the high void rate.
Indeed, the upper layer is generally applied, directly or via a bonding layer; onto a base layer consisting of dense coated materials. This layer made of dense coated materials does not transmit the heat from the upper layer to the lower layer entirely, but causes the temperature to drop by approx. 1° C. per centimeter of thickness of the layer. Contrary to that, the intermediate layer according to the invention enables to reduce this temperature by approx. 2° C. by centimeter of thickness.
According to the embodiment selected, the carriageway of the invention exhibits either of the following technical characteristics, considered individually or with all their technically possible combinations:
The intermediate layer comprises draining coated materials.
The void rate of the intermediate layer ranges from about 25 to about 30%; advantageously, it amounts to approx. 30%.
The base layer consists of hard bitumen, possibly with a polyethylene additive, which creates a rigid support in order to distribute adequately the loads applied by heavy vehicles. The hard bitumens used to this effect exhibit a ball ring temperature (standardised temperature at which bitumen softens) above 50° C. The thickness of the base layer ranges, advantageously, from 6 to 8 cm. The coated materials treated with this hard bitumen, with or without polyethylene additive, must exhibit a complex module, measured according to the French standard NF P 98-260-2, greater than 14,000 MPa. Advantageously, this complex module exhibits a value ranging between 14,000 MPa and 18,000 MPa.
Let us mention that the French standard NF P 98-260-2 relates to the determination of the complex module by sine wave flexion of a tar mixture and that the complex module is the ratio between a stress and a relative complex deformation of a tar mixture whose behaviour is considered as linear viscoelastic. Determination of the complex module is performed at four temperatures, at least, spaced by no more than 10° C. and for each temperature, at three frequencies at least, regularly spaced, of a sine wave load.
The intermediate layer consists of bituminous coated materials obtained from stone chips whose size grading and shape enable to provide for a void rate of approx. 30%. These coated materials contain a very small quantity of sand, advantageously lower than 10%. The thickness of the intermediate layer is advantageously approx. 4-5 cm.
For comparison purposes, it has been stated that the void rate of a layer consisting of draining coated materials is approx. 20%.
The upper layer is rough in order to improve the braking effect of the trucks. Its thickness is advantageously approx. 2-3 cm.
The carriageway comprises a bonding layer applied on the intermediate layer. Advantageously, this bonding layer consists of cold-cast coated materials. This bonding layer improves adhesion between the various coated materials and ensures, together with the upper layer, the tightness of the intermediate layer.
The insulating effect of the intermediate layer is obtained by a high void rate of the bituminous concrete used for the construction of this layer. The void rate or the void percentage of the bituminous concrete depends at the same time on the discontinuity of the size grading of the stone chipping selected and
Colas S.A.
Greenblum & Bernstein P.L.C.
Pezzuto Helen L.
LandOfFree
Wheel rut-resistant carriageway and process for obtaining... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Wheel rut-resistant carriageway and process for obtaining..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wheel rut-resistant carriageway and process for obtaining... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2604292