Road structure – process – or apparatus – Process – In situ treatment of earth or roadway
Patent
1994-04-25
1995-08-29
Buiz, Michael Powell
Road structure, process, or apparatus
Process
In situ treatment of earth or roadway
E01C 700
Patent
active
054454735
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an improved crack anti-rise system inserted between the structural layer and the road carpet of a carriageway. It further relates to a process for producing such a system.
Road or airport carriageways are generally formed from a number of layers, namely a surface layer, known as the road carpet, based on a material of the surface coating type or alternatively of the bituminous concrete type, and one or a number of lower layers forming the structural layer of the carriageway, based on materials treated with hydraulic binders such as cements, blast furnace slags, pozzolana, fly ash or bituaninous binders.
For structures containing hydraulic binders, various mechanical and thermal stresses of static nature, for example setting contraction and thermal contraction of the materials, or of dynamic nature, namely stresses related to traffic, to which carriageways are subjected lead to cracking of the structural layer, the cracks generated being transmitted more or less rapidly to the road carpet to then appear at the surface of the latter. The presence of surface cracks in the carriageway makes it possible for water to enter into the body of the said carriageway, which causes rapid and significant deterioration of the latter.
In order to prevent or at least delay the appearance of cracks in the road carpet of a carriageway, the structural layer of which is subjected to cracking, various solutions have been proposed, such as: run onto the structural layer in order to uncouple the movements of the latter and those of the road carpet which surmounts it, grids having satisfactory mechanical characteristics, or alternatively covering the nonwoven with a layer of approximately five centimeters of a bituminous concrete which constitutes the road carpet.
Such solutions have not led to satisfactory results, the cracks reappearing more or less rapidly at the surface.
A better solution, proposed in the citation FR-A-2,592,411, consists in interposing, between the structural layer and the road carpet, a nonwoven geotextile interface impregnated with a bituminous binder consisting of an asphalt modified, for example, by a copolymer of styrene and of a conjugated diene such as butadiene.
It has now been found that the behaviour of the crack anti-rise systems of the type of that described in the citation FR-A-2,592,411 could be improved by joining a layer of aggregates coated with a bituminous binder to the geotextile layer, itself impregnated with a bituminous binder.
The crack anti-rise system according to the invention, which is inserted between the structural layer and the road carpet of a carriageway, is of the type containing a layer of a geotextile impregnated with a first bituminous binder and it is characterized in that it also includes a layer of aggregates coated with a second bituminous binder, which is joined to the layer of geotextile impregnated with a first bituminous binder.
According to a first embodiment, the crack anti-rise system is arranged so that, between the structural layer and the road carpet of the carriageway, the layer of geotextile impregnated with the first bituminous binder lies on the structural layer of the carriageway, whereas the layer of aggregates coated with the second bituminous binder is covered by the road carpet.
According to a second embodiment, the crack anti-rise system is arranged so that, between the structural layer and the road carpet of the carriageway, the layer of aggregates coated with the second bituminous binder lies on the structural layer of the carriageway, whereas the layer of geotextile impregnated with the first bituminous binder is covered by the road carpet.
The layer of aggregates coated with the second bituminous binder can advantageously be a layer of sand coated with the said binder. The layer of aggregates coated with the second bituminous binder can also consist of a layer of a surfacing run on while cold or alternatively of a draining surfacing layer.
Geotextile is understood to mean, according to the invention, any tightly-structure
REFERENCES:
patent: 4650820 (1987-03-01), Decroix
patent: 5290123 (1994-03-01), Barnes et al.
Highways, vol. 58, No. 1959, Jan. 1990, Croydon GB, pp. 12-14 Buist & Ineson Geogrids in Reinforcing Asphaltic Pavements.
Chaverot Pierre
Lopez Emile
Buiz Michael Powell
Koch Materials Company
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