IE902957A1

IE902957A1 - Geotextile for reinforcing asphalt layers

Info

Publication number: IE902957A1
Application number: IE295790A
Authority: IE
Original assignee: Hoechst Ag
Priority date: 1989-08-16
Filing date: 1990-08-15
Publication date: 1991-02-27
Also published as: JPH03180602A; EP0413295A1; PT94995A; DE3926991A1

Abstract

There is described a geotextile which is used in particular in the restoration of worn bituminous road surfaces as an interlayer between the old and the new road surface. The geotextile is a composite formed from a nonwoven and a woven, knitted, laid or otherwise constructed fabric of defined yarn position. The nonwoven is preferably constructed as a Raschel material, in which case the nonwoven and the fabric of defined yarn position are bonded together by the weft-laying Raschel technique. The geotextile described has particularly advantageous reinforcing and sealing properties and is characterised by good layability.

Description

Description GEOTEXTILE FOR REINFORCING ASPHALT LAYERS The present invention relates to a geotextile for rein5 forcing asphalt layers in road construction.

Geotextiles have been used for many years in the renovation of worn bituminous pavements in the form of an interlayer between the old and the new pavement. However, geotextiles can also be used between the pavement and the support layer in the building of new roads. The functioning and the advantages of such geotextiles were discussed at a conference from March 8, 1989 to March 10, 1989 in Li&ge, Belgium (Reflective Cracking in Pavements, Assessment and Control).

In practice, essentially two fundamental concepts have become established. One provides for the use of nonwovens which are customarily in the form of spunbondes formed from continuous filaments and of polypropylene or, owing to the higher melting point, increasingly also polyester (cf. for example Die Asphaltstrafie” 1/88, p. 15ff, or Installation Guide for Paving Fabric in Asphalt Overlays from Hoechst Fibre Industries, USA). On the other hand, use is made of lattice fabrics formed from high— strength polyester yarns (cf. for example Bitumen, Teer, Asphalt, Peche, Volume 25, April 1974). A recent addition are grids, which comprise oriented perforated films formed from a cast or extruded plastic, usually polypropylene .

The chief advantage of a nonwoven between the pavement and the ground is a certain buffer effect which is intended to prevent, or at least delay, the formation and propagation of cracks. In addition, the bitumenimpregnated nonwoven acts as a water barrier which is intended to prevent the penetration of surface water into - 2 the support layer. As has been found In practice, however, nonwovens are frequently not satisfactory in preventing crack formation and propagation due to vertical movements or very large horizontal movements, which must presumably be ascribed to their inadequate strength and extensibility characteristics.

Even though lattice fabrics, owing to their better strength properties are efficient at absorbing relative movements between the pavement and the support layer and thus are more effective in preventing crack formation and propagation, they have the disadvantage, however, that cracks can pass through the coarse mesh holes from 20 to 40 mm in size. Another disadvantage is that they offer virtually no barrier to the penetration of surface water.

And, owing to their stiffness, such lattice fabrics present laying problems, which frequently leads to inadequate attachment and thus to premature detachment of the asphalt layer.

The present invention has for its object to provide a geotextile for the reinforcement of asphalt layers in road construetion which is particularly effective in preventing crack formation and propagation in the asphalt layers, which possesses a good sealing effect against the penetration of surface water, and which is easy to lay.

This object is achieved according to the present invention when the geotextile comprises a composite material consisting of two components, one of which is a nonwoven while the other is a woven, knitted, laid or grid fabric or some other sheetlike structure of defined yam 0 arrangement.

Composite materials formed from a nonwoven and a sheetlike structure of defined yam arrangement are already known per se. For instance, DE-U-7,133,997 describes a composite material formed from a crimped polyamide fiber nonwoven and a needled-in continuous filament lattice - 3 fabric, which are held together by a water-resistant binder. This composite material is used as an erosionpreventing damming material in dyke and canal construction.

By contrast, the geotextile constructed according to the present invention is used to reinforce asphalt layers in road construction. As has been found, the geotextile constructed according to the present invention has a surprisingly high resistance to crack formation and propagation. This is likely to be due to a combination effect between the advantageous properties of the two components of the composite. In addition, the geotextile constructed according to the present invention possesses an excellent sealing action which prevents the passage of water and thus also of organic and inorganic constituents.

Preferably, the composite material is constructed as a Raschel material in which the two components of the composite material are held together by the weft inser20 tion Raschel technique. This is a form of warp knitting in which the nonwoven is reinforced in some directions by yarns, preferably high-strength yarns. This warp-knitting technique is carried out on so-called Raschel machines. A particularly suitable Raschel machine for producing a composite material constructed according to the present invention is the RS 3 MSU-V model from Karl Mayer, Textilmaschinenfabrik GmbH, Obertshausen. A Raschel material produced by the weft insertion technique with a web inlay exhibits a particularly strong bond between the two components of the composite material.

However, good results are also obtained on bonding together the two components of the composite material by needling, by adhesive bonding or by stitching. The bond between the two components must be sufficiently strong to ensure that the geotextile will not weaken due to delamination of the composite material.

The nonwoven can be produced from polypropylene, polyethylene, polyamide, polyacrylonitrile or any other suitable raw material; preference, however, is given to polyesters, in particular polyethylene terephthalate, owing to their high temperature resistance.

The nonwoven is preferably constructed as a spunbonded formed from continuous filaments. The nonwoven may have been consolidated mechanically, thermally or chemically; mechanical consolidation is preferred, on account of the flexibility and the absorptive capacity for bitumen of such a nonwoven. The basis weight of the nonwoven is preferably within the range from 50 to 300 g/ „m2, preferably from 100 to 180 g/ m2.

The choice of raw material for the second component of the composite material, for the woven fabric say, is similar to that in the case of the nonwoven. Particular preference is given to making the two components of the composite material from the same raw material, i.e. in particular from polyesters, irrespectively of whether the composite material contains a woven, laid, lattice or knitted fabric or is constructed as a Raschel material. The basis weight of the second component of the composite material is preferably within the range from 100 to 500 g/ m2. The breaking strength of the second component of the composite material should be from 10 to 200 kN/m, preferably above 25 kN/m (the breaking strength in question being the breaking strength of a sheetlike structure lm in width). The breaking extension is preferably within the range from 5 to 35 4, preferably from 10 to 20 %.

If the composite material has been constructed as a Raschel material with a nonwoven layer, then the breaking strength of the second component of the composite material corresponds to the breaking strength of the composite material itself, since the nonwoven, owing in particular to its high extensibility, does not make any significant contribution to the breaking strength.

The bond between the geotextile and the two asphalt layers is obtained with an adhesive, for example pure bitumen. On using other adhesives, the ultimate amount of adhesive must be determined beforehand. The amount of adhesive must correspond at least to the pore volume of the composite material and must allow for loss of adhesive into the damaged layer. The relevant requirements are summarized in the Specification Guide for Paving Fabrics of TASK FORCE 25.

In a particularly preferred embodiment, the nonwoven is a Trevira spunbond into which high-tenacity Trevira hochfest yarns have been integrated by the weft insertion Raschel technique or which has been bonded to a woven fabric made of high-tenacity Trevira hochfest yarns by stitching.

As mentioned, the composite material constructed according to the present invention exhibits a particularly high resistance to crack formation and transmission. Here the nonwoven component ensures an optimal bond between the asphalt and the geotextile; it also prevents any passage of water and forms a buffer which absorbs the forces due to the cracks. Advantageously, the composite material is used with the nonwoven face downward.

In the event of larger cracks, due in particular to the demolition of adjoining buildings and/or ground movements, frost heaves or other stresses, the force is absorbed in particular by the high-strength second component of the composite material.

Claims

1. Claims HOE 89/F 263

1. A geotextile for reinforcing asphalt layers in road construction, comprising a composite material formed from two components, one of which is a nonwoven while the other is a woven, knitted, laid or grid fabric or some other sheetlike structure of defined yam arrangement.

2. The geotextile as claimed in claim 1, wherein the composite has been construeted as a Raschel material in which the two components have been integrated in one another by the weft insertion Raschel technique.

3. The geotextile as claimed in claim 1, wherein the two components of the composite material have been bonded together by needling, adhesive bonding or stitching.

4. The geotextile as claimed in at least one of the preceding claims, wherein the second component of the composite material is made of high-tenacity yarns.

5. The geotextile as claimed in at least one of the preceding claims, wherein the nonwoven has been constructed as a spunbond from continuous filaments.

6. The geotextile as claimed in at least one of the preceding claims, wherein the nonwoven is made of polyester, in particular polyethylene terephthalate.

7. The geotextile as claimed in at least one of the preceding claims, wherein the two components of the composite material are made of the same raw material.

8. The geotextile as claimed in at least one of the preceding claims, wherein the nonwoven has been consolidated by mechanical means.

9. The geotextile as claimed in at least one of the preceding claims, wherein the basis weight of the nonwoven is within the range from 50 to 300 g/ m z , preferably from 100 to 180 g/ m 2 .

10. The geotextile as claimed in at least one of the preceding claims, wherein the basis weight of the second component of the composite material is within the range from 100 to 500 g/ m 2 .

11. The geotextile as claimed in at least one of the preceding claims, wherein the breaking strength of the - 7 second component of the composite material is within the range from 10 to 200 kN/m, preferably from 25 to 200 kN/m.

12. The geotextile as claimed in at least one of the preceding claims, wherein the breaking extension of the second component of the composite material is within the range from 5 to 35 %, preferably from 10 to 20 %.

13. A geotextile as claimed in claim 1, substantially as hereinbefore described.