REINFORCING MAT FOR REINFORCING ASPHALT

Abstract: The invention relates to a reinforcing mat (1) for reinforcing a top layer of a ground, which top layer consists of bitumen, asphalt or a hydrocarbon-containing material of like nature, in which the reinforcing mat (1) is a mat woven with longitudinal wires (2, 3) and provided with reinforcement elements (4) running in the transverse direction of the mat, in which the reinforcement elements (4) consist of helically twisted steel profiled wires of essentially rectangular cross section.

Description: REINFORCING MAT FOR REINFORCING ASPHALT The invention relates to a reinforcing mat for reinforcing the top layer of a ground or road, which top layer consists of bitumen, asphalt or a hydrocarbon-containing material of like nature, in which the reinforcing mat is a mat woven with longitudinal wires and provided with reinforcement elements running in the transverse direction of the mat. A reinforcing mat which has been utilized with success for reinforcing asphalt is sold by the applicant, N.V. BEKAERT S.A., under the name "Mesh Track". "Mesh Track" is a galvanized steel wire woven mat or mesh, reinforced at regular intervals by two- or three-wire strands fitted in the trans- verse direction of the mat. Special methods for embedding a reinforcing mat in asphalt roads are described, for example, in European patent applications 429.106 and 505.010 submitted by N.V. Bekaert S.A. One important purpose of embedding such a reinforcing mat in asphalt roads is to prevent the formation of cracks and tracks in the asphalt roads. The formation of cracks and tracks in asphalt roads is prevented by the reinforcing mat, which acts to reinforce the asphalt of the road by absorbing the tensile stresses, while the asphalt transfers the compressive stresses. In addition, the transverse reinforcements provide a better distribution of the loads and the granulated asphalt material gets jammed in the mesh openings of the mat. It has been determined that the reinforcement elements fitted in the transverse direction of the reinforcing mat function primarily to absorb the tensile stresses caused by the heavy traffic. This prevents the sideways displacement of the asphalt road, thus preventing the formation of cracks in the longitudinal direction of the road. It is of great importance that the reinforcement elements fitted in the transverse direction of the mat should be sufficiently anchored in the asphalt road to effectively reinforce this road and thus to prevent the formation of cracks and tracks. When the anchoring of the reinforcement elements is improved, it then becomes possible to obtain better reinforcement of the asphalt with the use of less reinforcement material. The first object of the invention is to provide a new type of reinforcing mat in which reinforcement elements fitted in the transverse direction of the mat produce a very firm anchoring in an asphalt road. Tests have demonstrated that the use of reinforcement elements consisting of helically twisted steel profiled wires of essentially rectangular cross-section considerably improves the anchoring. Furthermore it has been determined that the reinforcement elements by preference consist of successive zones of essen- tially the same length, in which each two successive zones are twisted at an angle of approximately 90° in relation to one another. In an especially preferred embodiment of the mat according to the invention, each two successive zones of the reinforcement elements are twisted alternately in clockwise and counterclockwise directions relative to one another at an angle of approximately 90°. One important advantage of the new reinforcing mat according to the invention is that the helically twisted reinforcement elements fitted in the mat function as distance blocks for the mat in the asphalt road which is to be reinforced, and this serves to improve the anchoring even further. Another important advantage of the new reinforcing mat according to the invention is that the mat according to the invention can easily be rolled up and unrolled. It is of great importance that during rolling up, and particularly also during unrolling, the reinforcement elements should not shift in the transverse direction of the mat. For the reinforcing mats known up to the present time with reinforcement elements in the form of two- and three-wire strands, however, it has been determined that while the rein- forcing mat is being unrolled onto the ground to be covered with asphalt the ends of the strands get caught in one another. This problem is totally avoided with the reinforcing mat according to the invention. The invention will be explained in more detail in the following description with reference to the accompanying drawing. In the drawing: Figure 1 is a view from above of a reinforcing mat accor- ding to the invention; Figure 2 shows in larger scale a special embodiment of a reinforcement element for a reinforcing mat. The embodiment of a reinforcing mat 1 according to the invention shown in Figure 1 comprises a woven or braided mat with hexagonal meshes. The hexagonal meshes are created by intertwisting two longitudinal wires 2 and 3 with one another, with reinforcement elements 4 being fitted into the torsions at regular intervals transverse to the mat 1. The reinforcement elements 4 by preference comprise helically twisted steel profiled wires with an essentially rectangular cross-section. The profiled wires 4 are helically twisted around their own axis. The longitudinal wires 2 and 3 and the reinforcement elements 4 are by preference made of steel wire, with the wires and the reinforcement elements by preference being galvanized. The longitudinal wires 2 and 3 can have, for example, a nominal diameter of 2.2 mm, while the profiled wires 4 have by preference an essentially rectangular cross-section of 2 mm x 6.5 mm. The profiled wires 4 are produced, for example, by flat-rolling wires of circular cross-section into bands with a cross-section of approximately 2 x 6.5 mm. It is obvious that the bands or profiled wires 4 should by preference have rounded edges after rolling. The hexagonal mesh openings or meshes of the reinforcing mat 1 have, for example, the following dimensions : 118 mm between the torsions in the longitudinal direction and 80 mm between the torsions in the transverse direction. The reinforcement elements or profiled wires 4 are fitted, for example, at a distance of 235 mm from one another. The pitch or the spacing between full revolutions in the twisting of the helically twisted wires or bands 4 is preferably adapted to the distance between the torsions in the transverse direction. This pitch is for example 40 mm, or essentially half of the distance between the torsions in the transverse direction of the mat. This results in the profiled wires 4 being better anchored or fixed in the mat 1. All of the dimensions given above are intended to serve only as examples. It is also possible to deform the profiled wires 4 helically by twisting or torquing the wires 4 around their own longitu- dinal axis, but with the wires 4 displaying an alternating series of torsions, or with the wires 4 displaying alterna- ting left and right revolutions or twisted alternatingly clockwise and counterclockwise. Figure 2 shows on a larger scale a reinforcement element 4 comprising consecutive zones 5, in which each two consecutive zones 5 are of essentially the same length, as for example 40 mm, and are twisted at an angle of approximately 90° in relation to one another. It is also possible here that each two succeeding zones 5 of the profiled wires 4 are twisted alternatingly clockwise and counterclockwise at an angle of approximately 90° with respect to one another.

Claims: CLAIMS 1. Reinforcing mat (1) for reinforcing a top layer of a ground or road, which top layer consists of bitumen, asphalt or a hydrocarbon-containing material of like nature, in which the reinforcing mat (1) is a mat woven with longitudinal wires (2, 3) and provided with reinforcement elements (4) running in the transverse direction of the mat, characterised in that the reinforcement ele- ments (4) consist of helically twisted steel profiled wires of essentially rectangular cross-section. 2. Reinforcing mat according to Claim 1, characterised in that the reinforcement elements (4) consist of successive zones (5) of essentially the same length, in which each two successive zones (5) are twisted at an angle of approximately 90° in relation to one another. 3. Reinforcing mat according to Claim 2, characterised in that each two successive zones (5) of the reinforcement elements (4) are twisted alternately in clockwise and counterclockwise directions relative to one another at an angle of approximately 90°.

Inventors: VANCRAEYNEST YVES, VEYS JOHAN, VANCRAEYNEST, YVES, VEYS, JOHAN
Applicants: BEKAERT SA NV, VANCRAEYNEST YVES, VEYS JOHAN, N.V. BEKAERT S.A., VANCRAEYNEST, YVES, VEYS, JOHAN
Application year: 1998
Main classification: E01C11
IPC codes: E01C11