Surface overlays (
The construction technique
A 50 mm layer of asphalt mix is placed and compacted . Closely followed by unrolling the geotextile over this surface , then heaps of asphalt mix are used to hold the geotextile in place during unrolling . A second 50mm asphalt is spread by
Fig (I-13) Use of geotextiles in permanent road construction
hand and then these layers are rolled. The remaining asphalt mix layers are then placed in the conventional manner (9) .
3-Surface overlays (Repair of permanent roads)
With time, the riding quality of a road surface will degrade through the formation of ruts and cracks which emanate from deep within the road construction (18) . Formation of cracks on pavement structures is unavoidable . If the pavement is only surface-dressed or resurfaced , these deep cracks will again emerge leading to premature collapse of pavement.(2) Although the effects of such reflective cracking cannot be removed without reconstruction of the entire bound pavement depth, (18) the use of geotextiles on the pavement before resurfacing has proved to be an economical method to reduce or even eliminate cracking from occurring (2) ,as shown in figure ( I-14)
In surface overlays , the main role of the geotextile appears to be that of a moisture barrier, preventing entry of moisture into the underlying cracked pavement layers which would otherwise accelerate deterioration of the pavement .( 26)