Surface overlays (
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)
The construction technique
As the geotextile is installed between the old and the new surfacing to improve crack resistance, it is vital that, when installing the geotextile, a good bond be achieved between old and new works. This involves first , coating the old surfacing with a hot tar spray , or an emulsion , before rolling out the geotextile .Once this is placed, the new surfacing is placed in the normal manner . Care must be taken to ensure that the laying temperature of the bituminous surfacing is well below that of the melting point of the geotextile. (18)
