Best Practices for Nonwoven Geotextile Interlayer

Pavement construction using the nonwoven geotextile interlayer has been a reported a success in US field trials so far. In addition, the Germans report ease in construction. The following is a summary of better construction practices reported in various German guidelines and related publications:

If the geotextile is used in an unbonded concrete overlay application, ensure that any potential for mechanical keying of the two cementitious layers is minimized through proper repair techniques.  Furthermore, excess slab movements should be stabilized before placement of the geotextile and overlay.  Better practices for these and other relevant items can be found in the Guide to Concrete Overlays (2nd Ed.), developed by the National Concrete Pavement Technology Center.

  • Sweep the underlying surface to remove loose debris before applying the interlayer.
  • Roll the geotextile out on the underlying layer.  The geotextile should be tight and without excess wrinkles and folds.  No process is specified for rolling out the layer; numerous techniques have been used based on available equipment and labor.  Below are pictures showing rolls of nonwoven geotextile.  Projects in Missouri and Kansas incorporated a forklift for placement while German contractors have been successful with rolling out the geotextile by hand.  Below are photos showing placement of geotextile.  The photo on the left shows the use of a forklift and the photo on the right shows the device uses by the Germans for placement by hand (photo of hand device for placement supplied by BASt).
  • Care should be taken to roll out the geotextile in a sequence that will facilitate good lapping practice and prevent folding or tearing by construction traffic.  For example, the end of a roll laid in the direction of paving should lie atop the beginning of the next roll, minimizing the potential for being disturbed by the paver. 

Nonwoven geotextile rollers

  • The geotextile should be secured to the underlying layer with pins or nails punched through 50- to 70-millimeter (mm) (2- to 2.75-inch (in)) galvanized washers or discs every 2 m (6 ft) or less.  Smaller washers or discs can increase the likelihood that the geotextile will separate from the underlying layer during subsequent placement of the concrete.
  • Additional fasteners can be used as needed to ensure that the geotextile does not shift or fold before or during concrete placement.

Geotextiles washer

  • If construction traffic is expected on the grade in front of the paver, no more than 200 meters (m) (650 feet (ft)) of geotextile should be installed in advance of the paving operation at any given time.  This will minimize the potential for damage before paving.
  • Driving on the interlayer should be kept to a minimum.  Tight-radius turns and excessive accelerations and braking should be avoided.
  • Do not place the geotextile on areas subject to excess traffic (e.g., crossovers). Installation of the geotextile should be delayed.
Tracks

(Photo supplied by BASt)

  • Where it occurs, edges of the geotextile should overlap by 20 ± 5 centimeters (cm) (8 ± 2 in).
  • No more than three layers of geotextile should overlap at any location.  This requires staggering of transverse seams of adjacent rolls to prevent four layers from coinciding at any location.
Interlayer overlap on road

(Photo supplied by Missouri/Kansas ACPA)

The free edge of the geotextile should extend beyond the edge of the new concrete and into a location that facilitates drainage by 10 cm (4 in) or more.  More specifically, the geotextile must terminate in or next to a drainable pavement layer, or be exposed in such a way that free drainage of water within the geotextile is not impaired. 

 

New concrete edge and geotextile