Geosynthetics in roads and pavements

Application of the Tack Coat 

Proper installation of the asphalt cement tack 

coat is crucial; mistakes can lead to early failure 

of the overlay.  Uncut paving grade asphalt 

cements are recommended with AC-20 and AR-

4000 being the most popular.  The grade of the 

tack coat is typically the same grade as used in 

the asphalt concrete overlay.  The maximum 

temperature of the tack coat is 325

°

F (163

°

C), 

and the minimum is between 280-290

°

F (138-

143

°

C).  Emulsions can be used successfully, 

but they must be applied at a higher rate and 

allowed to cure completely. 

 

 

The asphalt cement distributor truck must be 

capable of uniform application of the tack coat. 

The bar should be adjusted to obtain uniformity 

and the correct width of spray, usually 2 to 3 

inches (5.1 to 7.6 cm) past the edge of the 

geosynthetic. The spray of the nozzles should 

overlap so that uniform double coverage occurs. 

Heavy spots, streaks, or gaps will cause 

problems in the system.  

 

For a typical paving fabric, the application rate 

is 0.25 gal/yd

2

 (1.13 l/m

2

). The waterproofing 

element of an interlayer system is dependent on 

the uniform application of this specified amount 

of tack coat.  The roughness of the surface, the 

porosity of the road, and the presence or 

absence of a leveling course will require slight 

modification of this application rate. Once in 

progress, the rate of application should be 

measured and verified. 

 

 

Paving Grid Laydown 

 

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                                                      GEOSYNTHETICS IN ROADS AND PAVEMENTS:                                                       21 

Subgrade Separation and Stabilization, Base Reinforcement, Overlay Stress Absorption and Reinforcement 

For more information please contact the Geosynthetic Materials Association at www.gmanow.com. 

Geogrid and geocomposite systems vary. 

 

Therefore, the manufacturer’s recommendations 

for tack coat, if any, should be followed.