How to Match the Geogrids and Geocomposites to Paving Work

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How to Match the Geogrids and Geocomposites to Paving Work

Dec 09, 2019

Biaxial Geogrids and geocomposites are both of the ever-expanding line of geosynthetics. These paving synthetics have different applications and provide different functions in paving applications. Each require different installation procedures for proper placement in order to obtain the desired design benefit.

Both of them may be beneficial in both small and large applications for parking lots, driveways, streets, highways, airports, sport yards and more. What is important is to determine what function or functions (benefits) that is trying to be obtained. Any or all of these functions can be obtained with the proper selection of the geosynthetic and geocomposite.


● A moisture barrier interlayer membrane is for the control of surface water infiltration that breaks down the bearing capacity of the subgrade.
●  Preventing crack reflection

Alligator Crack Reflection
a. Geotextile Paving Fabric – Minimal -Medium
b. Hybrid GeoMat – Medium - more
c. GeoGrid Paving - Maximum
d. GeoGrid Composite - Maximum

Medium Crack Reflection
a. Hybrid GeoMat
b. Paving GeoGrid - Maximum
c. GeoGrid Composite - Maximum

Large Crack and Joint Reflection
a. Paving GeoGrid - Maximum
b. GeoGrid Composite – Maximum

A combination of moisture barrier interlayer membrane and of the medium to large crack reflections.
a. Hybrid GeoMat – Medium
b. GeoGrid Composite – Maximum large cracks and joints

Geogrids, which are manufactured from a variety of materials including fiberglass, polyethylene and polyester, are used for unstable base reinforcement. Metal grids were used in World War II to make rapid runways and roads. Paving Geogrids are used for internal asphalt overlay reinforcement. They are very rigid, look like a fence and have openings (apertures) that can vary in size from small to large. They have very low or no elongation (stretch) and a high modulus that gives them high strength, maximum reinforcement and reflection crack prevention. 

Paving GeoGrids come in various widths from 2 feet to 16 feet. The majority are manufactured from 5 to 13 feet wide. Width needs to be taken into consideration when installing. Smaller widths require more installation passes and usually more time to complete the installation. Smaller widths may install driving faster than slower with wider widths and have less wrinkles, depending on the manufacturer.

Paving GeoGrids must adhere to the pavement, so the paver does not lift them. They can adhere depending on the manufacturer differently.
A. A preinstalled adhesive that does not require a tack coat (oil)
B. With a light Geotextile fabric attached for adhering to a lite tack coat (oil)
C. Impregnated with a bitumen coating (oil similar to tack coat) that requires less or no tack coat
D. Geocomposites with a thicker paving fabric that requires a tack

A Geogrid combined with a Geotextile Filter Fabric is called geogrid geotextile geocomposite. It provides both reinforcement, crack prevention and the interlayer membrane once the fabric is impregnated. It uses the same tack coat (oil) quantities for a paving fabric.

Installation by hand is easier than a fabric because of its rigid state but is very time consuming and labor intensive in the number of laborers necessary.

Machine placement is fastest. It requires some different installation techniques than fabric. Any tensioning needs to be to a minimum. If bars for alignment are used, they should roll and not glide over especially if coated with an adhesive or bitumen impregnated.  The material does not stretch (elongate) and stretching system is detrimental. The grid must unwind freely with little or no impedance.

Placing grids on curves with grids will almost always require hand placement and the cutting of pie shaped wedges. The overlaps will be based on the manufacturer recommendation.

Each manufacturer has various grids, some with different thicknesses and each has different recommendations and requirements for application and tack coat (oil) and for placement of adjoining rolls for horizontal and longitudinal overlaps.There are no standard ASTM specifications for grids.

Some grids will overlap at joints and some grids will butt up. The same for dealing with cut wrinkles. Thinner grids may overlap while thicker grids may butt up. There may be a difference also when used within a chip seal.

Binders for grids can be hot tack coat or rapid set emulsions depending on their manufacturer recommendations. Oils will vary between .06 to .18 gallons per square yard without fabric. Emulsions require a 30% increase in application rate to account for evaporation and the extra installation time. Bitumen pre-impregnated grids and composites requires approximately 25% less tack coat during installation between 0.10 to 0.15 gallon per square yard.

The gallon per square yard for geosynthetic geocomposite is determined by the fabric weight. A 4.1-ounce ASTM 288-217 paving fabric will use a 0.22 - 0.25 gallon per square yard. The variance is determined if the application is on a new fresh oiled leveling course or an old asphalt. Installation considerations for a Geosynthetic Geocomposite are different than if installing a paving fabric alone.

Grids that have adhesive or are bitumen impregnated may stick together creating tension when unwinding especially the rolls on the bottom of piles or van that have been compressed.

Regarding Paving Grids and Geocomposites, ask the questions: specification, equality, increased or decreased tack coat, type of tack coat (oil), roll widths, size and material of the roll's interior cores. All will influence on your production time, costs and ultimately bottom line. Knowing the answers will help you make a correct decision on the selection and planning your installation.

Shanghai Yingfan Environmental Engineering Co., Ltd.