Geogrid for Road Construction: Types, Applications and Selection Guide

Road construction over weak or unstable ground can present significant engineering challenges. Soft subgrades, repeated traffic loading, aggregate movement and pavement deformation may affect road performance and increase maintenance requirements.

Geogrids are geosynthetic reinforcement materials used in various road and ground stabilization systems. Their open-grid structure allows interaction with surrounding soil or aggregate, helping improve the performance of appropriately designed reinforced layers.

However, not all geogrids are designed for the same purpose. Biaxial geogrids are commonly considered for road base reinforcement, uniaxial geogrids are used in directional soil reinforcement, and fiberglass geogrids are applied in selected asphalt pavement reinforcement systems.

This guide explains the main geogrid types, their road construction applications, important technical specifications and how to select a suitable product.

1. What Is a Geogrid in Road Construction?

A geogrid is a geosynthetic material with an open-grid structure formed by interconnected ribs, yarns or other reinforcement elements.

Unlike continuous geotextile fabrics, geogrids have apertures through which surrounding soil or aggregate can interact with the reinforcement structure.

In road construction, geogrids are commonly incorporated into selected pavement or soil layers to improve reinforcement and aggregate confinement.

Depending on the product and engineering design, a geogrid may help:

• Limit lateral movement of aggregate
• Improve interaction between aggregate and reinforcement
• Distribute loads within a reinforced layer
• Reduce deformation in selected road structures
• Support construction over weak subgrades
• Improve the performance of reinforced embankments

The actual benefits depend on the geogrid properties, soil conditions, aggregate characteristics, loading and installation quality. A geogrid does not automatically increase road bearing capacity or guarantee a longer pavement service life.

2. Main Types of Geogrids Used in Road Engineering

Geogrids can be classified according to their material, manufacturing structure and reinforcement direction.

2.1 Biaxial Geogrid

A biaxial geogrid provides tensile properties in two principal directions: machine direction (MD) and cross-machine direction (CMD).

Plastic biaxial geogrids are commonly manufactured through extrusion, punching and stretching processes.

Their open-grid structure allows aggregate particles to interact with the ribs and apertures.

Typical road applications include:

• Road base reinforcement
• Unpaved road stabilization
• Aggregate base confinement
• Temporary construction platforms
• Selected soft-subgrade applications

When selecting a biaxial geogrid, check tensile properties in both directions, aperture geometry, junction characteristics and compatibility with the aggregate.

2.2 Uniaxial Geogrid

A uniaxial geogrid is designed to provide its primary tensile reinforcement in one principal direction.

It is commonly used in engineered soil reinforcement systems where the main tensile demand acts along a defined direction.

Typical applications include:

• Reinforced road embankments
• Steep slopes
• Retaining walls
• Mechanically stabilized earth structures
• Selected approach embankments

Uniaxial geogrids should not be automatically substituted for biaxial products in road base applications. The product must match the reinforcement direction and design requirements.

2.3 Fiberglass Geogrid

Fiberglass geogrids are manufactured using fiberglass yarns, commonly with a protective coating.

They are used in selected asphalt pavement reinforcement applications.

Potential functions include:

• Reinforcement between asphalt pavement layers
• Stress distribution within pavement systems
• Crack-control support
• Rehabilitation of selected existing pavement structures

Fiberglass geogrids used in asphalt systems are different from plastic biaxial geogrids used in granular road bases. Their installation requirements, surface preparation and bonding conditions must follow the pavement design and product instructions.

2.4 Triaxial and Multidirectional Geogrids

Some geogrids use triangular or multidirectional aperture structures to interact with aggregate in more than two principal directions.

These products are available in the wider geosynthetics market for selected aggregate stabilization applications.

Their performance should be evaluated using product-specific specifications and relevant design evidence. Buyers should confirm the exact structure and availability with the manufacturer rather than assuming that all geogrid suppliers offer this product type.

3. How Does Geogrid Reinforce a Road Base?

A geogrid is commonly placed within or at the base of an aggregate layer, depending on the design.

When aggregate is compacted around the grid, the particles interact with the grid apertures and ribs. This interaction can help limit lateral aggregate movement under loading.

The reinforcement mechanism may involve:

3.1 Aggregate Interlock

The aggregate particles interact with the geogrid apertures and ribs.

The effectiveness of this interaction depends on aperture size, aggregate gradation, particle shape and grid stiffness.

A product should be selected to suit the aggregate used in the project.

3.2 Lateral Restraint

Under repeated loading, aggregate particles may move laterally.

A suitably designed geogrid-reinforced layer can provide restraint against this movement and help maintain the integrity of the aggregate structure.

3.3 Load Distribution

Geogrid reinforcement may influence stress and strain distribution within a road base system.

The resulting performance depends on the geogrid stiffness, subgrade strength, base thickness, traffic loading and design method.

Research on geosynthetic-reinforced unpaved roads identifies factors such as wheel loads, subgrade strength, aggregate properties, interlock and geosynthetic stiffness as important design considerations.

Therefore, product selection should be based on the complete road structure rather than tensile strength alone.

4. Typical Road Construction Applications

4.1 Unpaved Roads

Unpaved roads often experience rutting and deformation when built over weak or moisture-sensitive subgrades.

A biaxial geogrid may be incorporated into the aggregate layer to improve aggregate confinement.

The design should consider:

• Subgrade strength
• Traffic volume
• Wheel loads and tire pressure
• Aggregate thickness and gradation
• Geogrid stiffness and aperture geometry
• Allowable rut depth

4.2 Highway and Road Base Reinforcement

Geogrids may be used in selected highway and paved-road structures to reinforce granular base or subbase layers.

The objective is to improve the behavior of the reinforced aggregate layer under traffic loading.

The design must consider the complete pavement structure, including asphalt thickness, base and subbase materials, subgrade conditions and expected traffic.

4.3 Soft Subgrade Stabilization

Soft soils can deform under construction equipment and repeated traffic loads.

A geogrid may be used as part of an engineered stabilization system to improve the interaction between the aggregate layer and the underlying soil.

For very soft soils, the design may also require a geotextile separation layer.

4.4 Road Embankments

Uniaxial geogrids may be used in reinforced soil embankments where tensile reinforcement is required in a defined direction.

The reinforcement layout, length, spacing, soil properties and long-term design strength must be determined by the project engineer.

4.5 Asphalt Pavement Reinforcement

Fiberglass geogrids are used in selected pavement rehabilitation and asphalt reinforcement systems.

The product must be compatible with the asphalt materials, tack coat or bonding system, installation temperature and pavement construction sequence.

A fiberglass geogrid should not be confused with a plastic road-base geogrid.

5. Geogrid Selection: What Technical Properties Should You Check?

Choosing a geogrid based only on its nominal tensile strength is insufficient.

The following properties should be reviewed according to the intended application.

5.1 Tensile Strength

Tensile strength indicates the force a geogrid can resist under a specified test configuration.

ASTM D6637/D6637M is used to determine geogrid tensile properties through single-rib or multi-rib tensile testing.

For biaxial products, review the required strength in both MD and CMD.

For uniaxial products, identify the primary reinforcement direction.

5.2 Tensile Strength at Specified Strain

Some engineering applications require tensile strength or stiffness at a specified strain rather than ultimate tensile strength alone.

Compare values at the same strain level and using compatible test methods.

5.3 Aperture Size and Geometry

Aperture geometry affects the interaction between the geogrid and surrounding aggregate.

The aperture should be compatible with the aggregate gradation and the intended reinforcement mechanism.

Do not select a product based only on visual appearance or the size of the openings.

5.4 Junction Strength

The junction connects the longitudinal and transverse ribs.

ASTM D7737/D7737M is a test method for individual geogrid junction strength. ASTM notes that this is an index test for the junction tested in isolation and that the result should not automatically be interpreted as in-service design performance.

5.5 Stiffness and Long-Term Performance

Depending on the application, stiffness, creep behavior, durability and installation damage resistance may be important.

For long-term soil reinforcement, the engineer should consider the applicable design strength and reduction factors rather than relying only on the product’s ultimate tensile strength.

6. Biaxial Geogrid vs. Uniaxial Geogrid

The two products serve different engineering purposes. One should not be substituted for the other without checking the design.

7. Geogrid and Geotextile: Should They Be Used Together?

In some road projects, geogrids and geotextiles are used together because they perform different functions.

A geogrid may provide reinforcement and aggregate confinement, while a geotextile can provide separation and filtration.

For example, a designed road structure may include:

• Prepared subgrade
• Geotextile separation layer
• Geogrid reinforcement layer
• Compacted aggregate base
• Pavement surface

This is only an illustrative arrangement. The actual layer order, compatibility and need for each material must be determined by the engineering design.

Using both products does not guarantee improved performance unless the system is designed for the site conditions.

8. Geogrid Installation in Road Construction

Correct installation is essential to achieving the intended performance.

A typical installation process includes:

1. Prepare the subgrade and remove unsuitable materials.
2. Check the surface for sharp objects, large depressions and standing water.
3. Confirm the geogrid type, roll identification and installation direction.
4. Unroll the geogrid according to the approved layout.
5. Maintain the specified overlaps or connections.
6. Place aggregate carefully to avoid displacement or damage.
7. Spread and compact the aggregate according to the construction specification.
8. Inspect the installed layer before placing the next pavement layer.

Overlap width, connection method and aggregate cover thickness should follow the product instructions and project specifications. They should not be presented as one universal value for every geogrid installation.

9. Geogrid Quality Control Checklist

Before purchasing or accepting geogrid materials, check:

• Product type and polymer material
• Machine-direction tensile strength
• Cross-machine-direction tensile strength, where applicable
• Strength at specified strain
• Aperture size and geometry
• Junction strength, where specified
• Roll width and roll length
• Product identification and batch traceability
• Test reports and applicable standard editions
• Packaging and transportation condition

For ASTM D6637/D6637M tensile testing and ASTM D7737/D7737M junction testing, confirm the exact method and edition stated in the project specification.

Test results should correspond to the actual product and relevant production batch.

10. Frequently Asked Questions

Which geogrid is commonly used for road construction?

Biaxial plastic geogrids are commonly considered for road base reinforcement and aggregate stabilization. The final choice depends on the road design and product properties.

What is the difference between uniaxial and biaxial geogrids?

Uniaxial geogrids provide their primary tensile reinforcement in one direction and are commonly used in reinforced walls, slopes and embankments. Biaxial geogrids provide tensile properties in two principal directions and are commonly used in road base applications.

Can geogrid be used on soft soil?

Yes. Geogrids may be incorporated into engineered stabilization systems over weak subgrades. The design must consider soil strength, aggregate properties, traffic loading and the geogrid’s mechanical properties.

Does geogrid replace aggregate in road construction?

No. Geogrid is a reinforcement material used with soil or aggregate. It does not replace the required granular layers unless a qualified design demonstrates an approved alternative structure.

What tensile strength is required for road geogrid?

There is no single tensile-strength value suitable for every road. Requirements depend on the design method, subgrade strength, traffic, aggregate and the required performance.

Can geogrid and geotextile be installed together?

Yes, when the engineering design requires both reinforcement and separation or filtration. Their arrangement and compatibility should be confirmed in the project specification.

What information is needed to request a geogrid quotation?

Provide the project application, geogrid type, required tensile properties, aperture requirements, roll dimensions, quantity, delivery destination and applicable test standards.

Conclusion

Geogrids can contribute to road construction by improving the interaction between reinforcement materials and surrounding aggregate or soil.

Biaxial geogrids are commonly considered for road base reinforcement, uniaxial geogrids for directional soil reinforcement, and fiberglass geogrids for selected asphalt pavement applications.

The correct selection should be based on subgrade conditions, traffic loading, aggregate characteristics, tensile properties, aperture geometry, installation requirements and engineering design.

Contact TINHY Geosynthetics to discuss geogrid options for road construction, subgrade stabilization and infrastructure projects. Share your technical specifications, roll dimensions and estimated quantity to request product information and a quotation.