Increasing Pavement Performance with Combigrid

Combigrid® is a combination of geosynthetic material and geogrid that delivers reinforcement, filtration, separation and drainage in one composite material. These geogrids are used mainly in conjunction with soft and low CBR soils where soil reinforcement in combination with separation and filtration is needed, such as in base reinforcement.

Combigrid®, with its high torsional rigidity and a strong interlocking of aggregate, provides exceptional resistance to rutting and prevents the migration and mixing of fines in the roadway system, preserving the integrity of the road.

The properties of Combigrid make it an ideal choice for increasing the performance of pavements, significantly reducing deformation in the subgrade which extends the service life of modern roads and reduces maintenance requirements.

How do combination geogrids like Combigrid increase pavement performance?

High strength at low elongation

A geogrid’s quality can be defined in many ways but success begins with the individual bars or ‘ribs’. It is in these bars that project performance rests: strength transfer, elongation, installation and degradation resistance and more.

The tensile performance and dependability of Combigrid® reinforcement is rooted in its flat, extruded geogrid bars and how they mobilise high-strength at low strain.

The elongation range combined with the stress/strain behaviour of an installed geogrid should effectively reduce shear deformations in the soil as a result of a compressive loading regime. The one-dimensional bar characteristics of Combigrid® form a structurally sound and stable geogrid. The bars are uniformly extruded and drawn in the manufacturing process giving the product unique high stress absorption capability at low strains.

As the geogrid is much stiffer in tension than the base aggregate, lateral stresses and strains in the reinforced base aggregate are reduced. This equates to significantly less vertical deformation, which results in less ruts and deformation over time.

Stiffness in multiple directions

The longevity of a geogrid-reinforced road is heavily dependent on the geogrid’s ability to develop high shear resistance between reinforcement and base aggregate. This strong interlocking effect means that lateral restraint of the base course aggregate is achieved, which reduces vertical deformation (rutting) as a result.

Stresses from traffic loads are most common in longitudinal and transverse directions, but diagonal stresses are also possible in certain pavement situations. For a geogrid to be well prepared for all applications and requirements (bi-axial and/or multiaxial) high radial stiffness at low strains is a desired performance parameter. This is the resistance with which the geogrid reduces lateral movement in the base aggregate in all possible stress directions.

The stiff, bi-axial geogrid bars of Combigrid® possess high multi-directional strength. The stability of the firmly welded flat junctions of Combigrid® create a rigid, stable, two-dimensional geogrid that locks the aggregate in place, even if radial movement occurs.

Other key characteristics

Torsional rigidity

Higher torsional rigidity equals a better traffic benefit ratio, which is the potential service life extension of a reinforced vs. an un-reinforced design. Combigrid® offers high torsional rigidity, meaning greater interlock strength, greater lateral restraint of the base course, and stronger reinforcement.

Robustness

The challenges of building sites include weather exposure, heavy equipment, imperfect soils, inexperienced handling of materials, and many other risks which can damage geosynthetic materials before or during installation.

This damage can impact the performance of the material and the overall structure, so it’s critical to look for a robust product.

Combigrid® is a robust reinforcement geogrid that is further enhanced by an embedded, extremely durable nonwoven geotextile. Bonded together in a single-layer product, these components provide the durability and strength to resist installation damage so that the reinforcement begins its service life in optimal condition.

Less aggregate required

Quarrying and processing aggregate to meet project specifications is an intensive process, and heavy haulage of suitable aggregate to site is costly and polluting.

Traditional construction practices such as these are major reasons why construction has a terrible carbon footprint and real economic cost.

Combigrid® reinforcement decreases the dependency on base course thickness because of the superior stress/strain characteristics of its geogrid bars. The elastic modulus of the base course is improved; loads are better distributed; aggregate does not migrate laterally or mix vertically. The road provides greater resistance to vertical stresses and exhibits reduced rutting or reflective cracking.

In short, the installation of Combigrid® saves on aggregate today and maintenance tomorrow.

Find out more

Combigrid® is engineered to perform a significant, multi-functional role for roadway and railway reinforcement, embankment reinforcement, load transfer platforms over pile caps, and other key base reinforcement applications.

For Combigrid specifications or to find out more, contact the engineering team at Global Synthetics.