Explanation of difference between Firm and Flexible Versions of Concrete Erosion Mats

Why Australian Concrete Mats Recommends Firm Erosion Mats for Most Applications

At Australian Concrete Mats, we manufacture both Flexible and Firm Concrete Erosion Mats (EM Roll Mats) because different projects and site conditions require different erosion control solutions.

Over time, however, our experience across drainage channels, roadside infrastructure, embankments, swales, access tracks, and civil construction projects has led us to recommend the Firm EM Roll Mat configuration as the preferred option for most applications.

This recommendation is based on:

  • long-term project performance,
  • installer feedback,
  • vegetation outcomes,
  • installation efficiency,
  • and durability observed across completed projects.

What’s the Difference Between Flexible and Firm EM Roll Mats?

Both systems utilise the same core structural materials and performance characteristics, including:

  • 40 MPa wet-cast concrete elements
  • 80/80 kN/m biaxial geogrid reinforcement
  • Non-woven geotextile underlay
  • Permeable open void areas
  • Vegetation-compatible design
  • Long-term erosion control performance
  • Equivalent hydraulic performance characteristics

The primary difference between the two systems is the amount of retained concrete between the individual concrete units.

Flexible EM Roll Mats

Flexible EM Roll Mats have the excess concrete removed between the individual concrete blocks. This creates maximum flexibility and allows the mat to conform in multiple directions.

This configuration can be beneficial on highly irregular surfaces or areas requiring maximum conformability.

Firm EM Roll Mats

Firm EM Roll Mats retain additional concrete between the individual units. This creates a more rigid and integrated mat structure while still maintaining permeability and vegetation establishment capability.

The retained concrete also helps protect and secure the underlying geogrid and geotextile underlay system.

Why We Recommend Firm EM Roll Mats

Based on project experience and long-term observations, Australian Concrete Mats generally recommends the Firm EM Roll Mat system for most drainage, embankment, and civil infrastructure applications.

Improved Long-Term Durability

One of the key advantages of the Firm configuration is improved long-term protection of the reinforcement layers beneath the concrete surface.

The retained concrete assists in protecting the:

  • geogrid reinforcement,
  • geotextile underlay,
  • and overall stabilisation system

from:

  • movement,
  • exposure,
  • environmental degradation,
  • and ongoing wear over time.

Based on completed projects and contractor feedback, this has consistently resulted in improved durability and long-term stability in active drainage and embankment environments.

Enhanced Stability Across Drainage Channels and Embankments

The Firm configuration provides increased rigidity across the mat surface while still allowing the system to conform to the required ground profile.

This increased rigidity assists in:

  • maintaining long-term slope and channel stability,
  • reducing localised displacement or movement,
  • and improving overall stabilisation performance.

This makes the Firm system particularly well suited to:

  • drainage channels,
  • roadside batters,
  • swales,
  • embankments,
  • and vegetated erosion control applications.

Faster and Easier Installation

Another major advantage of the Firm EM Roll Mat system is installation efficiency.

Because the retained concrete bonds the non-woven geotextile underlay to the underside of the mat, the system behaves as a more integrated product during handling and installation.

This provides several practical on-site benefits, including:

  • smoother rollout during installation,
  • reduced folding or bunching of the geotextile,
  • less manual straightening,
  • improved alignment,
  • and faster overall installation times.

By comparison, the Flexible version is intentionally more pliable. While this can assist on highly irregular terrain, it can also make the system more “floppy” during rollout and placement.

As the geotextile underlay in the Flexible version is less bonded to the underside of the concrete units, it can occasionally fold or shift beneath the mat during installation, requiring additional on-site adjustment.

Many contractors and installers have found the Firm EM Roll Mat system to be quicker, easier, and more efficient to install across both embankment and drainage applications.

Do Firm EM Roll Mats Still Allow Vegetation Growth?

Yes.

A common misconception is that the Firm configuration prevents vegetation growth because it contains more retained concrete between the units.

In practice, Australian Concrete Mats has seen excellent vegetation establishment outcomes on Firm Mats across:

  • roadside embankments,
  • drainage channels,
  • swales,
  • access tracks,
  • and civil infrastructure projects.

The system remains permeable through the open void areas, allowing:

  • water infiltration,
  • root establishment,
  • and long-term vegetative integration.

Over time, vegetation naturally softens the system’s appearance, while permanent erosion protection remains beneath the surface.

Vegetated Embankment Installation Method

For vegetated embankment applications, Australian Concrete Mats generally recommends the following process:

  1. Prepare a stable and free-draining subgrade
  2. Install and anchor the Firm EM Roll Mats
  3. Place suitable topsoil over the surface of the mats
  4. Apply seed or hydromulch over the topsoil layer

Over time, vegetation establishes through the open void areas and integrates naturally with the mat system.

The concrete units can also assist in retaining moisture beneath the surface, helping support vegetation establishment and reducing evaporation during dry periods.

Suitable Soil and Revegetation Materials

Australian Concrete Mats recommends the use of:

  • suitable locally sourced topsoil,
  • stable free-draining subgrades,
  • and seeding or hydromulching methods appropriate for the local environment.

As soil classifications and environmental conditions vary across Australia, detailed revegetation specifications should always be confirmed by the project’s environmental consultant or geotechnical advisor.

Proven Across Real Projects

Australian Concrete Mats has supplied Firm EM Roll Mats across a wide range of civil and infrastructure applications throughout Australia, including:

  • roadside drainage,
  • vegetated swales,
  • erosion control channels,
  • access tracks,
  • roadside embankments,
  • and stabilised batters.

Project outcomes have demonstrated that Firm EM Roll Mats continue to provide:

  • effective erosion protection,
  • long-term durability,
  • vegetation establishment capability,
  • and improved installation efficiency.

Choosing the Right System

Both Flexible and Firm EM Roll Mats have an important role depending on project requirements and site conditions.

However, based on our experience across completed projects and long-term field performance, Australian Concrete Mats generally recommends the Firm EM Roll Mat system as the preferred solution for most erosion control, drainage, and vegetated embankment applications.

For assistance selecting the right system for your project, contact us at Australian Concrete Mats to discuss your application requirements.

REQUEST A QUOTE