Are you seeking a solution to prevent and control erosion along channels, levees, riverbanks, outfalls, or wave action on shorelines? These applications require robust and permanent erosion control. Two products you may compare are tied concrete block mats and fabric-formed concrete lining.
Tied concrete block mats offer numerous advantages over fabric-formed concrete lining, from time and cost savings during installation to superior long-term performance. In this post, we will provide an informative comparison of the two different systems.
Flexamat install
Fabric-Formed Concrete Lining Installation
Fabric-formed concrete lining consists of geotextile forms filled with a specialized concrete grout mix.
A common misconception is that this solution can be installed manually. While the geotextile forms can be placed with hard labor, the lining installation requires bringing expensive concrete pumps on-site to pump grout into the forms. It also requires coordination with a local concrete provider to match the specific concrete mix.
Along with these headaches, the contractor must arrange for concrete trucks to haul up to 10 cubic yards of concrete at a time to the site. This can require multiple truckloads of material, even for relatively small projects.
Access for concrete trucks is difficult on most sites, making installation of Fabric Formed Concrete problematic.
Most projects that require permanent erosion control are not conveniently located near roads that can be easily accessed by heavy-duty concrete boom pump trucks — much less the concrete trucks themselves.
The coordination required to send specialized boom pumps and numerous concrete truck drivers to a site with difficult access is a logistical nightmare for a contractor. Even sites with relatively good access can be extremely challenging, especially if the armor must be installed in multiple locations.
Pumping the concrete into the geotextile forms is not an easy task. Extreme care must be taken to not overfill the forms. Significant overages on concrete are common if the forms are even slightly overfilled.
Typical undermining of a fabric formed concrete system
Contractors must also be very mindful not to overfill the geotextile forms to the point that the forms burst open. When this happens, the contractor has a mess to clean up — which is further complicated if the contractor is working along natural waterways where any pollution is unacceptable.
Fabric Formed Concrete Lining requires access for large and expensive concrete pump trucks.
Another downside of fabric-formed concrete lining is its inherent negative impact on water quality. The wet cement that is pumped into the geotextile forms has a pH as high as 12.9, and a rise in pH due to fabric-formed concrete is harmful to aquatic life.
Concrete slurry from Fabric Formed Concrete Lining polluting waterway
Tied Concrete Block Mat Installation
Tied concrete block mats (TCBMs) consist of concrete blocks that are locked together and embedded into a high-strength geogrid. TCBMs are precast and do not require expensive concrete machinery on-site to produce. The mats are packaged into rolls, making transportation and installation simple.
TCBMs are available in custom sizes with clear labels identifying each roll. The Flexamat technical team provides specific project mat layouts, making the installation as smooth as possible.
Since TCBMs are packaged in rolls, transporting them to difficult-to-access areas is much easier compared to a concrete pump mat installation. The rolls can be lifted with standard construction equipment that is already on-site, such as excavators and skid steers.
TCBM rolls have been efficiently delivered to remote sites by helicopters and barges — areas impossible to access with the concrete pumping equipment required for fabric-formed concrete lining installations.
While the high pH of fabric-formed concrete lining has a negative impact on water quality, TCBMs do not because this solution is a precast system. Additionally, the risk of wet concrete spilling into waterways is eliminated with TCBMs.
Fabric-Formed Concrete Performance
Once the concrete within the geotextile forms has cured, fabric-formed concrete lining is no longer a flexible system.
The rigid concrete lining cannot flex with natural ground movement associated with settling or freeze and thaw cycles. Cracks will develop within the lining. Once this happens, water can seep under the system and undermine it. Small cracks within the system can allow large cavities to develop under the rigid lining. These cavities are not only dangerous but will also lead to eventual failure.
Some fabric-formed concrete mat manufacturers offer systems that have designated openings within the concrete lining. These open spaces allow room for vegetation to grow. Unfortunately, they also give water a path to flow under the system. These rigid concrete-lined systems do not offer the flexibility needed to accommodate vegetation as it grows and moves.
Fabric-formed concrete lining installations are hazardous to humans and wildlife. This type of armor creates a slick surface that does not provide adequate traction for vehicles, humans, or animals to safely traverse. Even armored areas with minimal slopes become slippery. Unfortunately, people have drowned or been crushed after sliding down the slick material.
Tied Concrete Block Mat Performance
Within the first year of TCBM installation, vegetation will become established within the matting. The mat remains forever flexible, resting tightly against the contours of the earth it armors.
This vegetation enhances the performance of the flexible concrete armor as the roots become entrenched within the layers of the Flexamat system. A wide array of native riparian vegetation, including grasses and willow trees, thrives within the flexible armor offered by TCBMs.
The vegetation also provides other water quality benefits:
Allows for infiltration of the initial flush of stormwater
Promotes the removal of automotive pollutants
Aids in the removal of other pollutants
Helps remove nitrogen, phosphorus, and carbon
Reduces thermal impact when compared to fabric-formed concrete systems
Provides a habitat for wildlife
Tied concrete block mats provide good traction for vehicles, humans, and wildlife. These mats are optimal for low-water crossings, boat ramps, and kayak and canoe launches. Humans and wildlife can safely exit slopes armored with TCBMs.
DECIDING BETWEEN CONVENTIONAL FABRIC-FORMED CONCRETE SYSTEMS OR TIED CONCRETE BLOCK MATS
Having to coordinate with concrete pump trucks — if they can even reach the site — creates significant installation hurdles for contractors who attempt to install fabric-formed concrete lining along slopes, basins, and channels.
Choosing fabric-formed concrete lining can bring the following additional drawbacks:
Safety liability
Adverse environmental impact
High construction costs
Susceptibility to performance issues
The need for specialized equipment for installation
OTHER ADVANTAGES OF FLEXAMAT TIED CONCRETE BLOCK MATS FOR EROSION & SCOUR PROTECTION
The ability to customize Flexamat concrete lining to your site’s demands, the efficiency of the installation process, and superior long-term performance are just a few factors that make TCBMs the preferred solution.
Besides protecting against erosion along slopes, levees, and stream banks, Flexamat provides good footing and a safer surface to traverse.
GET IN TOUCH WITH FLEXAMAT TO LEARN MORE ABOUT HOW TIED CONCRETE BLOCK MATS ARE THE SOLUTION FOR YOUR SITE
Check out product specifications, explore our extensive project profile library, and https://www.flexamat.com/erosion-control-gallery.
If you have questions about whether Flexamat (or another TCBM) is the right product for your site, don’t hesitate to reach out — we are happy to supply additional information! Get in touch with our technical team today.
Comments