Frequently Asked Questions
A: The fabric serves two primary functions. A temporary form while the concrete sets and a filter that allows water to release while retaining cementitious material and aggregates. Therefore life expectancy is immaterial.
A: A phenomenon known as the "case hardening" effect is a result of a higher percentage of the cement in the cement-rich, fine aggregate concrete mix, being drawn to the surface of the fabric-forms by the expelled excess mixing water. This layer of concrete impregnates the woven fabric, permanently adhering the fabric to the concrete and assisting with the prevention ultra-violet degradation. As a result, it is uncommon for the fabric to break down. Empirical evidence shows the fabric still in place decades after installation.
A: No. Research has shown the alkalinity can affect polyester at elevated temperatures and long term exposure, but because concrete sets in as little as 30 minutes and the temporary nature of the fabric form, there are no negative affects under these conditions.
A: It is generally recommended that manufactured revetments are installed on 2:1 or flatter slope. However, it is not uncommon to see revetments installed on 1.5:1 or even greater slopes if slope and hydraulic stability can be maintained. Q: Do FFC revetments stabilize a slope? A: Surface applied revetments do not address slope stability but instead provide protection to slope erosion and bed degradation. Proper slope design and compaction are required.
A: Surface applied revetments do not address slope stability but instead provide protection to slope erosion and bed degradation. Proper slope design and compaction are required.
A: No, the FFC is designed so that the unit weight can resist uplift, drag, and sliding. Staples or anchors are only used in extreme cases where the FFC weight is not sufficient to resist hydraulic forces.
A: Yes. Various installation methods are available depending on the depth, volume, flow and velocity of the water.
A: During the pumping process, the fabric contracts as it is filled. This contraction averages 10% in each direction.
A: Unlike pre-cast ACB mats, each project is design specific to the installed dimensions given. Individual panels can range from 5,000 ft2 to 8,500 ft2. These individual panels are then field connected with zippers or stitching to generate one single "mat".
A: Depend on the selected style. Both the ABM and FPM mats require filter fabric, while it is suggested for USM as well.
A: Installation costs vary greatly due to concrete and labor prices, as well as the logistical nature of the project, but in general FFC installation is 30% less than rip rap, pre-cast ACB’s, concrete cloth, HydroTurf, or gabion mattresses.