Geotextile Grout-Filled Mattress (GGFM): Types and Design

Fabric formed concrete (FFC) uses woven geotextile fabric as a flexible formwork, pumped on site with cement grout to produce a hard concrete erosion protection layer that follows the surface profile. Grouted mattress (GGFM) is the type used for canal lining, slope protection and bank revetment. Concrete Canvas is a thinner, different product. This guide explains how the technology works and which product suits which application.

Fabric formed concrete is an established technique: fabric is used as formwork for concrete, and the fabric stays in place as part of the finished structure. Modern grout-filled mattress systems rely on consistent, purpose-made geotextile fabric, and the fabric can be accepted against a manufacturing quality control specification such as GRI GT16.

Fabric formed concrete systems are used on irrigation, flood defense and river training works. This guide explains the technology, the different product types, and how to select the right system for a specific application.

How Fabric Formed Concrete Works

All fabric formed concrete systems share the same principle: a fabric formwork is positioned on the surface to be protected, then cement grout is injected under pressure, filling the fabric and hardening into a concrete layer. The fabric remains in place permanently, providing a protective outer skin over the concrete.

The key advantage over conventional formwork is that the fabric is flexible. It drapes over and conforms to irregular slopes, curved channel inverts and existing eroded surfaces, so a perfectly flat subgrade is not required. How much water can be present during placement is set by the method statement and project design.

The Main Types of Fabric Formed Concrete

1. Grouted Mattress (GGFM), the Primary System

Two layers of woven polypropylene geotextile are stitched together at regular intervals to create internal cells, then pumped with fine-aggregate cement grout on site. HydroBase mattress is available in thicknesses from 75 mm to 200 mm, and the design velocity rises with thickness, from 2.5 m/s at 75 mm to 6.0 m/s at 200 mm. The system is covered in detail across this website: see Standard Grouted Mattress, Filter Point Grouted Mattress, and Vegetated Grouted Mattress.

2. Concrete Canvas

A proprietary product made of a fiber matrix impregnated with dry cement, with a waterproof backing, that hardens when water is added. No pump is needed. It forms a thin rigid concrete layer and is generally used for ditch lining, minor erosion protection and similar light duties. Its thin section makes it a different choice from grouted mattress for high-velocity hydraulic applications; confirm its limits on the manufacturer's data sheet.

3. Geotextile Tube (Filled with Grout)

A closed cylindrical geotextile tube filled with grout or slurry to form a large, stable unit used for shoreline protection, breakwaters and berm construction. It is not a mattress system. It is used as a discrete gravity structure rather than a continuous lining, and is common in coastal and port engineering.

4. Concrete Mattress (Precast Block Type)

Individual precast concrete blocks connected by ropes or cables to form an articulated mat. It is not fabric formed, because the concrete is cast in conventional molds before deployment. It is included here because the term "concrete mattress" is sometimes used loosely in older specifications. See Articulated Concrete Mattress Guide.

Grouted Mattress vs Concrete Canvas: Which Is Better?

Source: HydroBase design guidance (velocity by thickness).

Applications of Fabric Formed Concrete

Fabric formed concrete of the grouted mattress type is specified across a range of hydraulic engineering applications:

• Canal lining: irrigation canals, water conveyance channels and drainage channels where seepage control and scour resistance are both required.
• Slope and embankment protection: reservoir upstream faces, highway embankments, levee faces and drainage channels.
• Bridge pier scour protection: collars and aprons around piers, with placement method and in-water conditions set by the method statement.
• River bank and training works: bank face revetment, low-flow channel lining and floodplain edge protection.
• Coastal and tidal revetments: seawall face protection and tidal inlet stabilization, where wave exposure is checked by the designer.

Key Design Considerations

Product standards: GRI GT16 from the Geosynthetic Research Institute is a manufacturing quality control specification for the geotextile fabric used in these systems. It does not cover grout strength, filled-mattress performance, thickness selection, hydraulic design or installation. Ask the supplier which test documents apply to your order. ASTM D4439 provides standard geosynthetic terminology used in procurement specifications.

For installation details, see our grouted mattress installation guide and our ACM technical guide.

Common Misunderstandings About GGFM

Several ideas about grout-filled mattress circulate in tenders and on forums, and some of them lead to poor decisions.

It is not a concrete slab. The cured mattress is a series of connected concrete cells held in a fabric. Because the cells are joined by the fabric, the mattress can bend with the ground, which a rigid slab cannot do.

It does not replace subgrade preparation. The mattress follows the surface it is laid on. A badly shaped or soft subgrade will show through, and loose material under the mattress can wash out.

Not every fabric is equal. Two products can look the same before filling. The weave, the restraint threads that set the thickness and the fabric strength decide how the mattress fills and performs, which is why acceptance is based on tested properties, not appearance.

The grout is part of the product. A good fabric filled with weak or poorly mixed grout will not meet its design strength. Grout mix control and strength testing belong in the quality plan from the start.

Where GGFM Does Not Suit

GGFM is a hard lining, so it is not the first choice where a living, planted bank is the goal. It is also a poor match for sites with no access for a concrete pump, or for very small repairs where hand-placed alternatives are simpler. If you are unsure, describe the site and the loads and ask for an honest recommendation, including alternatives.

What GGFM Means When You Place an Order

If your specification calls for a geotextile grout-filled mattress, name the system you mean in the enquiry: standard, filter point or vegetated. State the design velocity, the area and the project location, and attach the drawings. Thickness ranges from 75 to 200 mm and is chosen from the velocity the lining must resist, while grout strength, curing and testing stay in your project specification rather than in the supplier's product data.

HydroBase makes the fabric at its 150,000 m² factory in Inner Mongolia, China. Stock sizes dispatch in 3 to 5 days, and custom-size panels take 5 to 7 working days to produce, which is worth allowing for if the geometry includes structures or irregular edges. Pricing is by project, so there is no list price to quote from. Send the details through the contact page and the engineering team replies within 48 hours.

Sources and Further Reading

Open each document to confirm its current edition and scope before you rely on it.

• GRI GT16: The manufacturing quality control specification for the geotextile fabric used in grout-filled mattress. Checked 2026-10-24 (link and title).
• Geosynthetic Institute specifications index: Index of GRI test and specification documents. Checked 2026-10-24 (link and title).
• ASTM geotechnical engineering standards: Catalogue page for ASTM geotechnical standards. Checked 2026-10-24 (link and title).
• CEN EN 13254, geotextiles for reservoirs and dams: European standard for geotextile characteristics in reservoirs and dams. Checked 2026-10-24 (link and title).

Frequently Asked Questions

Is fabric formed concrete the same as grouted mattress?

Grouted mattress is a type of fabric formed concrete used in hydraulic engineering. When a tender specifies "fabric formed concrete mattress" or "geotextile grout-filled mattress," both usually refer to woven geotextile fabric pumped with cement grout on site. Concrete Canvas is a different proprietary product that also relies on fabric but is not the same as grouted mattress.

Can fabric formed concrete be used underwater?

Grouted mattress can be placed in or near water, and the method is a common choice for scour protection and bank repairs where dewatering is difficult. Whether underwater placement is suitable on a given project, and under what conditions, is set by the project design and the contractor's method statement.

What are the limitations of fabric formed concrete?

It provides surface protection, not structural load-bearing capacity. The cured mattress is hard to modify after installation, so final geometry should be confirmed before ordering. Placement on steep slopes needs a careful grout injection plan, and freezing conditions need protection of the fresh grout. The project specification and method statement set these controls.

HydroBase manufactures grouted mattress fabric in its factory in Inner Mongolia, China, with capacity of 40,000 m² per day across 150+ production lines. Send us your project details, such as design velocity, area, location and drawings, and our engineering team will reply within 48 hours. Project pricing is individual.

New to the system? Start with what a grouted mattress is and how it works.