Coating Geotextile Fabric
Spraying elastomeric coatings onto geotextile fabric creates seamless, reinforced liners for ponds, lagoons, landfills and containment areas. The fabric acts as a carrier and reinforcement; the coating provides the barrier.
Coating geotextile fabric is a construction method in which a spray-applied elastomer, usually a polyurea or polyurea hybrid, is applied to a sheet of geotextile that has been laid over prepared ground or a structure. The result is a fabric-reinforced, spray-applied liner. The geotextile provides a continuous carrier that can bridge soil, gravel and irregular surfaces, and it reinforces the membrane. The coating fills and seals the fabric, forming a seamless barrier. The method is used for ponds, lagoons, landfill caps and cells, wastewater basins, secondary containment coatings and some waterproofing membranes.
What geotextile is
Geotextiles are permeable fabrics made from synthetic polymers, most commonly polypropylene or polyester. Two main types are used:
- Nonwoven geotextiles. Fibers are bonded by needle-punching or heat. They have a felt-like texture and absorb coating well, which helps the coating lock into the fabric. Needle-punched nonwovens are the most common choice for spray liners.
- Woven geotextiles. Yarns are woven in a grid. They have higher tensile strength in the weave directions but a smoother surface that some coatings do not penetrate as well.
Fabrics are specified by mass per unit area, thickness, tensile strength, puncture resistance and polymer type. Fabric selection is usually set by the coating manufacturer or project engineer.
Why spray onto fabric
- Seamless membrane. Fabric panels are joined, then the coating forms a continuous film over the joints.
- Bridging. The fabric spans gaps and soft ground that would not support a coating alone.
- Reinforcement. The fabric adds tear and puncture resistance to the membrane.
- Conformance. Fabric drapes over slopes, corners, pipes and penetrations.
- Speed. Fast-set spray elastomers cure within seconds to minutes, so large areas can be lined quickly.
Typical construction sequence
- Subgrade preparation. Grade, compact and remove sharp rocks, roots and debris. Slopes are shaped to design.
- Anchor trench. Excavate a trench around the perimeter to secure the liner edge.
- Fabric deployment. Roll out geotextile panels down slopes, with overlaps per the specification. Panels are joined by sewing, heat bonding or overlapping, depending on the system.
- Detailing. Fabric is cut and fitted around pipes, posts and penetrations, with additional layers at stress points.
- Spray application. The coating is applied in multiple passes to build thickness, first wetting the fabric, then building film. Overlap areas and details receive attention.
- Inspection. Thickness, continuity and visual defects are checked.
- Anchor trench backfill and any protective cover.
Coatings used
- Aromatic polyurea and hybrids. Commonly used where the liner is covered or UV appearance is not critical. Aromatic materials can yellow and chalk in sunlight (see aliphatic vs aromatic coatings).
- Hybrid systems formulated for liner work. ArmorThane’s EnviroThane, for example, is a polyurea hybrid sprayed on geotextile for landfill, pond and wastewater liners.
- UV-stable topcoats where exposed liners need color retention.
Chemical compatibility with the stored liquid must be verified with the manufacturer (see chemical resistance testing).
Quality control
- Coverage and thickness. Because fabric absorbs coating, thickness above the fabric is checked with gauges or by cutting samples, and coverage is tracked against material use (see volume solids and coverage).
- Holiday testing to find pinholes, where suitable for the system (see holiday testing).
- Visual inspection for dry spots, wrinkles, bridging and unwetted fabric.
- Adhesion at terminations to concrete, pipes and structures.
- Weather records to confirm application within limits (see environmental conditions for coating).
Design considerations
- Slope stability. Liners on steep slopes need adequate anchoring and may need cover soil designs checked by engineers.
- Gas and water under the liner. Gas vents and underdrains may be required to prevent uplift.
- Puncture protection. Additional fabric layers or cushion under the liner on rough subgrades.
- Penetrations. Pipes and structures need detailed terminations.
- Regulatory requirements. Landfill and wastewater liners are often subject to permits and specifications.
Advantages and limitations
Advantages
- Seamless, monolithic membrane.
- Good performance on complex shapes.
- Quick return to service.
Limitations
- Requires skilled applicators and appropriate spray equipment.
- Weather-sensitive during application.
- Thickness control on fabric takes experience.
- Not every coating is suitable for continuous immersion or every chemical.
In practice
In practice, fabric-reinforced spray liners are planned around the site. The subgrade is graded and cleared of sharp objects, the fabric is laid out and anchored, and seams are overlapped. The crew then sprays the coating to saturate the fabric and build the specified thickness. Thickness checks, visual inspection for pinholes and, where specified, spark testing confirm continuity before the liner is put into service.
Key terms
- Nonwoven geotextile. A felt-like fabric made from bonded fibers, commonly used as a coating carrier.
- Woven geotextile. A fabric made from interlaced tapes or yarns, generally stronger but less absorbent.
- Fabric weight. The mass per area of the fabric, which affects how much coating it absorbs.
- Wet-out. Full saturation of fabric fibers by the coating.
- Seam overlap. Overlap between fabric rolls that is coated through to create continuity.
Frequently asked questions
Does the fabric stay in the liner?
Yes. The fabric becomes part of the membrane as reinforcement.
Can geotextile liners be repaired?
Usually, damaged areas can be cleaned, patched with fabric and resprayed following the manufacturer’s procedure.
Is spray-on fabric lining the same as a geomembrane?
It serves a similar purpose. Geomembranes are factory-made sheets welded on site. Spray-applied fabric liners are formed in place.
Related entries
- Secondary containment coatings
- Waterproofing membranes
- Water and wastewater coatings
- Polyurea coatings
- Landfill and lagoon liners (new)
- Hybrid polyurea coatings (new)
Educational reference. Coating performance varies by formulation. Always follow the manufacturer’s product data sheet, safety data sheet and your project specification.
[…] onto concrete and other substrates. The result is a seamless, fabric-reinforced membrane (see coating geotextile fabric). Spray-applied liners are often used for lagoons, ponds, containment areas, wastewater basins, […]