How to Match Geotextiles to Paving Work

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How to Match Geotextiles to Paving Work

Dec 09, 2019

Using Geotextiles
Woven Geotextile Fabric are higher-grab tensile strengths per ounce. They are thin and were found to be ineffective as a paving fabric since they have no interior plane to hold asphalt oil and therefore could not form an impermeable membrane. They also did not perform well as an asphalt reinforcement synthetic to reduce cracking or as a filtration fabric.

Woven Geotextile Fabric have primarily two manufacturing processes and filaments. Woven slit films (tapes) are flat and have less filtration properties. They are best used in silt retention, separation and stabilization applications for their lower elongation and higher strength. Woven polypropylene geotextile fabric use round thick filaments and have apertures that permit for much better filtration and are best used in erosion control, slope protections or reinforcement where conductivity of water is desired.


Woven fabrics can be very beneficial in a rehabilitation project when a complete replacement of pavement is needed, and a new base installed prior to paving. They separate the base rock from the subgrade assuring a long term integrity and can add reinforcement stabilization by assisting in spreading the shear from local to general.

Non Woven Geotextile Fabrics are primarily used in paving, filtration, drainage, separation and pond cushioning. The nonwoven fabric provides an interior plane (dimensional thickness) which allow for air passage in drainage (membrane cushioning), a better transfer of moisture in forming a filter cake in filtration and absorption of oil to saturate the fabric forming a membrane. Nonwoven fabrics can absorb up to 13 times their weight.

Nonwovens use thin filaments of polypropylene or polyester that can be needle-punched from short or long staple fibers or long continuous filaments.Polypropylene fabric is slightly more absorbent to oil.Its only drawback is that it has a lower shrinkage and melt point. It can be damaged during installation under certain circumstances by very hot oil.

Polyester fabric is stronger per ounce with a higher shrinkage and melt point making it more resistant to damage during installation. 

Needle-punched (or entangled) fabrics are formed using two types of filaments. Barbed needles go up and down through the filaments entangling the strands together forming the fabric.

Long continuous filaments are spun together (spun process)
Long staples of filaments 6 inches to 12 inches are arranged on a carded conveyor system.Needle-punched fabric is thicker, fuzzy, softer and more pliable making them ideal for the paving application. They install smoother with fewer wrinkles due to their high elongation (stretch). Numerous reports state the fuzzy side placed into the asphalt oil provides reinforcement at the interface. The fuzzy side provides a greater effective surface area of the fabric offering better adhesive and shear strength with less slippage.

Nonwoven fabrics can be manufactured by one of three different processes for paving fabric which have a standard specification and installation procedures under AASHTO 288-17.

The most significant in the specification is 4.1 ounces per square yard and ultimate elongation greater than 50%. Not all agencies or engineers use AASHTO M288-17. Some have their own specifications and several states use 4.6 ounce. This will affect the tack coat application. A 4.1-ounce AASHTO M288-217 paving fabric will use a 0.22 - 0.25 gallon per square yard. The variance is determined if the application is on a new fresh oiled leveling course or an old asphalt. A heavier fabric will require more tack coat.

Needle-punched and one side heat-bonded (calendared) which is the most desirable and best paving fabric.
● Needle-punched (non-heat-bonded, calendared)
● Needle-punched Heat-bonded two sides (calendared)
A heat bonding (calendaring) is a finish that is applied to finish nonwoven needle punched fabric at the end of the manufacturing process. This can be applied to one or both sides of the fabric. This has special benefits to a paving fabric. 

One sided heat bonded and one side fuzzy is the most beneficial and desirable paving fabric. It has numerous benefits:
● Has one fuzzy side that bonds to the oil better at the interface.
● Reduces oil bleed through.

Provides a tough wearing side that does not delaminate under foot traffic, construction vehicles and if necessary public traffic.
The only installation problem that can occur is that the heat bonded on one side fabric can be placed upside down with the heat-bonded side down and the fuzzy side up. This presents the same delamination problems as non-heat bonded fabrics and additionally can cause fabric slippage from construction vehicles and if traffic drives on it. The heat-bonded side must be placed up to the traffic. The fuzzy side must be placed down to the old pavement.

Often manufacturers roll their material for machine placement, so the fabric comes off the roll and goes underneath the roll rather than coming off the top and this places the heat bonded side up and fuzzy side down. The roll must be loaded correctly onto the machine.  

A non-calendared nonwoven needle-punched fabric is primarily for other than paving applications (filtration, separation, drainage liner cushioning). It creates paving construction problems with no tough wearing side. It almost always delaminates from any vehicle contact and even from oil oily foot traffic. FHWA-Texas report 261-2 mentions delimitation as a major problem with non-heat-bonded fabrics delaminating and fuzzing up in the wheel paths of traffic during construction. These problems create increased labor and slow construction. The damaged membrane in the wheel paths reduces long term performance. For this reason, it is best to use a calendared fabric with a tough wearing course for foot and vehicle traffic.

Dual sided calendaring creates a thinner, stiffer fabric. It is much harder to install and is more likely to have slippage, its wrinkles can be large and transverse the full width of the fabric. Its thinness has significant tack coat (oil) bleed through problems. These problems create increased labor and slow construction.

Paving fabric comes in a standard width of 12.5 feet but other sizes from 3 feet to 18 feet wide depending on the manufacturer are available or can be specially made upon request. Check what sizes your distributor stocks.
Both hot tack coat (oil) and rapid set emulsions can be used. Rapid set emulsions slow construction and must break completely before fabric is placed.

Hot bitumen tack coat is generally the preferred oil to use. The fabric can be placed into the oil almost immediately. One consideration is fabric shrinkage and melting. The oil is hotter than where fabric begins to shrink and melt. In the mornings and late evenings when the asphalt temperature is cool the oil cools rapidly and little delay is needed between spreading of the oil and fabric placement. In the day time when the sun has heated the asphalt to as much as 200 degrees the oil cools much slower and a delay between oil spreading and fabric placement may be needed to prevent shrinkage and melting of the fabric. Asphalt temperature is usually not a problem since the fabric is oil saturated and insulated from the higher temperature.

Overlaps and slit wrinkles require a double application of oil or the two thicknesses will not have enough oil to saturate both to form the membrane and bond the asphalt.
Shanghai Yingfan Environmental Engineering Co., Ltd.