Petromat ®

The Petromat® System extends the life of new asphalt concrete (AC) pavements and AC overlays. The Petromat System consists of Amoco’s Petromat non-woven polypropylene fabric which is field saturated with an asphalt cement tack coat. When placed between pavement layers, the Petromat system becomes an integral part of the roadway section, forming a barrier to water infiltration and absorbing stresses to reduce reflective and fatigue cracking of the new AC surface layer. Since 1965, the economical Petromat System has had an outstanding record of improving pavement performance while reducing maintenance and roadway life-cycle costs. Paving fabric systems are currently being used at a rate of over 15,000 equivalent lane miles per year in North America alone.



Moisture Barrier

Function: The greatest source of damaging water in road structural sections is precipitation infiltration through pavements. Most pavements do not have adequate drainage systems to quickly remove infiltrated water. If a pavement base is saturated as little as 10% of the time, the useful life of that pavement will be reduced by 50%. The Petromat fabric, when saturated with the asphalt cement tack coat, becomes a moisture barrier in the pavement, minimizing surface water infiltration. The American Association of Highway and Transportation Officials (AASHTO) 1993 flexible pavement design methodology gives a substantial structural credit to unbound roadbase materials when they are well drained and not allowed to become saturated. By minimizing water infiltration, the Petromat System moisture barrier will keep the road base more well drained and will therefore maximize the structural strength of unbound roadbase materials.

In rehabilitation of an existing pavement, capping the surface with the Petromat System can be a much more efficient and cost effective way to control moisture problems than retrofitting edge drain systems to typically poor draining road bases.

Performance: Both laboratory and field testing have shown pavements to be 10 to 1000 times less permeable when the Petromat System is incorporated as an interlayer. A complete treatise on the need for pavement moisture control and the effectiveness of paving fabric systems as moisture barriers may be found as a Transportation Research Board (TRB) Circular and is summarized as Tech Note 4, by Amoco Fabrics and Fibers Company. The electronic circular, EC006, may be found on the TRB web site as an online publication at Also shown in the referenced paper is the need for a uniform application of the proper amount of asphalt cement tack coat for the Petromat System to achieve the desired very low permeabilities.

Stress Absorbing Interlayer

Function: Petromat paving fabric, saturated with asphalt cement, forms a substantial interlayer media within which stresses can be absorbed. Stresses associated with limited movement along cracks and joints in existing AC or Portland cement concrete (PCC) pavements are absorbed within the paving fabric system and therefore, are not translated, or reflected, up into the asphalt concrete layer over the system. If there is excessive movement of existing cracks or joints, there are more robust membrane interlayer products available, such as, Petrotac®, Pro-Guard®, or PetroGrid®, for pavement treatment.

Also, asphalt concrete flexible pavement will eventually develop fatigue cracking due to tensile stresses while flexing. The inclusion of the Petromat System interlayer results in a layered pavement with greatly reduced tensile stresses compared to monolithic pavements with no interlayer. The result is a dramatic increase in the fatigue life of new pavements or overlays.

Performance: Laboratory simulation of comparable pavements both with and without the Petromat System indicated a 100 to 1000% increase in the number of pavement loadings before fatigue or reflective cracking appeared over the Petromat System. Field performance indicates a 50 to 150% increase in overlay life before fatigue or reflective cracking occurs in overlays over the Petromat System versus the same thickness control sections with no fabric. A comprehensive study, Maxim Technologies (1997), examined available paving fabric research and empirical evidence to find that properly applied paving fabric systems, such as the Petromat System, equate to an additional 0.1 to 0.15 foot (3 to 4.4 cm) thickness of AC overlay for the retardation of reflective cracking. The study, which may be viewed at, cited both the moisture barrier environmental benefits and the stress absorbing interlayer functions as the reasons for success of paving fabric systems. Widespread field evaluations have verified the effectiveness of the Petromat System as shown below:

Petromat, Number One In The Business

Petromat, the original paving fabric, is the most widely used paving fabric in the world for the following reasons:

Petromat is Designed Specifically For Pavement Application:

  • a heat set side on top to minimize asphalt cement tack coat bleed-through and to protect against damage from construction traffic,
  • a special blend of fiber sizes to promote rapid, uniform tack coat saturation and to give the interlayer stability while holding the asphalt cement in place indefinitely, and
  • an engineered amount of stretch to ease installation while maintaining stability.

Choice of Styles: Petromat styles 4598 and 4599 are the most widely recommended and used paving fabrics. Style 4598 meets the requirements of AASHTO guideline specification M 288-96.

Cost-effective: The installed cost of the Petromat System (fabric and asphalt cement tack coat) is typically less than half the cost of 0.1 foot of AC. For extending pavement life, the Petromat System is therefore much less expensive than placing additional asphalt concrete to get the same performance or increasing roadway maintenance. Use of paving fabrics generally yields a savings in pavement rehabilitation system costs of more than $7,000 per lane mile.

Versatile: The Petromat System is effective within new AC pavements, below AC overlays over rigid and flexible pavements, and below surface treatment(chip-seal) pavements. It can improve the performance of highways, city streets, parking areas, airport pavements, bridge

PETROMAT® 4597 is a nonwoven polypropylene geotextile produced by Propex, and will meet the following Minimum Average Roll Values (MARV) when tested in accordance with the methods listed below. PETROMAT 4597 is used as a moisture barrier and stress absorbing interlayer beneath asphalt overlay or a chip seal and exceeds AASHTO M288 requirements for paving fabric.

PETROMAT 4597 conforms to the property values listed below1. Propex performs internal Manufacturing Quality Control (MQC) tests that have been accredited by the Geosynthetic Accreditation Institute – Laboratory Accreditation Program (GAI-LAP). MARV2 

% U.S. Manufactured Inputs   100% 100%
% U.S. Manufactured   100% 100%
Mass/Unit Area ASTM D-5261 4.6 oz/yd. 156 g/m.
Tensile Strength (Grab) ASTM D-4632 120 lbs 534 N
Elongation ASTM D-4632 50% 50%
Asphalt Retention ASTM D-6140 0.24 gal/yd. 1.1 l/m.
Melting Point ASTM D-276 320 °F 160 °C
UV Resistance
% Retained at 500 hrs
ASTM D-4355 70% 70%