Geosynthetic interlayers can improve the tensile strength and modulus of elasticity of pavements for longer-lasting roads.

Interlayer technology helps arrest reflective cracking for longer-lasting pavements.

We owe a great deal to the Romans. Not only did they leave us with the basis for our legal system in the U.S. and much of Europe, but they also were the first to understand the benefits of a high-quality road network, laying the foundation for modern road design and construction. Roman roads were the best in the world at the time, but today, through technologies such as interlayers, we’ve learned how to greatly improve on their legacy and build stronger roads that can last for decades, while carrying traffic that would have been unimaginable to the Romans.

Everyone knows America’s transportation infrastructure could use a little help, to say the least. Highways and interstates that were once the envy of the developed world are now fading into disrepair in many places, and it’s becoming increasingly expensive to maintain road quality. When cracks and potholes form, contractors are often hired to repave roads with a fresh overlay of hot mix asphalt. But applying a new overlay is like applying a Band-Aid to a deep wound because the damage in the underlying pavement will quickly come to the surface. Cracked pavements repaired with a new asphalt overlay are susceptible to reflective cracking, where the original cracks migrate upward to the surface. Cracks return at a rate of about 1 inch per year, so a 1- or 2-inch-thick overlay does not deliver a long-term solution.

Engineers are increasing the use of interlayer technology that can arrest reflective cracking, lengthening the lifespan of a road while reducing routine maintenance work on fixing potholes and cracks. For example, two kinds of interlayers from Tensar — the GlasGrid pavement reinforcement system and the GlasPave waterproofing paving mat — do just that.

GlasGrid is an interlayer comprised of a grid structure made from fiberglass strands coated with an elastomeric polymer. This design makes for greatly increased tensile strength and a higher modulus of elasticity that works to prevent the spread of reflective cracking in pavement. The interlayer has proven to be effective across geographic regions, from hot, dry deserts to cold, wet subarctic areas.

Waterproofing roads also improves durability, and Tensar’s GlasPave interlayer adds the waterproofing function. Like GlasGrid, GlasPave also uses fiberglass fibers for improved tensile strength, but instead of forming a grid, the fiberglass strands in GlasPave are embedded into high-performance polyester mats. This results in a system that allows the tack coat to saturate the mat, creating a membrane that prevents water from penetrating and damaging the pavement structure.

Geosynthetic reinforcement has seen significant strides in recent years. The Romans may have given us a solid foundation for building modern roads, but we’ve come a long way from a technological standpoint from merely milling old pavement surfaces and adding new overlays. The use of interlayers can do wonders for our infrastructure problem, building roads that will last for the next generation of Americans.

Information provided by Tensar International (, a full-service provider of specialty products and engineering services based on advanced soil stabilization and reinforcement technologies that offer cost-effective alternatives to traditional construction methods.