From the microchip to the fiber optic cable to the computer, technology powers just about every aspect of our lives. These innovations also have advanced the way we build our roads. The road building industry has produced concepts and products like Superpave, automatic control systems, stringless paving, perpetual pavement and ’smart roads,’ all of which are helping not only to construct today’s roads, but lay the foundation for future projects.
Advanced Machinery
One of the keys to building smoother roads is having advanced paving equipment with better control.
Blaw-Knox offers a microprocessor-based automatic grade and slope system on its Blaw-Kontrol II, both in mechanical and sonic versions. The system includes diagnostics, variable sensitive adjustment, digital readouts and adjustability on the fly, providing contractors with one source for both paving and automation.
According to Ike Downs of Ingersoll-Rand, the parent company of Blaw-Knox, “The need for automated controls, diagnostics and maintenance services will increase.”
Bomag’s single-drum rollers feature Terrameter, a microprocessor-based system that measures the movement of the unit’s drums. This determines the consistency of the pave, or the change in material stiffness over successive passes. The results of the compaction can be shown to the operator in a simple red light, green light system or by a Light-Emitting Diode (LED) display.
Power Curbers Inc. collaborated with Sauer Sunstrand to develop its Network Control System. The system eliminates the need for manual recalculation by offering automatic corrections for elevations and alignment. This not only saves time, reports Power Curbers, but ensures an easier, more precise pave.
Sensors and Liquid Crystal Display (LCD) readouts keep the operator on track and result in a more precise pave. According to O.L. Beaver, vice president of engineering, Power Curber, “Since the control is better, the ride is improved.”
A big part of technology is the ability to not only do things better, but faster and more cost-effectively.
Tim Messinger of Messinger Inc., manufacturer of Curb Fox paving equipment, said the company, “offers automatic line and grade control even on the least expensive slipform pavers. This technology does not necessarily improve roads, but enables more contractors to pave the roads at a lower cost.”
Advanced Materials
Superpave is a type of hot mix asphalt (HMA) that uses coarser, more angled particles to achieve more contact between the aggregate, making it stronger than dense-graded material.
Superpave, like other HMAs, can contain inconsistencies that make it difficult to compact the mixture between certain temperatures. The top of a mixture cools faster than the bottom, so a mix can only be consistently smoothed and compacted while the mixture is very hot or after the entire mixture has cooled to a uniform temperature.
These middle temperatures are referred to as “tender zones.” These critical tender zones make it necessary for compaction to be done within a certain temperature range in order to maintain the roads density and subsequent smoothness and longevity.
A consistent flow of materials and its compaction is essential to assure uniform paving pace. If work has to stop and start due to tender zones, the result is a lack of road smoothness and density.
Pavements that lack sufficient density can be permeable to water and air, which can lead to water damage, oxidation, raveling, cracking and low pavement strength.
Advanced Technology
A host of technologies are being developed to combat this problem. Infrared technology is being used to ensure that temperatures are correct and pavement is laid down and compacted in the proper time frame.
3-D technology is helping contractors accomplish paving in a continuous flow, saving time and providing improved accuracy as well. A collaboration between Gomaco and Leica-Geosystems has produced the 3-D machine-control system. Among other things, the system eliminates the need for a string line.
A 3-D picture of the plans is loaded into the Command Center and stations are set up around the job site. Using radio links to the stations and the loaded information, the Command Center coordinates the information which helps the Network Controller guide and steer the paver through the project.
Perpetual pavement and smart roads are two innovations that are paving the way for future road building. Perpetual pavement is said to have a life expectancy of 50 years and is constructed in three layers, two permanent layers and a surface layer that is easier to maintain. The permanent layers are designed to be strong, flexible and resistant to cracking from the bottom.
The surface layer is made of rut-resistant HMA that lasts years before any need for maintenance. When that time comes, however, the road design accommodates restoration without having to remove the road structure, saving time and money. In theory, this method produces a road that is stronger, smoother, safer and longer lasting.
However, according to a concept paper by Mark Buncher of the Asphalt Institute; and David Newcomb of the National Asphalt Pavement Association, “Construction of a perpetual pavement requires great attention to detail and a commitment to build it with quality from the ground up.”
The paper continued, “The foundation of the roadway must be able to support paving and compaction operations. This layer must also be well compacted, smooth and stiff enough to support construction traffic, as well as provide resistance to rollers.”
Just as with other paving methods using HMA, good construction practices result in good road performance, according to the paper.
Advanced Roads
Smart roads are constructed with sensors and fiber-optic cable that feed information back to designers and engineers reporting on asphalt conditions and cracking. These sensors and cables monitor concrete stress, asphalt strain, soil pressure, moisture penetration, frost depth, and vehicle weight and speed. A control center monitors sensor feedback on road conditions and performance.
One such smart road is located on a 5.7-mi. (9.2 km) stretch of road between Interstate 81 and Blacksburg, VA. The road is a joint project between the Virginia Department of Transportation and the Virginia Tech Transportation Institute, and features a 30,000-sq.-ft. control center.
The U.S. Department of Transportation has already allocated $93.9 million worth of funding for such smart road projects in 41 states and the District of Columbia under the Intelligent Transportation System (ITS) program.
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