Since the completion of the SuperPave™ program, the popularity of gyratory compactors has never ceased to grow. Why? Because it’s a smart tool, and with lots of features.
When Superpave Mix Design was launched, pavement designers quickly forgot all there is to know about the traditional Marshall method. The new method, based on Gyratory Compaction, was not only faster but also great at delivering more affordable long-term results. And laboratories could finally get rid of those noisy hammer compactors!
While the first generation of gyratory compactors were heavy and bulky, the latest machines are now compact and lightweight. New and environmentally friendly technologies are used to apply the test parameters such as angle and vertical force, now automatically controlled.
Thanks to closed-loop control, they’re also more accurate than before. At the same time, technical specifications based on mix volumetric properties are becoming more common: gyratory compactors have finally become the ultimate QC/QA tool. Gyratory compactors have become standard equipment for mobile laboratories: they combine two great advantages —fast QC/QA testing with portability. This also means that Road Authorities can now perform final controls on the mix conformity directly at the job site.
Material technologies are evolving, and the same is happening to design methods. Performance-oriented procedures, like Balanced Mix Design, are progressively replacing volumetric-only design procedures. All these performance tests require specimens with accurate volumetric and dimensional properties.
The real-time control of volumetric parameters allows the gyratory compactor to produce sample with accurate specification. Specimens from gyratory compactors can then be used to determine dynamic modulus, fatigue, permanent deformation and cracking with AMPTs or dynamic UTMs.
Has the development of gyratory compaction technology come to an end? Probably not.
The possibility to also measure shear resistance adds to the opportunity to correlate the volumetric properties of the mix, such as percentage of voids and density, to performance characteristics, typically the resistance to permanent deformation. Plus, it is true to say that researchers like gyratory compaction, so they’re trying to extend its use to other construction materials. Testing procedures for zero-slump concrete are already here, with other research projects currently started, like the search for an alternative procedure for Proctor density of compacted soil layers.
Gyratory compactors made their way into asphalt pavement laboratories in the mid 90’s and are probably here to stay there for the long run. Already new applications are being developed that will specify methods for use with alternative materials such as soil or rubberized asphalt.