The problems is that after asphalt has been exposed to the environment for extended periods of time, its material properties can change, making it more susceptible to deterioration. Seasonal changes lead to potholes, cracking, and consequently lots of repairs.
To design asphalt that can withstand varying temperatures for specific environments, engineers must take into account the viscoelastic dynamic Young's modulus of the asphalt, a measurement used to describe the material's stiffness. This led Swedish Peab Asfalt to develop a new testing method that uses mechanical resonance frequency measurements and numerical calculations as a way to determine stiffness.
"In cold weather, asphalt concrete that is too stiff can lead to cracking and degradation," said Anders Gudmarsson, R&D manager at Peab Asfalt. "In warmer temperatures, on the other hand, asphalt with too much flexibility can lead to permanent deformation."
During the frequency response test, resonance measurements are taken on an asphalt sample to find the material's dynamic response (pictured). The sample used in the test can be of any size or shape, which makes the test both easier and faster when compared with previous methods.
After the experimental test, measurements are read by the simulation app, where the stiffness – in this case, the dynamic modulus – of the asphalt is computed for a wide range of frequencies. The simulation app works with frequency response curves and determines the material properties of the asphalt being tested.
"Stiffness testing of asphalt concrete was possible before, but conventional test methods were expensive, complicated, and time-consuming to perform," said Gudmarsson. "Our new method is much more economical and the availability of a simulation app for optimising the findings means that any engineer can easily take advantage of it."