Understanding the fundamental material properties of low-noise poroelastic road surfaces

Abstract

The main purpose of this study was to characterise the fundamental material (stiffness) properties of the poroelastic road surfaces (PERS) relevant to the pavement design. The research encompassed preparation of five variants of PERS mixtures in the laboratory based on the combinations of rubber, aggregate and binder components. Two standard test procedures were utilised: stress–strain sweep test and dynamic modulus E* test. First, stress–strain sweep test was performed at 1 mm/min strain rate to investigate the PERS mixtures' elastic characteristics. Hysteresis loops were plotted between force and strain change, which indicated that in all the mixes, the samples were stable to resist against higher hysteresis losses during successive cycles of testing. Also, lower losses were observed with increasing rubber contents; the results can be used in optimising the rubber content in the PERS to further assess rolling resistance and friction. Next, dynamic modulus E* test was performed on the PERS. The dynamic moduli varied based on the blending of rubber and aggregates proportion; the PERS mixes with higher amount of aggregates and lower amount of rubber had higher moduli. A comparison of moduli between the PERS mixtures and a typical asphalt concrete (AC) mix indicated that the PERS were softer than the AC mix by about 20–1500 times; the softness characteristics of the PERS would plausibly provide higher noise-dampening response. The methods employed so far covered stress–strain, and stiffness characteristics, which could be used in pavement design and the evaluation of rolling resistance and noise-reducing properties. Although this study is just a portion of a much more comprehensive laboratory test programme, these tests along with the upcoming laboratory tests are envisaged to aid in selecting the most promising PERS materials for the application on trafficked roads.

Keywords:

• poroelastic road surfaces
• stress–strain
• dynamic modulus E*
• phase angle
• master curve

Acknowledgements

The authors would like to acknowledge Mr. Hassan Hakim, VTI-Swedish National Road and Transport Research Institute, for his valuable assistance in laboratory mechanical testing. The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 226313.