Dynamic Stiffness of Bituminous Mixtures for the Wearing Course of the Road Pavement—A Proposed Method of Measurement

Abstract

Stiffness is an important mechanical characteristic of asphalt mixtures used in the wearing course. It is one of the determining factors in the generation of tyre/road noise. The dynamic stiffness of the upper layer of the road surface depends on the physical and mechanical properties of the materials it is composed of, and traffic load. Determination of dynamic stiffness, both in laboratory conditions and in situ, requires consideration of many other factors. Tests of dynamic properties of road surfaces in field conditions are most often conducted with the help of modal hammers. Impulse excitation results are usually less accurate than those in the application of modal exciters. The test stand was constructed, comprising a tripod, 32-channel and 24-bit data acquisition system, exciter, signal amplifier, impedance head, single-axis piezoelectric accelerometers and a stinger. The test stand and the proposed method of measuring dynamic stiffness do not require the determination of the resonance frequency of the tested specimen and can be used both on various types of bituminous mixtures of varying shape and dimensions, as well as directly on the upper surface of the wearing course of bituminous pavements. The test results showed that the type of bituminous mixture used in the wearing course significantly affects its dynamic stiffness. The dynamic stiffness level of asphalt concrete, stone mastic asphalt and porous asphalt layers was determined to be similar. The addition of rubber granulates significantly reduced its rigidity, which is very beneficial from the point of view of reducing the tyre/road noise.

Investigation of the Dynamic Stiffness of Poroelastic and Asphalt Concrete Layers under In Situ and Laboratory Conditions

“…That is why the authors of this study developed their own test stand for broadband measurement of dynamic stiffness of vibro-insulating materials and bituminous composites using the Resonant and Non-resonant Methods. The test stand and the results of preliminary tests related to the laboratory testing of the influence of different static and dynamic loads on the dynamic stiffness of cylindrical samples of rubberised asphalt mixtures, stone mastic asphalt (SMA) mixtures and asphalt concrete (AC) were presented in [ 2 ]. The obtained results were characterized by very high repeatability and strong coherence of signals recorded with the use of an impedance head.…”

“…In the test stand, described in detail by the authors in [ 2 ], the input excitation in the exciter was transferred to the tested structure (road surface or tested samples) via a drive rod (a so-called stinger) and an impedance head mounted at the opposite end (according to guidelines [ 24 ]), which allowed for the simultaneous measurement of driving-point force and acceleration.…”

“…In a previous study [ 2 ] it was emphasized that to improve the test stand it is necessary to conduct further tests (on samples in laboratory conditions and in situ on road surfaces) with the use of a stiffer stinger.…”

“…The first configuration of the test stand was presented in [ 2 ]. This paper presents the modifications introduced in the previously built test stand and also presents the results of dynamic stiffness measurements carried out directly on poroelastic pavements and on asphalt concrete pavement (in situ tests), as well as the results of tests carried out in laboratory conditions on samples cut from these pavements.…”

Evaluation of Linear Deformation and Unloading Stiffness Characteristics of Asphalt Mixtures Incorporating Various Aggregate Gradations

“…In recent years various researchers have carried out experimentation on the stiffness properties of asphalt mixtures [10][11][12]. The effect of mixture stiffness on the fatigue life of asphalt pavements was investigated [13][14][15].…”