A method for determining the appropriate frequency for testing asphalt mixtures in the laboratory

Determination of the properties of viscoelastic materials like asphalt mixtures in laboratory requires applying loads that are representative of real loading. Traffic loads in the laboratory are simulated using different waveforms, through combinations of amplitude and frequency. This study proposes a simple and practical approach for determining the loading frequency for laboratory applications, based on linear elastic computer simulations of different pavement structures under various loading configurations. Two methods were investigated to find the influence zone of the load in the pavement and the frequency of the load based on the assumed load velocities. These two approaches resulted in different frequencies. As simulation of the waveform using the first method (using a predetermined drop in normalized horizontal stress) is not practical for simulation of waveforms. Use of the second method,developed based on analysis of shape of stress distribution is recommended as the reasonable and feasible approach.