Rheological model parameters determination based on laboratory studies

Different types of models are used to study the stress-strain behavior of asphalt concrete mixture during compaction. For modeling it is necessary to know the values of model parameters in the whole range of changes in the characteristics of the compacted material. The aim of the paper is to develop a methodology for determining model parameters based on the results of laboratory creep-recovery testing of asphalt-concrete mixture. In the paper, a model reflecting elastic, visco-elastic and visco-fluid properties of the compacted material is adopted. A differential equation representing the law of behavior of the asphalt-concrete mixture layer under load is obtained. The stages of creep-recovery testing are analytically described, namely: rapid loading with a constant load and deformation under this load; load removal and recovery. Initial conditions for the mentioned stages are determined. Taking into account the initial conditions, analytical expressions of the laws of deformation of the model under the action of a constant load and in the process of recovery are obtained. The methodology of laboratory experiments on creep-recovery is described, according to the results of which the required values of the model parameters with minimum absolute error are obtained. The developed methodology allows to determine the parameters of the model describing the stress-strain behavior of asphalt-concrete mixture of different density and temperature. Consequently, it is possible to simulate the behavior of the asphalt concrete mixture layer at the preliminary, main and final stages of compaction in order to determine the effective operating modes of compaction equipment.