engleski

Nonlinear model for analysis of asphalt mixtures.

The behavior of asphalt mixtures is described by linear or nonlinear viscous material models, usually with temperature-dependent properties. One of the simplest rheological models suitable for the analysis of asphalt mixtures is Burger's model. It consists of a Kelvin and a Maxwell element connected in series. In this work, we introduced nonlinearity into the classical Burger model since the springs are described by an exponential force-displacement law. The laboratory experiments used for testing asphalt specimens are based on indirect tensile tests. In these tests, a cylindrical specimen is loaded along the edge to failure while force and displacement are recorded. Viscous materials are sensitive to the rate of loading, so the load is applied very slowly. Burger's rheological model is shown in Figure 1 and is mathematically formulated with equation (1), which is a system of algebraic differential equations. In total, our model has six parameters: viscosities µM and µK, moduli EM and EK, and non- physical parameters aM and aK. The experiments were performed in two phases according to the standard HRN EN 12697- 23:2003. In the first phase, the specimens were tested to determine the effect of temperature and bitumen- to-sand ratio on the peak force at failure. In the second phase, the specimens with extreme results were further tested. The tests were performed in the laboratory of the Faculty of Civil Engineering in Rijeka. The resulting force-displacement curve was plotted until the failure of the specimen and presented in Figure 1. The force-displacement curve resulting from equation (1) is also shown in Figure 1 for comparison. No specific procedure was used to estimate the model parameters, so there is clearly room for improvement. We are developing a model to estimate parameters from indirect tension tests for asphalt. At this stage, no specific method has been used to estimate the model parameters. Further work will include appropriate inverse methods for estimating the relevant parameters.

asphalt mixtures ; indirect tension test, Burger's rheological model, parameter analysis

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