Backcalculation is commonly used for determining stiffness moduli of pavement courses and its subgrade based on in situ deflection tests. However, the in situ test results are dependent on the frequency domain, which in turn has a significant influence on the backcalculation results. In this paper, one of the methods for normalising the frequency of load and displacement functions obtained from a dynamic impulse generated by a falling weight deflectometer (FWD) test is verified. The assessment of the method is carried out based on backcalculation results of pavement deflection tests induced by both the dynamic and static loads and an independent numerical experiment. The analysis carried out in this paper shows that the normalisation of vertical displacements and pavement loads to the values corresponding to the frequency of 0 Hz improves the accuracy of the backcalculation results. It can be concluded that the frequency normalisation procedure is an effective way for standardising the boundary conditions in the backcalculation of flexible pavements.

The thermal properties of pavement layers made of concrete with varying bulk densities are a particularly interesting topic in the context of development road technologies. If a hybrid layer system is used as a starting point, with thin asphalt layers (from 1 cm to 4 cm) laid on top of a foam concrete layer, thermal properties begin to play a crucial role. The main research problem was to create a test method enabling the assessment of the influence of solar heating on the thermal parameters of the building material, especially cement concrete. For this reason, this paper is concerned specifically with the assessment of a new methodology for testing and calculating the value of the thermal diffusivity coefficient of samples made of concrete varying bulk densities. In this case, using the proprietary concept the authors built a solar simulator using a multi-source lighting system. The analysis of the results of laboratory tests and numerical analyses allowed the authors to observe that there is a strong correlation between the bulk density of samples heated and the thermal diffusivity parameter, which appears in the unidirectional heat transfer equation. The strength of this relationship has been expressed with the coefficient of determination and amounts to 99%. The calculated values of the coefficient of thermal diffusivity for samples made of foam concrete range from $0.16\times {10}^{-6}$$\frac{{\mathrm{m}}^2}{\mathrm{s}}$ to $0.52\times {10}^{-6}$$\frac{{\mathrm{m}}^2}{\mathrm{s}}$ and are lower (from 2.5 to 8 times) than the value determined for samples made of typical cement concrete.

Taking into consideration the key parameters of a FEM based pavement model, such as type, shape of mesh of finite elements, boundary conditions and dimensions, the authors compared the obtained values of elastic moduli with the results of calculations based on the classical theory of elastic layers positioned on elastic half-space (LET). The properties FEM model have been described for which the obtained difference between identified values of elastic moduli with respect to LET method is less than 10%. Moreover, in the majority of cases it has been concluded that the module of relative error of the values of elastic moduli identified with both methods depends on the depth of the layer within the model.

W pracy przedstawiono wyniki badań laboratoryjnych mieszanek mineralno-asfaltowych (MMA) typu beton asfaltowy, które zawierały w swoim składzie dodatek asfaltu naturalnego Gilsonite w ilości 4% w stosunku wagowym do masy asfaltu, dozowany dwiema metodami: „na mokro" lub „na sucho”. Zakres przeprowadzonych badań laboratoryjnych obejmował oznaczenie modułów sztywności w badaniach pośredniego rozciągania, modułów sztywności metodą pełzania pod obciążeniem statycznym oraz odporności na działanie wody i mrozu. Na podstawie analizy statystycznej otrzymanych wyników badań laboratoryjnych dokonano oceny istotności różnic w uzyskanych właściwościach MMA zawierających dodatek Gilsonite dozowany różnymi metodami, w porównaniu do wartości uzyskanych na mieszance referencyjnej. Ustalono, że metoda dozowania („na mokro" lub „na sucho") dodatku asfaltu naturalnego Gilsonite do analizowanej mieszanki mineralno-asfaltowej typu beton asfaltowy nie ma istotnego wpływu na wartości modułów sztywności oznaczonych metodą IT-CY, metodą pełzania, a także na wartości wskaźnika wytrzymałości na rozciąganie pośrednie ITSR.

On the example of the road pavement of a semi-rigid structure, this paper presents the concept of the parameters estimation of the experimental section tested after 30 years of use. In the context of the lack of technical history data of the analyzed road section, the resultant (conventional multilayer system, which is pavement and its subgrade) stiffness was analyzed in relation to the moment it was built. The analysis was performed using the concept of multilevel loadings, with the use of FWD-type equipment. The considerations are related to the slope coefficients of linear regression obtained on the basis of a research program in the range of the loads up to 90 kN. There were compared the differences between slope of the regression function for the force-deflection relation between the results of the deflection measurements of the test section after 30 years of use and the slope coefficients for the pavement structure parameters estimated on the basis of both expert judgments and computer simulations, as well as the back forecast. For the forecast, the properties of the stochastic process determined by the Poisson distribution were used.