The paper presents the results of laboratory investigation on asphalt binders relaxation at low temperature, carried out in a ductilometer using the tensile test with continuous force measurement. Polymer modified asphalt binder samples consisting of a 50/70 penetration grade bitumen mixed with a concentrate of styrene-butadiene-styrene (SBS) modified bitumen—a 160/220 penetration grade bitumen modified with a SBS copolymer in the amount of 9%—were tested. Therefore, polymer modified binders containing 3%, 4.5%, 6% and 7.5% SBS, respectively, were obtained and investigated. Tensile tests were performed at −16 °C on samples before aging and subjected to short-term aging (RTFOT). Test results in the form of relaxation curves have been mathematically described using a modified generalized Maxwell model. Based on the acquired results, it was shown that the increase of the SBS copolymer content in asphalt binder precipitates the relaxation process, while aging slows down this phenomenon. It has also been proven that with increased content of SBS elastomer in asphalt binder, the effect of short-term aging on binder’s stress relaxation ability at low temperatures is reduced.

The tests and analyses presented in the paper are related to the 20/30, 35/50 and 50/70 penetration grade road bitumens as well as the asphalt binders obtained through modification of the 35/50 and 50/70 bitumens. The latter were modified by adding to it 3%, 5% and 7% of the Gilsonite natural asphalt and 15%, 25% and 35% of the Trinidad Epuré Z 0/8 natural asphalt. The aim of the study was to assess the changes in the functional and rheological properties of theroad bitumens that were modified by adding to them the Gilsonite and Trinidad Epuré natural asphalts. The modified asphalt binders were subjected to the laboratory simulated short-term and long-term aging, where two methods, designed as part of the Strategic Highway Research Program, were used, i.e. the Rolling Thin Film Oven Test and the Pressure Aging Vessel, respectively. The study of the asphalt binders both those that were subjected to aging and those unaged includes thermal susceptibility (the Penetration Index) and resistance to cracking at low temperatures by tests carried out using the Bending Beam Rheometer. The analysis of the results revealed that the unfavourable impact of the aging process on the asphalt binder properties is limited if a suitable amount of the natural asphalt is used as a modifier.

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.

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.

The main purpose of this work is to get to know the structural and functional properties of fly ashes, i.e. industrial waste from lignite-fired power plant, from the perspective of their use as fillers for hot-mix asphalt (HMA). Analysis of the results of laboratory tests: grain-size distribution, specific surface, air voids of dry compacted fillers, stiffening properties in bituminous mastics showed that the fly ashes do not meet the requirements for fillers to HMA, because they cause too much stiffening impact. The results of extensive research has shown that these ashes can be used for the HMA, as so-called the mixed fillers with the participation of limestone filler used traditionally.