2,437 research outputs found
Experimental investigation of rutting in the different phases of asphalt mixture
No full textRutting is one of the most severe failure mechanisms for asphalt pavements. This phenomenon is due to the accumulation of permanent deformation during the pavement service life. The behavior of asphalt mixture is highly affected by the properties of the asphalt binder used in the mix design. For this reason, the Multiple Stress Creep and Recovery (MSCR) test procedure was recently introduced with the objective of better evaluating the rutting resistance while replacing the conventional Superpave parameter, G*/sinδ. Good understanding of the rutting mechanism within the asphalt binder component is essential for correctly studying the mutual interactions of the asphalt mixture components: binder, fine aggregate and large particles. This paper presents the results of an experimental campaign consisting of MSCR tests performed on asphalt binder, mastic and fine aggregate matrix which compose a typical mixture for binder layer. All the tests were conducted using a Dynamic Shear Rheometer (DSR). The classical plate-plate configuration having 25 mm diameter and 1 mm gap was selected for asphalt binder and mastic tests. The cylindrical geometry was used for torsional tests on fine aggregate matrix presenting aggregate as large as 1.16mm. A single testing temperature of 60°C and three different stress levels, 100, 1600, 3200 Pa, were imposed. The results indicate that creep and recovery are function of filler concentration and stress level
INVESTIGATION OF VIRGIN AND RAP BINDER WITH A COMBINED VOIGT-ARRHENIUS MODEL
No full textThe use of Reclaimed Asphalt Pavement (RAP) represents a valuable solution for the construction of road infrastructure, both from an economical and environmental viewpoint. Although higher amount of RAP is commonly recycled in paving mixture, the interaction between virgin and aged binder and the effective response of the binders’ blend are still matter of investigation. In the present work different bituminous blends obtained by mixing virgin binder with RAP and artificially aged binder at various percentages, are used to evaluate the rheological behavior of the material through Dynamic Shear Rheometer (DSR) tests. Based on the experimental complex moduli of virgin, laboratory aged binder, and RAP binder, the Voigt and the Arrhenius models are combined to predict the response of the two types of bituminous blends: virgin plus artificially aged and virgin plus RAP binders. The predictions are then compared to the experimentally measured complex moduli of the binders’ blends. The results show that a combination of the Voigt and Arrhenius models is capable of providing very good predictions of the rheological properties over the entire spectrum of temperatures from -30°C to +80°C
Investigation on the low temperature properties of asphalt binder: Glass transition temperature and modulus shift factor
No full textThis paper investigates the effect of the glass transition temperature, T-g, and the use of modulus shift factors b(T) on the measured rheological properties of asphalt binders at low temperatures. First, temperature-frequency (T-f) sweep tests are performed with the Dynamic Shear Rheometer (DSR) on asphalt binder, and, the corresponding T-g is calculated. Next, modulus shift factors b(T) is applied to the modulus data measured at temperatures below T-g in the Cole-Cole plot. Finally, a visual comparison of master curves and the parameter assessment of 2 Spring 2 Parabolic 1 Dashpot (2S2P1D) model are used to evaluate the effect of b(T). A significant increase in dynamic shear modulus is observed when the DSR test is performed below T-g, while b(T) can take into account this phenomenon on the shape of the curves in the Cole-Cole plot. Hence, the combined use of the horizontal shift factor, a(T), and modulus shift factor, b(T), is recommended when the DSR tests are performed at temperatures lower than the corresponding asphalt binders T-g. (C) 2020 Elsevier Ltd. All rights reserved
A New Binder-Fast-Characterization-Test Using a Dynamic Shear Rheometer and Its Application for Rejuvenating Reclaimed Asphalt Binder
No full textA simple method using a dynamic shear rheometer is proposed for determining high-temperature key parameters of asphalt binders in place of the ring-and-ball softening point, currently used in Germany. The test was recently introduced in the German standards under the name Bitumen-Typisierungs-Schnell Verfahren (BTSV), which translates to Binder-Fast-Characterization-Test. Two key parameters are obtained as the result of the test: the temperature T-BTSV, at which the shear modulus is equal to 15.0 kPa, and the corresponding phase angle delta(BTSV). While T-BTSV provides information on material hardness, dBTSV indicates the degree of modification. Based on these two parameters, a classification system is proposed for different asphalt binder grades commonly used in Europe. Additionally, the procedure was applied for rejuvenating aged asphalt binder extracted from reclaimed asphalt pavement (RAP). A linear relation is observed for the two key parameters when blending RAP binder with different proportions of rejuvenator. These findings were used to evaluate the effectiveness of different rejuvenating additives
A novel method to characterise asphalt binder at high temperature
No full textThe current experimental method used in Europe to characterise asphalt binder at high temperature is based on the Ring & Ball softening point. However, for modified binders it was demonstrated that such a method is unable to correctly characterise the material. In the present work, an alternative solution to determine the high-temperature properties of asphalt binders using the dynamic shear rheometer (DSR) is proposed: the Binder-Fast-Characterisation-Test (BTSV) (Bitumen-Typisierungs-Schnell-Verfahren, in German). Two parameters are identified for the rheological characterisation of asphalt binders: the temperature T-BTSV, which is related to the Ring & Ball softening point and is an indicator of the binder stiffness, and the phase angle delta(BTSV), which provides information on the degree of binder modification. These two key parameters are used to discriminate among the different asphalt binder domains in the high-temperature range
Investigation on the Effect of Physical Hardening and Aging Condition on Low-Temperature Properties of Asphalt Binder Based on BBR
No full textLow-temperature properties of asphalt binders are fundamental for designing asphalt mixture in cold regions. This is especially true for alternative technologies such as Warm Mix Asphalt (WMA), for which a temperature reduction during production may potentially lead to substantial benefits in terms of long-term aging conditions. At low temperature, asphalt binder is conventionally characterized based on creep tests conducted with the Bending Beam Rheometer (BBR) in ethanol at a single conditioning time of 1 h. However, asphalt binders undergo significant time-dependent stiffening, often referred to physical hardening, when stored at such low temperatures. In this paper, the effect of aging temperatures and physical hardening on the low temperature rheological properties is experimentally investigated and modeled. First, BBR tests are performed on four long-term aged asphalt binders, which were previously short-term aged at three different temperatures (123 degrees C, 143 degrees C, and 163 degrees C), after three different conditioning times: 1 h, 24 h and 72 h. Next, the creep stiffness, S(t), relaxation parameter, m-value, and difference in critical temperature, Delta T-c are calculated and compared. Finally, the Huet model is fitted to the experimental data with the goal of comparing the effect of aging temperatures and physical hardening on the rheological parameters. Results indicate that physical hardening causes a significant increase in creep stiffness in the first 24 h while only moderate contribution is obtained when condition time is extended. In addition, the reduced production temperature of 40 degrees C can significantly improve the aging properties of asphalt binders at low temperatures while mitigating the effect of physical hardening
Influence of warm mix additives on viscosity and coating properties of asphalt binders modified with crumb rubber
No full textIn the present research four types of Warm Mix Asphalt (WMA) additives are investigated with the aim of identifying the most appropriate additive for improving Crumb Rubber Modified Binders (CRMBs) in terms of viscosity and coating properties. Viscosity tests are performed on the CRMBs with Dynamic Shear Rheometer and Rotational
Viscosimeter, while the binder aggregate affinity is then evaluated. The experimental findings indicate that wax results in a larger reduction of viscosity for CRMBs together with good workability at significantly lower production temperatures. In addition, no CRMB modified with WMA additives shows moisture damage potential
Investigation on the Combined Recycling of Reclaimed Asphalt Pavement and Steel Slag in Asphalt Mixture at Low Temperature
No full textIn this paper the effect of the combined use of different amount of Reclaimed Asphalt Pavement (RAP) and Electric Arc Furnace Steel Slag (EAFSS) on the low temperature properties of asphalt mixture is investigated with two experimental methods: Bending Beam Rheometer (BBR) mixture creep and Semi-Circular Bending (SCB) fracture tests. Creep stiffness, m-value, thermal stress, critical cracking temperature, fracture energy and fracture toughness are derived, and then, statistically and graphically compared. The results indicate that mixtures with 100% EAFSS show similar low temperature creep and fracture behavior compared to conventional mixtures, while the presence of RAP results in poorer material performance also when EAFSS is included in the mix design
Effects of polyacrylonitrile fibres and high content of RAP on mechanical properties of asphalt mixtures in binder and base layers
No full textPublisher Copyright: © 2022 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.In this present study, the effects of polyacrylonitrile fibres and high content (50%) of Reclaimed Asphalt Pavement (RAP) on the mechanical properties of asphalt mixtures in binder and base layers were studied. This is the first time that the effect of high RAP content on the mechanical properties of fibre reinforced asphalt mixtures (FRAM) was evaluated, while the low temperature performance was not usually conducted in previous studies. Results indicated that the addition of polyacrylonitrile fibres worsens the moisture susceptibility resistance, but improves the rutting, stiffness properties, fatigue performances, and cumulative fatigue damage of the mixtures with and without RAP. No significant effects on the low temperature cracking resistance were found when fibre was used, while a remarkable improvement in the crack propagation resistance properties was observed. Therefore, the use of polyacrylonitrile fibres improves in general the mechanical responses of the mixture, especially in the stiffness response.Peer reviewe
Application of the IS-MP-IA model to the German economy and policy implications
No full textExtending the IS-MP-IA model developed by Romer (2000) and applying the GARCH (Engle, 1982, 2001) methodology, the author finds that equilibrium GDP in Germany is positively affected by stock market performance and real exchange rate appreciation, and negatively influenced by the expected inflation rate, the government deficit/GDP ratio, and the U.S. federal funds rate. The relatively low deficit/GDP ratio of 1.83% in 2003 indicates that its fiscal condition was healthy. However, some other EU members may need to exercise fiscal discipline. Because real appreciation has a positive impact on output, a stronger euro may not be a concern for Germany but may be worried by those EU member nations which depend upon exports to stimulate their economies.
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