Modeling of the Rheological Properties of Asphalt Binder and Asphalt Mortar Containing Recycled Asphalt Material

Abstract The use of recycled materials in asphalt pavements increased significantly over the years, determining well known environmental and economic benefits. Many research agencies and road authorities evaluated the impact of Recycled Asphalt Pavement (RAP) on pavement performance. Nevertheless, the mechanism governing the interaction between virgin asphalt binder and aged RAP binder is not well understood. In this paper, the effect of RAP on the rheological properties of asphalt binders and mortars is experimentally evaluated, and theoretically modeled with the objective of defining a relationship between the linear viscoelastic (LVE) properties of binders and those of the corresponding mortars. Three asphalt binder types, obtained by blending a hard and a soft binder at three different percentages, were mixed with three different contents of a Selected fraction of Recycled Asphalt Pavement, called SRAP, for preparing the asphalt mortar samples. Dynamic Shear Rheomether tests were performed on binders and mortars to determining the complex modulus over a wide range of temperatures and frequencies. The rheological properties of the compound of virgin and RAP binder were evaluated by using a new approach based on a modified version of the Nielsen model, avoiding the extraction and recovery method. The results were then modelled by using the analogical 2S2P1D model, consisting of one spring, two parabolic and one-dashpot elements combined in series and then assembled together with a second spring in parallel. Based on test results, a simple experimental relationship between the characteristic times of the binder and the percentage of RAP in the mortar was found

Recommendation of RILEM TC237-SIB on cohesion test of recycled asphalt

This recommendation describes how to evaluate the presence of potentially active bitumen in recycled asphalt (RA) materials through the cohesion test. The experimental protocol is designed according to the research performed by the RILEM Technical Committee 237-SIB ‘‘Testing and characterization of sustainable innovative bituminous materials and systems’’ with the purpose, to develop a new, simple and fast method for the characterization of RA while limiting the need for conventional rheological tests. The guidelines in this recommendation focus on the testing procedure including specimen preparation, data analysis and provide information on the preparation of a tests report

Low-Temperature Properties across the Different Phases: From the Binder to the Mixture

In this study, a method that can be used to replicate the fine aggregate matrix (FAM) in the field condition as accurately as possible was experimentally validated, and the low temperature performance was measured and evaluated. First, an AC 22 TS mixture is selected as the reference material. The method based on a shift of the grading curve by a mathematic adaptation to the boundary sieve (DFAIB) is used to generate the grading curves of the FAM. Next, small sample beams of asphalt binder, mastic, FAM, and mixture are tested with the bending beam rheometer to evaluate the material's response at low temperatures across the different phases. The results of the BBR study show that the FAM phase has a higher stiffness than binder and mastic with a close behavior to the mixture. The results suggest that the FAM could be potentially adapted for discriminating among different mixtures

Experimental investigation of rutting in the different phases of asphalt mixture

Rutting 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

The 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

Experimental investigation of rutting in the different phases of asphalt mixtures

Rutting is one of the most severe failure mechanisms for asphalt pavements. This phenomenon is due to the accumulation of permanent deformation in consequence of traffic loading. 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 mixture which compose a typical mixture for asphalt 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 mixture presenting aggregate as large as 1.16 mm. 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 functions of filler concentration and stress level

Prediction of the complex modulus of asphalt mixture containing RAP materials from the rheological properties of mortars

In this paper, the properties of mortars that proportionally contain the same amount of fresh and RAP binder which can be found in the asphalt mixture, with respect to the specific material phase, are modeled with the objective of predicting the rheological behavior of the corresponding recycled mixture. For this purpose, Dynamic Shear Rheometer (DSR) tests are performed to determine the complex moduli of asphalt binders and mortars, which are then used as input in the empirical Hirsch and Witczak models. Based on the better predictions obtained from the latter, a modified formulation of the Witczak model was successfully derived to predict the mixture complex modulus directly from the experimental data of the corresponding asphalt mortar. The predictions obtained with the newly proposed expression of the Witczak model, closely match the laboratory measured complex modulus of asphalt mixtures. This can be used as input in the Mechanistic-Empirical Pavement Design Guide to analyze stress, strain, and deflection of asphalt pavements

Back-calculation method for determining the maximum RAP content in Stone Matrix Asphalt mixtures with good fatigue performance based on asphalt mortar tests

This paper presents a simple method to determine the amount of Reclaimed Asphalt Pavement (RAP) that can be added to Stone Matrix Asphalt (SMA) mixtures without compromising the fatigue resistance. Dynamic Shear Rheometer tests (DSR) on binder and mortars composed with fine RAP particles, called Selected Recycled Asphalt Pavement (SRAP) are used together with the Nielsen model to back-calculate the norm of the complex modulus of the bituminous blend of fresh and RAP binder. Fatigue properties are derived from parameter G∗sinδ and Linear Amplitude Sweep tests. The analysis indicates that a limiting SRAP binder content of 23% can be included in SMA mixtures with satisfactory fatigue performance