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The process of reclaimed asphalt pavement (RAP) recycling may occur multiple times during the life of the pavement. This study investigates the effect of multiple recycling on binder properties by employing a virgin 3045 PEN grade binder that was aged in the laboratory intended to simulate aging of binders in RAP. The aged binder was rejuvenated using two bio-oils and one softer binder. The doses of the bio-oils and softer binder were determined by matching the continuous high-temperature performance grade (PGH) of the rejuvenated RAP binder to that of the virgin binder. This aging and rejuvenation cycle was repeated three times. Finally, fatigue and rutting performance of the binder was evaluated for the three reuse levels. Results indicate that the material can be reused up to three cycles keeping good performance on fatigue or rutting. However, care should be taken regarding the cumulative effect of bio-oils causing an over-softening effect on the of the RAP. [ABSTRACT FROM AUTHOR]

Asphalt pavement is under different climatic conditions throughout its service life, which means that fatigue cracking does not occur at a specific temperature, but at a temperature range. The main objective of this paper is to evaluate the influence of different temperatures in the fatigue life of two asphalt binders: a non-modified binder (penetration grade 30/45) and a highly polymermodified binder (HPMB). The fatigue resistance characterization was performed by means of a linear amplitude sweep (LAS) test at the temperatures of 10, 15, 20, 25, and 30°C using a dynamic shear rheometer (DSR). From the dynamic shear modulus (|G*|) results, adhesion loss was observed between the binder and the rheometer parallel plate at the lower temperature of 10°C,while at higher temperatures (25 and 30°C) plastic flow was observed rather than fatigue damage. Therefore, considering that the actual test procedure does not specify the testing temperature, the evaluation of failure mechanism is essential to validate test results, because the random selection of test temperature might lead to inconsistent data.

The addition of polymers on asphalt binders aims to enhance their performance, especially at high temperatures, which correspond to rutting resistance. The Superpave rutting parameter (|G*|/sinδ) has been considered to be inadequate to characterize the performance of modified materials, therefore the Multiple Stress Creep and Recovery (MSCR) test was developed, providing the parameter non-recoverable compliance (Jnr). This research has the main objective of correlating asphalt binders performance-based characterization with rutting resistance of asphalt mixtures, and presents results obtained for one conventional (50/70 penetration grade) and two modified asphalt binders (2.1% RET and 1.9% RET) regarding their rheological characteristics. With the use of the dynamic shear rheometer (DSR), master curves and MSCR results were obtained for the three binders. In addition, permanent deformation tests were performed on the asphalt mixtures by means of laboratory traffic simulation. The rutting characterization indicated higher permanent deformation resistance for the modified binders for the asphalt binder and the asphalt mixture testing. The main conclusions were that the use of modified binder reduced in approximately 50% the Jnr values and the rut depth; also, the asphalt binders’ characteristics were able to predict the asphalt mixtures rutting resistance.

Cold recycled asphalt mixtures (CRAMs) may present a compressive resilient modulus dependent on the stress state. Currently, there is no widespread consensus on a triaxial resilient modulus (TxRM) model for CRAM analysis. A widely accepted TxRM model would favour the analysis of CRAM's layered pavement systems. This paper assessed the adequacy of different TxRM models of CRAM's specimens with different compositions, aggregate gradation and physical characteristics. Based on the literature, three different TxRM models were selected. The models' non-linear estimation was performed through Levenberg–Marquardt algorithm. Model selection analysis was based on residuals square sum root (RSSR) assessment. Ni et al.'s model was found to be the most adequate for CRAM's TxRM modelling based on RSSR analysis. The model selection was done regardless of aggregate gradation, binder type/content, air void content, RAP content, TxRM values range, active filler type and curing time of the tested specimens. [ABSTRACT FROM AUTHOR]

This research evaluated recycled asphalt mixtures (RAMs) for application as wearing course in heavy traffic highways. The main objectives were to investigate the effect of different RAP contents and the effect of a recycling agent (RA) on the mechanical properties of RAMs. Recycled asphalt mixtures with low (10, 20 and 25%) and high (35, 50 and 65%) RAP contents were evaluated. Two of these mixtures (25 and 50% RAP content) were also evaluated after the addition of the RA. The results indicate that conditioning the RAP during the production of RAMs influences the RAP binder activation and the mechanical behaviour of the mixtures. RAMs with high RAP contents presented better resistance to permanent deformation and resulted in satisfactory resistance to fatigue cracking due to the activation of the RAP asphalt binder. Finally, the addition of the RA improved fatigue resistance for higher amounts of RAP without reducing rutting resistance. [ABSTRACT FROM AUTHOR]

There is limited information on the characteristics and performance of paving mixtures made with 100% bio-binders. Moisture damage resistance of this type of mixture is a concern since the components of the bio-binder may have a higher affinity with water than asphalt binders. In this context, this paper presents a moisture damage susceptibility evaluation of wood-based bio-binder-aggregate interfaces in terms of energy parameters calculated from surface free energy components. The bio-binder was used as a total replacement for asphalt binders, and the responses were compared to a neat- and a highly modified-asphalt binder, considering different aggregate sources. Results suggest the bio-binder has similar moisture damage resistance to the neat asphalt binder and higher resistance than the highly modified asphalt binder, providing a first indication for the potential use of this bio-binder as 100% asphalt binder replacement. However, additional research is still required to validate these findings at the mixture level. [ABSTRACT FROM AUTHOR]

Featured Application: White water-based paints with high-volume solids and well-graded glass beads, characterized by uniformity and curvature coefficients, improve pavement marking service life. Pavement marking retroreflectivity, a critical factor for safe driving, depends on the characteristics of both the paint and the embedded glass beads. However, traditional methods for predicting pavement marking service life often overlook these materials properties. This study investigates the influence of paint and glass bead characteristics on pavement marking retroreflectivity performance and addresses the characterization of glass bead size distribution by the coefficient of uniformity and curvature. Three field test sites on a Brazilian highway with various paint and glass bead combinations were evaluated. A statistical model, GAMLSS (Generalized Additive Model for Location, Scale, and Shape), was adjusted to evaluate the performance of the markings' retroreflectivity as a function of paint and glass bead characteristics. The model revealed that well-graded glass beads increased retroreflectivity by around 10%, while paints with a higher volume of solids improved service life around 65%. Therefore, the results show that acrylic water-based paints with higher volumes of solids and well-graded glass beads with better shape characteristics should be preferred to improve pavement markings' retroreflectivity and service life. The statistical model identified the key characteristics with the greatest impact on pavement marking retroreflectivity, offering valuable insights for real-world applications, which will assist pavement marking practitioners and road authorities in selecting appropriate materials to achieve enhanced durability. [ABSTRACT FROM AUTHOR]

This article investigated the effect of waste polyethylene (PE) on the modified asphalt binders' rheological behavior from a statistical point of view. The interlaboratory testing results from the RILEM Technical Committee 279 Valorization of Waste and Secondary Materials for Roads Task Group 1 were used for this purpose. First, an unaged 70/100 penetration graded neat binder was selected as the reference material. Next, a single 5 % content of waste PE additives (PE-pellets and PE-shreds) was mixed with a 95 % neat binder to prepare two PE modified binders. Then, dynamic shear rheometer-based temperature-frequency sweep tests were performed over a wide range of temperatures and frequencies to evaluate the rheological properties of these three binders. Different rheological behaviors were observed in the isochronal plots at high temperatures. Based on a reproducibility precision requirement proposed for phase angle, 28°C was set as the transition temperature across the rheological behaviors. Next, according to the three rheological behaviors defined in a previous study by the authors, statistical analysis was introduced to identify sensitive rheological parameters and determine the thresholds. Results indicate that the phase angle measured above 28°C and 1.59 Hz can be used as a sensitive parameter to discriminate the three rheological behaviors of PE modified binders. The thresholds among different behaviors were also calculated as an example for phase angle measured at the highest common testing temperature of 70°C. Additional experimental evaluations on more types of PE modified binders, especially at intermediate and high temperatures, are recommended to better understand their influence on the rheological behavior of PE modified binders. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the behavior in terms of the permanent deformation of four cold recycled asphalt mixtures stabilized with asphalt emulsion and foamed asphalt. The analysis was conducted considering three flow number test procedures adapted for cold recycled mixtures: (i) ABNT NBR 16505 (method A); (ii) adaptation of the FN test for CRAM according to Kim and Lee's method (method B); (iii) 3D-Move analysis software simulation of pavement structures to address the stress magnitude for the FN test (method C). The influence of the curing process on the performance of the materials was also verified. The study used an extensive database of computed pavement responses from the four different asphalt pavement structures of the experimental section subjected to axial loading of a tandem axle using the 3D-Move pavement response analysis program. The FN results using the 3D-Move data (method C) demonstrated the good mechanical behaviour with respect to permanent deformation of the cold recycled mixtures subject to axial stress and temperature. The method proposed by Kim and Lee (method B) showed little efficacy for the analysis of the CRAMs tested in this work. The ABNT NBR 16505 method (method A), conventionally used for HMA, highlighted the influence of temperature (60°C) on the CRAM mixtures. For all FN test conditions, the curing was a preponderant factor for the performance of cold recycled asphalt mixtures and should be carefully evaluated to simulate the early stage of the mixtures in the field. It is also important to verify the influence of humidity and temperature on the permanent deformation mechanism of cold recycled asphalt mixtures. [ABSTRACT FROM AUTHOR]

The mechanical behavior of cold recycled asphalt mixtures (CRAM) is influenced by its composition and limited studies have focused on exploration of nonlinear elastic behavior of CRAM. This study evaluates the effect of the nonlinear elastic properties of a CRAM as base course material on pavement structure using KENLAYER and multilayered elastic analysis (análise elástica de múltiplas camadas, or AEMC) simulations. The results indicate that the pavement structure and the active filler type have significant impact on the deflection and stresses within the pavement structure. Besides, considering the CRAM as nonlinear elastic material reduces the horizontal strains within the CRAM layer and the vertical stresses on top of the underlying layer as compared to the linear elastic scenario. Pezo's model better characterizes the CRAM's nonlinear elastic behavior compared to other models. Even though a small correspondence was observed between model predicted strain values and in situ measured data, the present study suggests that the higher bearing capacity of the CRAM layer in the nonlinear elastic scenario can lead to an improved pavement load capacity with a thinner structure resulting in lower construction costs. [ABSTRACT FROM AUTHOR]

Cold recycled asphalt mixtures (CRAMs) are generally comprised by reclaimed asphalt pavement, virgin aggregates, bitumen stabilising agents (asphalt emulsion or foamed asphalt) and active filler (Portland cement or hydrated lime). Depending on the type and content of each mixture constituent, the CRAM may exhibit different mechanical behaviours. The aim of this study is to evaluate the influence of mixture composition on the mechanical behaviour of CRAMs. The materials used were collected during the construction of an experimental test section and were used as base course mixtures. From triaxial resilient modulus test and dynamic modulus test, it was found that the type and content of bitumen stabilising agent and active filler substantially influence the behaviour of the CRAM. From triaxial resilient modulus tests, it was observed that the mixtures with cement addition behaved similarly to cementitious materials (independent of the confining pressure), while the ones with hydrated lime resembled a granular material (dependent of the stress-state). The dynamic modulus test results indicated that the CRAMs also exhibit viscoelastic properties. Besides, the test provided a clear difference between mixtures stabilised with either asphalt emulsion or foamed asphalt. [ABSTRACT FROM AUTHOR]

This paper calls attention to important issues that have not been considered regarding linear amplitude sweep (LAS) test in previous publications: Is the relationship between the storage modulus logarithm [ logG′(ω) ] and frequency logarithm [ log(ω) ] linear in the whole range of experimental frequencies? If not, what is the influence on the fatigue life of asphalt binders calculated using the AASHTO protocol? In which range of frequencies is the relation between the storage modulus logarithm [ logG′(ω) ] and frequency logarithm [ log(ω) ] linear in the whole range of experimental frequencies? Does fatigue life follow a normal distribution? Several tests were conducted using three different types of asphalt binder [neat, crumb rubber–modified (CRM), and styrene–butadiene–styrene (SBS)–modified asphalt]. Residual analysis showed a lack of fit, indicating the inadequacy of the linear model in the whole range of experimental frequencies. This inadequacy may suggest that the protocol produces an overestimation of the binder fatigue life. In addition, a sequential search reveals that the relationship between logG′(ω) and log(ω) is linear in a limited subset of frequencies. The empirical distribution of the fatigue life is built by an extensive Monte Carlo simulation. [ABSTRACT FROM AUTHOR]

The development of the multiple stress creep and recovery (MSCR) test represented an improvement in the evaluation of the rutting susceptibility of asphalt binders. However, the creep and recovery times of the current test protocol (1 and 9 s, respectively) may not be adequate to predict performance under extremely heavy and slow traffic conditions or to allow full recovery of polymer-modified binders. Highly modified asphalt binders have been increasingly used in pavements under severe traffic and weather conditions, and, because of the higher polymer content in these materials, they can be more sensitive to variations in loading times and stresses. However, the influence of different loading times has not been investigated in detail for these materials yet. In this article, the effect of longer creep and recovery times on the MSCR test was evaluated for a highly modified asphalt binder, and the results were compared with those obtained for a neat asphalt binder and a regular styrene-butadiene-styrene (SBS) modified binder. Tests were carried out at the high performance grading temperature of each binder. and three situations were analyzed: (i) the increase of creep time to 2, 4, and 8 s; (ii) the increase of recovery time to 240 and 500 s; and (iii) the increase of both times simultaneously, to 2/18 s and 3/27 s. The highly modified binder analyzed was more susceptible to variation in creep and recovery times than the other binders and showed considerable increase in compliance due to nonlinear behavior, although there is no evidence that this was caused by the high polymer amount in this material. The results support the need of further investigation in this subject for future refinements in the MSCR test protocol and the specification criteria for slow or standing traffic, so that the susceptibility to longer loading times can be properly considered. [ABSTRACT FROM AUTHOR]

Pavement deflection is generally obtained by means of Falling Weight Deflectometer (FWD) tests, which provide an evaluation of the structural behavior of highway constructions and indicate the evolution of pavement damage through time. This paper evaluated FWD data, backcalculated moduli, and deflection basin parameters (DBPs) (radius of curvature, area, structural curvature index, base damage index, and base curvature index) to analyze the structural performance of an experimental road pavement test section with four different asphalt pavement segments. The segments had different base layer materials, and they were constituted by one flexible structure (unbound granular base layer), one semi-rigid (cement-treated base layer), one cold recycled asphalt mixture layer stabilized with asphalt emulsion (CRAM-EM), and one cold recycled asphalt mixture layer stabilized with foamed asphalt (CRAM-AF). The field monitoring had eight surveys that included the evaluation of surface distresses and deflection measurements along 3 years of study. The backcalculated moduli of the asphalt layer, base, and remaining pavement structure presented an overall good correlation with the DBPs evaluated. [ABSTRACT FROM AUTHOR]

The use of 'interlayers' that tolerate high tensile and shear strain that exists above cracks in deteriorated pavements is becoming an interesting solution to prevent reflective cracking. Recent advances in polymer technology have led to binders that can be used to produce interlayer mixtures with good mechanical properties. In this study, two polymer-modified asphalt binders were evaluated, both from the production of strain relief asphalt mixtures used as interlayers in the field. The binder characterization was presented in two groups: (i) the empirical tests required in the Brazilian specification and (ii) the rheological properties (frequency/temperature sweep and MSCR tests). Results showed that the difference in rheological properties of the asphalt binder used for strain relief asphalt mixtures did not follow the same difference obtained according to the empirical tests of the Brazilian specification. The G*/sinδ and MSCR parameters (Jnr and percentage of recovery) were able to differentiate the asphalt binders, but the MSCR parameters were more sensitive. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Saúde e Sociedade is the property of Universidade de Sao Paulo, Faculdade de Saude Publica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The water diffusion attributable to concentration gradients is among the main mechanisms of water transport into the asphalt mixture. The transport of small molecules through polymeric materials is a very complex process, and no single model provides a complete explanation because of the small molecule's complex internal structure. The objective of this study was to experimentally determine the diffusion of water in different fine aggregate mixtures (FAM) using simple gravimetric sorption measurements. For the purposes of measuring the diffusivity of water, FAMs were regarded as a representative homogenous volume of the hot-mix asphalt (HMA). Fick's second law is generally used to model diffusion driven by concentration gradients in different materials. The concept of the dual mode diffusion was investigated for FAM cylindrical samples. Although FAM samples have three components (asphalt binder, aggregates, and air voids), the dual mode was an attempt to represent the diffusion process by only two stages that occur simultaneously: (1) the water molecules are completely mobile, and (2) the water molecules are partially mobile. The combination of three asphalt binders and two aggregates selected from the Strategic Highway Research Program's (SHRP) Materials Reference Library (MRL) were evaluated at room temperature [23.9°C (75°F)] and at 37.8°C (100°F). The results show that moisture uptake and diffusivity of water through FAM is dependent on the type of aggregate and asphalt binder. At room temperature, the rank order of diffusivity and moisture uptake for the three binders was the same regardless of the type of aggregate. However, this rank order changed at higher temperatures, suggesting that at elevated temperatures different binders may be undergoing a different level of change in the free volume. [ABSTRACT FROM AUTHOR]