Virgin Binder Research Articles

Low- and intermediate-temperature behaviour of polymer-modified asphalt binders, mastics, fine aggregate matrices, and mixtures with Reclaimed Asphalt Pavement material

The long-term effects of SBS-modified binders and rejuvenators on the properties of high-RAP mixtures, especially the cracking resistance, have not been resolved. Therefore, this paper evaluates the cracking resistance of polymer-modified asphalt binders, mastics, fine aggregate matrices (FAMs) and mixtures containing RAP material and a rejuvenator. A series of laboratory tests is performed on different asphalt material scales, including a frequency sweep test; a BBR test for asphalt binders, mastics and FAM mixes; and a dynamic modulus test and the Illinois flexibility index test for asphalt mixtures. Short-term ageing and long-term ageing are also considered for different asphalt material scales. The results show that the asphalt binders and mixes containing RAP materials have similar Glover-Rowe (G-R) values and flexibility index (FI) values to those of the virgin binders and mixtures that are only subjected to short-term ageing. These results indicate that a rejuvenator can partially decrease the stiffness of the RAP material before long-term ageing; however, the cracking resistance of asphalt materials obviously decreases after long-term ageing. Asphalt materials containing RAP are more susceptible than virgin asphalt material to thermal cracking, and the rejuvenator does not improve the long-term cracking resistance of high-RAP material. The correlations between different laboratory ageing conditions for the asphalt binder, mastic, FAM and mixture are analysed. Binders subjected to PAV 20 h ageing present rheological properties equivalent to those of mixes subjected to the long-term oven ageing (LTOA) protocol for 5 d at 85°C. Binders subjected to PAV 40 h ageing present rheological properties equivalent to those of loose mixtures subjected to the LTOA protocol for 12 h at 135°C. The cracking resistance parameters of the binders, mastics and FAMs are also compared with the cracking resistance parameters of the mixture, and the results illustrate that the G-R parameters of asphalt binder, mastic and FAM are well correlated with the G-R parameter and FI parameter of the mixture. Moreover, the G-R parameter can predict the cracking performance of the asphalt mixture.

Impacts of high modulus agent and anti-rutting agent on performances of airfield asphalt pavement

Polymer modifiers have been widely used in asphalt binders to improve the high temperature performances and rutting resistances in airfield pavement. The objective of this study was to investigate the high and low temperature performances of three polymers and styrene–butadienestyrene (SBS) modified binders before and after a short-term aging procedure, and the performances of their corresponding mixtures. A series of tests were performed to determine the effects of polymers on the binders and mixtures, such as rheological properties of the modified binders and engineering performances of mixtures at high and low temperatures. The test results show that, compared with the SBS modified binders, the polymer modifiers remarkably influenced on the virgin binders, and the high temperature performance of virgin binders with a high polymer modifiers content is similar to that of the SBS modified binders, but both SBS and polymers have negative impacts on low temperature performance. In terms of asphalt mixture, the polymer can enhance the adhesion of asphalt to improve the rutting resistance, and has appreciable effect on dynamic stability and moisture stability, but only the SBS modified asphalt mixtures with polymers have better pavement performance, the polymer modified virgin asphalt mixtures are still not applicable to the airfield pavement.

Engineering and microscopic characteristics of natural rubber latex modified binders incorporating silane additive

ABSTRACT Asphalt pavement structures in countries with tropical climates are prone to experience distress, mainly due to water related damage. This study aims to evaluate the effects of ZycoTherm on the behaviour of natural rubber latex (NRL) modified asphalt binders. The morphology of the modified asphalt binders was also investigated. Two different percentages of NRL were incorporated in this study, at 3% and 6% respectively based on the weight of the asphalt binder. The modified asphalt binders (with or without ZycoTherm) were analysed based on softening point, penetration value, rotational viscosity, complex modulus, phase angle, rutting potential, and torsional recovery (TR). Subsequently, the spreadability of NRL in the asphalt binder was observed using a polarising optical microscope. The results indicate that the addition of NRL improved the performance of the asphalt binder in terms of its G*/sinδ parameter. An agglomerated network of mixed microstructures was formed in the modified asphalt binder matrix irrespective of the aging condition. Meanwhile, the morphology structure of virgin and short term-aged binders prepared with ZycoTherm indicates uniform dispersed network monographs. From the modified asphalt binder test results, it can be deduced that asphalt binders prepared with ZycoTherm exhibit superior resistance towards rutting potential.

Application of different modifiers for improvement of chemical characterization and physical-rheological parameters of reclaimed asphalt binder

Bitumen extracted from reclaimed asphalt pavement (RAP) materials is known as reclaimed asphalt binder (RAB). Many studies have been conducted to evaluate effect of the rejuvenating agents in physical-rheological and chemical properties of the RAB. The aim of this study is to evaluate the effects of other modifiers such as soft bitumen and polymer modified bitumen (PMB) in performance of RAB-containing asphalt binders in comparison with rejuvenators. In this study, changes in physical-rheological parameters and chemical structure of RAB-containing binder mixes were investigated by different modifiers including softer bitumen, rejuvenator and the waste polymer modified bitumen (WPMB). Penetration, softening point, rotational viscosity, dynamic shear rheometer (DSR), saturates, aromatics, resin and asphaltenes (SARA) fractionation, Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM) tests were performed for this purpose. Results showed that the rejuvenator and softer bitumen had the greatest effect on the improvement of the physical-rheological and chemical properties of the RAB-containing binder mixes, respectively. So that, the rejuvenator, softer bitumen and the WPMB improved fatigue resistance and chemical structure of the RAB-containing binder mixes to the level of that of the virgin binder when the RAB content was limited to 100%, 50% and 30% RAB, respectively. Moreover, results indicated that there are good correlations between chemical and physical-rheological parameters. Meanwhile, colloidal index of the binder mixes was a good indicator for estimating the superpave fatigue parameters of asphalt binders.

Assessment of the binder blending in bituminous mixtures based on the development of an innovative sustainable infrared imaging methodology

Reclaimed Asphalt (RA) is more and more used in the road recycling industry because it allows reducing the consumption in non-renewable raw materials such as virgin bitumen which comes from the petroleum distillation. As bitumen is oxidation-sensitive, some technical issues are however raised about the mix design and the binder blending between the aged and virgin binders. Particularly, the question lies on the ability of the virgin binder to mix with the RA aged binder to form a homogeneous product in defined manufacturing conditions. To answer this question, most of road studies extract with a chlorinated solvent the total bituminous binder from the asphalt mixture to characterize then oxidation or rheological properties. However, this solvent extraction technique is based on a complete binder dissolution which may alter physicochemical properties of the mixture. The objective is also to develop a solvent-free and non-destructive methodology to in situ assess the binder blending in manufactured mixtures. Using infrared imaging ATR microscopy, homogeneity is defined from spatial distributions in carbonyl functions and the methodology is developed on modeled binder mixtures. The influence of the aged binder temperature and mixing time is then investigated on the binder blending. Results show that high and close temperatures between binders are necessary but not sufficient to obtain a homogeneous mixture whereas a longer mixing time improves the binder blending. The developed chemomap methodology also allows demonstrating the influence of manufacturing process parameters on the binder blending in road asphalt mixtures. At the binder scale, the present work constitutes an interesting, rapid and economical approach to optimize the manufacturing parameters of the asphalt mixture design. The innovative infrared imaging methodology also opens perspectives to gain a better knowledge about molecular distributions and homogeneity of any hydrocarbon mixture which constitutes an essential criterion for the performance of more sustainable materials.

Infrared Spectroscopy Analysis of the Blending of Virgin and RAP Binders in Hot Recycled Asphalt Mixture with CTBN as Tracer

Abstract This study conducted an infrared analysis of a recycled asphalt mixture that contains a high percentage of reclaimed asphalt pavement (RAP) and uses carboxyl-terminated butadiene acrylonitrile (CTBN), which has an absorption peak at 2,238 cm−1, as a tracer in the virgin asphalt. The infrared spectroscopy results of the asphalt test specimens containing 1–15 wt. % of CTBN indicated that 5 wt. % virgin asphalt is most appropriate. Infrared spectroscopy was performed on specimens of recycled asphalt mixture that contained 45 % RAP, and a statistical analysis was performed on the results. The results indicated that the virgin and RAP asphalt binders were not completely mixed, as is typically assumed. The blending degree of the virgin binder and RAP binder in the outer layer of the RAP aggregate particles was higher than that in the inner layer. The blending degree is inhomogeneous and has a three-dimensional hierarchy that depends on the depth and location of the asphalt mastic membrane over the aggregate.

Comparison of Chemical and Microstructural Properties of Virgin and Reclaimed Asphalt Pavement Binders and Their Saturate, Aromatic, Resin, and Asphaltene Fractions

The chemical properties and microstructural features of two straight-run virgin asphalt binders (PG 52-34 and 58-28) and a reclaimed asphalt pavement (RAP) binder as well as their corresponding saturate, aromatic, resin, and asphaltene (SARA) fractions were examined. Additionally, the properties of the binders with laboratory and plant mixture blending were also observed. Examining the corresponding SARA fractions revealed that the increases in the carbonyl index of RAP relative to the virgin binders were mainly found in the resin and asphaltene fractions, while the increase in the sulfoxide index is mainly found in the asphaltene fraction. The chemical properties were examined using Fourier transform infrared spectrometry. The RAP binder showed a significant increase in the indices of the carbonyl (IC═O) and sulfoxide (IS═O) functional groups compared to the virgin binders. The plant blended binders showed that additional silo storage at the plant increases the carbonyl index. The microstructural feature...

A Method to Quantify Reclaimed Asphalt Pavement Binder Availability (Effective RAP Binder) in Recycled Asphalt Mixes

State highway agencies recognize the environmental and economic benefits of utilizing reclaimed asphalt pavement (RAP) in asphalt mixes. Currently, most agencies assume all of the RAP binder content is available for mix design purposes. However, the percentage of available or effective RAP binder in the asphalt mix is usually less than 100% and not quantified, which could yield dry asphalt mix with a high air void content, potentially leading to premature distress. The term available or effective RAP binder refers to the binder that is released from the RAP, becomes fluid, and blends with virgin binder under typical mixing temperatures. This study proposes a method to estimate the RAP binder availability factor (BAF) which can be used to adjust the virgin binder content in RAP mixes to ensure that the mix design optimum binder content is achieved. In this method, asphalt mixes were prepared so that, after mixing and conditioning, the RAP material can be separated from the virgin aggregate, which allows for a thorough evaluation of the extent of RAP binder availability in the asphalt mix. This method was verified in a preliminary experiment and then used to estimate the BAF of RAP from different sources, and a correlation between RAP BAF and the high temperature performance grade (PG) of each RAP source was established. Finally, factors affecting the RAP BAF were also evaluated such as mixing temperature, conditioning period, the use of recycling agents (or rejuvenators), and the method of adding the recycling agent to the mix.

Performance Characteristics of Asphalt Binders containing Sodium-Alginate Hollow Fibers and Recycled Materials

Self-healing products such as hollow-fibers filled with an asphalt rejuvenator present an emerging technology that would enhance an asphalt mixture’s resistance to cracking damage. The objective of this study was to evaluate the rejuvenating efficiency of sodium-alginate fibers containing a rejuvenator product using asphalt binder blends containing extracted binder from recycled materials. The effects of adding extracted binder from recycled materials and sodium-alginate fibers on asphalt binder blends were evaluated by conducting a series of chemical and binder tests. HP-GPC and FTIR test results showed that the addition of fibers in blends containing recycled materials resulted in an increase in the HMW/LMW ratios. Some of the added polymeric fibers are thought to have increased the HMW fraction, thus leading to increase in the HMW/LMW ratio. The increase of the HMW fraction suggests that some of the fibers, which are polymers, caused the increase in the HMW/LMW ratios. MSCR test results showed that a binder blend with extracted binder from recycled materials and sodium-alginate fibers would have less rutting susceptibility than a conventional virgin binder would.

An investigation on the relationship between FTIR indices and surface free energy of RAP binders

The performance of RAP bituminous mixes depends on the properties of the binder in the RAP material. Surface free energy of a binder, which is a fundamental property of materials, can be used to explain moisture damage, rutting, fracture and healing potential of bituminous mixes. Similarly, different chemical properties of binders can be used to estimate their mechanical properties. The relationship between the surface free energy of the binders and their chemical composition (in terms of functional groups) has been investigated in this study. For this purpose, blends of a virgin binder (VG30 grade) and the RAP binder extracted from a RAP material were prepared. Surface free energy of the binder blends was measured using sessile drop technique. The chemical composition of the blends was obtained using Fourier transform infrared spectroscopy (FTIR) analysis. Different ageing and healing indices were calculated from FIR analysis. Different ageing indices are found to have good correlation with surface free energy and its components. No significant relationship could be observed between healing indices and surface free energy of the binder blends. The correlations presented in the study between different indices estimated from FTIR analysis and the surface free energy components obtained by sessile drop method will be useful in furthering the understanding of the characteristics of binders, especially RAP binders.

Development of Dynamic Modulus–Based Mixture Blending Chart for Asphalt Mixtures with Reclaimed Asphalt Pavement

AbstractThe current practice of using the binder blending chart to select a performance grade of the virgin binder may not be applicable for mixtures containing more than 25% reclaimed asphalt pave...

Evaluation of crumb rubber modification and short-term aging on the rutting performance of bioasphalt

In this study, the high temperature performances of ten combinations of bioasphalt and crumb rubber particles were evaluated by DSR and MSCR tests. Testing results indicated that short-term aging and crumb rubber modification increased the complex shear modulus and reduced the phase angle. In addition, the crumb rubber modified bioasphalt significantly reduced the unrecovered creep compliance and increased the percentage recovery. It can be concluded that the bioasphalt exhibited higher rutting resistance than the virgin binder and it can be used like traditional binder in term of rutting performance. In addition, crumb rubber greatly increased the rutting performance of bioasphalt.

Comparison between bitumen aged in laboratory and recovered from HMA and WMA lab mixtures

Oxidative ageing is an important phenomenon affecting asphalt concrete. Currently, binder short-term ageing, occurring during mixture production and laying, is simulated worldwide through rolling thin film oven test (RTFOT), which was developed assuming that the mixture is produced at conventional hot mix asphalt (HMA) temperatures around 160 °C. However, since ageing is strongly influenced by temperature, lower production temperatures imply less material ageing so that the introduction of warm mix asphalt (WMA) technologies could potentially require some adjustments in the ageing simulation procedures. This study aims at determining which RTFOT temperature simulates WMA short-term ageing more closely. To this end, the chemical and the mechanical characteristics of one type of bitumen, recovered from two asphalt mixtures (WMA and HMA) prepared and short-term aged in laboratory, were compared to those of the same virgin binder short-term aged in laboratory with RTFOT at different temperatures (123 °C and 163 °C). Both conventional and rheological tests show higher ageing levels for the binder recovered from HMA with respect to the binder aged with RTFOT at 163 °C, whereas the binder recovered from WMA generally provides an ageing level lower than the binder aged with RTFOT at 163 °C. These results are also confirmed by the chemical analysis using FTIR which indicate higher oxidation levels for the hot mix process compared to the warm mix. These preliminary results confirm that it is necessary to identify an appropriate ageing temperature for the short-term ageing simulation of WMAs with RTFOT.

A solvent free method to characterize the effect of recycled asphalt shingles on virgin asphalt binder

Abstract: The current design guideline of asphalt mixtures containing recycled asphalt shingles requires accurate characterization of shingle binder and its effect on virgin binder. This characterization employs hazardous solvents to extract and recover the shingle binder prior to testing. The objective of this study was to determine whether an enhanced mortar characterization method, which eliminates the need for chemical solvents by testing mortars composed of virgin binder and fine shingle fraction, can be used to predict the rheological properties of shingle binder blends with virgin binder. Superpave binder tests (dynamic shear rheometer and bending beam rheometer) were performed on six mortars combinations of two shingle sources and three virgin binders. The change in true grade of virgin binders caused by shingle binder was quantified by using a parameter named grade change rate (°C/%shingle binder). True grades of shingle binder blends predicted by grade change rate were compared to values measured on manually-prepared binder blends at multiple binder replacement rates of 15%, 30% and 100%. High and low temperature grades measured on blended binders were successfully predicted by the enhanced mortar approach. Moreover, the critical low-temperature parameter (delta Tc), which has been used to describe the embrittlement introduced by shingle binder, was also accurately predicted by using the stiffness-based and relaxation-based grade change rate. In conclusion, the enhanced mortar approach not only provides accurate estimates of the rheological properties of binder blends, but also eliminates the exposure to hazardous solvents currently employed during the extraction and recovery of the recycled binder.

Evaluation of fatigue behavior of high reclaimed asphalt binder mixes modified with rejuvenator and softer bitumen

Reclaimed asphalt binder (RAB) is aged bitumen extracted from milling of deteriorated asphalt pavement materials. The objective of this study was to analyze the effect of a new rejuvenator as well as softer bitumen on regenerating fatigue characteristics of the RAB-containing binder mixes as compared to the virgin (control) binder. In this study, firstly fatigue resistance of binder mixes containing different percentages of RAB was evaluated by temperature sweep, linear amplitude sweep (LAS) and time sweep tests. Secondly, correlations between different fatigue test methods were established. Results showed that use of rejuvenating agent improved fatigue performance of binder mixes containing up to 100% RAB to the level of that of the control binder. On the other hand, the softer bitumen improved fatigue behavior of asphalt binders containing up to 50% RAB in comparison with the control binder. Based on the obtained results, the current fatigue Superpave criteria (G∗.sinδ) correlated well with parameter B (LAS parameter). In addition, the fatigue lives obtained from the LAS test have good correlation with strains at peak stress in stress-strain curve. Furthermore, Results indicated that there was a fair agreement between fatigue lives obtained using the LAS and the time sweep tests.

Effect of Partial Blending on High Content Reclaimed Asphalt Pavement (RAP) Mix Design and Mixture Properties

Reclaimed Asphalt Pavement (RAP) material, especially high RAP content mixture, is nowadays receiving more interest in asphalt pavement construction. When determining the optimum asphalt content (OAC) in RAP mixture design, RAP partial blending is sometimes neglected and total blending is assumed. Such an assumption influences the virgin binder content determination and can contribute to the poor fatigue and cracking performance of high RAP pavement in the field. This paper studied the impact of RAP partial blending on the OAC of mixtures with varied RAP content up to 40%. A Laboratory Hamburg Wheel Tracking Test, an IDT fracture test, and an SCB test were performed on mixtures designed by different methods to evaluate rutting and cracking performance. In particular, a partial blending design method was proposed to improve the mixture performance by adjusting the virgin binder content through the RAP blending ratio. It was found that the optimum virgin binder content decreased as the RAP content increased; the Superpave volumetric method required the lowest OAC while the partial blending method required the highest OAC. The rutting performance of the RAP mixtures considering partial blending was slightly lower than other mixtures. However, all RAP mixtures showed better rutting resistance than virgin mixtures. The cracking performance of the high RAP mixtures was significantly improved if the partial blending effect was considered in the design.

A Mechanical Approach to Quantify Blending of Aged Binder from Recycled Materials in New Hot Mix Asphalt Mixtures

In the paving industry, there is increased interest in using recycled materials like recycled asphalt shingles (RAS) and reclaimed asphalt pavements (RAP) due to the valuable asphalt binder contained within them. The major concern with using these materials is that the binder they contain is highly aged, which could lead to reduced mixture durability. Therefore, a method is needed to quantify the extent to which the aged binders from these materials blend with virgin binder when producing mixtures in order to understand better their effects on mixture performance. In this study, a new approach to quantify the amount of blending that occurs between aged RAS and RAP binders and a virgin binder was developed. Asphalt binders were extracted and recovered from RAS and RAP stockpiles and blended with a PG64-28 virgin binder in varying proportions. The master curves of these mixtures were constructed at 20°C. Asphalt mixtures containing different proportions of the same RAS and RAP stockpiles were then designed and the dynamic moduli of the mixtures were measured to construct mixture master curves at 20°C. The binder master curves for each blending proportion were then substituted into a locally calibrated Hirsch model to predict the mixture master curves. Comparison of the measured and predicted mixture master curves suggested that the aged binder from RAS and RAP blends with the virgin binder less than 40% and 60%, respectively. Cracking tests were also conducted to validate the proposed degrees of blending from a mixture mechanical performance point of view.

Effect of rejuvenator addition location in plant on mechanical and chemical properties of RAP binder

ABSTRACTRejuvenators can restore the reclaimed asphalt pavement (RAP) binder for another service period. To achieve this, homogeneous distribution of rejuvenator and good diffusion into reclaimed asphalt binder film has to be ensured. Ten potential rejuvenator addition locations are summarised, and two most promising are compared in full-scale study: spraying of rejuvenator on cold reclaimed asphalt on the feeding belt before heating versus addition of rejuvenator to hot reclaimed asphalt in mixer. RAP samples were collected at various places in the production line to evaluate the effect of rejuvenator addition location on softening point, penetration, rheology and chemical composition of extracted binder. The results revealed that passing through the extreme temperatures in the RAP heating drum does not sacrifice mechanical performance or increase chemical ageing of the rejuvenated binder. A benefit of early rejuvenator addition is that it provides a longer residing time of rejuvenator on the binder and thus potentially may allow higher binder activation and better blending of RAP binder with rejuvenator and virgin binder. This has to be evaluated through mixture tests.

Laboratory Observation and Evaluation of Asphalt Blends of Reclaimed Asphalt Pavement Binder with Virgin Binder using SEM/EDS

In this paper, microscopic technique tests were carried out to observe and evaluate the degree of blending between reclaimed asphalt pavement (RAP) binder and virgin binder in hot mixed asphalt mixture. To this end, titanium dioxide (TiO2) was selected as a tracer to tag virgin binder. Scanning electron microscope/energy dispersive spectrometer (SEM/EDS) experiments were conducted on compacted recycled asphalt mixtures and virgin asphalt mixtures. The element mass ratio of titanium over sulfur (Ti:S) was proposed as an quantitative indicator of blending ratio to accurately evaluate the degree of partial blending between RAP and virgin binders. The SEM/EDS images visually displayed the partial blending in high RAP mixtures. Different partial blending patterns were observed under different handling processes. The results of EDS tests indicated that with the increase of the RAP content, the blending degree of virgin and aged binder decreased rapidly, and the homogeneity of blended binder became weakened. In addition, aging process and recycling agent could improve the efficiency of RAP binder as it is blended with virgin one, and it should be noted that the inter-diffusion of old and new binders need enough time. This methodology provides a systemic approach to determine the degree of binder blending in RAP mixture.

Nonrecoverable Behavior of Polymer Modified and Reclaimed Asphalt Pavement Modified Binder under Different Multiple Stress Creep Recovery Tests

Chinese transportation agencies usually use the styrene–butadiene–styrene (SBS) modified binder and rejuvenators when applying higher reclaimed asphalt pavement (RAP) in surface courses. However, the rutting performance of RAP binder containing SBS binder and rejuvenators remains a problem. In order to better evaluate the rutting performance of asphalt binder, recently, a multiple stress creep recovery (MSCR) test (AASHTO T 350) was proposed and approved. This paper critically reviewed the AASHTO T 350 test method and AASHTO M 332 specification by carrying out a series of MSCR tests. A total of 18 types of SBS modified and modified RAP binders were tested. The effect of a rejuvenator on the rutting performance was analyzed. Three different MSCR tests were conducted considering different stress levels and creep recovery cycles, including test conditions of AASHTO T 350. The results indicated that AASHTO T 350 can grade the binders based on the nonrecoverable creep compliance and stress sensitivity parameters. Since SBS modified binders always have lower Jnr values at lower stress levels, higher stress levels and more creep recovery cycles are recommended to better evaluate the rutting resistance of binder. The addition of RAP decreased the Jnr values while the addition of rejuvenator had the opposite effect. The added SBS modified binder and rejuvenator have a negligible effect on the percentage recovery. It is suggested that a suitable rejuvenator dosage and virgin binder type should be chosen carefully to guarantee the rutting performance of RAP binder.