Search

Asphalt is one of the most common materials in the pavement industry and faces thermal cracks, fatigue cracks, and rutting mechanical defects due to its temperature-dependent behavior. Polymer-modified asphalt (PMA) binders are being considered to reduce the impact of the mentioned. This study reports the laboratory assessment of asphalt binder containing petroleum resin (PE). PG 64-22 was used as a base binder and modified with PE modifiers at different content (0, 5, 10, 15 and 20%, by the weight of the binder). The PE-modified binders were artificially short-term and long-term aged using rolling thin film oven (RTFO) and pressure aging vessel (PAV), respectively. The physical and rheological properties of the binders were evaluated using rotational viscometer (RV), dynamic shear rheometer (DSR) and bending beam rheometer (BBR). Furthermore, multiple stress recovery (MSCR) test was performed to investigate the percent recovery of the PE-modified binder. The results of this study indicated that (1) the addition of PE modifier increases the binder viscosity, (2) PE modifier has the potential to improve the rutting resistance of the binders, (3) PE modifier is observed to have increased the %rec of the binders, and (4) PE modifier is found to have negative effect on the fatigue and low-temperature cracking resistance of the binders.

In between thermal-oxidative (heat and oxygen) and photo-oxidative (ultraviolet irradiation and oxygen) aging process of bitumen, photo-oxidative aging mainly depends on the optical properties of the asphalt binder. The higher the reflection (or the lower the absorption of the binders), the better the pavement serviceability. The literature review indicates that there is limited research conducted on the optical properties of the binder with wax additives. In this paper, the optical properties of commonly used binders (PG 64-22, Rubber modified binder, and SBS modified binder) containing wax additives (LEADCAP and Sasobit) were investigated using UV-Vis spectrometer. The result of this study showed that (1) the addition of modifiers (crumb rubber and SBS) with the base binder slightly increases the absorption of the binder; (2) the binder types and aging level have significant contribution on optical properties; (3) in general, the aged binders were observed to have higher reflectivity compared to the unaged binders; and (4) the addition of wax additives is observed to have a significant effect on the optical properties.

The study presents an experimental evaluation of performance properties of two different production processes of warm rubberized binder. Two types of rubberized binder were produced through dry process and wet process and two of the available wax additives were added into the rubberized binders (i.e., LEADCAP and Sasobit). Rubberized binders with wax additives were artificially short-term and long-term aged using the rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were carried out on the binders through the rotational viscometer (RV), the dynamic shear rheometer (DSR), and the bending beam rheometer (BBR). In general, the results of this study indicated that (1) the viscosity properties have been found to be similar between dry and wet processes, (2) the rubberized binders manufactured by wet process were observed to have the higher rutting resistance than those by dry process, (3) the wet process resulted in better performance in the fatigue cracking test than the dry process, and (4) the blending method was found to have little influence of stiffness properties. Keywords: Rubberized binder, Dry process, Wet process, Viscosity, Rutting, Fatigue cracking

The crumb rubber modified (CRM) binder was evaluated considering the general operating temperatures of high, intermediate, and low temperatures. CRM binders were produced with four different contents (0, 5, 10, and 15%) using the base asphalt binder (PG64-22). Then, they were artificially aged by a rolling thin-film oven (RTFO) and pressure aging vessel (PAV). Superpave binder tests using a rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR) was applied to characterize the performance of the original and aged binders. Multiple stress creep recovery (MSCR) tests were also performed for deeper rutting characterization. The results of this study are as follows: (1) the presence of PR increases the binder viscosity, (2) the integration of CRM greatly improved the rutting resistance of the binder, and it was found that PR also improved the rutting characteristics, and (3) it is observed that PR is detrimental to the cracking properties of CRM binders.

The study presents an experimental evaluation of performance properties of rubberized polymer modified asphalt (PMA) binders to compare two types of ground tire rubber (GTR): normal and treated. Styrene-butadiene-styrene (SBS) modified asphalt binder (PG 76-22) is used as a base PMA binder to produce rubberized PMA binder. The rubberized PMA binders were artificially short-term and long-term aged using the rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were carried out on the binders through the rotational viscometer (RV), the dynamic shear rheometer (DSR), and the bending beam rheometer (BBR). Additionally, the multiple stress creep recovery (MSCR) test was accomplished to investigate the rutting properties. In general, the results of this study indicated that (1) the viscosity properties are found to be dependent on GTR types and amounts, as expected, (2) the rutting properties of PMA binders are expected to be improved through the use of GTR, (3) the addition of GTR is observed to be effective in improving the cracking performances of PMA binder, and (4) in general, the PMA binders with treated GTR showed better performance properties, compared to the PMA binders with normal GTR.

In this study, thermoplastic polyurethane (TPU) and styrene-isoprene-styrene (SIS) were utilized to enhance asphalt binder properties. Superpave asphalt binder tests and multiple stress creep recovery (MSCR) were conducted to evaluate the physical and rheological performance (viscosity, rutting, and cracking properties) of the asphalt binders before and after short-term aging and after the long-term aging process. The results showed that (i) TPU has a positive effect on workability, including the mixing and compaction processes, which was evident from the reduced binder viscosity, (ii) asphalt binders with TPU and SIS showed better rutting resistance compared to the SIS binders without TPU, (iii) the cracking resistance of asphalt binders was found to be improved significantly with the addition of TPU, and (iv) TPU has the potential to be considered as a sustainable polymer modifier for producing bearable asphalt binders by improving rutting and crack resistance without increasing the melting temperature of the asphalt binders.

The demand of strong polymer modified asphalt (PMA) binder is growing due to the increase of traffic and necessity to reduce the early deterioration of pavement due to cracking. In this study, physical and rheological properties of asphalt binder modified with a potential new polymer named styrene-isoprene-styrene (SIS) were investigated through the rotational viscometer (RV), the dynamic shear rheometer (DSR), and the bending beam rheometer (BBR). In order to have a depth understanding on the SIS binder at micro level, micro-morphological observations were conducted using optical microscopy, atomic force microscopy (AFM), environmental scanning electron microscopy (ESEM), and ellipsometry. The result of this study showed that (1) the addition of SIS modifiers increased the viscosity and had a positive effect on rutting resistance of the binder; (2) the addition of 5%, 10%, 15%, and 20% SIS content increased the rutting resistance by 600%, 3000%, 5600%, and 6400%, respectively; (3) the higher the SIS content, the better the cracking resistance of the binder and it is observed to have improved the stiffness by 26% and 51% with the addition of 5% and 10% content of SIS, respectively; (4) AFM images showed the significant correlation between the stiffness and microstructural properties of the binder; (5) the dominance of new oval phase over network structure was evident in ESEM images and observed to have significant correlation to the high stiffness of the binder; and (6) with the percentage increase of SIS modifier, the binder is found to have higher absorption at UV wavelength.

Physical and rheological properties of asphalt binder modified with Styrene-Isoprene-Styrene (SIS) were investigated through the rotational viscometer (RV), the dynamic shear rheometer (DSR), and the bending beam rheometer (BBR). In order to have a depth understanding on the SIS binder at micro level, morphological observations were conducted using optical microscopy. The result of this study showed that (1) the addition of SIS modifiers increases the viscosity and has positive effect on rutting resistance of the binder; (2) the higher the SIS content, the better the cracking resistance of the binder.

Performance properties of polymer modified asphalt (PMA) binders with Styrene-isoprene-styrene (SIS), petroleum resin (PE), and ground tire rubber (GTR) were evaluated at high, intermediate, and low temperatures. Styrene-butadiene-styrene (SBS) PMA binder of PG 76-22 was used as a base binder. The PG76 SBS PMA binders were blended with SIS, PE, and three different GTR contents (0, 5, and 10%). The binders were artificially short-term and long-term aged using rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were conducted on the binders through rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR). Multiple stress creep recovery (MSCR) test was also performed to evaluate the rutting property. The results of this study indicated that (1) the addition of PE can decrease the binder viscosity, (2) although the incorporation of GTR and SIS significantly improve the rutting resistance of the binders, the effect of PE is found to be insignificant, (3) PE is observed to have positive effect on the cracking properties of control PG76 SBS PMA binder blended with SIS and GTR, and (4) incorporation of PE might be an useful option to improve the workability of high performance PMA binder in lieu with maintaining good rutting and cracking resistance.

The effect of blending time on the viscosity of rubberized binder with wax additives was evaluated through the rotational viscometer at 135 °C and 120 °C. The 10% crumb rubber modified (CRM) binders were produced with four blending periods (1, 30, 60, and 90 min), and then mixed with two commercial wax additives. Three different testing periods of 30, 120, and 240 min were applied to the rotational viscosity test to evaluate the viscous properties depending on the blending time. From the results, it is concluded that (1) the addition of wax additives can significantly decreases the binder viscosity, (2) all the viscosity values of CRM binders are observed to increase after certain time, regardless of the addition of wax additives, (3) CRM mixes with wax additives are expected to have a better haul management, based on the less viscosity change, (4) in general, the effect of blending time at 177 °C on the viscous property of CRM binder is found to be insignificant. Keywords: CRM, Wax additive, Blending time, Rotational viscosity

This paper reviews techniques and analyses performed on microstructure of the asphalt binder and mixture using Scanning Electron Microscopy (SEM) and Environmental Scanning Electron Microscopy (ESEM). An extensive insight on the SEM and ESEM principle and techniques, different sample preparation methods and instrument techniques for capturing the micromorphology of the binder and mixture have been presented. The difference between SEM and ESEM in terms of challenges and limitation regarding the analysis of bitumen has been explained. In depth discussions on the surface properties, fracture morphology, network structure, dispersion, phase morphology, structural and strength mechanism, adhesion, deform mechanism and the formation of fibril structures of asphalt binder and mixture have been provided. Recommendations and useful techniques are outlined for future research to obtain any correlation between the microstructure and physical/rheological properties of the asphalt binder/mixture.

This paper addresses the laboratory experiment of performance properties of recycled CRM binders containing artificially aged CRM binders with wax additives. The warm CRM binders were produced using two wax additives (LEADCAP and Sasobit) and then short-term and long-term aged using the rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. The recycled CRM binders were aged through the RTFO and PAV procedures. A set of Superpave binder tests were carried out on the binders through the rotational viscometer, the dynamic shear rheometer (DSR), and the bending beam rheometer (BBR). In general, the results of this study indicated that (1) the addition of long-term aged (LTA) CRM binder can significantly increase the viscosity of the recycled CRM binders as expected, (2) the wax additives in recycled CRM binders were still effective to improve the viscosity and rutting properties even after experiencing the aging process, (3) the CRM binders containing wax additives showed the higher rutting resistance compared to the control CRM binders, (4) the recycled CRM binder containing wax additives was found to have less resistance to fatigue and low temperature cracking, (5) wax warm additives into the recycled CRM binders seemed to have a significant role for cracking properties, based upon their substantial amount. Keywords: CRM binder, Wax additives, Rotational viscosity, Recycling, Rutting

Gas metal arc (GMA) brazing was employed to join hot-dip galvanized steel sheets (GI) in lap joint configuration using CuSi3 filler. The effects of brazing current and speed on the joint characteristics such as bead geometry, microstructure, weldability, microhardness and tensile shear strength were studied. The bead geometry was assessed by examining the bead shape, width, contact angle, penetration width and depth of the fused zone. The microstructural investigations were performed using scanning electron microscopy (SEM), and composition was determined using energy dispersive spectroscopy (EDS). The formation of Fe-Si phases was noticed in the bead which was found to increase with brazing current and brazing speed. The pores were nucleated in GI lap joint at highest current 80 A and lower brazing speeds 60–70 cm/min. The bead shape and size, joint strength, weldability were found best at a combination of 70 A and 80 cm/min which could be attributed to a uniform distribution of Fe5Si3(Cu) in the bead. It is suggested that for a pore-free bead structure, the heat input should lie in the range of 58.5–93.6 J/mm for the arc brazing of GI sheets.

Warm mix asphalt (WMA) has been used in pavement industry since 2000. While there were several studies related to WMA performances, recycling characteristics of WMA binders are not investigated in detail. Rudimentary performances of recycled binder with wax warm additives were evaluated through a series of Superpave binder tests. WMA binders were produced using two wax additives of LEADCAP and Sasobit, and then artificially short-term and long-term aged using the rolling thin film oven and pressure ageing vessel procedures. The control binder was mixed with aged binders at two recycling contents of 15% and 30%. Superpave binder tests were carried out on the binders through the rotational viscometer, the dynamic shear rheometer, and the bending beam rheometer. In general, the results of this study indicated that (1) the addition of warm asphalt additives considerably improves the high-temperature properties of control and recycled binders, (2) the recycling contents played a significant role in determinati...

In this study, performance properties of polymer-modified asphalt (PMA) binders are evaluated depending on ground tire rubber (GTR) and styrene-isoprene-styrene (SIS). Styrene-butadiene-styrene- (SBS-) modified asphalt binder of PG 76-22 is used as a base binder to manufacture the rubberized PMA binder. The rubberized PMA binders are blended using SIS modifier. The binders were artificially short-term and long-term aged using rolling thin-film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were conducted on the binders through rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR). Furthermore, multiple stress creep recovery (MSCR) test and atomic force microscopy (AFM) microstructural analysis were performed. The results of this study indicated that (1) the viscosity properties seem to be highly dependent on GTR and SIS contents, (2) the addition of SIS is observed to have a significant effect on improving the rutting performances of rubberized PMA binders, (3) the cracking properties are considered to be improved significantly through SIS modification, and (4) in general, the rubberized PMA binders with SIS showed the best performance for rutting and cracking among all the binders used in this study.

The engineering properties of asphalt binders depend on the types and amounts of additives. However, measuring engineering properties is time-consuming, requires technical expertise, specialized equipment, and effort. This study develops a deep regression model for predicting the engineering property of asphalt binders based on analysis of atomic force microscopy (AFM) image analysis to test the feasibility of replacing traditional measuring estimate techniques. The base asphalt binder PG 64-22 and styrene&ndash, isoprene&ndash, styrene (SIS) modifier were blended with four different polymer additive contents (0%, 5%, 10%, and 15%) and then tested with a dynamic shear rheometer (DSR) to evaluate the rheological data, which indicate the rutting properties of the asphalt binders. Different deep regression models are trained for predicting engineering property using AFM images of SIS binders. The mean absolute percentage error is decisive for the selection of the best deep regression architecture. This study&rsquo, s results indicate the deep regression architecture is found to be effective in predicting the G*/sin &delta, value after the training and validation process. The deep regression model can be an alternative way to measure the asphalt binder&rsquo, s engineering property quickly. This study would encourage applying a deep regression model for predicting the engineering properties of the asphalt binder.

PURPOSES : The performance properties (indirect tensile strength, rutting resistance, and resilient modulus) of recycled aged CRM mixtures and their correlation with Superpave binder properties (viscosity, high failure temperature, G*sinδ, and stiffness) were investigated. METHODS: A series of Superpave binder tests was performed by using a rotational viscometer, DSR, and BBR to evaluate the performance properties. In addition, the CRM mixes were artificially aged through accelerated aging processes, and their properties were evaluated. The correlation between the properties of recycled aged CRM binders and the engineering properties of recycled aged CRM mixtures was experimentally determined. RESULTS : The rut depth values decreased and the ITS values increased with increasing high failure temperature. In general, the resilient modulus properties seemed to be poorly correlated with the high-temperature values, regardless of the aggregate source. CONCLUSIONS: The recycled aged CRM binders and mixtures can lead to satisfactory performance, and the properties of these binders are strongly correlated with the engineering properties of the mixtures.

Cracking properties of crumb rubber modified (CRM) asphalt binders containing wax additive were evaluated through the dynamic shear rheometer test at 25 °C and the bending beam rheometer test at −12 °C. The CRM binders were produced using three rubber contents of 5%, 10%, and 15% by the binder weight, and then mixed with two commercial wax additives of LEADCAP and Sasobit. Three states of original, short-term and long-term aging were applied to evaluate the cracking properties using rolling thin film oven and pressure aging vessel. From the results, it is concluded that (1) the increase of rubber content significantly decreases the binder stiffness at lower temperature, (2) the higher the rubber content, the lower the G*sinδ of CRM binders with wax additives at intermediate temperature, and (3) the rubber can be used to improve the cracking resistance of asphalt binders modified with wax.

The study presents an experimental evaluation of the rheological properties of control and polymer modified asphalt (PMA) binders containing wax additives and a comprehensive comparison between these two binder types. The control and PMA binders with the additives were produced using two of the available warm asphalt processes (i.e., LEADCAP and Sasobit) and then artificially short-term and long-term aged using the rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were carried out on the binders through the rotational viscometer (RV), the dynamic shear rheometer (DSR), and the bending beam rheometer (BBR). In general the results of this study indicated that (1) the addition of wax additives into the control and PMA binders decreases the viscosity, as expected; (2) the reduction rate of viscosity was quite similar for both the binders with wax additives; (3) the percentage increase of rutting resistance due to the additives was much higher for the control binder, compared to the PMA binder; (4) both the control and PMA binders showed the similar trends in terms of fatigue cracking and low temperature cracking behavior after the addition of wax additives. Keywords: PMA, Wax additives, Viscosity, Rutting, Fatigue cracking, Stiffness

To successfully process concrete, it is necessary to predict and control its flow behavior. However, the workability of concrete is not completely measured or specified by current standard tests. Furthermore, it is only with a clear picture of cement hydration and setting that full prediction and control of concrete performance can be generalized. In order to investigate the rheological properties of blended cement pastes, a rotational viscometer (RV) was used to determine the flow characteristics of ordinary and blended pastes to provide assurance that it can be pumped and handled. Additionally, a dynamic shear rheometer (DSR) was used to characterize both the viscous and elastic components of pastes. Ordinary Portland cement paste and blended pastes (slag, fly ash, and silica fume) were investigated in this study. The stress and strain of the blended specimens were measured by the DSR, which characterizes both viscous and elastic behaviors by measuring the complex shear modulus (the ratio of total shear stress to total shear strain) and phase angle (an indicator of the relative amounts of recoverable and nonrecoverable deformation) of materials. Cement pastes generally exhibit different rheological behaviors with respect to age, mineral admixture type, and cement replacement level.

In this paper, the micromorphology of asphalt binders with wax warm additives is investigated by atomic force microscopy (AFM) and optical microscopy before and after aging. Performance gra...

Rheological properties of crumb rubber modified (CRM) binder with wax warm additive were evaluated at high, intermediate and low temperatures. CRM binders were blended using two wax additives and then artificially short-term and long-term aged using the rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were carried out on the binders through the rotational viscometer (RV), the dynamic shear rheometer (DSR), and the bending beam rheometer (BBR). In general, the results of this study indicated that (1) the wax additives into asphalt binder obviously decrease the viscosity; (2) the addition of wax additives is effective to improve the rheological properties of asphalt binder in high-temperature; (3) the use of crumb rubber positively influenced rutting and cracking properties; (4) the addition of LEADCAP showed the improvement of thermal cracking resistance in low-temperature.

The phase separation between polymer additives and virgin asphalt binders during hot storage is an important issue in the asphalt industry. Traditionally, it has been customary to evaluate the degree of phase separations in polymerized asphalts by laboratory testing, such as the cigar tube test (CTB). However, the test circumstances, temperature, and storage time vary depending on different standards used in many countries. Based on a comprehensive literature review, the range of temperatures and oven storage times were selected to be 140–180°C and 2–7 days, respectively. The phase separation of 11 storage stability conditions selected from 12 different places using crumb rubber modified asphalts (CRMAs) were compared and evaluated in this study. The CRMAs produced in the laboratory were made with PG 64-22 virgin binder and ambient crumb rubber with various concentrations (10, 15, and 20% by weight of virgin binder). The CTB was used as the storage stability test method, and percent separation was...

This research investigates the oxidative aging levels of polymer-modified asphalt (PMA) mixes using gel permeable chromatography (GPC), which can help to simplify the quantification of asphalt aging. Warm-mix asphalt (WMA) technologies, namely, Aspha-min and Sasobit, were especially adapted to the PMA mixes for the purpose of the aging reduction. A short-term oven aging (STOA) procedure was used under 135 and 154°C for 2 and 4 h, respectively, to simulate the asphalt binders aged during the field operations (i.e., production, hauling, and paving construction). The aging levels were analyzed based on large molecular size (LMS) of the binders extracted from the mixes. A rolling thin-film oven (RTFO) method was also utilized using PMA binders containing those WMA additives under 135 and 163°C for 85 minutes for comparison purposes. The results showed that (1) aging time and temperature were important parameters to influence the aging; (2) the STOA procedure had a higher aging level than the RTFO meth...

The objective of the study in this paper was to investigate the influence of warm mix additives on polymer-modified asphalt (PMA) mixtures in regards to engineering properties. Twelve PMA mixtures (four control PMA mixtures and eight warm PMA mixtures) were prepared by using two additives (Aspha-min and Sasobit), two binder sources, and two aggregate sources. An evaluation of all PMA mixtures included the following testing procedures: tensile strength ratio, asphalt pavement analyzer, resilient modulus, and indirect tensile strength after longterm oven aging. The results from this research generally indicated that (1) the PMA mixtures containing the additives can satisfy the current Superpave mixture requirements (including moisture susceptibility and rutting resistance) and (2) no statistical differences existed between the control and the warm PMA mixtures for the properties that the authors evaluated in this study, suggesting using of WMA technologies in PMA mixes has no negative effect on the mixture’s engineering properties.

This paper presents the results of an experimental programme to investigate the effects of the concrete mix parameters on the mechanical properties of aerated lightweight aggregate concrete (ALAC). The compressive strength, modulus of elasticity, split tensile strength and Poisson ratio were investigated for 60 different concretes, with densities ranging from 551 to 1948 kg/m3. The two primary mix design variables studied were the volume percentage of air in the matrix (A/M) and the volume percentage of matrix of the total mix (M/T). The test results indicate that both the compressive strength and modulus of elastic are strongly dependent on A/M. However, the effect of M/T depends on the relative strength of the matrix and aggregate. Both compressive strength and modulus increase with matrix content, for the aggregate used and for A/M ratios of approximately 22% and less; otherwise, they decrease. The coefficient of the split tensile strength as a function of density for the aggregate used is lower than that for normal weight concrete. Regression techniques were used to derive models for the properties of the concrete which give adequate predictions.

This study presents a laboratory evaluation on rutting resistance of Open Graded Friction Course (OGFC) mixes made with different polymer modifiers and coarse aggregate sizes. For this research work, six mix designs for three polymer modifiers (3% SBS modified, 6% LDPE modified, and 12% rubber modified) and two aggregate sizes (13 mm and 10 mm) were carried out to determine the optimum asphalt contents. The OGFC specimens were fabricated using the Superpave gyratory compactor at a compaction level of 50 gyrations. The air void contents and final rut depths of the mixtures were measured by the Corelok system and the Asphalt Pavement Analyzer (APA), respectively. In general, the results indicated that the polymer modifier plays an important role in the rutting resistance of the OGFC mixes used in this study. With respect to the coarse aggregate size, it was found to have little effect on the rutting potential.

This paper presents a research to recycle the waste vinyl (waste polyethylene film: WPE film) in asphalt mixtures for improving the performance properties of the mixtures. Conventional Marshall mix designs were carried out with varying WPE contents, and the best performing content of WPE film was determined from the previous study. Also, asphalt mixtures with two commercial polymer modifiers, low-density polyethylene (LDPE) and a styrene–butadiene–styrene (SBS), were used to compare the effectiveness of WPE-modified mixture. The strength characteristics such as Marshall stability and indirect tensile strength (ITS) were evaluated, and the wheel tracking test, result of which is generally considered to reflect the field performance, was conducted to measure the rutting resistance of the asphalt mixtures. From the results of this study, asphalt mixture with waste vinyl showed much better rutting resistance than normal asphalt mixture without WPE. It is hypothesized if an optimum content of waste vinyl is used, it is expected that the waste vinyl will be effective as much as commercial modifier in improving the performance of asphalt pavements.

This study was initiated to investigate the aging characteristics of binders due to the reaction with the crumb rubber. For this laboratory study, the crumb rubber modified (CRM) and control binders were aged using an oven aging method. Also, asphalt mixtures with CRM or control binders were made and subjected to short-term and long-term aging treatments. The properties of these aged binders were evaluated using gel permeation chromatography (GPC) test procedures. The results from this study showed that: (1) the higher CRM percentage resulted in the higher large molecular size (LMS) value of asphalt binder under the binder aging conditions, and the rate of increase in the LMS value was found to have a relation to the CRM percentage. The asphalt binders with higher CRM percentages (15% and 20%) had a trend the LMS values decrease after a certain level. This finding is thought to be related to the required time for the rubber to be fully digested; (2) after subjecting to the long-term oven aging, the asphalt mixtures with the control and CRM modified binders were found to have statistically insignificant differences in aging level, measured using the LMS values. The very thin film thickness of binder in asphalt mixture and the aging temperature of 100 °C insufficient to enable a reaction were considered to be the main reasons that no differences were observed from the standpoint of the aging effect.

This study addresses the rheological investigation of properties of warm mix asphalt (WMA) binders containing long-term aged binders. The recycled binders with the additives were produced using two (i.e., zeolite Aspha-min® and wax Sasobit®) of the available warm asphalt processes. The main rheological factors selected in this study were relationships between loading and response as a function of time, temperature and frequency using a Bohlin Dynamic Shear Rheometer II. The results indicated that the addition of Sasobit® into recycled binders played an important role in determination of the binder properties evaluated in this study. The use of lower performance grade (PG) as a virgin binder (PG 58-28 in this study) was critical on offsetting the change of rheological binder properties due to the warm additives and the aged binders.

The incorporation of crumb rubber into asphalt pavement mixes is designed to enhance binder properties through reducing the binder’s inherent temperature susceptibility. During the interaction process, crumb rubber particles swell after absorbing a portion of the oils in the binder, resulting in the increase of binder viscosity. In this study, the Crumb Rubber Modified (CRM) asphalt binders were produced using virgin binder of Performance Grade (PG) 64-22 and ambient rubber with various concentrations (10%, 15%, and 20% by weight of virgin binder) in the laboratory. Rheological analyses (flow behavior, elasticity, loading dependence, and temperature dependence) of the control virgin binder and the CRM binders were conducted using a Bohlin Dynamic Shear Rheometer (DSR) II. The results indicated that (1) the use of crumb rubber as a modifier seemed to improve the penetration resistance of the asphalt binder because of the increased viscosity at 60oC, (2) its advantage was more apparent at lower frequencies of loading, and (3) the asphalt binder with higher crumb rubber contents was observed to have better resistance to permanent deformation at higher temperatures and elasticity at lower temperatures.

The main objective of using warm mix asphalt (WMA) is to reduce emissions and improve the workability by lowering the mixing and compaction temperatures of asphalt mixes through different mechanisms. Since warm asphalt is a relatively new technology, not much research has been conducted on various mix compositions. While some of the concerns about WMA have been addressed, the interaction of warm mix additives with modified binders, especially crumb rubber modified (CRM) binder, is not known in great detail. This paper presents the data on rheological tests conducted on rubberized binders containing warm asphalt additives. Binders from five different sources were modified using 10% crumb rubber by weight of the virgin binders. Two of the available warm asphalt technologies, Aspha-min® and Sasobit®, were used to produce the warm asphalt binders. From the tests, it was observed that the addition of the warm asphalt additives significantly reduce the permanent deformation of the binders, increase the viscosity at 60 °C and the complex modulus, G*, and decrease the phase angle, δ, at high frequencies and low temperatures compared with the CRM binders.

The application of crumb rubber in asphalt mixtures is intended to improve the binder properties by reducing the binder’s inherent temperature susceptibility. This research investigated the interaction effects of CRM binders as a function of various blending treatments in the laboratory. For this study, CRM binders were produced using seven blending times (5, 30, 60, 90, 120, 240, and 480 min), three blending temperatures (177, 200, and 223 °C), and four rubber contents (5%, 10%, 15%, and 20% by weight of asphalt binder). The results from this study showed that (1) The interaction time and interaction temperature for CRM binders were observed to have significant effect on the binder properties; (2) The longer time and higher temperature for interaction of CRM binders resulted in an increase in the high failure temperature and the viscosity. This is thought to be due to the increase in the rubber mass through binder absorption. However, this study found that the control binder of PG 64-22 had little change of the binder properties as a function of interaction conditions; (3) The CRM percentage influence is statistically significant on the viscosity and G*/sin δ values. Also, the asphalt binder with higher CRM percentage showed a higher large molecular size (LMS) value, and the increase in CRM percentage is considered to result in the additional loss of the low molecular weight in the asphalt binder to the CRM.

This paper presents an experimental analysis of the long-term properties of rubberised binders containing warm asphalt additives. The rubberised binders were manufactured at 10% by binder weight using five different binder sources and the binders with the additives were produced using two (i.e. Aspha-min® and Sasobit®) of the available warm asphalt processes. The rubberised warm asphalt binders were artificially short-term and then long-term aged through the rolling thin film oven and pressure ageing vessel procedures. Superpave binder tests were carried out on the binders using the rotational viscometer, the dynamic shear rheometer (DSR) and the bending beam rheometer (BBR). In general, the results of this limited study indicated that (1) the addition of the warm asphalt additives into the rubberised binders showed positive effects on increasing rutting resistance, (2) the rubberised binders containing the additives were less resistant to fatigue cracking at intermediate temperatures than the control rub...

This study presents an experimental evaluation for the performance properties of polymer modified asphalt (PMA) binders containing warm mix asphalt (WMA) additives. The PMA binders with the additives were produced using two of the available warm asphalt processes (i.e., Aspha-min and Sasobit) and three PMA binders graded as performance grade (PG) 76-22. The warm PMA binders were artificially short-term and then long-term aged using the rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were carried out on the binders through the rotational viscometer (RV), the dynamic shear rheometer (DSR), and the bending beam rheometer (BBR). In general, the results of this research indicated that (1) the addition of the WMA additives into the PMA binders showed positive effects on increasing rutting resistance at high temperature (based on the high failure temperature values from the DSR test); (2) the PMA binders containing the additives were observed to be less resistant to fatigue cracking at intermediate temperatures compared to the control PMA binders (based on the G*sin δ values at 25 °C from the DSR test); and (3) the addition of wax additive represented a possible lower resistance on low temperature cracking (based on the stiffness and the m-value at –12 °C from the BBR test).

This paper investigates the change in micromorphology of two binders and their respective warm mix asphalt binders before and after aging using atomic force microscopy (AFM) and optical microscopy. The control (PG 64-22) and crumb rubber modified (CRM) binders were blended with two different types of wax additives (L, a wax-based composition including crystal controller, and S, a long chain aliphatic hydrocarbon) and then artificially short-term and long-term aged using the rolling thin film oven and pressure aging vessel procedures. L is a wax based composition including crystal controller and S is a long chain aliphatic hydrocarbon. The AFM tapping-mode imaging technique was used to analyze the microstructure and the Superpave asphalt binder test was used to measure the rheology properties. In general, the results of this study indicated that (1) a correlation was observed between the changes in micromorphology (the distribution of dispersed domains and matrix) and rheology properties regardless of the aging, binder, and wax types; (2) the addition of crumb rubber into the base binder decreased the dimension of the catana phase (“bee-like”) structure, which increased the quantity of these structures; (3) the opposite trend was found between the aged control binder and the aged CRM binder regarding the size of the bee-like structure; (4) the long-term aging seemed to have a significant effect on the microstructures of the warm control and CRM binders; and (5) the inclusion of S and L was observed to have a similar trend for both binder types in terms of increased size of the bee-like structure and no bee-like structure, respectively.

Both the RTFO (rolling-thin film oven) aging of asphalt binders and the STOA (short-term oven aging) of asphalt mixtures are designed to simulate aging during the construction of hot mix asphalt (HMA) pavements. Many studies have been conducted evaluating the aging effects on asphalt binders since their properties can be easily measured using many conventional tests, such as rotational viscometer, DSR (dynamic shear rheometer), and BBR (bending beam rheometer). However, studies on asphalt mixture aging have been limited to mechanical properties such as strength and fatigue characteristics because considerable effort is required to identify the aging of the asphalt binder in a mixture. This study evaluated the effects of short-term oven aging on asphalt mixtures using the GPC (gel-permeation chromatography) procedure. Nine asphalt mixtures, using three different binder sources, were prepared and five short-term aging methods were used to evaluate these mixes. For comparison, the RTFO aging was also conducted for nine asphalt binders. The aging of a binder within asphalt mixtures, including polymer-modified mixtures, could be identified under various short-term aging conditions. Statistical analysis of the GPC test results indicated that two commonly used short-term aging methods in the laboratory, a 154 °C oven aging for 2 h and a 135 °C oven aging for 4 h, are not significantly different, based on the increase in the large molecular size (LMS) ratios. The RTFO aging method was found to have less effect on binder aging than the short-term oven aging methods of asphalt mixtures.

The recycling of hot-mix asphalt pavements containing a crumb rubber modifier (CRM) has been an area of interest since CRM was first used in asphalt paving materials over 40 years ago. Studies on the recycling of rubberized asphalt concrete materials have focused mainly on the mixture properties at the location of in-field paving. However, for the long-term performance characterizations, there is a need to investigate the aging properties of rubberized binders and the subsequent recycling properties of these aged rubberized binders. To address this issue, the previous research was conducted to identify performance properties of recycled aged CRM binders using Superpave binder test methods. The research results indicated that the recycled aged CRM binders can result in satisfactory binder performance meeting current Superpave binder requirements. This paper presents a limited study that uses gel permeation chromatography (GPC) to characterize the aging process of recycled aged CRM binders as a function of ...

The warm-mix asphalt (WMA) refers to technologies that allow a significant reduction of mixing and compaction temperatures of asphalt mixes through lowering the viscosity of asphalt binders. Several studies have been carried out evaluating the properties of WMA, and it is found that warm mix additives work in different ways either in reducing the viscosity of the binder or allowing better workability of the mix at lower temperatures. In terms of rubberized asphalt mixtures, they are generally produced and compacted at higher temperatures than conventional mixtures, based on the field experience. If the technologies of warm-mix asphalt are incorporated, it is expected to reduce the mixing and compaction temperatures of rubberized asphalt mixtures to those of conventional mixtures. This study was initiated to investigate the effects of compaction temperature on rubberized mixes containing the warm mix additives. For this, four Superpave mix designs for two asphalt binders and two aggregate sources were cond...

Reclaimed asphalt pavement (RAP) comprises one of the largest recycled materials, and warm mix asphalt (WMA) technologies become more commonly used due to their promising advantages in the United States and Europe. This paper addresses the laboratory investigation of performance properties of WMA binders containing aged binders. The recycled binders with the additives were produced using two (i.e., zeolite Aspha-min® and wax Sasobit®) of the available warm asphalt processes. The recycled WMA binders were artificially short-term and then long-term aged through the rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were carried out on the binders through the rotational viscometer, the dynamic shear rheometer (DSR), and the bending beam rheometer (BBR). In general, the results of this study indicated that (1) the additives and aged binders played an important role in determination of the binder properties; (2) the use of lower PG grade as a virgin binder (PG 58-28 in this study) was critical on offsetting the increase of binder stiffness caused by the addition of WMA additives and aged binders; and (3) even at the low recycling percentage of 15%, the lower PG grade was needed to get the results meeting current Superpave binder requirements.

This paper presents an experimental analysis of the relationship between molecular sizes of mixed rubberized binders (aged rubberized binders + virgin rubberized binders) and the engineering properties of recycled aged rubberized mixtures. Gel permeation chromatography (GPC) was utilized to characterize the molecular size change of rubberized binders depending on three aging levels and four long-term aged (LTA) binder percentages. Rubberized mixtures were artificially long-term aged in the laboratory, and the aged rubberized mixtures were recycled at 0%, 15%, 25%, and 35% (by weight of total mixture) using typical recycling guildelines. Samples of laboratory-prepared recycled aged rubberized mixtures were tested for indirect tensile strength (ITS) in dry and wet states, rutting resistance, resilient modulus, and ITS after long-term aging in the laboratory. In general, the results indicated that the compositional changes of mixed rubberized binders have good correlations with the engineering properties of recycled aged rubberized mixtures, except for the resilient modulus.

Several studies have been conducted evaluating the properties of warm mix asphalt (WMA), and it is observed that warm asphalt additives work in different ways to either reduce the viscosity of the binder or to allow better workability of the mix at lower temperatures. In terms of rubberized asphalt mixtures, they are compacted at a higher temperature than conventional mixtures, based on the field experience. If the technologies of warm mix asphalt are incorporated, it is expected to reduce the mixing and compaction temperatures of rubberized asphalt mixtures to those of conventional mixtures. This paper presents the high temperature properties of rubberized binders containing warm asphalt additives. Rubberized binders were produced at 10% by binder weight using five binder sources, and the binders with the additives were produced using two (i.e. Aspha-min® and Sasobit®) of the available processes and artificially short-term aged through the rolling thin film oven (RTFO) method. Tests were conducted on the binders using the rotational viscometer and the Dynamic Shear Rheometer. The results indicated that the viscosity properties of rubberized binders can be changed significantly through the use of warm asphalt additives. Also, the addition of the additives was found to improve rutting resistance of the rubberized binders.

Both the rolling thin film oven test (RTFOT) and the short-term oven aging (STOA) methods are used in the laboratory to represent the aging of an asphalt binder during plant mixing, transportation and paving. The RTFOT is conducted at 163 °C for 85 min, and the recommended STOA methods are to heat the loose mix in a forced draft oven either at 135 °C for 4 h or at 154 °C for 2 h dependent on the asphalt binder’s stiffness. The actual time of short-term aging in the field varies depending on hauling distances or paving times. This research was initiated to compare the aging effects of the RTFOT and the STOA methods using the gel permeation chromatography (GPC) and selected Superpave binder tests. For this study, nine asphalt binders were prepared, and five aging periods were used for the RTFOT and four aging treatments were selected for the STOA. Loose asphalt mixes were obtained from six field projects. The results of GPC test showed that the RTFOT method has less aging effect on the binders than the STOA methods for asphalt mixtures prepared in the laboratory. Given the limited number of samples from the field, it was difficult to find any correlation of short-term aging between the laboratory and the field. The longer the aging time in the RTFOT led to an increase in the high temperature viscosity and the high failure temperature of asphalt binders, the only exception being the rubber-modified binders. The GPC was effective in evaluating the aging effect of rubber-modified binders using different RTFOT aging times.

This paper presents a limited study that characterizes the recycling of artificially aged crumb-rubber modified (CRM) mixtures depending on their recycling percentage and aggregate type. Eight mixtures [six recycled mixtures containing rubberized reclaimed asphalt pavement (RAP) and two control virgin mixtures] were designed and tested. Two types of aggregates were used in this research project. The rubberized RAP used in the study was artificially aged in the laboratory using an accelerated aging processes. The percentages of the RAP, by total weight of the mix, incorporated into the recycled mixtures were 15%, 25%, and 35%. Evaluation of all mixtures included the following testing procedures: tensile strength ratio (TSR), asphalt pavement analyzer (APA), resilient modulus, and indirect tensile strength (ITS) after long-term oven aging. The results from this study showed that (i) the recycled aged CRM mixtures (with 15%, 25%, and 35% rubberized RAP) can satisfy the current Superpave mixture requirements, including moisture susceptibility and rutting resistance, and (ii) in general, there was no significant difference between the control and the recycled CRM mixtures for the properties evaluated in this study.

This research investigates the influence of compaction temperature on rubberized asphalt mixes and binders. For this, four Superpave mix designs for four asphalt binders (control, 3% styrene–butadiene–styrene (SBS)-modified, 10% rubber-modified, and 15% rubber-modified) were carried out. A total of 160 specimens were manufactured at four compaction temperatures of 116, 135, 154, and 173 °C. The binders were artificially short-term aged for 2 h at the mixture compaction temperatures prior to the binder tests. The results from this study showed that: (i) the control and SBS-modified mixtures could have almost the same air–void contents at a wide range of compaction temperatures; (ii) the compaction temperatures significantly affected the volumetric properties of the rubberized mixes; (iii) the aging difference of asphalt binder in the mixture depending on the compaction temperature is not considered to be a main factor affecting the volumetric properties of the mixtures.

The application of crumb rubber modifier (CRM) in asphalt mixtures is intended to improve the properties of binder by reducing the binder’s inherent temperature susceptibility. During the interaction with asphalt binder, the CRM particles absorb a portion of the oils in asphalt binder and the particles swell; therefore increasing the viscosity and stiffness of the CRM binder. Still, the performance properties of CRM binders in hot mix asphalt (HMA) pavement are considered to be unclear due to the various interaction effects of CRM with asphalt binders, depending on the CRM percentage, source and size. In this study, a laboratory investigation was conducted on the properties of CRM binders as a function of CRM processing method and percentages. A total of twenty-four CRM binders (3 binder sources ∗ 2 CRM processing methods ∗ 4 CRM percentages) were produced and artificially aged through an accelerated aging process. Evaluation of the CRM binders included the following testing procedures: Viscosity at high temperature, performance properties at high and intermediate temperatures, and cracking properties at low temperature. The results from this study indicated that the higher CRM percentages for CRM binders seemed to lead to a higher viscosity, a better rutting resistance and a less chance for low temperature cracking. In general, the ambient CRM was found to be more effective on producing the CRM binders that are more viscous and less susceptible to rutting and cracking.

The compaction temperature of crumb rubber modifier (CRM) asphalt mixes needs to be determined cautiously because the viscosity and the amount of the CRM binder affects the compactability of the mixtures. In this study, a laboratory investigation was carried out on the volumetric properties of CRM mixtures fabricated using the Superpave gyratory compactor (SGC) and the Marshall compactor as a function of compaction temperature. Two CRM binders were incorporated into HMA mixtures. Two other mixtures were produced with the control binder (PG 64-22) and SBS-modified binder (PG 76-22) and used for comparison purposes. The CRM binders were produced using one base binder (PG 64-22) with 10% or 15% ambient CRM (−40 mesh) by weight of the binder. For this research, the Superpave and the Marshall mix designs for four different asphalt binders were conducted to determine the optimum asphalt contents (OAC). A total of 128 specimens were manufactured using the SGC and the Marshall compactor at various compaction temperatures (116, 135, 154, and 173 °C). The volumetric properties were obtained and analyzed using the statistical methods. The results from this study indicated that (1) the compaction temperatures used in this study significantly affected the volumetric properties of the CRM mixtures, regardless of the compaction methods (the SGC and the Marshall compactor); (2) the CRM mixtures in both the SGC and the Marshall compactor showed the higher VMA values than the control and SBS-modified mixtures; (3) a general trend of the volumetric properties as a function of compaction temperature and compaction method was found for the CRM mixtures used in this study.

The compaction conditions (e.g., compaction temperature and compaction level) of crumb rubber modified (CRM) asphalt mixtures should be determined carefully because the viscosity and amount of the CRM binder affects the compactability of the mixtures. Furthermore, the properties of CRM mixtures relating to the compaction conditions have not been studied in great detail. In this study, a laboratory investigation was conducted on the volumetric and rutting properties of CRM mixtures as a function of compaction conditions. For this research work, four Superpave mix designs for four different asphalt binders (control, SBS modified, 10% rubber modified, and 15% rubber modified) were carried out to determine the optimum asphalt contents. A total of 260 specimens were fabricated using the Superpave gyratory compactor at four compaction temperatures (116, 135, 154, and 173°C) and five compaction levels (20, 40, 60, 80, and 100 gyrations). The volumetric properties were obtained and analyzed, and the rutting resistance of the mixtures was measured using the asphalt pavement analyzer. The results from this study indicated that: (1) the compaction temperatures used in this study significantly affected the volumetric properties of the CRM mixtures, unlike the control and SBS-modified mixtures; (2) in general, the air void contents of the mixtures were significantly influenced by the compaction levels; and (3) as expected, the higher air void contents of the CRM mixtures seemed to have a detrimental effect on the rutting resistance.