Author: M. Zeng Publisher: ISBN: Category : Asphalt binder Languages : en Pages : 6
Book Description
Modeling techniques were employed to establish the relationship between the rheological properties (G* and ?) of asphalt binders and asphalt-aggregate mixtures. Results of this study indicate that the complex modulus and phase angle of the mixture can be represented by the same parameters obtained from the binder under the conditions of material linearity. This relationship is independent of frequency (or loading time) and temperature. For typical dense graded asphalt mixtures, the relationship is not significantly affected by the characteristics of both the asphalt binder and the aggregate. The relationship between the complex moduli of the asphalt binder and mixture can be mathematically modeled by the generalized power function. This function is more precise than the Heukelom and Klomp model (HK expression) and bilogarithm linear model (BL approximation), particularly at low and high modulus values. The generalized power function can differentiate asphalt binder as a viscoelastic liquid and asphalt mixture as a viscoelastic solid under the action of shear loading. The relationship of the phase angles, as an integrated part of rheological property of a viscoelastic material, between asphalt binders and mixtures can be modeled by a modified haversine function. This function completes the modeling of rheological properties as a whole for the first time and also reflects the fundamental material difference between the binder and the mixture in viscoelastic theory. Characterizing the asphalt mixture properties through the binder properties not only can save tremendous efforts in testing an asphalt mixture, but also can simplify the pavement performance prediction.
Author: Kevin D. Stuart Publisher: ISBN: Category : Asphalt Languages : en Pages :
Book Description
The overall objective of this study was to determine if the Superpave high-temperature rheological properties of polymer-modified asphalt binders correlate to asphalt mixture rutting resistance. An emphasis was placed on evaluating polymer-modified asphalt binders with identical (or close) high-temperature performance grades (PG's), but varied polymer chemistries. Eleven asphalt binders were obtained for this study: two unmodified asphalt binders, an air-blown asphalt binder, and eight polymer-modified asphalt binders. High-temperature asphalt binder properties were measured by a dynamic shear rheometer (DSR). Mixture rutting resistance was measured by repeated shear at constant height (RSCH), and the French Pavement Rutting Tester (French PRT). The first objective was to verify the findings of a previous study using a different aggregate. In the previous study, it was found that the Superpave high-temperature asphalt binder properties correlated to mixture rutting resistance with few outliers, and a change in high-temperature PG from 70 to 76 increased rutting resistance. However, the correlation between RSCH and asphalt binder G*/sind (delta) depended on DSR frequency. The data suggested that a low DSR frequency, such as 0.1 rad/s, might provide a better grading system than the standard DSR frequency of 10.0 rad/s. This would require a change in the current asphalt binder specification. A diabase aggregate was used in a previous study. The data using a second aggregate, a limestone aggregate, in combination with four of the asphalt binders, agreed with the findings from the diabase mixtures. The second objective was to retest the diabase mixtures at 70 degrees Celsius using RSCH. The test temperatures used in the previous study were 50 degrees Celsius for RSCH and 70 degrees Celsius for the French PRT. The polymer-modified asphalt binders had continuous high-temperature PG's ranging from 71 to 77. Therefore, it was recommended that the test temperature for RSCH be increased to 70 degrees Celsius. Again, the correlation between RSCH and G*/sind was dependent on DSR frequency. The data suggested that a low DSR frequency, such as 0.1 rad/s, might provide a better grading system. However, it is not known whether this finding applies to pavements, or is related to the accelerated nature of the RSCH test. Furthermore, G*/sind (delta) at 0.1 rad/s did not clearly provide a better correlation to RSCH than the high-temperature PG's of the asphalt binders. The degree of correlation between the French PRT and G*/sind at 70 degrees Celsius did not depend on DSR frequency, and there was only one outlier. A correlation between the French PRT and high-temperature PG provided no obvious outliers. No changes to the specification are recommended based on the French PRT results.
Author: John C. Hardin Publisher: ASTM International ISBN: 0803119887 Category : Asphalt cement Languages : en Pages : 237
Book Description
A dozen papers from a December 1993 symposium in Dallas/Fort Worth, Texas. Among the topics are why the new proposed rheological properties of asphalt binders are required and how they compare to conventional properties, the development and use of the SHRP direct tension specification test, oxidatio
Author: S. Anjan kumar Publisher: ISBN: Category : Aging Languages : en Pages : 12
Book Description
This paper presents the results of investigations on the rheological properties of modified asphalt binders and their influence on the performance of asphalt mixes. Asphalt mixes with modified binders such as styrene butadiene styrene polymer, crumb rubber, natural rubber, and waste plastics were evaluated for their rheological properties and compared to the properties of asphalt mixes with unmodified VG30 (viscosity grade) asphalt binder. The dynamic modulus values and rutting characteristics of the asphalt mixes were studied with due consideration to different levels of aging and temperature variations. Studies on the rheological properties showed that the energy dissipated by unmodified asphalt (VG30) binder is higher than that of modified asphalt binders. Long-term aged natural rubber and waste plastic modified asphalt binders showed significant increase in the properties compared to unmodified asphalt binder (VG30). Reduced temperature susceptibility of polymer modified asphalt binder showed that only polymer modification can enhance both high temperature rutting resistance and low temperature thermal cracking resistance of asphalt mixes. The transient nature of polymer modified asphalt mix from viscoelastic solid-like to viscoelastic fluid-like condition is significantly shifted to higher temperature compared to that of the mix with unmodified asphalt binder. Aging and rutting indices showed that rubber modified asphalt mixes are highly susceptible to aging. Statistical analysis of test results showed that the process of modification of asphalt binder, aging, and temperature during the test influence the rheological and rutting characteristics of asphalt mixes significantly. Correlation between the asphalt binder properties and its influence on the rutting resistance are found to be statistically significant. The analysis using least significant difference showed that polymer modified asphalt binder significantly improves the aging and rutting resistance of asphalt mixes compared to unmodified asphalt binder.
Author: Mohammad Solaiman Khan Publisher: ISBN: Category : Asphalt Languages : en Pages : 314
Book Description
The rheological, chemical and microstructural properties of asphalt binders change with oxidative aging which is accelerated at elevated temperatures. Aging stiffens asphalt binders and increases the embrittlement of asphalt mixtures which would lead to fatigue cracking and eventually pavement failure under repetitive traffic loading. This study explored the feasibility of using antioxidant additives and copolymers with antioxidant agents to retard oxidative aging of asphalt binders. The performance of the additives was evaluated at the binder and mastic levels. The laboratory experiments included two unmodified binders, various antioxidant additives and copolymers, and three aggregate types. The fatigue characteristics of asphalt binders and mastic were determined before and after aging and an aging index was defined to evaluate the effect of the additives on aging. The results demonstrated that certain antioxidants and copolymers such as Redicote AP, Solprene, and Calprene may retard the aging and improve the rheological properties of the asphalt binders. In addition, the results of mastic testing confirmed the favorable effect of certain antioxidants on improving the resistance to fatigue cracking. Furthermore, the type of aggregate was found to influence the rate of aging of asphalt mixtures. Based on the rheological and fracture test results on asphalt binders and mastic, the effect of antioxidants was further investigated and validated at spectroscopic, chemical and microstructural level using Fourier-transform infrared spectroscopy (FTIR), Gel-permeation chromatography (GPC) and Atomic Force Microscopy (AFM), respectively. The spectroscopic analysis with FTIR supported the efficacy of the additives in retarding aging by reducing the carbonyl growth in aged binders. The chemical analysis with GPC confirmed that both Redicote and Solprene were capable of reducing the large molecular size fraction in binders subjected to long-term aging. The image analysis with AFM provided insight on the spatial distribution, surface roughness parameters and micromechanical properties (i.e., adhesion, stiffness) of various phases and the effect of aging on the micro-rheology of antioxidant-modified binders. The last part of this study examined the effect of aging on the viscoelastic response of asphalt mixture using the Prony series representation and a newly developed parameter called aging state variable 'A'. The dynamic modulus test data was used for the analysis. The aging state variable 'A' was found to capture the effect of aging temperature and duration of aging on the viscoelastic properties of asphalt mixtures.
Author: Shivani Rani Publisher: ISBN: Category : Asphalt Languages : en Pages : 16
Book Description
Different technologies, namely foamed asphalt, synthetic waxes, zeolites, and chemical additives, are used to produce warm mix asphalt (WMA). This study was undertaken to evaluate the effect of using different amounts of an amine-based chemical WMA additive on the rheology, performance grade (PG), and moisture-induced damage potential of an asphalt binder (PG 58-28). Superpave specifications were used to evaluate the rheological properties and PG of the asphalt binder. Also, a mechanistic approach-based on the surface free energy (SFE) method was used to evaluate the moisture-induced damage potential of the asphalt binder combined with commonly used aggregates in an asphalt mix. It was found that the dynamic viscosity of the asphalt binder was not significantly affected after blending it with the WMA additive. It was also observed that the Superpave high-temperature PG and the rutting factor did not reduce by an increase in the WMA additive content. However, the continuous low-temperature PG of the asphalt binder decreased with an increase in the amount of WMA additive. Furthermore, it was found that the fatigue resistance increased after blending the binder with the WMA additive. The SFE results of the asphalt binder revealed that the WMA additive used in this study reduced the moisture-induced damage potential of the asphalt mixes. However, the extent of this improvement was found to largely depend on the aggregate type. The outcomes of this study are expected to help better understand the influence of amine-based chemical WMA additives on rheological and long-term performance of asphalt mix.
Author: Yuan He Publisher: ISBN: 9781339825762 Category : Languages : en Pages :
Book Description
As virgin pavement material sources become scarcer and costlier the use of higher quantities of reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS) in the production of new asphalt mixes becomes increasingly desirable. RAP/RAS binder in the mix has different levels of aging. Through oxidation, the binder becomes stiffer and more rigid than virgin binder, and thus results in a pavement material that is more brittle and susceptible to fatigue and thermal cracking. The purpose of this dissertation study was to investigate the interactions between new and age binders and evaluate asphalt mixes performance. A major concern associated with the use of high percentages of RAP and/or RAS is the level of blending between virgin and age-hardened binders, because the performance of the mix can be highly influenced by the properties of the composite binder. The blending between new binder and age-hardened RAP binder can be explained through diffusion mechanisms. This research used asphalt binder testing and diffusion and aging theory to investigate the evolution of blending between virgin and RAP binders during asphalt mix production, storage, and placement. The rheological properties of a two-layer asphalt binder sample composed of virgin and simulated RAP binder were measured using a dynamic shear rheometer (DSR) after conditioning following hot mix asphalt (HMA) and warm mix asphalt (WMA) time-temperature paths during mixing and placement. The diffusion and aging coefficients for the composite binder were estimated by comparing measured shear stiffness values with those predicted using a diffusion model and considering asphalt binder aging over time. The diffusion model is solved numerically based on the finite control volume approach. Results show that the HMA results in nearly full blending of the new and aged binders following the time-temperature paths used in this study; while the WMA results in only partial blending. Traditionally, the properties of blended binders in asphalt mixes containing RAP and RAS are evaluated through rheological testing of the binder extracted and recovered from a mix. However, this approach has long been criticized for being labor intensive, for potentially altering the chemistry of the binder and consequently changing the binder rheology, for forcing blending of binders that may not have been present in the mix, and for creating hazardous material disposal issues. The research presented in this dissertation proposes an alternative approach for characterizing blended binders by testing the linear viscoelastic properties of a fine aggregate matrix (FAM) asphalt mix using a torsion bar fixture in a DSR. A procedure has been developed for preparation and testing of small FAM cylindrical FAM specimens. The results demonstrated that this testing is sensitive to FAM mixes made of different virgin binders, RAP/RAS contents, with and without rejuvenating agent. More importantly, FAM mix testing shows similar results as that from DSR binder testing and full mix testing in terms of rankings of master curves and Black diagrams. Statistical analysis (ANOVA) on stiffness values from FAM testing also provides the same conclusion to that at binder and mix levels. Therefore, FAM approach has the potential to be used as a substitute to stiffness testing for mix comparison purposes. It is also a less expensive and more efficient testing approach than the full mix testing.The combined effect of RAP, RAS, and different virgin binder sources and grades on performance of the blended binders and asphalt mixes was also investigated. Previous studies have indicated that RAP, RAS, and virgin binder grades each has certain effects on performance of the mix. The addition of RAP/RAS undermines fatigue and thermal performance and improves rutting resistance. The virgin binder grade should be carefully chosen based on the percentages of RAP/RAS in the mix. Results from unconfined RLT appears to show that reducing the binder grade when using more than 25 percent RAP results in rutting performance similar to the original grade. Therefore, it is likely safe for high temperatures if the binder grade is reduced to meet the low and intermediate temperature requirements. Asphalt binders contain different organic molecules, and thus their chemical compositions vary according to the source of the oil used in their production. Virgin binders from different sources blend differently with the age-harden oxidized binder in RAP/RAS. Therefore, depending on the level of blending between virgin and oxidized binders, the performance of the mixes could vary substantially. Findings from this work indicated that virgin binder source had some effect on the blended materials. Additional research that came from the testing approaches to complete the investigation of RAP/RAS with this dissertation were also investigated. All the asphalt mixes used in this study were designed following Caltrans modified Superpave mix design procedure and tested using an Asphalt Mixture Performance Tester (AMPT). The effects of specimen preparation variables in terms of compaction method, compaction level, test temperature, stress state, and deformation measurement location when using the AMPT to predict mix stiffness and permanent deformation were evaluated. The best approach using Superpave testing equipment that appears to best characterize expected rutting performance as defined by previous calibrated RSCH results were also investigated.
Author: M. Zeng
Author: Kevin D. Stuart
Author: 
Author: John C. Hardin
Author: S. Anjan kumar
Author: David A. Anderson
Author: Mohammad Solaiman Khan
Author: Shivani Rani
Author: Akhtarhusein Asgarali Tayebali
Author: Yuan He