A new short-term aging model for asphalt binders based on rheological activation energy (original) (raw)
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A method to estimate the rheological properties of aged asphalt binders without actually aging them
Aroon Shenoy, 2002
Asphalt binder stiffens due to aging during the mixing and lay down operations as well as during the service life of the pavement. The aging processes in the field have been simulated in the laboratory through the use of accelerated test procedures and tracked through rheological characterization of the aged asphalts. However, the laboratory aging procedures along with the rheological characterization of the aged samples are time-consuming processes. Some researchers have been seeking methods to shorten the time involved in generating this information, while others have been suggesting improvements in the test procedures to get reproducible and reliable data, and still others are attempting to find the procedures that would give information in the laboratory that is closer to the reality in the field. In all cases, it is the rheological properties of the aged binders that are used for characterizing the extent of aging. The present work is a step in the same direction but chooses a different approach. A method is proposed to shorten the time involved in generating the information on the aged binder rheology. The suggested procedure aids in estimating the rheological properties of aged asphalts without actually going through the aging process. In order to establish the procedure, rheological data on unaged asphalts are compared with rheological data on aged samples after the Rolling Thin Film Oven Test (RTFOT) and Pressure Aging Vessel (PAV)-aging. It is shown that estimates of the specification temperatures based on the high and intermediate temperature rheological properties of the aged asphalts can be obtained without actually aging the binders in the laboratory. By eliminating the laboratory aging procedures to obtain rheological properties of the aged asphalts, there is a great saving in time and the information is obtained rapidly.
Effect of long-term ageing on the rheological properties of rejuvenated asphalt binder
Road Materials and Pavement Design, 2019
Recycled asphalt products are increasingly being used in asphalt concrete pavements to improve pavement sustainability. Asphalt recycling, while it is undoubtedly an environmentally sustainable practice, includes asphalt binder that is already oxidised. Aged binder is highly brittle and becomes a driving factor for cracking related distresses. As a result, use of recycled materials can have a significant negative impact on pavement performance, specifically when used in increased amounts and cold climatic conditions. In order to improve the performance of asphalt concrete mixtures with recycled materials, rheological properties are changed by adding rejuvenators. In asphalt industry, rejuvenators are either used at an initial virgin state of the binder to reduce mix ageing or blended at a later stage in recycled materials to improve the properties of aged mix. The current study focuses on evaluating the performance of asphalt mixes prepared by blending rejuvenators in already aged binders. Virgin PG 64-22 binder was aged using RTFO and PAV and further mixed with three different kinds of rejuvenators namely Hydrolene 90T, Kendex@ME, and Hydrogreen S at 3%, 6% and 9% by weight of the total binder. To study the behaviour of rejuvenated asphalt binder samples over a long period of time, mixed asphalt samples were then aged for 5, 10, 15, 20, 40 and 60 h in the PAV. Frequency sweep tests were conducted to characterise binder rheology, and parameters such as Glower-Rowe, crossover frequency, and Superpave rutting parameter were calculated. A comparative analysis was carried out to determine the impact of increased ageing and rejuvenator addition in varying amounts on the performance of asphalt mixes. A significant correlation was found out between the types of rejuvenator used in different dosages and the level of ageing in the asphalt binder.
Impact of Asphalt Modifier Dosage on Modified Binder Rheology and Chemistry with Long-Term Aging
Asphalt modifiers/additives are increasingly used in pavement industry. Additives are commonly used as softeners to decrease the binder performance grade (PG), while polymer modifiers are usually used for heavy traffic applications to reduce permanent deformations. Recently, rejuvenators have been used in recycled pavement applications to reduce cracking susceptibility and as retarders to moisture damage. These modifiers can be derived from crude petroleum and sometimes from a bio-based feedstock. The origin of crude binder and modifier source affects the resulting binder-modifier chemical interaction. The inherent chemical variability affects the rheological performance of modified binders. It also impacts the aging potential of these binders and thereby affecting its long-term field performance. In this study, binders modified with softeners/rejuvenators at various dosages were evaluated for their performance under long-term aging. Rheological characterization of modified binders was determined using frequency sweep, linear amplitude sweep, and low temperature performance with parameters such as Glover-Rowe, R-value, crossover frequency, ∆Tc, while the chemical characteristics were determined using Fourier transform infrared spectroscopy (FTIR), and thin layer chromatography and flame ionization detection (TLC-FID). An optimum dosage of the rejuvenator studied was recommended to maximize performance of the modified binder.
IAEME, 2019
This the second part of an article written with the purpose of summarizing and describing the most important aspects that the pavement engineer should know about the aging of asphalt binders and asphalt mixtures. The first part presented the changes in physical and chemical properties undergone in asphalt binders and asphalt mixtures when they age. This article shows the most widely used methods for simulating the aging of asphalt materials. Additionally, the most popular and currently used techniques for reducing aging effects in mechanical response and durability of asphalt mixtures in service are presented.
Aging of Rejuvenated Asphalt Binders
Advances in Materials Science and Engineering, 2017
An important concern that limits the RAP content in asphalt mixtures is the fact that the aged binder that is present in the RAP can cause premature cracking. Rejuvenators are frequently added to high RAP mixtures to enhance the properties of the binder. There is no existing method to predict the longevity of a rejuvenated asphalt. This study investigated the aging of rejuvenated binders and compared their durability with that of virgin asphalt. Various samples with different types and proportions of RAP, virgin binder, and rejuvenator were aged by RTFO and three cycles of PAV. DSR and BBR tests were conducted to examine the high-temperature and low-temperature rheological properties of binders. Results indicated that the type and dosage of the rejuvenator have a great influence on the aging rate and durability of the binder. Some rejuvenators make the binder age slower, while others accelerate aging. These observations confirm the importance of evaluating the long-term aging of rec...
Asphalt Binder Laboratory Short-Term Aging: Effective Parameters and New Protocol for Testing
Journal of Materials in Civil Engineering, 2020
Rolling thin film oven (RTFO) is widely used to simulate asphalt binder short-term aging. However, there is a general interest to improve the current short-term aging protocol especially for reducing the aging time. Besides, there are some doubts about the capability of RTFO in the simulation of aging of highly polymer modified asphalt binders which is mainly due to improper dispersion of such binders in the bottles during rotating and creeping of highly viscous binder out of the bottles during rotation. This work addresses the effect of time, temperature, airflow rate, and weight of asphalt binder on the laboratory short-term aging of asphalt binders and proposes an alternative protocol that can reduce the aging time and resolve some of the current short-term aging protocol shortcomings. In the first part of this study, two asphalt binders, from different sources, were examined in RTFO at different combinations of the above-mentioned test parameters. The high-end continuous performance grading temperature (estimated by dynamic shear rheometer), and carbonyl index (estimated by Fourier transform infrared spectroscopy) were considered as the two responses for quantification and qualification of laboratory aging. The statistical analysis showed that the first order terms of time, temperature, and weight as well as their interactive terms were statistically significant. However, the effect of airflow rate, within the studied range, was insignificant. Based on the findings of the first part of study, an alternative protocol was proposed for the study of short-term aging in a RTFO. One unmodified and three highly modified binders were aged in a RTFO under the current and proposed aging conditions for comparative purposes. According to the obtained rheological (high-and low-end continuous performance grading temperature and viscosity) properties as well as the chemical characteristics (carbonyl index, saturate-aromatic-resin-asphaltene fractions, and oxygen content), it was shown that the proposed laboratory short-term aging protocol not only can reduce the aging time of the conventional protocol, but also that it is applicable to both neat and polymer-modified modern asphalt binders.
True characterization of asphalt binders requires finding the rheological behavior at different temperature and stress levels. Asphalt binder's performance in the field mainly depends on its aging conditions that govern different rheological parameters. Five asphalt binders were tested in the laboratory at different aging conditions, using the dynamic shear Rheometer. The main objectives were to characterize the high temperature load response of asphalt binders under cyclic and static loading conditions. Two testing procedures have been adopted in the laboratory to investigate the high temperature stiffness and creep compliance of asphalt binders. Result shows that stiffness of asphalt binder increases and creep compliance decreases with aging. Creep compliance (J nr ) is temperature and stress sensitive parameter and behaves linear visco-elastic up to a stress level of 3.2 kPa. Temperature sensitivity depends upon the grade of asphalt binder.
Journal of Testing and Evaluation, 2009
Rubberized asphalt has been used to improve the mechanical characteristics (e.g. rutting resistance, fatigue life, friction, and skid resistance) of hot mix asphalt (HMA) mixtures. The objective of this research was to investigate the rheological characteristics of the rubberized asphalt binders after various long-term aging procedures, using the penetration index (PI), the dynamic shear rheometer (DSR), the bending beam rheometer (BBR), and high pressure-gel permeation chromatographic (HP-GPC) testing. The experimental design included the use of three binder sources, three binder grades (PG 64-22, PG 64-22+10%-40 ambient rubber, and PG 76-22) and three aging states, i. e., virgin, rolling thin film oven (RTFO), and pressurized aged vessel (PAV (4 test temperatures [65, 80, 100, and 110 o C] and 5 aging durations [15, 20, 40, 80, and 144 hours] under the pressure of 2070 kPa). The test results show that, as expected, the use of crumb rubber can effectively improve the PG grade and aging resistance of the virgin asphalt binder. A series of rheological properties (e.g., penetration, stiffness, m-value, percentage of large and small molecular sizes) illustrate that the PG 64-22 binder, mixed with 10%-40 ambient rubber, yields similar or improved rheological properties in comparison with PG 76-22 using 3% Styrene-butadiene-styrene (SBS) polymer after various long-term aging procedures.
Model developments of long-term aged asphalt binders
Construction and Building Materials, 2012
h i g h l i g h t s " This study developed a series of models to simulate long-term aged asphalt binders. " ANN models are more effective than regression models. " And these ANN models were easily implemented in a spreadsheet. " Aging temperature, duration and molecular sizes are the most important factors.