An alternative method for short- and long-term ageing for bitumen binders (original) (raw)
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Construction and Building Materials, 2008
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.
A LABORATORY STUDY ON SHORT TERM AND LONG TERM AGEING OF BITUMEN USING MODIFIERS
The ageing of bitumen binder has an influence on how long is in service a road coating. Thus, it is important to have reliable methods to predict pavement behaviour with time. During its service period, bitumen suffers a gradual loss of its desirable properties due to continuous exposure of bitumen to environment and traffic. To determine changes of binder characteristics with respect to time, one must expose bitumen to the influence of external factors which results in oxidation, evaporation and exudation of bitumen components thus hardening of the bitumen. In the present study two modifiers i.e. Styrene Butadiene Styrene (SBS), an elastomer and Crumb Rubber, obtained from discarded tyres are used, to modify VG30 bitumen. The changes in conventional and rheological properties of VG30 modified with different percentages of SBS(5% to 7%) and Crumb Rubber(7% to 9%) before and after ageing are studied. The rheological properties of binders in terms of their complex modulus (G*) which depicts stiffness and overall resistance to deformation, storage modulus (G' = G*×cosδ) which measures energy stored during a loading cycle, loss modulus (G " = G* × sinδ) which measures the energy dissipated during a loading cycle and phase angle (δ), measures the viscoelastic character of bitumen are studied using Physica Smart Pave Asphalt Rheometer. The properties are tested at different temperature varying from 58˚C till failure at frequency 10 rad/sec. Short and Long Term ageing is simulated by Rolling Thin Film Oven Test and Pressure Ageing Vessel respectively. Conventional tests shows hardening of bitumen due to ageing and increase in viscosity and temperature susceptibility characteristics due to addition of modifiers. Complex Modulus G* increases with increase in % of modifier and test temperature, G* values are greater after RTFOT ageing which indicated hardening of bitumen and considerably greater after PAV ageing due to prolonged ageing. Rutting resistance (G*/sinδ) values are greater for modified bitumen indicating better rutting resistance. The third rheometer measurement Loss modulus (G* × sinδ) is carried out on PAV aged residue, to evaluate fatigue cracking property of binder.
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.
Impact of different ageing levels on binder rheology
International Journal of Pavement Engineering, 2015
This paper evaluates the variability of binder rheology for different ageing levels and the influence of ageing at different testing temperatures. Three different ageing levels were applied on a single type of bitumen with a penetration grade of 70/100.The artificial ageing of the binder was performed using the rolling thin-film oven test and the pressure ageing vessel. The rheological behaviour was investigated at low temperatures with the bending beam rheometer (BBR) and at medium and high temperatures with the dynamic shear rheometer (DSR). Several experiments were conducted to determine the range of stiffness and complex modulus results, the type of distribution comparing real and theoretical models, and the effects of ageing on the variability of the rheological behaviour. It was shown that not only the mean results from BBR and DSR tests change with ageing, but also the variability of the results changes with ageing. This would have an impact on mechanistic-empirical pavement design because it would influence the calculated stresses and strains as well as the calculated reliability.
Effects of exposure time and temperature in aging test on asphalt binder properties
International Journal for Computational Civil and Structural Engineering
The effect of temperature level and its exposure time in hot mix asphalt production stages on the conventional and rheological properties of asphalt cements have been investigated through experimental study. A series of Rolling Thin Film Oven (RTFO) Test was conducted at the temperature/time combinations for 135, 150, 163 ºC and 40, 80, 120 minutes. Dynamic mechanical characteristics of the binders were detected by dynamic shear rheometer tests. The results show that the variations in exposure time and temperature distinctly changed the properties of binders in a wide range. It is recommended that for a better simulation of short term aging in production and construction stages, RTFO test temperature and curing time should be adjusted according to the real individual field conditions. Also, in order to give information about the aging behavior of a specific binder for possible field conditions, the test results should be presented for a number of temperature-time combinations.
Effect of short-term ageing temperature on bitumen properties
Road Materials and Pavement Design, 2017
Properties of asphalt mixtures after ageing are fundamental parameters in determining longterm performance (e.g. durability) of these materials. With increasing popularity of reduced temperature mixtures, such as warm-mix asphalt, WMA, the question remains how a reduction in short-term ageing affects the properties after long-term ageing of bituminous materials. This paper aims to improve our understanding of the effect of asphalt manufacturing temperature on ageing and the resulting mechanical properties of bituminous binder by studying the effect of short-and long-term ageing of different bitumen samples as a function of short-term ageing temperatures. For this purpose, round robin experiments were conducted within the RILEM technical committee (TC) 252 chemo-mechanical characterisation of bituminous materials by 10 laboratories from 5 countries using four binders of the same grade (70/100 pen) from different crude sources. The short-term ageing was carried out using the standard procedure for rolling thin film oven test (RTFOT), but varying the temperatures. Long-term ageing was carried out using the standard procedure for pressure aging vessel (PAV) in addition to RTFOT. For the mechanical characterisation, rheological data were determined by using the dynamic shear rheometer (DSR) and conventional tests, with needle penetration and softening point using the ring and ball method. The results show that although different short-term ageing temperatures showed a significant difference in the mechanical properties of the binders, these differences vanished after long-term ageing with PAV.
Jurnal Teknologi, 2017
Polymer modified bitumen (PMB) has been used for many years to improve the performance of asphalt concretes against premature pavement defects. In this research, modified samples were prepared with 2%, 3%, 4%, 5% and 6% Linear Low Density Polyethylene (LLDPE) polymer by weight of bitumen binder. The influence of LLDPE polymer was evaluated through binder properties test which includes penetration, softening point, storage stability, temperature susceptibility, rutting, fatigue and thermal oxidative aging resistance from a dynamic shear rheometer (DSR) measurements at a temperature of 20 OC to 60 OC. Results show that LLDPE polymer has a significant effect on binder properties. Penetration decreases and softening point increases with increasing LLDPE content on the modified binder after aging, which implies LLDPE improves the thermo oxidative aging resistance of the binder. Furthermore, the storage stability test shows that at higher LLDPE concentrations phase separation may occur. D...
XXVI PIARC World Road Congress, Abu Dhabi, 2019
In the wake of a growing bitumen binder variability resulting from economic and geopolitical constraints leading to changes in crude oils and refining processes, the asphalt industry is facing challenges of quality, consistency and early pavement failures in the form of cracking and raveling in particular. New, innovative and relevant analytical tools and approaches are being developed particularly at the Western Research Institute (WRI) to address the challenges and advance from trials and errors to modelling and predictions. Studies launched by WRI have demonstrated the proof of concept, and the validation of chemometric correlations; linking chemical composition of bitumen binders to their physical properties and their performance in mixes. Relevant strong correlations were obtained for compositional fractions, chemical functionalities, and thermal parameters with binder rheological properties, specification parameters, as well as asphalt mix properties, through a study with a road contractor. Hence, the binder impacts mixture stiffness and fatigue resistance, but less prominently in mixture resistance to moisture-induced damaged, rutting resistance and compaction properties, where aggregates become more prominent. Other important results confirmed some performance indicators from binder to mixes, such as the stiffness modulus, fatigue parameters, thermal cracking parameters (relaxation and cracking temperature), and rutting resistance. New possible indicators were detected like the binder glass transition and crossover temperatures as well as their difference, named temperature of intermediate region (TIR) with respect to cracking resistance and healing propensity. The effect of long term aging, particularly with respect to cracking, was also evaluated. Many of these results have been obtained through two major projects: the Asphalt Industry Research Consortium launched by WRI which is ongoing on a very wide binder range aiming to chemically fingerprint binders to predict their mechanical properties as well as their aging susceptibility and their compatibility with various modifiers or recycled materials. The second project is the ongoing National Cooperative Highway Research Program 09-60 project. This involves studying the impact of binder resistance to internal restraint damage mechanism on mixture cracking, and the influence of other thermal cracking factors such as, long-term aging and reversible time-dependent physical hardening. The ultimate goal of this project is to develop and propose new and more relevant specification parameters to avoid age-induced surface damage in the form of transverse cracking, block cracking, and raveling.
Investigations of Physical and Rheological Properties of Aged Rubberised Bitumen
Several road pavement distresses are related to rheological bitumen properties. Rutting and fatigue cracking are the major distresses that lead to permanent failures in pavement construction. Influence of crumb rubber modifier (CRM) on rheological properties of bitumen binder such as improvement of high and intermediate temperatures is investigated in the binder's fatigue and rutting resistance through physical-rheological changes in this research. The bitumen binders were aged by rolling thin film oven (RTFOT) to simulate short-term aging and pressure aging vessel (PAV) to simulate long-term aging. The effects of aging on the rheological and physical properties of bitumen binders were studied conducting dynamic shear rheometer test (DSR), Brookfield viscometer test, softening point test, and penetration test. The results showed that the use of rubberised bitumen binder reduces the aging effect on physical and rheological properties of the bitumen binder as illustrated through lower aging index of viscosity, lower aging index of * /sin , and an increase in Tan with crumb rubber modifier content increasing, indicating that the crumb rubber might improve the aging resistance of rubberised bitumen binder. In addition, the results showed that the softening point increment (Δ ) and penetration aging ratio (PAR) of the rubberised bitumen binder decreased significantly due to crumb rubber modification. Furthermore, the higher crumb rubber content, the lower * sin after PAV aging, which led to higher resistance to fatigue cracking bitumen.