Re-refined Engine Oil Bottoms Research Articles

Effects of temperature and age on stress relaxation in straight and modified asphalt binders from a northern Ontario pavement trial

The effects of temperature and age on stress relaxation were investigated for a set of seven asphalt binders from a northern Ontario pavement trial. It was found that between binders, there were rather wide variations for different modes of relaxation. The first peak in the relaxation spectrum, originating from the rapid relaxation within the mobile saturates domains, was relatively insensitive to ageing. The second and third peaks at higher relaxation times changed more with both laboratory ageing and temperature changes. The straight-run Cold Lake asphalt binder showed the least amount of change, and this can likely explain its superior field performance. High styrene–butadiene (SB and SBS) polymer loadings, the presence of polyphosphoric acid (PPA), or re-refined engine oil bottoms (REOB) all resulted in solid-like behaviour, delayed stress relaxation, and associated reduced lifecycles.

Preliminary Study on New Alternative Binders through Re-Refined Engine Oil Bottoms (REOBs) and Industrial By-Product Additives.

Recent studies have worked towards addressing environmental issues such as global warming and greenhouse gas emissions due to the increasing awareness of the depletion of natural resources. The asphalt industry is seeking to implement measures to reduce its carbon footprint and to promote sustainable operations. The reuse of several wastes and by-products is an example of a more eco-friendly activity that fulfils the circular economy principle. Among all possible solutions, the road pavement sector encourages, on one hand, the use of recycled materials as a partial replacement of the virgin lithic skeleton; on the other hand, it promotes the use of recycled materials to substituting for a portion of the petroleum bituminous binder. This study aims to use Re-refined Engine Oil Bottoms (REOBs) as a main substitute and additives from various industrial by-products as a full replacement for virgin bitumen, producing high-performing alternative binders. The REOBs have been improved by utilizing additives in an attempt to improve their specific properties and thus to bridge the gap between REOBs and traditional bituminous binders. An even larger amount of virgin and non-renewable resources can be saved using these new potential alternative binders together with the RAP aggregates. Thus, the reduction in the use of virgin materials is applied at the binder and the asphalt mixture levels. Rheological, spectroscopic, thermogravimetric, and mechanical analysis were used to characterize the properties, composition, and characteristics of the REOBs, REOB-modified binders, and asphalt mixes. Thanks to the rheological investigations of possible alternative binders, 18 blends were selected, since they behaved like an SBS-modified bitumen, and then they were used for producing the corresponding asphalt mixtures. The preliminary mechanical analysis of the asphalt mixtures shows that six mixes have promising responses in terms of stiffness, tensile resistance, and water susceptibility. Nevertheless, the high variability of recycled materials and by-products has to be taken into consideration during the definition of alternative binders and recycled asphalt mixtures. In fact, this study highlights the crucial effects of the chemical composition of the constituents and their compatibility on the behaviour of the final product. This preliminary study represents a first attempt to define alternative binders, which can be used in combination with recycled aggregates for producing more sustainable road materials. However, further analysis is necessary in order to assess the durability and the ageing tendency of the materials.

Quantification of re-refined engine oil bottoms (REOB) in asphalt binder using ATR-FTIR spectroscopy associated with partial least squares (PLS) regression

Re-refined Engine Oil Bottoms (REOB) has been used in recycled asphalt materials for flexible pavements in recent decade, due to its effects on softening aged binder and relatively low cost. However, concerns on the pavement performance of those materials including REOB in asphalt binders have been reported and linked to the use of REOB. Consequently, methods for detecting and quantifying REOB in asphalt binders have seen increased interest to control the use of these recycled oils. This study is for the first time to introduce the use of the Partial Least Squares (PLS) regression in Attenuated Total Reflection-Flourier Transformed Infrared (ATR-FTIR) spectroscopy analysis of asphalt binders for determining REOB content. The PLS regression analysis gives the advantage of using the whole ATR-FTIR spectroscopy of REOB blends. The results show that an accurate prediction model can be derived by using the PLS regression analysis on the ATR-FTIR spectra of REOB blends.

Rheology measurements of recycling oils and their aging resistance in asphalt binders

ABSTRACT Adding recycling oils (also called as ‘recycling agents’ or ‘rejuvenators’) into the asphalt mixtures with Reclaimed Asphalt Pavement (RAP) and Recycled Asphalt Shingles (RAS) is a widely adopted strategy for improving potential resistance to cracking of recycled asphalt pavements. This study investigates the rheolgoical properties of two Bio-Oils and two Re-refined Engine Oil Bottoms (REOB) by using Dynamic Shear Rheometer (DSR) and Rotational Viscometer (RV) tests at various testing conditions, as well as their chemical properties by using the Fourier Transform-Infrared Spectroscopy (FTIR) measurement. The results are compared for the recycling oils after the Rolling Thin-Film Oven (RTFO), 20- and 40-hours Pressure Aging Vessel (PAV) aging. Furthermore, these four recycling oils were blended with a base binder at a high ratio (50%) and measured for their complex shear modulus and viscosity at various aging levels, as well as their infrared spectra. At the end, two recycling oils were selected to blend with a base binder at low ratios (2.9% and 5.7%) and measured for the standard Performance Grade (PG) properties and PG plus characteristics. The results of oil-asphalt low ratio blends indicate that recycling oil’s content plays an important role in aging behaviour of the binders, not only the type of recycling oils.

Influence of Asphalt Binder Formulation and Source on the Performances of Binders with the Same Continuous PG WALAA S. MOGAWER, ALEXANDER J. AUSTERMAN,

The objectives of this research study were to determine the effects of asphalt binder formulation and source on the performance of binders with the same continuous Performance Grade (PG) using recently developed asphalt binder and mixture tests and provide recommendations, if needed, concerning the following: (1) the effect of asphalt binder formulation and source on performance, (2) the current PG specification and (3) the tests used in this study. Various asphalt binders were formulated so they would have the same continuous high and low PGs which would meet the AASHTO M 320 specifications for a PG 58-28 binder. Other binders were formulated to meet the AASHTO M 320 specifications for a PG 64-28 binder. Thus, there were two target PG’s. Three sources of straight run asphalt binders were obtained, although one source was eliminated because for most of the modifiers obtained for this study, the target PGs could not be met. This showed that whether a continuous PG can be achieved through modification is dependent on binder source and modifier type. The modifiers used in the formulations consisted of two sources of re-refined engine oil bottoms (REOB), aromatic oil, polyphosphoric acid (PPA) and an air-blown asphalt, either alone or in combination. It is believed these modifiers are becoming more commonly utilized to supply the required PG asphalt binders for today’s paving industry. Asphalt binder formulation and source had an effect on fatigue cracking, cohesion, adhestion, moisture susceptibilty and non-load associated cracking even though the binders had closely matching continuous PGs based on high and low temperature properties. They had no effect on rutting performance except when measured by the MSCR, or thermal cracking performance except when measured by the EBBR. In conclusion, not all asphalt binders with the same continuous PG will perform identically in regard to all distresses.

Long-Term Aging Performance Analysis of Oil Modified Asphalt Binders

Oil modification of asphalt binders is a widely adopted strategy for meeting low temperature performance grade (PG) specifications. There is no shortage of data characterizing the rheological benefits of several oil modifiers. Current AASHTO M320/M332 specifications evaluate low-temperature performance using the bending beam rheometer which measures creep stiffness and relaxation properties of the asphalt binder after 20 h of aging using a pressure aging vessel (PAV). In this study, extended aging effects on oil and polymer modified binders are investigated using three oil-modified binders compared against a control binder using PG and PG+ testing methods. The oils evaluated include bio-oil and re-refined engine oil bottoms. All binders were subjected to a rolling thin film oven and 20-h PAV aging, as well as extended PAV aging of 40 and 60 h. Binders are evaluated using multiple stress creep recovery, AASHTO TP123 dynamic shear rheometry elastic recovery, and linear amplitude sweep tests in addition to standard PG methods. The results show that many of the rheological benefits supplied by the oils tend to diminish after 40 h of PAV aging. However, the long-term effects depend greatly on the type of oil used, as well as the type of polymer modification used. The results suggest that 20-h PAV aging may not be sufficient to predict the long-term performance of the binder, and that extended aging periods (40-h PAV aging) should be considered when selecting oil modified asphalts.

Laboratory Performance of Asphalt Mixtures Containing Re-Refined Engine Oil Bottoms Modified Asphalt Binders

The increasing use of hardened oxidized asphalt binders in recycling materials such as recycled asphalt pavement (RAP) and recycled asphalt shingles (RAS) has increased the need to use re-refined engine oil bottoms (REOB) as a recycling agent. However, conflicting conclusions on the effect of REOB on mixture performance have been reported in the literature. The objective of this study was to characterize the laboratory performance of conventional asphalt mixtures and mixtures containing REOB modified asphalt binders. Four 12.5-mm asphalt mixtures, containing 0%, 5%, 10%, and 15% REOB modified asphalt binders, were designed to meet Superpave design criteria. A suite of laboratory tests was utilized to ascertain the mechanistic behavior of the mixtures considered. Mechanistic tests were performed to evaluate the high-, intermediate-, and low-temperature properties and moisture susceptibilities of laboratory produced mixtures using the Hamburg Loaded-Wheel Tester (LWT), the Semi-Circular Bending (SCB) test, and the Thermal Stress Restrained Specimen (TSRST), respectively. Results showed that the addition of REOB did not adversely affect the rutting and moisture susceptibility of the mixtures. Similar low-temperature mixture performance was observed with an REOB dosage up to 10%, while a mixture with 15% REOB showed significantly reduced low-temperature cracking performance. A decreasing trend in SCB Jc with an increasing REOB content was observed indicating a negative effect of REOB on intermediate-temperature cracking resistance.

Determining re-refined engine oil bottom content in asphalt binders using a handheld X-ray fluorescence instrument

Re-refined engine oil bottoms (REOB) are major modifiers used to produce softer binders from stiffer binders. Studies have revealed that pavements constructed with REOB-modified binders experience premature cracking and ravelling problems much sooner than usual. Therefore, some state agencies in the US have enacted regulatory measures on the use of REOB-modified binders in their contracts. To implement these measures, there is a need of a well-verified, cost friendly test method that can accurately estimate REOB contents in binders used in these contracts on site. This paper presents a simple method that fulfils this objective. The method involves the measurement of element concentrations in an unknown sample using a portable X-ray fluorescence (XRF) instrument, the identification of the most likely sources of this sample using normalised sulphur-versus-vanadium concentration plot, and the estimation of REOB content in the sample using the calibration curves of zinc, calcium and molybdenum elements. Researchers developed and verified this method using 384 calibration and 24 verification samples. Test results show the proposed method can quantify REOB content in binders with reasonable accuracy. Test results also show that this portable XRF-based REOB estimation method is as effective as a previous benchtop instrument-based REOB estimation method.

Relationships between simple asphalt mixture cracking tests using Ndesign specimens and fatigue cracking at FHWA’s accelerated loading facility

Current methods and criteria for asphalt mix design and quality assurance testing are unable to discern the true impact of recycled materials such as RAP, recycled shingles, ground tyre rubber, re-refined engine oil bottoms, or products aimed at enhancing performance such as polymer-modified binders, fibres, or even WMA. There is an urgent need to implement reliable tests to assess the cracking resistance of asphalt mixtures. This study used test specimens compacted to Ndesign in four simple tests: the Cantabro test, a modified version of the Texas Overlay test, the Semi-Circular Bend test, and the Indirect Tensile test from which IDT strength and two other index parameters were obtained. The relationships between results from these tests and the fatigue cracking of the FHWA’s ALF test lanes were used to assess how well test methods could differentiate actual performance. The study also examined variability data for test results and how that impacted the utility of the tests to discern mixtures from one another. Results of this study indicate that the IDT Nflex Factor and the Cantabro test provide the strongest relationship to fatigue cracking in the field and are able to detect differences among common mixture variables. Both tests are simple, quick, and have very low costs to implement.

Laboratory Performance of Asphalt Mixtures Containing Recycled Asphalt Shingles and Re-Refined Engine Oil Bottoms

AbstractThe use of recycled materials, such as recycled asphalt shingles (RAS), has received considerable attention for its potential to decrease production costs and enhance the sustainability of ...

Effect of Extended Aging on Asphalt Materials Containing Re-Refined Engine Oil Bottoms

The use of re-refined engine oil bottoms (REOBs) in asphalt pavements is a topic of much debate because the aging susceptibility and quantity of the additive in the binder may affect field performance. In this study, four mixtures with varying REOB contents (up to 15%) were long-term oven aged by using a high-temperature, short-duration method (135°C, 24 h) and compared with existing data on mixtures aged with more conventional short-term and long-term oven-aging procedures. The recovered binders underwent Superpave® grading, double-edge notched tension, and extended bending beam rheometer testing, and the binders were subjected to dynamic modulus, cyclic fatigue testing in the asphalt mixture performance tester, and thermal stress restrained specimen testing. Results showed a general insensitivity when short-term oven-aged (135°C, 4 h) materials were compared with long-term oven-aged (85°C, 5 days) materials, whereas the aging process at 135°C over 24 h resulted in substantial changes to the stiffness and relaxation properties across high-, intermediate-, and low-temperature modes. The difference between the stiffness-based and slope-based low-temperature performance grades appears to be an indicator for REOB modification, with the test for physical hardening of the binder being more sensitive than standard bending beam rheometer testing. The details in this paper provide information for the asphalt pavement community to consider as specifications. Standard practices are developed to address REOB modification.

Investigation of Sterol Chemistry to Retard the Aging of Asphalt Binders

The addition of petroleum-derived oils (aromatic or paraffinic) and bioderived oils (typically low-viscosity, unsaturated hydrocarbons modified to remove acid functionality) to bitumen has become a burgeoning business to facilitate the use of increasing amounts of reclaimed asphalt pavement, reclaimed asphalt shingles (RAS), and combinations. These additives have been marketed as softening agents, to reduce high- and low-temperature performance grades, and as rejuvenators. Given the aging mechanism of bitumen and chemical changes that occur during aging, it is unlikely that any true form of rejuvenation is possible. In this paper data are provided on investigations into the use of a chemical class known as sterols, which can be obtained from seed oils and tall oil to retard the aging of bitumen. Investigations were carried out with RAS, with re-refined engine oil bottoms, and with the accelerated aging of bitumen and bituminous mixtures that contained sterol chemistry. The results demonstrated that, relative to controls without sterol, increases in the bitumen rheological index were reduced, and decreases in the colloidal index were reduced, as were decreases in the difference between bitumen low-temperature stiffness critical temperature and bitumen m-value critical temperature (ΔTc). Investigations with atomic force microscopy of bitumen samples with sterol additive, compared with those without, were used to understand the sterol additive function as the bitumen was aged.

Using binder and mixture space diagrams to evaluate the effect of re-refined engine oil bottoms on binders and mixtures after ageing

This study addresses the New England state transportation agencies concerns associated with the use of Re-refined Engine Oil Bottoms (REOB) in asphalt binders and mixtures. The effect of REOB on the physical and rheological properties of a straight run asphalt binder was investigated after short-term and long-term aging and after extended long-term aging. Also, the effect of REOB modified binders on the performance of asphalt mixtures after short and long-term aging was evaluated in terms of moisture damage, rutting, and cracking. Rheological results showed that the addition of REOB caused the binders to age more relative to the straight run binder. The results also indicated that the use of higher dosages of REOB can cause increased binder aging. Overall, when the results from the particular mixture tests used in this study were plotted on a Performance Space Diagrams, the diagrams did not provide evidence that using REOB decreases performance.

Asphalt mixtures containing RAS and/or RAP: relationships amongst binder composition analysis and mixture intermediate temperature cracking performance

The use of recycled asphalt shingles (RAS) as a partial replacement for petroleum-based virgin asphalt binder has received considerable attention in recent years. The objective of this study is to correlate the molecular structure and corresponding compositional analysis of asphalt binders of conventional asphalt mixtures as well as of mixtures containing RAS and/or reclaimed asphalt pavement (RAP) with their cracking potential at intermediate temperature. Laboratory testing evaluated the molecular composition of asphalt binders obtained from asphalt mixtures evaluated in this study using thin layer chromatograph/FID (Iatroscan) and gel permeation chromatography (GPC). Fracture resistance of laboratory produced mixtures was assessed using the Semi-Circular Bend (SCB) test at intermediate temperature. Molecular fractionation through GPC of RAS samples confirmed the presence of associated asphaltenes in greater concentrations than RAP samples. High concentrations of high molecular weight asphaltenes decrease the fracture resistance of the asphalt mixtures. The use of rejuvenating agents, Cyclogen-L, Hydrogreen, asphalt flux and Re-refined engine oil bottoms did not reduce the concentration of the highly associated asphaltenes, further they failed to improve the cracking resistance of the asphalt mixtures evaluated in this study.

Detection and Estimation of Re-Refined Engine Oil Bottoms in Asphalt Binders: Texas Department of Transportation’s Approach with Wavelength Dispersive X-Ray Fluorescence Spectroscopy

The Texas Department of Transportation investigated the use of wavelength dispersive X-ray fluorescence (WDXRF) spectroscopy to estimate the amount of re-refined engine oil bottoms (REOB) in asphalt binders. The objectives of this investigation were to use WDXRF to detect and quantify REOB in binder samples and to evaluate the accuracy of the quantified content. The detection of REOB in asphalt binders was determined by the presence of the elements phosphorus, molybdenum, zinc, copper, calcium, and potassium. Quantifying REOB content was achieved by determining the intensity of these elements and correlating that intensity with a known dosage of REOB with the use of a calibration standard. More than 100 binder and REOB combinations were prepared, and four calibration standards were developed for this study. The data analysis determined that correlations were specific to binder and REOB combinations. Significant error was introduced into the analysis when the REOB content for a sample was quantified according to a calibration curve that did not include the same binder and REOB. In one case, as much as a 92.0% error was introduced by that approach. To reduce this error and provide a reliable method, vanadium (V) and sulfur (S) intensities were used to select the appropriate calibration standard. Error was reduced by as much as half or more when the REOB content was quantified on the basis of selecting a calibration standard with similar S and V intensities.