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Properties of asphalt binder modified by bio-oil derived from waste cooking oil
Construction and Building Materials 102 (2016) 496–504
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Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Properties of asphalt binder modified by bio-oil derived from waste cooking oil Zhaojie Sun a, Junyan Yi a,b,⇑, Yudong Huang b, Decheng Feng a, Chaoyang Guo c a
School of Transportation Science and Engineering, Harbin Institute of Technology, Harbin 150090, China School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150090, China c Laboratory of molecular engineering for asphalt, China Academy of Transportation Sciences, Beijing 100029, China b
h i g h l i g h t s A kind of bio-oil derived from waste cooking oil is used as asphalt modifier. Chemical compositions of bio-oil and control asphalt are investigated. Bio-oil can reduce the deformation resistance of control asphalt. Bio-oil can improve the stress relaxation property of control asphalt. Bio-oil and control asphalt have good compatibility under static heated storage.
a r t i c l e
i n f o
Article history: Received 9 June 2015 Received in revised form 7 October 2015 Accepted 28 October 2015 Available online 13 November 2015 Keywords: Bio-oil Asphalt modifier Chemical composition Complex modulus Creep stiffness
a b s t r a c t The properties of asphalt binder modified by bio-oil derived from waste cooking oil were researched. Firstly, four components separation test and fourier transform infrared spectroscopy (FT-IR) test were carried out to investigate the chemical compositions of experimental materials. Then the physical and mechanical behaviors of bio-oil modified asphalt binders were studied by penetration grading tests, rotational viscosity (RV) test, separation tendency test, dynamic shear rheometer (DSR) test and bending beam rheometer (BBR) test. Four components separation test results indicate that bio-oil is mainly composed of aromatics, resins and saturates. Almost no chemical reactions between bio-oil and control asphalt are noticed through FT-IR test results. The addition of bio-oil decreases the softening point and viscosity, increases the penetration and ductility of control asphalt binder. Separation tendency test results demonstrate that bio-oil and control asphalt have good compatibility under static heated storage conditions. Furthermore, the addition of bio-oil decreases the complex modulus and creep stiffness, increases the phase angle and m-value of asphalt binder, which means that adding bio-oil could reduce the deformation resistance and elastic recovery performance of control asphalt, and improve the stress relaxation property and also helps to the improvement of thermal cracking resistance of control asphalt. Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction Petroleum asphalt, which is the by-product of petroleum refining, is commonly used in pavement construction. But petroleum is increasingly scarce as a non-renewable resource, resulting in the short supply of petroleum asphalt. Finding asphalt substitute is a new way to resolve the problem. Utilizing some waste materials from other industries to partially substitute asphalt, can not only reduce asphalt consumption but also improve the pavement performance of asphalt. This will also have great economic and ⇑ Corresponding author at: School of Transportation Science and Engineering, Harbin Institute of Technology, Harbin 150090, China. E-mail address: [email protected] (J. Yi). http://dx.doi.org/10.1016/j.conbuildmat.2015.10.173 0950-0618/Ó 2015 Elsevier Ltd. All rights reserved.
social significance to resources recycling and sustainable development. In recent years, many researchers were looking for the substitute or modifier of traditional asphalt binder. The potential applications of alternative binders or modifiers, such as bio-binder from microalgae, fractionated bio-oil, cotton seed oil, crude glycerol, organo montmorillonite nanoclay and so on, have been investigated [1–8]. Yang et al. [9] also studied the performance of asphalt binder partially substituted by a kind of bio-oil, which was obtained by waste wood fast pyrolysis. Their works indicated that the addition of bio-oil increased the high temperature performance of asphalt binder, reduced the mixing temperature of the asphalt mixture, and it had adverse effects on the medium and low temperature performance of the asphalt binder. Fini et al.
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[10,11] investigated the performance of asphalt binder modified by bio-binder, which was produced from the thermochemical conversion of swine manure. The test results showed that the addition of bio-binder improved the low temperature properties, but it decreased the high temperature grade of asphalt binder. Peralta et al. [12,13] prepared bio-binder by fast pyrolysis of plant residue. It was found that this bio-binder could be used as modifier, additive or antioxidant of asphalt binder. The basic performance of bio-binder met the specification requirements for asphalt binder, and the incorporation of rubber could significantly improve the bio-binder properties. Although numerous researchers produced asphalt substitutes or modifiers from biomass materials, few of them focused on waste oil products [14–17]. In China, there is a great amount of waste cooking oil produced every year, which is believed more than 5 million tons. In recent years, biodiesel were obtained from waste cooking oil through alkaline catalysis procedure [18–20]. However, about 10% bio-oil by-product was coproduced during the biodiesel production [6]. This bio-oil is black viscous liquid mixing with glycerin and soap, which has been thought as a potential asphalt or asphalt modifier substitute. In this paper, this bio-oil was used as asphalt modifier, and the properties of bio-oil modified asphalt had been researched to investigate the effect of bio-oil on the asphalt binder performance. Four components separation test, FT-IR test, viscosity grading tests, separation tendency test, DSR test and BBR test were conducted to primarily study the effect of bio-oil on the chemical, physical and mechanical behaviors of asphalt binder. Different from normal PG grading test conditions, the effect of aging was not included in this study during the DSR and BBR tests.
2.3. Materials preparation At first, control asphalt was uniformly heated in a temperature-regulated heating mantle and continuously stirred using a high shear mixer. Then, 0%, 2%, 4%, 6% and 8% bio-oil were added into control asphalt by weight when test temperature reached 135 °C, and then blended for 40 min by high shear mixer with a speed of 5000 r/min to achieve a homogeneous mixing state. The IDs of asphalt binders used in this study were presented in Table 2.
2.4. Experimental methods Firstly, four components separation test and FT-IR test were carried out to analyze the chemical properties of BP and AMB. Then, the physical and mechanical behaviors of AMB were studied with penetration grading tests, RV test, separation tendency test, DSR test and BBR test. The experimental methods used in this study referred to Chinese specification (JTG E20-2011). The flowchart of this study was presented in Fig. 2.
2.4.1. Four components separation test According to T0618, four components separation tests were conducted to analyze the chemical components differences between bio-oil and control asphalt. In the test process, 0.5–1.0 g sample was dissolved in n-heptane. In this procedure, asphaltenes were firstly separated. The n-heptane soluble fractions were poured into vitreous adsorption column filled with active alumina, then the saturates, aromatics and resins were separated using n-heptane, toluene and toluene/ethanol (1:1 by volume) [21,22].
2.4.2. Fourier transform infrared spectroscopy (FT-IR) test FT-IR tests were performed to analyze the functional groups differences between BP and AMB. Test samples were dissolved in carbon disulfide with 5 wt. % concentration, dropped onto KBr table and controlled the thickness of the film to be appropriately 150 lm, then scanned at 32 times with test spectrum range from 400 to 4000 cm1 [16].
2. Materials and experimental methods 2.1. Asphalt binder In this study, 40/60 penetration grade asphalt from Jilin province of China was used as control asphalt. Its basic properties were shown in Table 1, which all met the requirements of Chinese specification (JTG F40-2004). The heating speed in softening point test is 5 °C/min, and the stretching speed in ductility test is 5 cm/min. 2.2. Bio-oil The bio-oil used in this study is black oily liquid, which is the by-product of waste cooking oil refining for biodiesel. As shown in Fig. 1, in the process of producing bio-diesel from waste cooking oil, free fatty acids in waste cooking oil were firstly converted into fatty acid methyl ester by methanol with the action of sulfuric acid catalyst, which process is called pre-esterification. Then the fatty acid glycerides in waste cooking oil were converted into fatty acid methyl ester by methanol with the action of potassium hydroxide catalyst, which process is called transesterification. Fatty acid methyl ester is the main component of bio-diesel, and the residue during these procedures is the bio-oil used in this study. Before adding bio-oil into the control asphalt, the physical properties of bio-oil were investigated. Specific, the moisture content of bio-oil is 3.1% by weight, and the density at 15 °C is 0.95 g/cm3. In addition, the rotational viscosity of bio-oil at room temperature (25 °C) is determined to be 146.3 mPa s. As the pre-esterification and transesterification process may introduce acid and alkali into the original mixtures, the pH value of bio-oil was also measured, which was found to be 6.1. Therefore the biooil was almost neutral.
2.4.3. Penetration, softening point and ductility tests According to T0604, the penetration tests were used to assess the hardness of asphalt materials. In the test process, a container filled with asphalt sample was stored in 25 °C water bath for 90 min, and then penetrated by a needle weighted 100 g, the penetration depth was measured as penetration in the unit of 0.1 mm. According to T0606, the softening point tests were used to identify the temperatures at which phase change occurred in asphalt materials. In the test process, two steel balls were placed on the horizontal disks of asphalt sample contained in vertically supported metal rings. The assembly was heated in water bath at 5 °C/min. The softening point was recorded as the average temperature at which the two disks softened enough to allow each ball, enveloped in asphalt, to fall a distance of 25 mm (1.0 in). It was also known as the ring and ball softening temperature (Tr&b) [23]. According to T0605, the ductility tests were used to measure the stretching length of standard asphalt sample before breaking under standard testing condition (5 cm/min stretching speed at 15 °C). It is usually considered that asphalt binder with low ductility has poor low temperature performance in service.
2.4.4. Rotational viscosity (RV) test According to T0625, Brookfield viscometer was used in rotational viscosity (RV) test to measure the flowing resistance of asphalt materials. In the test process, a cylindrical spindle with specific diameter and effective length rotates inside a container filled with asphalt binder at restricted speed. In this research, the test temperature was 60 °C.
Table 1 Properties of 40/60 penetration grade asphalt. Properties
Units
Requirements
Test results
Test methods
Penetration @25 °C Softening point Ductility @15 °C Flashing point Density @15 °C Wax content After short-term aged (RTFOT)
0.1 mm °C cm °C g/cm3 % % % cm
40–60 P49 P30 P260 — 62.2 6±0.8 P63 P10
43.0 52.3 150 310 1.13 1.7 0.75 70.2 110
T0604 T0606 T0605 T0611 T0603 T0615 T0610
Mass loss Retained penetration ratio @25 °C Retained ductility @15 °C
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Fig. 1. Bio-oil preparation technology.
Table 2 IDs of asphalt binders used in this study. Binder types
IDs
Bio-oil product Control asphalt 98% Control asphalt mixing 96% Control asphalt mixing 94% Control asphalt mixing 92% Control asphalt mixing Asphalt modified by bio-oil
BP A0 A2 A4 A6 A8 AMB
with with with with
2% 4% 6% 8%
bio-oil bio-oil bio-oil bio-oil
by by by by
weight weight weight weight
2.4.5. Separation tendency test According to T0661, the separation tendency tests were carried out to investigate the segregation potential for bio-oil modified asphalt. In the test process, an aluminum foil tube filled with asphalt sample was vertically put in an oven at 163 °C for 48 h, and then was cut horizontally into three equal sections after being cooled. The softening points of the top and bottom sections were measured. If the difference was less than 2.5 °C, it was believed that the bio-oil and control asphalt had good compatibility [24].
2.4.6. Dynamic shear rheometer (DSR) test According to T0628, the dynamic shear rheometer (DSR) tests were performed to measure the complex modulus and phase angle parameters of asphalt materials with frequency scanning test mode, without considering the effect of ageing. The test temperatures included 0 °C, 10 °C, 20 °C, 30 °C, 40 °C, 50 °C and 60 °C. At each temperature, frequency range of 0.1–60 Hz was applied. Strain controlled mode was used in this test, and the applied strain level was controlled to be 0.5%. This strain level was determined through investigating the linear behavior range of bio-oil modified asphalt. The 8 mm diameter plate and 2 mm gap were used when test temperatures were lower than 40 °C, otherwise, the 25 mm diameter plate and 1 mm gap were used.
2.4.7. Bending beam rheometer (BBR) test According to T0627, the bending beam rheometer (BBR) tests were conducted to measure the stiffness and m-value parameters of asphalt materials at low temperatures, also without considering the effect of ageing. The test temperatures included 18 °C, 24 °C and 30 °C.
Fig. 3. Four components separation test results.
3. Results and discussions 3.1. Four components The four components separation test results were presented in Fig. 3. It can be noted that the asphaltenes content in bio-oil is less than 1%, which could be neglected during the study. Compared with the control asphalt used in this study, the asphaltenes and aromatics contents in bio-oil are much smaller, while the saturates and resins contents in bio-oil are relatively higher. Therefore, similar to distillate products, the bio-oil can be considered as not containing asphaltenes. It should be noticed that the columns associated with bio-oil do not sum up to 100% in Fig. 3. In fact, there are two calculation methods for percentages of four components in Chinese specification
Fig. 2. Flowchart of bio-oil modified asphalt test.
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(T0618 JTG E20-2011). The first one recommend measuring the components of asphaltenes, aromatics and saturates in separation test, then obtaining the component of resins by hundred percent minus the components of asphaltenes, aromatics and saturates. In this case, columns associated with bio-oil would sum up to 100%. The second method is to obtain the percentages of four components by measuring the real residue weight of different component in four components separation test. Therefore, if there are some volatile substances in bio-oil during the separation test, a difference between the final residue and original weights of raw material would exist. Therefore the columns associated with bio-oil in Fig. 3 do not sum up to 100%.
3.2. Functional group The absorption peak wavenumbers and corresponding functional groups were shown in Table 3 by analyzing the IR spectra of BP and AMB. It is obvious that both BP and A0 have saturated hydrocarbons and amides. Besides, BP has lipids, while A0 has aromatic compounds and sulfinyl compounds. After adding bio-oil into control asphalt, the IR spectra of A4 and A8 have new absorption peaks. However, it is interesting that these new absorption peak positions are coincident with that in BP IR spectrum, and no other new absorption peaks are found, which indicates that biooil and control asphalt are physically blended and almost no chemical reactions between them are found.
Fig. 4. Penetration test results of AMB.
3.3. Penetration, softening point and ductility The penetration, softening point and ductility test results of AMB were shown in Figs. 4–6. Fig. 4 showed that the penetration increased with the addition of bio-oil. It was also noticed that the penetration increased faster when bio-oil content was more than 4%. Fig. 5 indicated that the softening point decreased uniformly with bio-oil content increasing. Fig. 6 showed that the ductility increased rapidly with bio-oil added, but reduced sharply when bio-oil content was more than 6%. The abnormal point at 8% addition may be due to the segregation of bio-oil into the control asphalt. Unlike penetration and softening point tests, the sample in ductility test will stretch to break with a 5 cm/min stretching speed. During this procedure, the diameter in the cross-section of sample will get smaller and smaller until less than a tenth of a millimeter. Considering the rather small scale of tested sample and the applied tensile loading mode, the segregation of bio-oil in the control asphalt could have more significant effect on the ductility test result. To sum up, bio-oil modified asphalt binders have higher penetration, lower softening point and larger ductility. In general, penetration and softening point indicate the viscosity of asphalt binder, while ductility represents the extensibility. In penetration grading system, the penetration depth, softening point and ductility are empirically correlated with asphalt binder performance. Asphalt binders with high penetration numbers, high ductility numbers and low softening points are normally used for cold climates while asphalt binders with low penetration numbers, low
Fig. 5. Softening point test results of AMB.
ductility numbers and high softening points are used for warm and hot climates. 3.4. Rotational viscosity The rotational viscosity test results of AMB were shown in Fig. 7. It could be found that the addition of bio-oil decreased the viscosity of asphalt binder because of dilution effect, and then reduced construction temperatures of AMB mixtures. Therefore, similar to warm asphalt mixture, the AMB mixtures are friendlier to the environment because of less energy consumption and asphalt smoke emission. But excessive addition of bio-oil in asphalt binder will reduce the service performance, as indicated in Figs. 4–6.
Table 3 Absorption peak wavenumbers and corresponding functional groups. Types
Absorption peak wavenumbers/cm1
BP A0 A4 A8 Functional groups
727 741 741 741 –(CH2)n–
— 760 752 757 C6H5-
— 820 817 820
— 884 878 882
— 1058 1038 1055 S@O
1181 — 1188 1190 –CO–O–
1380 1379 1379 1379 C–CH3
1467 1465 1465 1464
— 1616 1611 1617 C6H5–
1748 — 1744 1745 –CO–O–
2861 2859 2874 2859 –CH2–
2945 2933 2943 2932
3486 3482 3486 3483 –CO–NH–
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3.5. Compatibility The separation tendency test results of AMB were presented in Fig. 8. Test results indicated that all the softening point differences of asphalt binders between top and bottom were less than 2.5 °C after being stored vertically in an oven at 163 °C for 48 h, which meant that the bio-oil and control asphalt had good compatibility. Therefore, it can be anticipated that there is no separation problem for AMB. 3.6. Complex modulus and phase angle at medium and high temperatures
Fig. 6. Ductility test results of AMB (@15 °C).
The complex modulus and phase angle data at different frequencies and temperatures were shifted horizontally to reference temperature based on time-temperature superposition principle (TTSP), and then fitted by generalized CAM model to obtain the master curves, which could characterize the mechanical behaviors of bio-oil modified asphalt at medium and high temperatures. According to generalized CAM model, the complex modulus master curve equation is as follows:
G ¼ Ge þ
Gg Ge
ð1Þ
m =k 0 k e
½1 þ ðf c =f Þ
where G is complex modulus, Ge ¼ G ðf ! 0Þ with Ge ¼ 0 for asphalt binder, Gg ¼ G ðf ! 1Þ, f c is a location parameter of fre0
quency with dimensions, f is the reduced frequency related to temperature and strain, k and me are shape parameters without dimensions. The phase angle master curve equation is as follows:
(
)md =2 0 2 lgðf t =f Þ d ¼ 90I ð90I dm Þ 1 þ Rd
Fig. 7. Rotational viscosity test results of AMB (@60 °C).
ð2Þ
where d is phase angle, dm is the phase angle value at the inflection point for phase angle master curve, f t is a location parameter of fre0 quency with dimensions at which dm occurs, f is the reduced frequency, Rd and md are the shape parameters without dimensions, 0 0 I doesn’t have explicit definition, I ¼ 0 if f > f t and I ¼ 1 if f 6 f t for asphalt binder, I 0 for asphalt mixture [25,26]. The definitions of generalized CAM model parameters were shown in Fig. 9, and the
Fig. 8. Separation tendency test results of AMB.
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Fig. 9. Definitions of generalized CAM model parameters.
Fig. 10. Typical fitting results of generalized CAM model.
Fig. 11. Master curves of AMB (@20 °C).
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Table 4 Fitting parameters of complex modulus master curve model. Asphalt types
A0 A2 A4 A6 A8
Fitting parameters (@20 °C) lgG⁄g
fc
me
k
R2
8.844 9.423 8.836 8.585 8.323
132.412 59.612 273.987 700.471 408.542
0.940 1.146 1.012 0.978 1.044
0.245 0.165 0.237 0.288 0.305
1.00 1.00 0.99 0.99 0.98
Table 5 Fitting parameters of phase angle master curve model. Asphalt types
A0 A2 A4 A6 A8
Fitting parameters (@20 °C) dm
ft
Rd
md
R2
34.668 35.545 45.374 49.132 51.651
987.352 5238.727 5024.362 4807.681 16210.226
1.724 3.788 4.521 3.701 3.813
0.948 2.493 3.143 2.411 2.405
0.97 0.96 0.95 0.93 0.92
typical fitting results of generalized CAM model were shown in Fig. 10. In this study, 20 °C was selected as the reference temperature. The complex modulus master curves and phase angle master curves of AMB were plotted in Fig. 11. The model fitting parameters were presented in Tables 4 and 5. Fig. 11(a) indicated that the complex modulus increased with the increment of loading frequency. And the complex modulus master curves were right horizontally shifted with bio-oil added, which meant that the addition of bio-oil decreased the complex modulus of asphalt binder in the whole frequency domain. Fig. 11(b) showed that the phase angle decreased with the increment of frequency, and the phase angle master curves were also right horizontally shifted with bio-oil added, which meant that the addition of bio-oil increased the phase angle of asphalt binder in the whole frequency domain. The complex modulus (G⁄) can be considered the sample’s total resistance to deformation when applied repeatedly shear loading, while the phase angle (d), is the lag between the applied shear stress and the resulting shear strain. Intuitively, the higher the G⁄ value, the stiffer the asphalt binder is. The phase angle is an
Fig. 12. Low-temperature parameters test data and fitting models of AMB.
Fig. 13. Creep compliance master curves of AMB based on generalized CAM model.
Z. Sun et al. / Construction and Building Materials 102 (2016) 496–504 Table 6 Fitting parameters of creep compliance master curve model. Asphalt types
A0 A2 A4 A6 A8
Fitting parameters (@-30 °C) lgG⁄e
lgG⁄g
fc
me
k
R2
3.399 3.316 3.367 3.167 3.182
67.452 68.658 72.624 69.954 70.704
213065.843 249984.087 249807.643 264481.456 257069.963
0.727 0.841 0.887 1.009 0.993
0.00315 0.00360 0.00361 0.00426 0.00417
0.98 0.98 0.97 0.96 0.95
indicator to demonstrate the ratio of viscosity and elasticity in polymer materials. The lower the phase angle is, the less viscous the material is, which means the asphalt binder is able to recover its original shape after being deformed by a load. Therefore, the addition of bio-oil could decrease the deformation resistance and elastic recovery performance of control asphalt. 3.7. Stiffness and m-value at low temperatures The stiffness and m-value test data of AMB at 60 s loading time were presented in Fig. 12. It could be found that the addition of bio-oil decreased stiffness and increased m-value (an indicator of stress relaxation capability) of asphalt binder, which implied less stress accumulation during cooling procedure, and the improvement of thermal cracking resistance for asphalt binder. Besides, the fitting equations and parameters were shown in Fig. 12, which indicating that both stiffness and m-value had good linear relationships with bio-oil content. The creep compliance (reciprocal of stiffness) data at continuous loading times were plotted in Fig. 13(a). It is noticed that the creep compliance curves at different temperatures can also be shifted horizontally to obtain the creep compliance master curve at reference temperature based on TTSP. The generalized CAM model, as shown in Eq. (1), was used to fit creep compliance master curves. The typical fitting result and creep compliance master curves of AMB were shown in Fig. 13, and corresponding fitting parameters were shown in Table 6. It could be found that the creep compliance increased with the increment of loading time, and the creep compliance master curves were left horizontally shifted in the whole time domain with bio-oil added, which meant that the addition of bio-oil increased the creep compliance for asphalt binder in the whole time domain. Creep stiffness is normally a measure of the thermal stresses in the asphalt binder resulting from thermal contraction. A higher creep stiffness value (lower creep compliance) indicates higher thermal stresses. Although Superpave performance grading recommend this test conducted on long-term aged sample, the higher creep compliance and m-value of bio-oil modified asphalt could indicate a good stress relaxation property, which was helpful to the improvement of thermal cracking resistance of binder. 4. Conclusions This paper has investigated the chemical, physical and mechanical properties of asphalt binder modified by bio-oil derived from waste cooking oil. Based on the results presented, several conclusions can be drawn: (1) Bio-oil is mainly composed by aromatics, resins and saturates. Compared with the 40/60 penetration grade asphalt, bio-oil has lower asphaltenes and aromatics contents, higher saturates and resins contents. Besides, almost no chemical reactions are noticed when mixing control asphalt with bio-oil.
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(2) The addition of bio-oil decreases softening point and viscosity, increases penetration and ductility of asphalt binder. The separation tendency test results of bio-oil modified asphalt demonstrate that bio-oil and control asphalt have good compatibility under static heated storage conditions. (3) The addition of bio-oil decreases complex modulus and increases phase angle for asphalt binder at medium and high temperatures, which means adding bio-oil could decrease the deformation resistance and elastic recovery performance of control asphalt. (4) The addition of bio-oil decreases stiffness and increases mvalue of asphalt binder at low temperatures, which indicates a good stress relaxation property and also helps to the improvement of thermal cracking resistance of binder. It can be concluded that the bio-oil derived from waste cooking oil can be used as asphalt modifier to mainly improve the low temperature performance of asphalt binder, especially in cold regions. In addition, the ageing susceptibility and mixture performance of bio-oil modified asphalt should be further researched. Acknowledgements Thanks for the financial support by China Postdoctoral Science Foundation (No. 2013M541393, 2015T80357), Heilongjiang Postdoctoral Science Foundation (LBH-Z13084), National Natural Science Foundation of China (Grant No. 51408154) and Open Fund of Key Laboratory of Road Structure and Material of Ministry of Transport (Changsha University of Science & Technology) (kfj140304). References [1] E. Chailleux, M. Audo, C. Queffélec, et al., Alternative Binder from microalgae: algoroute project, Alternative Binders for Sustainable Asphalt Pavements, 2012. [2] R.C. Williams, J. Satrio, M. Rover, et al., Utilization of fractionated bio-oil in Asphalt, in: DVD-ROM Proceedings of the 88th Annual Meeting of the Transportation Research Board, Washington (DC), 2009. [3] M. Chen, F. Xiao, B. Putman, et al., High temperature properties of rejuvenating recovered binder with rejuvenator, waste cooking and cotton seed oils, Constr. Build. Mater. 59 (2014) 10–16. [4] N. Guo, Z. You, Y. Zhao, et al., Laboratory performance of warm mix asphalt containing recycled asphalt mixtures, Constr. Build. Mater. 64 (2014) 141–149. [5] M.A. Raouf, C.R. Williams, General rheological properties of fractionated switchgrass bio-oil as a pavement material, Road Mater. Pavement Des. 11 (sup1) (2010) 325–353. [6] F. Yang, M.A. Hanna, R. Sun, Value-added uses for crude glycerol-a byproduct of biodiesel production, Biotechnol. Biofuels 5 (13) (2012) 1–10. [7] R. Kluttz, Considerations for use of alternative binders in asphalt pavements: material characteristics, Transp. Res. E Circular E-C165 (2012). [8] G. Liu, M.F.C. Van de Ven, A.A.A. Molenaar, et al., Organo montmorillonite nanoclay: alternative modifier to sustain durability of asphalt pavement, Transp. Res. E Circular E-C165 (2012). [9] X. Yang, Z.P. You, Q.L. Dai, Performance evaluation of asphalt binder modified by bio-oil generated from waste wood resources, Int. J. Pavement Res. Technol. 6 (4) (2013) 431–439. [10] E.H. Fini, S.H. Yang, S. Xiu, Characterization and application of manure-based bio-binder in asphalt industry, in: Transportation Research Board 89th Annual Meeting, 2010 (10–2871). [11] E.H. Fini, I.L. Al-Qadi, Z. You, et al., Partial replacement of asphalt binder with bio-binder: characterisation and modification, Int. J. Pavement Eng. 13 (6) (2012) 515–522. [12] J. Peralta, R.C. Williams, M. Rover, et al., Development of rubber-modified fractionated bio-oil for use as noncrude petroleum binder in flexible pavements, Transp. Res. E Circular E-C165 (2012). [13] J. Peralta, M.A. Raouf, S. Tang, et al., Bio-renewable asphalt modifiers and asphalt substitutes, in: Sustainable Bioenergy and Bioproducts, Springer London, 2012, pp. 89–115. [14] A. Zofka, I. Yut, Investigation of rheology and aging properties of asphalt binder modified with waste coffee grounds, Transp. Res. E Circular E-C165 (2012). [15] J.C. Seidel, J.E. Haddock, Soy fatty acids as sustainable modifier for asphalt binders, Alternative Binders for Sustainable Asphalt Pavements Washington DC, 2012.
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Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Properties of asphalt binder modified by bio-oil derived from waste cooking oil Zhaojie Sun a, Junyan Yi a,b,⇑, Yudong Huang b, Decheng Feng a, Chaoyang Guo c a
School of Transportation Science and Engineering, Harbin Institute of Technology, Harbin 150090, China School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150090, China c Laboratory of molecular engineering for asphalt, China Academy of Transportation Sciences, Beijing 100029, China b
h i g h l i g h t s A kind of bio-oil derived from waste cooking oil is used as asphalt modifier. Chemical compositions of bio-oil and control asphalt are investigated. Bio-oil can reduce the deformation resistance of control asphalt. Bio-oil can improve the stress relaxation property of control asphalt. Bio-oil and control asphalt have good compatibility under static heated storage.
a r t i c l e
i n f o
Article history: Received 9 June 2015 Received in revised form 7 October 2015 Accepted 28 October 2015 Available online 13 November 2015 Keywords: Bio-oil Asphalt modifier Chemical composition Complex modulus Creep stiffness
a b s t r a c t The properties of asphalt binder modified by bio-oil derived from waste cooking oil were researched. Firstly, four components separation test and fourier transform infrared spectroscopy (FT-IR) test were carried out to investigate the chemical compositions of experimental materials. Then the physical and mechanical behaviors of bio-oil modified asphalt binders were studied by penetration grading tests, rotational viscosity (RV) test, separation tendency test, dynamic shear rheometer (DSR) test and bending beam rheometer (BBR) test. Four components separation test results indicate that bio-oil is mainly composed of aromatics, resins and saturates. Almost no chemical reactions between bio-oil and control asphalt are noticed through FT-IR test results. The addition of bio-oil decreases the softening point and viscosity, increases the penetration and ductility of control asphalt binder. Separation tendency test results demonstrate that bio-oil and control asphalt have good compatibility under static heated storage conditions. Furthermore, the addition of bio-oil decreases the complex modulus and creep stiffness, increases the phase angle and m-value of asphalt binder, which means that adding bio-oil could reduce the deformation resistance and elastic recovery performance of control asphalt, and improve the stress relaxation property and also helps to the improvement of thermal cracking resistance of control asphalt. Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction Petroleum asphalt, which is the by-product of petroleum refining, is commonly used in pavement construction. But petroleum is increasingly scarce as a non-renewable resource, resulting in the short supply of petroleum asphalt. Finding asphalt substitute is a new way to resolve the problem. Utilizing some waste materials from other industries to partially substitute asphalt, can not only reduce asphalt consumption but also improve the pavement performance of asphalt. This will also have great economic and ⇑ Corresponding author at: School of Transportation Science and Engineering, Harbin Institute of Technology, Harbin 150090, China. E-mail address: [email protected] (J. Yi). http://dx.doi.org/10.1016/j.conbuildmat.2015.10.173 0950-0618/Ó 2015 Elsevier Ltd. All rights reserved.
social significance to resources recycling and sustainable development. In recent years, many researchers were looking for the substitute or modifier of traditional asphalt binder. The potential applications of alternative binders or modifiers, such as bio-binder from microalgae, fractionated bio-oil, cotton seed oil, crude glycerol, organo montmorillonite nanoclay and so on, have been investigated [1–8]. Yang et al. [9] also studied the performance of asphalt binder partially substituted by a kind of bio-oil, which was obtained by waste wood fast pyrolysis. Their works indicated that the addition of bio-oil increased the high temperature performance of asphalt binder, reduced the mixing temperature of the asphalt mixture, and it had adverse effects on the medium and low temperature performance of the asphalt binder. Fini et al.
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[10,11] investigated the performance of asphalt binder modified by bio-binder, which was produced from the thermochemical conversion of swine manure. The test results showed that the addition of bio-binder improved the low temperature properties, but it decreased the high temperature grade of asphalt binder. Peralta et al. [12,13] prepared bio-binder by fast pyrolysis of plant residue. It was found that this bio-binder could be used as modifier, additive or antioxidant of asphalt binder. The basic performance of bio-binder met the specification requirements for asphalt binder, and the incorporation of rubber could significantly improve the bio-binder properties. Although numerous researchers produced asphalt substitutes or modifiers from biomass materials, few of them focused on waste oil products [14–17]. In China, there is a great amount of waste cooking oil produced every year, which is believed more than 5 million tons. In recent years, biodiesel were obtained from waste cooking oil through alkaline catalysis procedure [18–20]. However, about 10% bio-oil by-product was coproduced during the biodiesel production [6]. This bio-oil is black viscous liquid mixing with glycerin and soap, which has been thought as a potential asphalt or asphalt modifier substitute. In this paper, this bio-oil was used as asphalt modifier, and the properties of bio-oil modified asphalt had been researched to investigate the effect of bio-oil on the asphalt binder performance. Four components separation test, FT-IR test, viscosity grading tests, separation tendency test, DSR test and BBR test were conducted to primarily study the effect of bio-oil on the chemical, physical and mechanical behaviors of asphalt binder. Different from normal PG grading test conditions, the effect of aging was not included in this study during the DSR and BBR tests.
2.3. Materials preparation At first, control asphalt was uniformly heated in a temperature-regulated heating mantle and continuously stirred using a high shear mixer. Then, 0%, 2%, 4%, 6% and 8% bio-oil were added into control asphalt by weight when test temperature reached 135 °C, and then blended for 40 min by high shear mixer with a speed of 5000 r/min to achieve a homogeneous mixing state. The IDs of asphalt binders used in this study were presented in Table 2.
2.4. Experimental methods Firstly, four components separation test and FT-IR test were carried out to analyze the chemical properties of BP and AMB. Then, the physical and mechanical behaviors of AMB were studied with penetration grading tests, RV test, separation tendency test, DSR test and BBR test. The experimental methods used in this study referred to Chinese specification (JTG E20-2011). The flowchart of this study was presented in Fig. 2.
2.4.1. Four components separation test According to T0618, four components separation tests were conducted to analyze the chemical components differences between bio-oil and control asphalt. In the test process, 0.5–1.0 g sample was dissolved in n-heptane. In this procedure, asphaltenes were firstly separated. The n-heptane soluble fractions were poured into vitreous adsorption column filled with active alumina, then the saturates, aromatics and resins were separated using n-heptane, toluene and toluene/ethanol (1:1 by volume) [21,22].
2.4.2. Fourier transform infrared spectroscopy (FT-IR) test FT-IR tests were performed to analyze the functional groups differences between BP and AMB. Test samples were dissolved in carbon disulfide with 5 wt. % concentration, dropped onto KBr table and controlled the thickness of the film to be appropriately 150 lm, then scanned at 32 times with test spectrum range from 400 to 4000 cm1 [16].
2. Materials and experimental methods 2.1. Asphalt binder In this study, 40/60 penetration grade asphalt from Jilin province of China was used as control asphalt. Its basic properties were shown in Table 1, which all met the requirements of Chinese specification (JTG F40-2004). The heating speed in softening point test is 5 °C/min, and the stretching speed in ductility test is 5 cm/min. 2.2. Bio-oil The bio-oil used in this study is black oily liquid, which is the by-product of waste cooking oil refining for biodiesel. As shown in Fig. 1, in the process of producing bio-diesel from waste cooking oil, free fatty acids in waste cooking oil were firstly converted into fatty acid methyl ester by methanol with the action of sulfuric acid catalyst, which process is called pre-esterification. Then the fatty acid glycerides in waste cooking oil were converted into fatty acid methyl ester by methanol with the action of potassium hydroxide catalyst, which process is called transesterification. Fatty acid methyl ester is the main component of bio-diesel, and the residue during these procedures is the bio-oil used in this study. Before adding bio-oil into the control asphalt, the physical properties of bio-oil were investigated. Specific, the moisture content of bio-oil is 3.1% by weight, and the density at 15 °C is 0.95 g/cm3. In addition, the rotational viscosity of bio-oil at room temperature (25 °C) is determined to be 146.3 mPa s. As the pre-esterification and transesterification process may introduce acid and alkali into the original mixtures, the pH value of bio-oil was also measured, which was found to be 6.1. Therefore the biooil was almost neutral.
2.4.3. Penetration, softening point and ductility tests According to T0604, the penetration tests were used to assess the hardness of asphalt materials. In the test process, a container filled with asphalt sample was stored in 25 °C water bath for 90 min, and then penetrated by a needle weighted 100 g, the penetration depth was measured as penetration in the unit of 0.1 mm. According to T0606, the softening point tests were used to identify the temperatures at which phase change occurred in asphalt materials. In the test process, two steel balls were placed on the horizontal disks of asphalt sample contained in vertically supported metal rings. The assembly was heated in water bath at 5 °C/min. The softening point was recorded as the average temperature at which the two disks softened enough to allow each ball, enveloped in asphalt, to fall a distance of 25 mm (1.0 in). It was also known as the ring and ball softening temperature (Tr&b) [23]. According to T0605, the ductility tests were used to measure the stretching length of standard asphalt sample before breaking under standard testing condition (5 cm/min stretching speed at 15 °C). It is usually considered that asphalt binder with low ductility has poor low temperature performance in service.
2.4.4. Rotational viscosity (RV) test According to T0625, Brookfield viscometer was used in rotational viscosity (RV) test to measure the flowing resistance of asphalt materials. In the test process, a cylindrical spindle with specific diameter and effective length rotates inside a container filled with asphalt binder at restricted speed. In this research, the test temperature was 60 °C.
Table 1 Properties of 40/60 penetration grade asphalt. Properties
Units
Requirements
Test results
Test methods
Penetration @25 °C Softening point Ductility @15 °C Flashing point Density @15 °C Wax content After short-term aged (RTFOT)
0.1 mm °C cm °C g/cm3 % % % cm
40–60 P49 P30 P260 — 62.2 6±0.8 P63 P10
43.0 52.3 150 310 1.13 1.7 0.75 70.2 110
T0604 T0606 T0605 T0611 T0603 T0615 T0610
Mass loss Retained penetration ratio @25 °C Retained ductility @15 °C
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Fig. 1. Bio-oil preparation technology.
Table 2 IDs of asphalt binders used in this study. Binder types
IDs
Bio-oil product Control asphalt 98% Control asphalt mixing 96% Control asphalt mixing 94% Control asphalt mixing 92% Control asphalt mixing Asphalt modified by bio-oil
BP A0 A2 A4 A6 A8 AMB
with with with with
2% 4% 6% 8%
bio-oil bio-oil bio-oil bio-oil
by by by by
weight weight weight weight
2.4.5. Separation tendency test According to T0661, the separation tendency tests were carried out to investigate the segregation potential for bio-oil modified asphalt. In the test process, an aluminum foil tube filled with asphalt sample was vertically put in an oven at 163 °C for 48 h, and then was cut horizontally into three equal sections after being cooled. The softening points of the top and bottom sections were measured. If the difference was less than 2.5 °C, it was believed that the bio-oil and control asphalt had good compatibility [24].
2.4.6. Dynamic shear rheometer (DSR) test According to T0628, the dynamic shear rheometer (DSR) tests were performed to measure the complex modulus and phase angle parameters of asphalt materials with frequency scanning test mode, without considering the effect of ageing. The test temperatures included 0 °C, 10 °C, 20 °C, 30 °C, 40 °C, 50 °C and 60 °C. At each temperature, frequency range of 0.1–60 Hz was applied. Strain controlled mode was used in this test, and the applied strain level was controlled to be 0.5%. This strain level was determined through investigating the linear behavior range of bio-oil modified asphalt. The 8 mm diameter plate and 2 mm gap were used when test temperatures were lower than 40 °C, otherwise, the 25 mm diameter plate and 1 mm gap were used.
2.4.7. Bending beam rheometer (BBR) test According to T0627, the bending beam rheometer (BBR) tests were conducted to measure the stiffness and m-value parameters of asphalt materials at low temperatures, also without considering the effect of ageing. The test temperatures included 18 °C, 24 °C and 30 °C.
Fig. 3. Four components separation test results.
3. Results and discussions 3.1. Four components The four components separation test results were presented in Fig. 3. It can be noted that the asphaltenes content in bio-oil is less than 1%, which could be neglected during the study. Compared with the control asphalt used in this study, the asphaltenes and aromatics contents in bio-oil are much smaller, while the saturates and resins contents in bio-oil are relatively higher. Therefore, similar to distillate products, the bio-oil can be considered as not containing asphaltenes. It should be noticed that the columns associated with bio-oil do not sum up to 100% in Fig. 3. In fact, there are two calculation methods for percentages of four components in Chinese specification
Fig. 2. Flowchart of bio-oil modified asphalt test.
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(T0618 JTG E20-2011). The first one recommend measuring the components of asphaltenes, aromatics and saturates in separation test, then obtaining the component of resins by hundred percent minus the components of asphaltenes, aromatics and saturates. In this case, columns associated with bio-oil would sum up to 100%. The second method is to obtain the percentages of four components by measuring the real residue weight of different component in four components separation test. Therefore, if there are some volatile substances in bio-oil during the separation test, a difference between the final residue and original weights of raw material would exist. Therefore the columns associated with bio-oil in Fig. 3 do not sum up to 100%.
3.2. Functional group The absorption peak wavenumbers and corresponding functional groups were shown in Table 3 by analyzing the IR spectra of BP and AMB. It is obvious that both BP and A0 have saturated hydrocarbons and amides. Besides, BP has lipids, while A0 has aromatic compounds and sulfinyl compounds. After adding bio-oil into control asphalt, the IR spectra of A4 and A8 have new absorption peaks. However, it is interesting that these new absorption peak positions are coincident with that in BP IR spectrum, and no other new absorption peaks are found, which indicates that biooil and control asphalt are physically blended and almost no chemical reactions between them are found.
Fig. 4. Penetration test results of AMB.
3.3. Penetration, softening point and ductility The penetration, softening point and ductility test results of AMB were shown in Figs. 4–6. Fig. 4 showed that the penetration increased with the addition of bio-oil. It was also noticed that the penetration increased faster when bio-oil content was more than 4%. Fig. 5 indicated that the softening point decreased uniformly with bio-oil content increasing. Fig. 6 showed that the ductility increased rapidly with bio-oil added, but reduced sharply when bio-oil content was more than 6%. The abnormal point at 8% addition may be due to the segregation of bio-oil into the control asphalt. Unlike penetration and softening point tests, the sample in ductility test will stretch to break with a 5 cm/min stretching speed. During this procedure, the diameter in the cross-section of sample will get smaller and smaller until less than a tenth of a millimeter. Considering the rather small scale of tested sample and the applied tensile loading mode, the segregation of bio-oil in the control asphalt could have more significant effect on the ductility test result. To sum up, bio-oil modified asphalt binders have higher penetration, lower softening point and larger ductility. In general, penetration and softening point indicate the viscosity of asphalt binder, while ductility represents the extensibility. In penetration grading system, the penetration depth, softening point and ductility are empirically correlated with asphalt binder performance. Asphalt binders with high penetration numbers, high ductility numbers and low softening points are normally used for cold climates while asphalt binders with low penetration numbers, low
Fig. 5. Softening point test results of AMB.
ductility numbers and high softening points are used for warm and hot climates. 3.4. Rotational viscosity The rotational viscosity test results of AMB were shown in Fig. 7. It could be found that the addition of bio-oil decreased the viscosity of asphalt binder because of dilution effect, and then reduced construction temperatures of AMB mixtures. Therefore, similar to warm asphalt mixture, the AMB mixtures are friendlier to the environment because of less energy consumption and asphalt smoke emission. But excessive addition of bio-oil in asphalt binder will reduce the service performance, as indicated in Figs. 4–6.
Table 3 Absorption peak wavenumbers and corresponding functional groups. Types
Absorption peak wavenumbers/cm1
BP A0 A4 A8 Functional groups
727 741 741 741 –(CH2)n–
— 760 752 757 C6H5-
— 820 817 820
— 884 878 882
— 1058 1038 1055 S@O
1181 — 1188 1190 –CO–O–
1380 1379 1379 1379 C–CH3
1467 1465 1465 1464
— 1616 1611 1617 C6H5–
1748 — 1744 1745 –CO–O–
2861 2859 2874 2859 –CH2–
2945 2933 2943 2932
3486 3482 3486 3483 –CO–NH–
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3.5. Compatibility The separation tendency test results of AMB were presented in Fig. 8. Test results indicated that all the softening point differences of asphalt binders between top and bottom were less than 2.5 °C after being stored vertically in an oven at 163 °C for 48 h, which meant that the bio-oil and control asphalt had good compatibility. Therefore, it can be anticipated that there is no separation problem for AMB. 3.6. Complex modulus and phase angle at medium and high temperatures
Fig. 6. Ductility test results of AMB (@15 °C).
The complex modulus and phase angle data at different frequencies and temperatures were shifted horizontally to reference temperature based on time-temperature superposition principle (TTSP), and then fitted by generalized CAM model to obtain the master curves, which could characterize the mechanical behaviors of bio-oil modified asphalt at medium and high temperatures. According to generalized CAM model, the complex modulus master curve equation is as follows:
G ¼ Ge þ
Gg Ge
ð1Þ
m =k 0 k e
½1 þ ðf c =f Þ
where G is complex modulus, Ge ¼ G ðf ! 0Þ with Ge ¼ 0 for asphalt binder, Gg ¼ G ðf ! 1Þ, f c is a location parameter of fre0
quency with dimensions, f is the reduced frequency related to temperature and strain, k and me are shape parameters without dimensions. The phase angle master curve equation is as follows:
(
)md =2 0 2 lgðf t =f Þ d ¼ 90I ð90I dm Þ 1 þ Rd
Fig. 7. Rotational viscosity test results of AMB (@60 °C).
ð2Þ
where d is phase angle, dm is the phase angle value at the inflection point for phase angle master curve, f t is a location parameter of fre0 quency with dimensions at which dm occurs, f is the reduced frequency, Rd and md are the shape parameters without dimensions, 0 0 I doesn’t have explicit definition, I ¼ 0 if f > f t and I ¼ 1 if f 6 f t for asphalt binder, I 0 for asphalt mixture [25,26]. The definitions of generalized CAM model parameters were shown in Fig. 9, and the
Fig. 8. Separation tendency test results of AMB.
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Fig. 9. Definitions of generalized CAM model parameters.
Fig. 10. Typical fitting results of generalized CAM model.
Fig. 11. Master curves of AMB (@20 °C).
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Table 4 Fitting parameters of complex modulus master curve model. Asphalt types
A0 A2 A4 A6 A8
Fitting parameters (@20 °C) lgG⁄g
fc
me
k
R2
8.844 9.423 8.836 8.585 8.323
132.412 59.612 273.987 700.471 408.542
0.940 1.146 1.012 0.978 1.044
0.245 0.165 0.237 0.288 0.305
1.00 1.00 0.99 0.99 0.98
Table 5 Fitting parameters of phase angle master curve model. Asphalt types
A0 A2 A4 A6 A8
Fitting parameters (@20 °C) dm
ft
Rd
md
R2
34.668 35.545 45.374 49.132 51.651
987.352 5238.727 5024.362 4807.681 16210.226
1.724 3.788 4.521 3.701 3.813
0.948 2.493 3.143 2.411 2.405
0.97 0.96 0.95 0.93 0.92
typical fitting results of generalized CAM model were shown in Fig. 10. In this study, 20 °C was selected as the reference temperature. The complex modulus master curves and phase angle master curves of AMB were plotted in Fig. 11. The model fitting parameters were presented in Tables 4 and 5. Fig. 11(a) indicated that the complex modulus increased with the increment of loading frequency. And the complex modulus master curves were right horizontally shifted with bio-oil added, which meant that the addition of bio-oil decreased the complex modulus of asphalt binder in the whole frequency domain. Fig. 11(b) showed that the phase angle decreased with the increment of frequency, and the phase angle master curves were also right horizontally shifted with bio-oil added, which meant that the addition of bio-oil increased the phase angle of asphalt binder in the whole frequency domain. The complex modulus (G⁄) can be considered the sample’s total resistance to deformation when applied repeatedly shear loading, while the phase angle (d), is the lag between the applied shear stress and the resulting shear strain. Intuitively, the higher the G⁄ value, the stiffer the asphalt binder is. The phase angle is an
Fig. 12. Low-temperature parameters test data and fitting models of AMB.
Fig. 13. Creep compliance master curves of AMB based on generalized CAM model.
Z. Sun et al. / Construction and Building Materials 102 (2016) 496–504 Table 6 Fitting parameters of creep compliance master curve model. Asphalt types
A0 A2 A4 A6 A8
Fitting parameters (@-30 °C) lgG⁄e
lgG⁄g
fc
me
k
R2
3.399 3.316 3.367 3.167 3.182
67.452 68.658 72.624 69.954 70.704
213065.843 249984.087 249807.643 264481.456 257069.963
0.727 0.841 0.887 1.009 0.993
0.00315 0.00360 0.00361 0.00426 0.00417
0.98 0.98 0.97 0.96 0.95
indicator to demonstrate the ratio of viscosity and elasticity in polymer materials. The lower the phase angle is, the less viscous the material is, which means the asphalt binder is able to recover its original shape after being deformed by a load. Therefore, the addition of bio-oil could decrease the deformation resistance and elastic recovery performance of control asphalt. 3.7. Stiffness and m-value at low temperatures The stiffness and m-value test data of AMB at 60 s loading time were presented in Fig. 12. It could be found that the addition of bio-oil decreased stiffness and increased m-value (an indicator of stress relaxation capability) of asphalt binder, which implied less stress accumulation during cooling procedure, and the improvement of thermal cracking resistance for asphalt binder. Besides, the fitting equations and parameters were shown in Fig. 12, which indicating that both stiffness and m-value had good linear relationships with bio-oil content. The creep compliance (reciprocal of stiffness) data at continuous loading times were plotted in Fig. 13(a). It is noticed that the creep compliance curves at different temperatures can also be shifted horizontally to obtain the creep compliance master curve at reference temperature based on TTSP. The generalized CAM model, as shown in Eq. (1), was used to fit creep compliance master curves. The typical fitting result and creep compliance master curves of AMB were shown in Fig. 13, and corresponding fitting parameters were shown in Table 6. It could be found that the creep compliance increased with the increment of loading time, and the creep compliance master curves were left horizontally shifted in the whole time domain with bio-oil added, which meant that the addition of bio-oil increased the creep compliance for asphalt binder in the whole time domain. Creep stiffness is normally a measure of the thermal stresses in the asphalt binder resulting from thermal contraction. A higher creep stiffness value (lower creep compliance) indicates higher thermal stresses. Although Superpave performance grading recommend this test conducted on long-term aged sample, the higher creep compliance and m-value of bio-oil modified asphalt could indicate a good stress relaxation property, which was helpful to the improvement of thermal cracking resistance of binder. 4. Conclusions This paper has investigated the chemical, physical and mechanical properties of asphalt binder modified by bio-oil derived from waste cooking oil. Based on the results presented, several conclusions can be drawn: (1) Bio-oil is mainly composed by aromatics, resins and saturates. Compared with the 40/60 penetration grade asphalt, bio-oil has lower asphaltenes and aromatics contents, higher saturates and resins contents. Besides, almost no chemical reactions are noticed when mixing control asphalt with bio-oil.
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(2) The addition of bio-oil decreases softening point and viscosity, increases penetration and ductility of asphalt binder. The separation tendency test results of bio-oil modified asphalt demonstrate that bio-oil and control asphalt have good compatibility under static heated storage conditions. (3) The addition of bio-oil decreases complex modulus and increases phase angle for asphalt binder at medium and high temperatures, which means adding bio-oil could decrease the deformation resistance and elastic recovery performance of control asphalt. (4) The addition of bio-oil decreases stiffness and increases mvalue of asphalt binder at low temperatures, which indicates a good stress relaxation property and also helps to the improvement of thermal cracking resistance of binder. It can be concluded that the bio-oil derived from waste cooking oil can be used as asphalt modifier to mainly improve the low temperature performance of asphalt binder, especially in cold regions. In addition, the ageing susceptibility and mixture performance of bio-oil modified asphalt should be further researched. Acknowledgements Thanks for the financial support by China Postdoctoral Science Foundation (No. 2013M541393, 2015T80357), Heilongjiang Postdoctoral Science Foundation (LBH-Z13084), National Natural Science Foundation of China (Grant No. 51408154) and Open Fund of Key Laboratory of Road Structure and Material of Ministry of Transport (Changsha University of Science & Technology) (kfj140304). References [1] E. Chailleux, M. Audo, C. Queffélec, et al., Alternative Binder from microalgae: algoroute project, Alternative Binders for Sustainable Asphalt Pavements, 2012. [2] R.C. Williams, J. Satrio, M. Rover, et al., Utilization of fractionated bio-oil in Asphalt, in: DVD-ROM Proceedings of the 88th Annual Meeting of the Transportation Research Board, Washington (DC), 2009. [3] M. Chen, F. Xiao, B. Putman, et al., High temperature properties of rejuvenating recovered binder with rejuvenator, waste cooking and cotton seed oils, Constr. Build. Mater. 59 (2014) 10–16. [4] N. Guo, Z. You, Y. Zhao, et al., Laboratory performance of warm mix asphalt containing recycled asphalt mixtures, Constr. Build. Mater. 64 (2014) 141–149. [5] M.A. Raouf, C.R. Williams, General rheological properties of fractionated switchgrass bio-oil as a pavement material, Road Mater. Pavement Des. 11 (sup1) (2010) 325–353. [6] F. Yang, M.A. Hanna, R. Sun, Value-added uses for crude glycerol-a byproduct of biodiesel production, Biotechnol. Biofuels 5 (13) (2012) 1–10. [7] R. Kluttz, Considerations for use of alternative binders in asphalt pavements: material characteristics, Transp. Res. E Circular E-C165 (2012). [8] G. Liu, M.F.C. Van de Ven, A.A.A. Molenaar, et al., Organo montmorillonite nanoclay: alternative modifier to sustain durability of asphalt pavement, Transp. Res. E Circular E-C165 (2012). [9] X. Yang, Z.P. You, Q.L. Dai, Performance evaluation of asphalt binder modified by bio-oil generated from waste wood resources, Int. J. Pavement Res. Technol. 6 (4) (2013) 431–439. [10] E.H. Fini, S.H. Yang, S. Xiu, Characterization and application of manure-based bio-binder in asphalt industry, in: Transportation Research Board 89th Annual Meeting, 2010 (10–2871). [11] E.H. Fini, I.L. Al-Qadi, Z. You, et al., Partial replacement of asphalt binder with bio-binder: characterisation and modification, Int. J. Pavement Eng. 13 (6) (2012) 515–522. [12] J. Peralta, R.C. Williams, M. Rover, et al., Development of rubber-modified fractionated bio-oil for use as noncrude petroleum binder in flexible pavements, Transp. Res. E Circular E-C165 (2012). [13] J. Peralta, M.A. Raouf, S. Tang, et al., Bio-renewable asphalt modifiers and asphalt substitutes, in: Sustainable Bioenergy and Bioproducts, Springer London, 2012, pp. 89–115. [14] A. Zofka, I. Yut, Investigation of rheology and aging properties of asphalt binder modified with waste coffee grounds, Transp. Res. E Circular E-C165 (2012). [15] J.C. Seidel, J.E. Haddock, Soy fatty acids as sustainable modifier for asphalt binders, Alternative Binders for Sustainable Asphalt Pavements Washington DC, 2012.
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