Evaluation of crumb rubber modification and short-term aging on the rutting performance of bioasphalt

Construction and Building Materials 193 (2018) 467–473

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Evaluation of crumb rubber modification and short-term aging on the rutting performance of bioasphalt Yu Chen a,⇑, Chuanjun Ji a, Hainian Wang a, Yumin Su b a b

School of Highway, Chang’an University, Middle Section of NanErhuan Road, Xi’an, Shaanxi Province 710064, China Department of Civil Engineering, National Kaohsiung University of Science and Technology, Sanmin, Kaohsiung 80778, Taiwan

h i g h l i g h t s  The bioasphalt exhibited higher rutting resistance than the virgin binder after short-term aging.  Higher rutting resistance of bioasphalt was observed with the addition of crumb rubber particles.  Crumb rubber had an upper limit role on the elastic behavior of binders with the increase of loading frequency. *

 Rutting factor G /sin(d) tests was still a valuable tool for the rutting resistance ranking of modified binders.

a r t i c l e

i n f o

Article history: Received 23 March 2018 Received in revised form 11 August 2018 Accepted 23 October 2018

Keywords: Bioasphalt RTFOT Rutting factor Non-recoverable creep compliance Crumb rubber

a b s t r a c t In this study, the high temperature performances of ten combinations of bioasphalt and crumb rubber particles were evaluated by DSR and MSCR tests. Testing results indicated that short-term aging and crumb rubber modification increased the complex shear modulus and reduced the phase angle. In addition, the crumb rubber modified bioasphalt significantly reduced the unrecovered creep compliance and increased the percentage recovery. It can be concluded that the bioasphalt exhibited higher rutting resistance than the virgin binder and it can be used like traditional binder in term of rutting performance. In addition, crumb rubber greatly increased the rutting performance of bioasphalt. Ó 2018 Elsevier Ltd. All rights reserved.

1. Background With the rising global competition for energy resources and decreasing reserves of petroleum supplies, the increasing prices of asphalt binder challenged the sustainable development of the asphalt pavement industry. Also, it was well known that conventional petroleum based asphalt contains toxic, heavy metals including nickel, lead, mercury, and arsenic, which posed health and environmental risks to nearby communities [1]. These challenges and concerns have encouraged the use of recycled materials, including reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) for asphalt pavement construction, and the exploration of alterative binders from other resources. Bioasphalt is an attractive asphalt alternative produced without the use of petroleum due to its reduced carbon footprint and com-

⇑ Corresponding author. E-mail addresses: [email protected] (Y. Chen), [email protected] (C. Ji), [email protected] (H. Wang), [email protected] (Y. Su). https://doi.org/10.1016/j.conbuildmat.2018.10.192 0950-0618/Ó 2018 Elsevier Ltd. All rights reserved.

petitive costs. Bio-oil is produced from everything like agricultural crops, municipal wastes, co-products from forestry and agriculture [2–4]. It was reported that bioasphalt has similar components as the petroleum asphalt binder, including saturates, arometics, resins and asphaltenes, and it contained similar percentage of carbon and hydrogen but higher percentage of nitrogen and oxygen as compared with petroleum based asphalt binder [4–6]. Three different types of bio-oils were produced through extraction from three different types of biomass [6], e.g. oakwood, switchgrass, and cornstalk. It was concluded that the rheological properties, i.e. temperature and shear susceptibilities, of the unmodified bio-binders derived from bio-oils vary in comparison to bitumen binders. Bio-oils derived from waste cooking oils has been reported to reduce the rutting resistance factor and the complex modulus of rejuvenated binders [7], to improve the low temperature performance of asphalt binder [8] and to reduce the softening point and viscosity of aged asphalt binder [9]. Meanwhile, wood-based bio-oils were reported to have lower high temperature performance grades and lower resistance to low temperature cracking

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Y. Chen et al. / Construction and Building Materials 193 (2018) 467–473

as compared to bitumen binders [6], to have better asphalt high temperature stability and lower low temperature performance [10,11], and to show a lower Jnr and greater recovery ability than those of conventional AC-20 [12]. In addition, researches on biooils generated from animal wastes indicated that although they can improve the low-temperature properties [4,13–15], it may decrease the high-temperature grade of the binder [13]. The loss of volatiles components and the oxidation of certain functional groups were observed during the bioasphalt aging process [16,17]. For the bioasphalt aging, researches have been concentrated on the chemical characterization of aged and unaged bioasphalt through FTIR [14,16,18] and ATR-FTIR [17]. Additional C@C, CAO, C@O and OH bonds were reported to be generated during the aging [16]. The rate of carbonyl (as a polar functional) formation was reduced with the introduction of biomodifier into the virgin binder [14,17]. In terms of rheological properties, reduction in viscosity for both unaged and RTFO unaged binder for bioasphalt was observed [14] and the viscosity aging index reduction was observed for bioasphalt [17]. The main distress mode for asphalt pavement under high temperature conditions (45–85 °C) was rutting failure [19]. Complex shear modulus and phase angle, often used as rutting factor, were proposed by the Superpave Design Guide. However, the efficiency of rutting factor for evaluation of the high temperature performance of modified binders has been questioned [20–23]. A new test, namely multiple stress creep recovery test (MSCR), was proposed by D’Angelo et al. [20] to evaluate the rutting resistance of asphalt binder. It was pointed out that there was some slight inconsistency between the DSR and MSCR test due to different loading magnitude and loading mode of the two tests [24]. It was suggested to conduct both the DSR and MSCR tests to obtain a comprehensive understanding of high temperature performance. MSCR test was considered as the best candidate for evaluation of the high temperature performance for modified binders [25] and it was found to correlate more accurately with the wheel rutting test results as compared with other test methods [26]. Therefore, it was important to evaluate the effects of short-term aging on the rutting resistance of bioasphalt, which can help to understand the role of mixing and placement on bioasphalt aging and to determine if bioasphalt can be used in traditional hot-mix asphalt. In addition, crumb rubber was added into the bioasphalt to evaluate its effect on the rutting resistance since bioasphalt was reported to have lower viscosity as compared with virgin binder [14,17] and crumb rubber can increase the resistance to high temperature rutting and low temperature cracking [27]. In addition, crumb rubber in asphalt was reported to have great benefits in energy saving and environmental effect compared with the landfill disposal and energy recovery [28]. 2. Objectives The objectives of this research work were:  to evaluate the effects of short-term aging and crumb rubber on the high temperature performance of bioasphalt;  to evaluate the effects of loading frequency/loading speed on the complex shear modulus and phase angle;  to compare the effectiveness of rutting factor and Jnr on the high temperature performance evaluation of bioasphalt; 3. Materials Materials used in this study were chosen to be representative of materials used in China for the construction of expressway. Technical properties of the virgin binder with penetration grade 70

based on the Standard Test Methods of Bitumen and Bituminous Mixtures for Highway Engineering [29] are presented in Table 1. The high temperature performance grade of this penetration grade 70 binder was determined to be 64. One wood-chips based bio-oil and the virgin binder were used this study to produce bioasphalt. The bio-oil was manufactured through a thermochemical process called fast pyrolysis on wood-chips by an energy company. During the fast pyrolysis process, biomass materials are rapidly heated in a vacuum and three main components were produced, including the organic vapor, pyrolysis gases and biochar. The bio-oil is obtained from the condensation of the volatile organic vapor. The extracted bio-oil has a dark brown color and it shows certain plasticity at room temperature and mobility at high temperature. In this study, bioasphalt refers to the mixture of very heavy and viscous tar-like bio-oil derived from biomass (rather than petroleum) via pyrolysis and petroleum based asphalt. The elemental composition of woodchips based bio-oil was shown in Table 2. Crumb rubber manufactured for asphalt pavement resurfacing was used in this study to evaluate its effects on the aging of bioasphalt. Its gradation can be found in Table 3. The production process of bioasphalt and crumb rubber modified bioasphalt are shown in Fig. 1 and Fig. 2, respectively. In this study, two Bio-oil contents (10% and 20%) (B10 and B20), two Crumb Rubber contents (5% and 10%) (CR05 and CR10) and two aging conditions (one Unaged and one RTFOT aged) were evaluated by both the DSR and the MSCR tests. A total of 10 material combinations can thus be obtained, the designation of which can be seen in Table 4. 4. Test method 4.1. Dynamic shear rheometer (DSR) The dynamic shear rheometer test, which was developed to characterize the viscous and elastic behavior of asphalt binders at medium to high temperatures, was used in this study to evaluate the effects of short-term aging on the high temperature performance of bioasphalt. Standard testing procedures as stated in AASHTO T315-12 were followed and it should be noted that DSR tests were performed on both the unaged binder and the shortterm aged binder in this study whereas all asphalt binders have to be conditioned by either RTFOT or Pressure Vessel Aging (PAV) before testing in the standard testing procedure. All tests were performed under the corresponding PG performance temperature, which was determined to be 64 °C for the penetration grade 70. The standard frequency 10 rad/sec (1.59 Hz) was used to create a shearing action for the 25 mm plates, which has a gap of 1 mm. The frequency sweep tests (0.01, 0.0215, 0.0464, 0.1, 0.215, 0.464, 1, 2.15, 4.64, 10, 21.5 and 25 Hz) were performed to monitor the rheological properties change under different loading speeds. 4.2. Multiple stress creep and recovery (MSCR) It was generally believed that the modifiers played a critical role on the binder resistance of plastic /permanent deformation. However, as stated earlier, the DSR test cannot capture the rutting performance enhancement of modifiers, especially elastomeric polymers. MSCR test was determined to be blind to the type of modifier used, which can eliminate the demand for tests designed for binder modification, like elastic recovery and force ductility tests. For MSCR tests based on AASHTO TP 70-13, cyclic loading with two loading magnitudes (0.1 kPa and 3.2 kPa) were applied on the DSR samples to obtain the non-recoverable creep compliance, which can better characterize the rutting resistance of asphalt binders [30] Each loading cycle consists of 1 s loading

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Y. Chen et al. / Construction and Building Materials 193 (2018) 467–473 Table 1 Technical properties of virgin binder with penetration grade 70. Property

Units

Technical requirements

Test results

Specification

Penetration Penetration index Softening point Ductility in 10 °C Density in15°C Dynamic viscosity in 60 °C

0.1 mm – °C cm g
cm 3 Pas

60–80 1.5–1.0 >46 >20 – >180

71.5 0.2043 49.5 113.2 1.029 274

T0604-2011 T0604-2011 T0606-2011 T0605-2011 T0603-2011 T0620-2011

After RTFO (163 °C, 85 min) Mass loss Residual penetration ratio Residual ductility(10 °C)

% % cm

0.8–0.8 >61 >6

0.121 74.6 8.3

T0610-2011 T0604-2011 T0605-2011

Table 2 Elemental compositions and characteristics of wood-chips based bio-oil.

Crumb Rubber

Parameter

Test Results

Elements (C, H, O, N) (%) Density (gcm-3) PH Viscosity in 135 °C (Pa
s) Viscosity at 500 °C (Pa
s) Flash point ( °C) Distillation residue (%) Moisture content (%)

(54–56, 5.5–7.2, 35–45, 0–0.2) 1.1 2.6 0.895 0.04–0.1 90–180 <=50 15–30

A).

Sieve Size (mm)

1.18

0.85

0.6

0.425

0.3

0.18

0.15

0.075

% Passing

100.0

100.0

100.0

84.9

56.1

32.9

26.8

14.6

1hour Shearing

C). Crumb Rubber Modified Asphalt

1hour Swelling

Asphalt Crumb Rubber Modified Bioasphalt

High-speed Shear Mixer

E).

10 minutes Shearing

Table 3 Gradation of crumb rubber particles.

Bio-oil

D). Manually Mix

Fig. 2. The Production Process of Crumb Rubber Modified Bioasphalt. Note: A). Heat the virgin binder to 180 °C and manually pre-mix it with crumb rubber particles; B). Mix it with high-speed shear mixer at 5000r/min for 1 h at 180 °C and store it in the oven at 180 °C for 1 h to let the crumb rubber fully swell; C). Crumb rubber modified asphalt; D). Adjust the asphalt temperature to 140 °C and manually premix with preprocessed bio-oil; E). Mix it with high-speed shear mixer at 5000r/min for 10 min at 140 °C; F). Test ready crumb rubber modified bioasphalt.

High-speed Shear Mixer

Bio-oil

B). Manually Mix

Asphalt

B). Manually Mix

F).

A).

High-speed Shear Mixer

C). 10 minutes Shearing Bioasphalt

Fig. 1. The Production Process of Bioasphalt. Note: A). Heat the virgin binder to 140 °C and manually pre-mix it with preprocessed bio-oil; B). Mix it with highspeed shear mixer at 5000r/min for 10 min at 140 °C; C). Test ready bioasphalt.

period and 9 s rest period. The non-recoverable creep compliance can be calculated for both loading stress levels. 5. Test results 5.1. DSR tests Based on the DSR tests, complex shear modulus G* and phase angle d (See Fig. 3), and thus rutting factor G*/sin(d) (See Fig. 4) can be obtained. As presented in Fig. 3, the binder was softened with the addition of bio-oil before RTFOT. On average, the complex shear modulus of bioasphalt was 14.9% lower than that of virgin binder. However, the binder was stiffened with the addition of bio-oil after RTFOT, which further confirmed the loss of volatiles components and the oxidation of certain functional groups during the bioasphalt aging process [16,17]. The complex shear modulus of bioasphalt was 34.5% and 53.6% higher than that of the virgin binder after RTFOT

for addition of 10% and 20% bio-oil, respectively. This short-term aging process was normally used to simulate the loss of smaller molecules in the asphalt binder due to the elevated temperatures during mixture production and placement. It indicated that the RTFOT process reversed the conception that the addition of biooil made the virgin binder softer but rather made it stiffer and more brittle. The effects of bio-oil addition can also be further evaluated through simple penetration tests as presented in Fig. 5. The descending order of penetration in Fig. 5 again confirmed that the addition of bio-oil indeed softened the binder before RTFOT and the bio-oil actually stiffened the binder after RTFOT, which was consist with the complex shear modulus results. The addition of crumb rubber modifier definitely increased the complex shear modulus of bioasphalts. The addition of crumb rubber increased the complex shear modulus for at least 48.1%. It can be concluded that RTFOT greatly increased the complex shear modulus of bioasphalt. The phase angle was independent of the addition of bio-oil for both before and after RTFOT conditions for binders without the addition of crumb rubber. As can be seen in Fig. 3, the phase angles for binders without the addition of crumb rubber are all close to 90°, which was the phase angle for purely viscous materials. It indicated that the behavior of those binders was similar to materials like water or thin oils under the testing conditions, where stress and strain shifted 90° from each other. On the other hand, the phase angle was clearly reduced once the crumb rubber was added (on average, it was reduced by 14.4%), which was accompanied by the increase of complex shear modulus. It indicated that the addition of crumb rubber lowered the damping effects of the binder and the complete dominance of

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Y. Chen et al. / Construction and Building Materials 193 (2018) 467–473

Table 4 The designation of material combination. Un-Aged 0% Bio 0% CR UB00CR00

RTFOT-Aged 10% Bio 0% CR UB10CR00

20% Bio 0% CR UB20CR00

0% Bio 5% CR RB00CR00

10% Bio 10% CR RB10CR00

10% Bio 0% CR RB10CR05

10% Bio 5% CR RB10CR10

20% Bio 10% CR RB20CR00

20% Bio

20% Bio

RB20CR05

RB20CR10

Note: Bio = Bio-oil; CR = Crumb Rubber.

90

G*

Phase Angle

10000

70

8000

G* (Pa)

80

60 50

6000

40

4000

30

Phase Angle (Ö)

12000

20

2000

10

0

0

Fig. 3. Complex shear modulus G* and phase angle at 64 °C and 10 rad/s.

A).

12000

100000 UB20CR00

10000

UB10CR00

10000

UB00CR00

8000

G* (Pa)

G*/sin(d ) (Pa)

RTFOT and it was increased with the increase of bio-oil content after RTFOT. RTFOT had similar effects on the rutting factor as it had on the complex shear modulus as presented in Fig. 3. Crumb rubber was proved to be able to dramatically increase the rutting factor. It should be noted that rutting factor G*/sin(d) had been reported to be ineffective in terms of rutting performance evaluation for polymer modified binders [20–22,31]. The effectiveness of rutting factor for rutting performance evaluation of binders with crumb rubber will be evaluated with MSCR results later in this study. The complex shear modulus and phase angle versus frequency were presented in Fig. 6 and Fig. 7, respectively. As it can be seen in Fig. 6, the complex shear modulus was reduced with the reduction of testing frequency, which was consistent with the phenomena that the complex shear modulus was lowered with the rising of

6000 4000

1000 100

2000 10

0 1 0.01

0.1

1

10

1

10

100

10

100

Frequency (Hz)

100

B). 100000

Fig. 4. Rutting factor G*/sin(d) at 64 °C and 10 rad/s.

RB20CR00 RB10CR00

10000

RB00CR00

G* (Pa)

100

Penetration (0.01mm)

90 80

1000 100

70 60

10

50 1 0.01

40

0.1

30 20

C).

Frequency (Hz)

100000 RB10CR05

10 10000

0 UB10CR00

UB00CR00

RB10CR00

Fig. 5. Penetration results of bioasphalts before and after RTFOT.

viscous component of the viscoelastic behavior was compromised. In other words, the addition of crumb rubber enhanced the role of elastic component and thus increased the rutting resistance. Therefore, the reduction of phase angle was proved to be a strong indication for the presence of modifiers in the asphalt binder under this testing condition. The rutting performance indicator G*/sin(d) as presented in Fig. 4 was reduced with the increase of bio-oil content before

RB20CR05 RB10CR10

RB20CR00

G* (Pa)

UB20CR00

RB20CR10

1000 100 10 1 0.01

0.1

1

Frequency (Hz)

Fig. 6. Complex shear modulus versus frequency. Note: A). UB00CR00, UB10CR00 and UB20CR00; B). RB00CR00, RB10CR00 and RB20CR00; C). RB10CR05, RB20CR05, RB10CR10 and RB20CR10.

Y. Chen et al. / Construction and Building Materials 193 (2018) 467–473

Peak Value

A).90

Phase Angle (Ö)

85

80 UB20CR00

75

UB10CR00 UB00CR00

70

65 0.01

0.1

1

Frequency (Hz)

10

100

0.215Hz

B).

90

Phase Angle (Ö)

85 80 RB20CR00

75

RB10CR00 RB00CR00

70 65 0.01

C).

0.1

1

10

1

10

Frequency (Hz)

100

90

Phase Angle (Ö)

85 80 75 RB10CR05

RB20CR05

RB10CR10

RB20CR10

70 65 0.01

0.1

Frequency (Hz)

100

Fig. 7. Phase angle versus frequency. Note: A). UB00CR00, UB10CR00 and UB20CR00; B). RB00CR00, RB10CR00 and RB20CR00; C). RB10CR05, RB20CR05, RB10CR10 and RB20CR10.

temperature based on the time–temperature superposition principle. The overall trend was the same as those observed in the DSR testing results, which was that the addition of bio-oil lowered the complex shear modulus before RTFOT (This trend can be observed from the detail data even though the complex shear modulus seemed to be independent of the bio-oil content as seen in Fig. 6-A; but the complex shear modulus was indeed close to each other); the higher addition content of bio-oil, the higher was the complex shear modulus after RTFOT (See Fig. 6-B); the higher addition content of crumb rubber, the higher was the complex shear modulus (See Fig. 6-C). For the effects of bio-oil content on phase angle, it can be observed that the higher addition content of bio-oil, the higher was the phase angle for binders before RTFOT (See Fig. 7-A). This was consistent with the observation that the addition of binder before RTFOT will enhance the role of viscous component as reported earlier. Meanwhile, a peak value of phase angle was observed at the frequency of 0.215 Hz (See Fig. 7-A). Similar observations had also been reported in the past [24,31]. Asphalt binder

471

exhibited the thixotropic /shears thinning behavior before the peak of the phase angle, where the viscosity of the binder decreased with the increase of shearing rate. This was reflected in Fig. 7-A as the increase of phase angle with the increase of shear rate. After equilibrium, however, viscosity or maximum phase angle in this case was observed, the binder started to behave as a shear thickening material and its viscosity increased by an increasing shear rate, which was reflected as the decrease of phase angle with the increase of shear loading rate. For the bioasphalt after RTFOT, the higher addition content of bio-oil, the lower was the phase angle and the higher was the role of elastic component of the binder when the testing frequency was >0.215 Hz (See Fig. 7-B). When the testing frequency was lower than 0.215 Hz, the phase angle was all close to 90° and it was the condition where binder can almost be described as purely viscous material. The role of elastic behavior was obviously enhanced with the increase of testing frequency, the evidence of which was that the role of elastic component increased with the decrease of temperature based on the time–temperature superposition principle. This trend was similar to that of the complex shear modulus. For bioasphalts with the addition of crumb rubber, the rising order of phase angle was RB20CR10, RB10CR10, RB20CR05 and RB10CR05 (See Fig. 7-C). It was clear that the phase angle of binders with 10% crumb rubber particles was lower than that of binders with 5% crumb rubber particles. At relatively low testing frequency (frequency <=0.1 Hz), the phase angle difference between RB10CR05 and RB20CR05 and the phase angle difference between RB10CR10 and RB20CR10 were negligible, which can be explained by the time–temperature superposition principle. At relatively high temperature (low loading frequency), all asphalt binders were close to being purely viscous and the phase angle was mainly determined by the crumb rubber content. On the other hand, at low temperature (high loading frequency), the effects of bio-oil content will be exhibited besides the crumb rubber content. It was the reason why larger phase angle differences between RB10CR05 and RB20CR0 and between RB10CR10 and RB20CR10 were observed. Meanwhile, it was interesting to note that there was a plateau value for the RB10CR10 and RB20CR10 and it would be safe to assume that RB10CR05 and RB20CR05would also reach a plateau value given higher testing frequency or lower testing temperature. At high testing frequency or low temperature, a structure of crumb rubber was probably formed and when this structure was fully engaged and relatively stable during the shear loading, its contribution to the elastic behavior of the binder reached its full potential and the phase angle reached minimum /plateau value in the meantime. It indicated that crumb rubber had an upper limit role on the elastic behavior of binders with the increase of loading frequency.

6. MSCR tests As stated earlier, MSCR test, being blind to binder modification, was developed for measuring the fundamental characteristics of asphalt binders at high temperature since DSR test was only developed for unmodified asphalts and it did not measure the benefits of elastomeric polymers. As can be seen in Figs. 8 and 9 for stress levels of 0.1 kPa and 3.2 kPa, respectively, were the nonrecoverable creep compliance (Jnr) and percentage of recovery (MSCR Recovery). Both results were reported by taking the average of 10 consecutive loading cycles for both 0.1 kPa and 3.2 kPa loading levels. It can be seen from both Figs. 8 and 9 that for binders without the addition of crumb rubber, the higher addition content of biooil, the higher was the non-recoverable creep compliance and worse was the rutting resistance before RTFOT; the higher addition

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Y. Chen et al. / Construction and Building Materials 193 (2018) 467–473

9

45

Jnr (/kPa)

Recovery

40

7

35

6

30

5

25

4

20

3

15

2

10

1

5

0

0

Recovery (%)

Jnr

8

Fig. 8. Non-recoverable creep compliance and percentage recovery under the loading of 0.1 kPa.

30

9

Jnr

8

Recovery

Jnr (/kPa)

20

6 5

15

4 3

10

2

Recovery (%)

25

7

5

1 0

0

Fig. 9. Non-recoverable creep compliance and percentage recovery under the loading of 3.2 kPa.

content of bio-oil, the lower was the non-recoverable creep compliance and better was the rutting resistance after RTFOT. This again proved that the addition of bio-oil definitely softened the binder before short-term aging and stiffened the binder after short-term aging. Meanwhile, it was clear that the addition of crumb rubber increased the rutting resistance by decreasing the non-recoverable creep compliance. For the effects of crumb rubber, the higher content of crumb rubber, the lower was the nonrecoverable creep compliance Jnr. Meanwhile, the nonrecoverable creep compliance of binders with 20% bio-oil was lower than that of binders with 10% biobinders. It should be noted that the unrecovered creep compliance of RB20CR05 was slightly lower than that of RB10CR05. It might be caused by the instability of bio-oil and the interaction between bioasphalt and crumb rubber particles. For percentage recovery, it was clear that all binders without the addition of crumb rubber particles had less than 5% recovery, which can be considered to have no ability to recover any induced

shear strain in the binder after unloading. However, once crumb rubber particles were introduced into the binder, the recovery capability was tremendously increased after the removal of shear loading as can be seen in both Figs. 8 and 9. It can also be seen that the higher addition content of crumb rubber, the higher was the recovery; the higher content of bio-oil, the higher was the recovery. To check the validity of DSR parameter G*/sin(d) for the evaluation of binder rutting resistance, its ranking order of tested binders were compared with MSCR non-recoverable creep compliance results as in Table 5. Both G*/sin(d) and Jnr indicated that RB20CR10 and UB20CR00 were the least and most prone to the accumulation of unrecovered permanent strain, respectively. As stated earlier, rutting factor G*/sin(d) was reported to be ineffective for the evaluation of high temperature performance of modified binders since only linear viscoelastic behavior was evaluated during the shear loading whereas rutting was considered as a nonlinear failure and polymer modified systems were engaged in the nonlinear range [20–22,31]. However, the ranking order in Table 5 indicated that rutting factor G*/sin(d) worked as well as Jnr in terms of binder rutting resistance evaluation, which was reported to correlate more accurately with wheel tracking results [26]. The validity of G*/sin(d) to rank both unmodified and modified binders was also reported elsewhere [26]. 7. Summary and Future work In this study, the high temperature performances of ten combinations of bioasphalt and crumb rubber particles were evaluated by using DSR and MSCR tests. It was found that bioasphalt was softened before short-term aging and stiffened after short-aging, which led to lower complex shear modulus and higher phase angle before RTFOT and higher complex shear modulus and lower phase angle after RTFOT, respectively. The crumb rubber modified bioasphalt exhibited much higher complex shear modulus and lower phase angle. There existed a peak value of phase angle for nonshort-term aged bioasphalts and a plateau value of phase angle for crumb rubber modified bioasphalts versus the shear loading frequency. In addition, the crumb rubber modified bioasphalts showed significantly lower unrecovered creep compliance and higher percentage recovery than bioasphalts and virgin binders. Rutting factor by DSR tests exhibited the same ranking order as the unrecovered creep compliance by MSCR tests. Based on the results presented in this study, the following conclusions can be made:  The bioasphalt actually exhibited higher rutting resistance than the virgin binder and it can be used like traditional binder in terms of rutting performance;  Crumb rubber modified bioasphalt greatly increased the rutting performance and crumb rubber had an upper limit role on the elastic behavior of binders with the increase of loading frequency;

Table 5 Testing data of G*/sin(d) and Jnr, and corresponding ranking order. Variable G*/sin(d) (kPa) Jnr at 0.1 kPa (kPa Jnr at 3.2 kPa (kPa Binder Ranking

1

) )

1

G*/sin(d) Jnr at 0.1 kPa Jnr at 3.2 kPa

UB20 CR00

UB10 CR00

UB00 CR00

RB00 CR00

RB10 CR00

RB20 CR00

RB10 CR05

RB20 CR05

RB10 CR10

RB20 CR10

1.247 8.180 8.551 10 10 10

1.283 7.391 8.191 9 9 9

1.487 6.456 7.060 8 8 8

2.709 3.386 3.746 7 7 7

3.646 2.384 2.580 6 6 6

4.163 2.205 2.362 5 5 5

6.331 0.991 1.222 4 4 4

6.625 0.962 1.197 3 3 3

7.678 0.662 0.861 2 2 2

10.602 0.405 0.505 1 1 1

Note: The binders were ranked from the most susceptible (No. 10) to the least (No. 1) to rutting.

Y. Chen et al. / Construction and Building Materials 193 (2018) 467–473

 Rutting factor G*/sin(d) based on DSR tests was still a valuable tool for the rutting resistance ranking of modified binders even though it was reported to have a poor correlation with wheel tracking results. Future work on this topic will include analyzing the fatigue cracking and low temperature cracking performance of bioasphalt and verify the binder test results with mixture tests. Chemical analysis will also be conducted on bioashpalt to better understand the aging mechanism. Conflicts of interest The authors declared that they have no conflicts of interest to this work. Acknowledgements This research is supported by the Special Fund for Basic Scientific Research of Central Colleges, Chang’an University (CHD310821171015 and CHD310821153503), and China Postdoctoral Science Foundation Grant (2013M542312 and 2014T70897). References [1] H. Vignesh, B.N.G. Ramesh, V. Manivasagan, S. Suganya, B.M. Eajas, Emerging Trends in Greener Pavements 2 (2), Esrsa Publications, 2013, pp. 1–14. [2] M.F. Demirbas, M. Balat, Recent advances on the production and utilization trends of bio-fuels: a global perspective, Energy Convers. Manage. 47 (15) (2006) 2371–2381. [3] D. Mohan, C.U. Pittman, P.H. Steele, Pyrolysis of wood/biomass for bio-oil: a critical review, Energy Fuels 20 (3) (2006) 848–889. [4] E.H. Fini, E.W. Kalberer, A. Shahbazi, M. Basti, Z. You, H. Ozer, Q. Aurangzeb, Chemical Characterization of Biobinder from Swine Manure: Sustainable Modifier for Asphalt Binder, 23(11) (2011) 1506–1513. [5] C.A. Mullen, A.A. Boateng, Chemical composition of bio-oils produced by fast pyrolysis of two energy crops, Energy Fuels 22 (3) (2008) 2104–2109. [6] M.A.R.M. Metwally, Development of Non-Petroleum Binders Derived from Fast Pyrolysis Bio-Oils For Use in Flexible Pavement, Iowa State University, 2010. [7] M. Chen, F. Xiao, B. Putman, B. Leng, S. Wu, High temperature properties of rejuvenating recovered binder with rejuvenator, waste cooking and cotton seed oils, Constr. Build. Mater. 59 (2014) 10–16. [8] H. Wen, S. Bhusal, B. Wen, Laboratory evaluation of waste cooking oil-based bioasphalt as an alternative binder for hot mix asphalt, J. Mater. Civ. Eng. 25 (10) (2013) 1432–1437. [9] H. Asli, E. Ahmadinia, M. Zargar, M.R. Karim, Investigation on physical properties of waste cooking oil – rejuvenated bitumen binder, Constr. Build. Mater. 37 (2012) 398–405. [10] R. Christopher Williams, J. Satrio, M. Rover, R. Brown, S. Teng, Utilization of fractionated bio-oil in asphalt, Transport. Res. Record 88 (2009). [11] X. Yang, Y. Zhanping, D. Qingli, Performance evaluation of asphalt binder modified by bio-oil generated from waste wood resources, Int. J. Pave. Res. Technol. 6 (4) (2013). 9.

473

[12] S.-H. Yang, T. Suciptan, Rheological behavior of Japanese cedar-based biobinder as partial replacement for bituminous binder, Constr. Build. Mater. 114 (2016) 127–133. [13] E.H. Fini, I.L. Al-Qadi, Z. You, B. Zada, Mills-Beale, Partial replacement of asphalt binder with bio-binder: characterisation and modification, Int. J. Pavement Eng. 13 (6) (2012) 515–522. [14] J. Mills-Beale, Z. You, E. Fini, B. Zada, C.H. Lee, Y.K. Yap, Aging Influence on rheology properties of petroleum-based asphalt modified with bio-binder, J. Mater. Civ. Eng. 26 (2) (2014) 358–366. [15] A. Onochie, E. Fini, X. Yang, J. Mills-Beale, Z. You, Rheological Characterization of Nano-particle based Bio-modified Binder, Transportation Research Board 92nd Annual Meeting (2013). [16] X. Yang, Z. You, J. Mills-Beale, Asphalt binders blended with a high percentage of biobinders: aging mechanism using FTIR and rheology, J. Mater. Civ. Eng. 27 (4) (2015). [17] M. Mousavi, F. Pahlavan, D. Oldham, S. Hosseinnezhad, E.H. Fini, Multiscale investigation of oxidative aging in biomodified asphalt binder, J. Phys. Chem. C (2016). [18] X. Yang, J. Mills-Beale, Z. You, Chemical characterization and oxidative aging of bio-asphalt and its compatibility with petroleum asphalt, J. Cleaner Prod. 142 (2017) 1837–1847. [19] M.C. Phillips, C. Robertus, Binder Rheology and Asphaltic Pavement Permanent Deformation: the Zero-Shear-Viscosity, Eurasphalt & Eurobitume Congress, Strasbourg, 7-10 May 1996. Volume 3. Paper E&E.5.134, Strasbourg, France, 1996. [20] J. D’Angelo, R. Kluttz, R.N. Dongre, K. Stephens, L. Zanzotto, Revision of the Superpave high temperature binder specification: The multiple stress creep recovery test, J. Assoc. Asphalt Pav. Technol. 76 (2) (2007) 123–162. [21] E. DuBois, Correlation between Multiple Stress Creep Recovery (MSCR) Results and Polymer Modification of Binder, Rowan University Department of Civil Engineering, 2014. [22] J. Zhang, L.F. Walubita, A.N.M. Faruk, P. Karki, G.S. Simate, B. Materials, Use of the MSCR test to characterize the asphalt binder properties relative to HMA rutting performance – a laboratory study, Constr. Build. Mater. 94 (2015) 218– 227. [23] J.B.S. Bastos, L.F.A.L. Babadopulos, J.B. Soares, Relationship between multiple stress creep recovery (MSCR) binder test results and asphalt concrete rutting resistance in Brazilian roadways, Constr. Build. Mater. 145 (2017) 20–27. [24] X. Yang, Z. You, High temperature performance evaluation of bio-oil modified asphalt binders using the DSR and MSCR tests, Constr. Build. Mater. 76 (2015) 380–387. [25] M.D.I. Domingos, A.L. Faxina, Susceptibility of asphalt binders to rutting: literature review, J. Mater. Civ. Eng. 28 (2) (2016) 04015134. [26] N. Saboo, P. Kumar, Analysis of different test methods for quantifying rutting susceptibility of asphalt binders, J. Mater. Civ. Eng. 28 (7) (2016). [27] F.L. Roberts, P.S. Kandhal, E.R. Brown, D.Y. Lee, T.W. Kennedy, Hot Mix Asphalt Materials, Mixture Design, and Construction, National Asphalt Pavement Association Education Foundation, Lanham, MD, 1996. [28] T. Wang, F. Xiao, X. Zhu, B. Huang, J. Wang, S. Amirkhanian, Energy consumption and environmental impact of rubberized asphalt pavement, J. Cleaner Prod. 180 (2018) 139–158. [29] Research Institute of Highway Ministry of Transport, Standard Test Methods of Bitumen and Bituminous Mixtures for Highway Engineering (JTG E20), China Communication Press, Beijing, 2011. [30] American Association of State Highway and Transportation Officials Multiple Stress Creep Recovery (MSCR) Test of Asphalt Binder Using a Dynamic Shear Rheometer (DSR) (AASHTO TP 70–13) 2013 Washington DC. [31] J. Mandula, T. Olexa, Study of the visco-elastic parameters of asphalt concrete, Procedia Eng. 190 (2017) 207–214.