Physico-chemo-rheological characterization of neat and polymer-modified asphalt binders

Construction and Building Materials 199 (2019) 471–482

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Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat

Physico-chemo-rheological characterization of neat and polymer-modified asphalt binders Chao Wang ⇑, Yang Wang Department of Road and Railway Engineering, Beijing University of Technology, Beijing 100124, PR China

h i g h l i g h t s
The macroscale performance of neat and modified asphalt binders are investigated from microscale chemical characteristics.
The aromatics composition strongly impacts the binder resistance to permanent deformation.
The large molecular size is found to be well correlated to binder fatigue resistance.

a r t i c l e

i n f o

Article history: Received 12 July 2018 Received in revised form 11 December 2018 Accepted 12 December 2018

Keywords: Asphalt binder Physical property Chemical characteristic Rheological performance

a b s t r a c t The physico-chemo-rheological properties of asphalt binder are critical for the long-term performance of asphalt pavement infrastructures. The objectives of this study are to characterize the physico-rheological properties of unmodified neat and polymer-modified asphalt binders with newly developed rheological performance tests, and further investigate the binder chemical properties as well as the possible performance relationship from macroscale to microscale perspective. Three neat asphalt binders and two styrene–butadiene–styrene (SBS) modified asphalt binders are selected in this study. The physical properties of asphalt binder include traditional penetration, softening point and ductility. The saturates, aromatics, resins and asphaltenes (SARA) fractionation test, gel permeation chromatography (GPC) and fourier transform infrared spectroscopy (FTIR) tests are respectively conducted to quantify the chemical composition, molecular weight distribution and structure properties of asphalt binders. The rheological rutting and fatigue resistance are evaluated through the multiple stress creep recovery (MSCR), linear amplitude sweep (LAS) and DSR-based elastic recovery (DSR-ER) tests. Experimental results indicate that the physical properties are only effective to distinguish the rheological performance of neat asphalt binders. The lower aromatics contents improve the binder rutting resistance and an unified relationship between aromatic contents and binder rutting performance is obtained for both neat and modified binders. In addition, increasing the amount of small asphalt molecules decrease the resistance to permanent deformation respectively for neat and modified binders. However, the small asphalt molecule is favorable for improving the binder fatigue performance. The large molecular size (LMS) parameter from GPC test is demonstrated a unified correlation to the fatigue life of both neat and modified binders. Ó 2018 Elsevier Ltd. All rights reserved.

1. Introduction Permanent deformation and fatigue cracking of asphalt pavements are the main distresses that impact the long-term durability of road infrastructure [1]. The field pavement failure is a rather complex behaviour that affected from both materials and structures; however, designing and manufacturing the asphalt paving materials with better expected performance definitely would be ⇑ Corresponding author. E-mail addresses: [email protected] (C. Wang), wy14030221wy@emails. bjut.edu.cn (Y. Wang). https://doi.org/10.1016/j.conbuildmat.2018.12.064 0950-0618/Ó 2018 Elsevier Ltd. All rights reserved.

beneficial for the overall pavement performance. In recent years, an increasing research interest is focused on the multiscale modeling of asphalt concrete. In this way, the viscoelastic properties and damage resistance from asphalt binder phase are gradually becoming crucial to predict the long-term performance of asphalt concrete and pavements. The strategic highway research program (SHRP) during late 1980s in the United States firstly introduced the dynamic shear rheometer (DSR) to quantify the fundamental viscoelastic properties of asphalt binder and further establish the binder performance grade (PG) specification [2,3]. Later, some new test protocols were proposed during the NCHRP 9–11 project to further characterize

C. Wang, Y. Wang / Construction and Building Materials 199 (2019) 471–482

the damage potential of both neat unmodified and modified asphalts [4–9]. In recent years, research effort is to integrate the newly developed damage-based test procedure that with both accuracy and testing efficiency into the current PG specification system [10]. Currently, several typical AASHTO specification tests are available to access the rutting and fatigue performance of asphalt binder respectively at high and intermediate temperature, which consist of basic rheological measurements for binder rutting and fatigue characterization [11], multiple stress creep recovery (MSCR) test for binder rutting potential evaluation [12–14], linear amplitude sweep (LAS) test for binder fatigue life prediction [15– 26], and DSR-based elastic recovery (DSR-ER) procedure for binder elasticity characterization [27–31]. Based on these newly developed asphalt binder rheological protocols, several researchers investigated the traditional physical properties (penetration, softening point and ductility) and rheological performance of neat asphalt binders and modified binders with various modifiers [32–36]. However, both observed physical and rheological testing results merely quantify the macroscale engineering performance and the reasonable explanation behind the distinguished binder macro-performance is still almost unknown. Therefore, it is meaningful and beneficial to further investigate the microscale chemical characteristics of asphalt binder to reveal the fundamental mechanism for binder performance and thus, the establishing of the physico-chemo-rheological characterization can provide a more comprehensive understanding for asphalt binder performance assessment. Asphalt is a complex mix of many different hydrocarbons so its chemical properties are strongly dependent on the crude oil resource and refinery process. Since there are large amounts of molecules in asphalt with distinguished chemical structures, it is impossible to separate and divide asphalt into individual pure substance. Generally, the chemical properties of asphalt binder can be characterized from three approaches namely the chemical composition, molecular weight distribution and functional group [37–39]. The chemical characteristic and its relationship to rheological modeling of asphalt binder are recently widely investigated especially for polymer modified asphalt binders [40–43]. The chemical components of asphalt binder can be typically separated into four parts of Saturates, Aromatics, Resins, and Asphaltenes (SARA). Some studies have demonstrated the impacts of SARA fractionation on binder rheology, damage/healing and aging behaviors [44–51]. The gel permeation chromatography (GPC) test, which was developed in 1960s to characterize the molecular weight distribution of polymers, can also be utilized to quantify the asphalt molecular weight distribution. Jennings et al. classified the asphalt molecules eluted during the first third of the time period as large molecular size (LMS), those eluted during the second third as medium molecular size (MMS), and those eluted in the last third as small molecular size (SMS) [52]. Following this three-part fractionating GPC approach, the physical properties and rheological performance under oxidative aging of asphalt binder can be relatively estimated [53–58]. The various chemical functional groups in asphalt can be correspondingly identified from fourier transform infrared (FTIR) test, in which the observed specific infrared spectra absorbance

indicates the molecules rotation or oscillation. Therefore, the change in functional groups of asphalt binder due to the oxidative aging or incorporation of various modifiers can be effectively identified [59–65]. The objectives of this study are to: (1) Characterize the physico-rheological properties of neat and polymer-modified asphalt binders with newly developed rheological performance tests; (2) Quantify the binder chemical properties and further investigate possible performance relationship from macroscale to microscale perspective. 2. Materials and testing 2.1. Materials Three neat asphalt binders with distinguished penetration grades and PG grades were selected for this study as given in Table 1. These neat binders were produced from the same crude oil and provided by the local material supplier. The N-3 neat binder is the typical unmodified asphalt used in Beijing area whereas the N-1 and N-2 neat binders are only utilized in middle asphalt layers to improve the permanent deformation resistance. The styrene–b utadiene–styrene (SBS) binder is the most widely applied polymer-modified asphalt in China and thus, two SBS binders with different modifier weights were also covered. The binder designation, penetration grades, PG grades and modification of the asphalt binders are also summarized in Table 1. All asphalt binders were firstly subjected to rolling thin film oven (RTFO) test to simulate the short-term aging effects during the pavement construction process [66]. Then the RTFO-aged binders were further characterized by means of physical, chemical and rheological tests.

25 20

Responses (mV)

472

15 10 5 LMS

MMS

SMS

0 22 23 24 25 26 27 28 29 30 31 32 33 34 35 Elution Time (mins) Fig. 1. Typical GPC chromatogram result.

Table 1 Summary of asphalt binders. Asphalt Binders

Designation

Penetration Grades

PG Grades

Modification

Neat Asphalt Binders

N-1 N-2 N-3 M-1 M-2

20–30 40–50 60–70 60–70 60–70

PG PG PG PG PG

/ / / 4% SBS Linear 4.5% SBS Linear

SBS Modified Asphalt Binders

82-16 70-22 64-22 82-22 82-28

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measured following the specification procedures of ASTM D5, ASTM D36 and ASTM D113 [67–69].

2.5

Absorbance

2.0

2.3. Chemical tests

1.5

2.3.1. SARA fractionation test The SARA composition of asphalt binder was tested by using the thin-layer chromatography according to ASTM D4124 [70]. The relative fractions of saturates, aromatics, resins and asphaltenes (SARA) can be identified based on their differences in solubility in organic solvents. Such a procedure has been widely used for the chemical composition characterization of asphalt binder [44–51]. Additionally, it should be pointed out that the SARA test for the two SBS modified binders probably only indicates the chemical composition of their base asphalt. Where does the SBS modifiers show up in the molecular composition of modified binders is a challenging concern and not covered within the scope of this study. However, it is still meaningful to conduct SARA test on SBS binders for the effort of blind-modification characterization of asphalt binders.

CH2

1.0

CH3 Benzene Ring

0.5 0.0 4000

3500

3000 2500 2000 1500 Wavenumber (cm-1)

1000

500

Fig. 2. Typical FTIR spectrum result.

2.2. Physical tests The specification and engineering requirements for asphalt binder in China are still established upon the traditional penetration test, softening point test and ductility test. In this study, these physical properties of all asphalt binders were respectively

10000

R0.1

100 R (%)

60%

10

40%

1

20%

0.1 0 (a)

R3.2

80%

50

100 Time (s)

150

200

0% (b)

N-1

N-2

N-3

1.2 Jnr0.1 1.0

Jnr3.2

0.8 Jnr (kPa-1)

Strain (mm/mm)

100%

N-1 N-2 N-3 M-1 M-2

1000

2.3.2. Gel permeation chromatography (GPC) test The GPC test was employed to separate the asphalt molecules depending on various molecular sizes and further quantify the molecular weight distribution. A Waters GPC system equipment with Waters 2410 differential refractive index detector were

0.6 0.4 0.2 0.0 (c)

N-1

N-2

N-3

M-1

M-2

Fig. 3. MSCR test results of tested binders: (a) time-strain curves (b) R results (c) Jnr results.

M-1

M-2

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utilized in this study. A series of three columns of Waters Styragel HT6E-HT5-HT3 was established for separating asphalt binder molecules by molecular size and all of the columns were kept at 35 °C in a column oven during the test process. The mobile phase was a tetrahydrofuran (THF) flowing at a rate of 1 mL/min. A GPC-based chromatogram that describing the asphalt molecular weight distribution is obtained as typically shown in Fig. 1, in which the molecular size gradually decreases from left to right. Following the classic three-part fractionating approach [52–58],

1.20

1.20

Neat Binders Modified Binders

1.00

Neat Binders Modified Binders

1.00

0.80

Jnr3.2 (kPa-1)

Jnr3.2 (kPa-1)

the GPC chromatographic profile is divided into 13 slices according to the elution time as shown in Fig. 2. The slices 1–5 are defined as the large molecular size (LMS), slices 6–9 represent the middle molecular size (MMS) and finally, small molecular size (SMS) cover the slices 10–13. Similar to previous SARA test, it should be recognized that the GPC testing on polymer modified asphalt also probably implies the molecular properties of the base asphalt since the molecular weight magnitudes of asphalt composites and SBS polymer

0.60 0.40

0.80 0.60 0.40 0.20

0.20 0.00

0.00

0

20

(a)

40 60 Penetration (0.1mm)

80

40

50

60 70 Softening Point (°C)

(b)

80

Fig. 4. Comparison of physical properties to MSCR-based Jnr3.2: (a) penetration vs. Jnr3.2 (b) softening point vs. Jnr3.2.

1.20 1.00

0.60 0.40

y = 7E-05e23.299x R² = 0.9127

0.80 0.60 0.40

0.20

0.20

0.00 0%

5%

10%

0.00 20%

15%

Saturates

(a)

1.20

30%

1.20

Jnr3.2 (kPa-1)

0.60 0.40 0.20

50%

Neat Binders Modified Binders

1.00

0.80

40% Aromatics

(b)

Neat Binders Modified Binders

1.00

Jnr3.2 (kPa-1)

Modified Binders

1.00

0.80

0.80 0.60 0.40 0.20

0.00

0.00

0% (c)

Neat Binders

1.20

Jnr3.2 (kPa-1)

Jnr3.2 (kPa-1)

1.40

Neat Binders Modified Binders

10%

20% Resins

30%

40%

0% (d)

10%

20% Asphaltenes

30%

Fig. 5. Comparison of SARA weight percent to MSCR-based Jnr3.2: (a) saturates (b) aromatics (c) resins (d) asphaltenes.

40%

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additives are totally distinguished. The possible molecular interaction between asphalt and SBS polymer and its modification impact on asphalt molecular properties are beyond the objectives of this study. Herein the GPC test was still utilized for SBS binder testing toward a possible modification-blind evaluation of asphalt binders. 2.3.3. Fourier transform infrared spectroscopy (FTIR) test A typical FTIR spectrum with noticeable absorption peaks is given in Fig. 2. The absorption peaks used in this study are 1600, 1460 and 1376 which correspond to the benzene ring, methylene (CH2) and methyl (CH3) in the asphalt, respectively. These functional groups are selected herein to compare with damage behaviors of asphalt binders since they were previously reported to indicate the flexibility of asphalt molecules and correlated well to the binder damage-healing behaviors [39,59]. A functional group index (I) is utilized to remove the sample film effect on peak absorbance [60], as calculated in Equations (1)–(3).

IB ¼

Area of the benzene ring band around 1600 cm1 Area of the spectral bands between 4000 and 500 cm1

ð1Þ

ICH2 ¼

Area of the CH2 band around 1460 cm1 Area of the spectral bands between 4000 and 500 cm1

ð2Þ

ICH3 ¼

Area of the CH3 band around 1376 cm1 Area of the spectral bands between 4000 and 500 cm1

ð3Þ

1.20

2.4.1. Multiple stress creep recovery (MSCR) test The MSCR test protocol (AASHTO TP70, 2010) was conducted to evaluate the asphalt binder rutting potential at high temperature [12]. The percent recovery (R) and non-recoverable compliance (Jnr) respectively at two stress levels (R0.1, Jnr0.1, R3.2, and Jnr3.2) can finally be calculated. 2.4.2. Linear amplitude sweep (LAS) test The LAS protocol (AASHTO TP101, 2014) was utilized to estimate the fatigue resistance of asphalt binder [15]. A newly integrated LAS-based fatigue modeling approach was employed in this study, which composes of three material-dependent characteristics, in terms of dynamic shear modulus mastercurve, damage characteristic curve, and failure criterion [22–23]. An Excel-based software namely the AsphaFATTM 1.0 was developed to efficiently complete the LAS test data interpretation followed by the final output of the fatigue law simulation of asphalt binder. 2.4.3. DSR-based elastic recovery (DSR-ER) test The DSR-ER test (AASHTO TP123, 2016) was run to measure the elasticity of asphalt binder especially for modified asphalt at intermediate temperature [27]. The performance indicator of elastic recovery (ER) is quantified from the percent recovery of the shear strain recorded from the monotonic shear and recovery process. At least two replicates were run for above physical, chemical and rheological tests. To ensure the coefficient of variation was

1.20

Neat Binders Modified Binders

1.00

0.80

Jnr3.2 (kPa-1)

Jnr3.2 (kPa-1)

1.00

2.4. Rheological tests

0.60 0.40

15%

16% LMS

(a)

1.20

17%

1.20 Neat Binders Modified Binders

1.00

0.60 0.40

67%

69% MMS

71%

73%

Neat Binders Modified Binders

0.80 0.60 0.40 0.20

0.20

(c)

0.40

(b)

0.80

0.00 10%

0.60

0.00 65%

18%

Jnr3.2 (kPa-1)

Jnr3.2 (kPa-1)

1.00

0.80

0.20

0.20 0.00 14%

Neat Binders Modified Binders

12%

14%

16% SMS

18%

20%

0.00 0.00 (d)

0.50

1.00 SMS/LMS

Fig. 6. Comparison of GPC parameters to MSCR-based Jnr3.2: (a) LMS (b) MMS (c) SMS (d) SMS/LMS.

1.50

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within 10%, a third or even more replicates were further needed to conduct. 3. Rutting resistance assessment at high temperature The permanent deformation potential of all five asphalt binders was identified through the MSCR procedure at a typical high temperature of 60 °C in Beijing area. The time-strain responses during the MSCR test are compared in Fig. 3(a) and it can be observed that

1.20

1.20

Neat Binders Modified Binders

0.80 0.60 0.40

0.00 0.014

0.015 IB

(a)

0.60 0.40

0.00 0.060

0.016

0.062

(b)

0.064 ICH2

1.20

Neat Binders Modified Binders

0.80 0.60 0.40

0.066

0.068

Neat Binders Modified Binders

1.00

Jnr3.2 (kPa-1)

Jnr3.2 (kPa-1)

1.00

0.80

0.20

0.20

1.20

Neat Binders Modified Binders

1.00 Jnr3.2 (kPa-1)

Jnr3.2 (kPa-1)

1.00

the N-3 binder displays the largest non-recoverable strain followed by N-2, M-1, M-2 and N-1 binder. The percent recovery (R) and non-recoverable compliance (Jnr) for each binder was calculated and respectively summarized in Fig. 3 (b) and (c). Generally, the two modified binders show higher R values and lower Jnr levels than neat binders, indicating better rutting resistance at high temperature. In addition, the N-1 binder presents the identical Jnr level to modified binders, which is consistent to the time-strain response results.

0.80 0.60 0.40 0.20

0.20 0.00 0.0140

0.00 0.0144

(c)

0.0148 ICH3

0.0152

4.0

0.0156

4.2

(d)

4.4 CH2/CH3

4.6

4.8

Fig. 7. Comparison of FTIR parameters to MSCR-based Jnr3.2: (a) IB (b) ICH2 (c) ICH3 (d) CH2/CH3.

N-1 N-2 N-3 M-1 M-2

6.E+05

3.E+05

0.E+00 0 (a)

5

10 Shear Strain (%)

15

20

10%

N-1 N-2 N-3 M-1 M-2

Strain Amplitude

Shear Stress (Pa)

9.E+05

1% 100 (b)

1000

10000 Nf

100000

1000000

Fig. 8. LAS test results of all tested binders: (a) stress–strain curves in standard LAS tests (b) simulation results of strain-controlled binder fatigue life.

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3.1. Physico-rheological properties The physical properties of penetration and softening point are the common physical indices for asphalt binder high temperature performance. The Fig. 4 (a) and (b) compare the MSCR-based Jnr3.2 values respectively to the corresponding penetration and softening point results. It is clearly shown that the Jnr3.2 decrease with lower penetration grade and higher softening point temperature when separately comparing neat binders and modified binders. However, one cannot identify the Jnr3.2 ranking merely either from

penetration or softening point if the asphalt modification information is unknown. In other words, to establish a modification blind selection for asphalt binder, a unified correlation is needed between physical properties and rheological performance among both neat and modified binders. 3.2. Chemo-rheological properties The percent weight of each SARA component is firstly compared to the MSCR-based Jnr3.2 results as given in Fig. 5. Though it is seen

30000

30000

Neat Binders

Neat Binders

Modified Binders

25000

Modified Binders

25000

20000

Nf

20000 Nf

15000

15000 10000

10000

5000

5000 0

0 0 (a)

20

40 60 Penetration (0.1mm)

0

80

20

40

60

Ductility (cm)

(b)

Fig. 9. Comparison between physical properties and LAS-based Nf: (a) penetration vs. Nf (b) ductility vs. Nf.

30000

30000

Neat Binders Modified Binders

25000

25000 20000

Nf

Nf

20000

15000

15000 10000

10000

5000

5000 0 20%

0 0%

5%

10%

15%

Saturates

(a)

30000

30%

40%

30000

Neat Binders Modified Binders

25000

20000

50%

Aromatics

(b)

Neat Binders Modified Binders

25000

Nf

20000

Nf

15000

15000

10000

10000

5000

5000

0

0

0% (c)

Neat Binders Modified Binders

10%

20% Resins

30%

40%

0% (d)

10%

20% Asphaltenes

30%

Fig. 10. Comparison of SARA weight percent to LAS-based Nf: (a) saturates (b) aromatics (c) resins (d) asphaltenes.

40%

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that the chemical composition effects on binder rutting resistance is rather complex from the Fig. 5(a), (c) and (d), it is also interestingly found that the aromatic weight well correlated to Jnr3.2 values for all tested binders in Fig. 5 (b). More importantly, the fitted relationship between aromatic and Jnr3.2 is completely independent on binder modification and thus, could be further utilized as a principle to explain the distinguished rutting resistance of different asphalt binders from a microscale perspective. This is to say, the weight percent of aromatic within asphalt should be taken special consideration whenever the permanent deformation is strongly concerned during the material selection and design process. The molecular weight distribution of all tested binders measured from GPC-based chromatographic profiles are quantified by percent of LMS, MMS and SMS parameters, which was calculated based on the three-part fractionating approach as previously introduced. In addition, the ratio of SMS and LMS is also included here since the SMS/LMS was reported to well connect to the asphalt binder rheological performance [39]. The relationship between these four GPC parameters and MSCR-based Jnr3.2 are summarized in Fig. 6. Compared with LMS and MMS parameters, it can be observed that both SMS and SMS/LMS parameters are more effective to distinguish the binder rutting resistance respectively for neat and modified binders. Increasing the SMS and SMS/LMS would gradually increase the binder Jnr3.2 levels, indicating significant rutting potential. Therefore, it can be concluded that the asphalt binder resistance to permanent deformation is much more sensitive to the amount of small asphalt molecules. It should be also mentioned that the correlation trend shown in Fig. 6(c) and (d) are still asphalt modification dependent, which probably

implies that the GPC-based analysis only is also not reliable for the modification blind selection of asphalt binders. The contents of benzene ring and the ratio of CH2 and CH3 are important indexes to represent the chemical structure of asphalt binders, which can be measured from the FTIR test. The comparison between FTIR-based functional group indices to MSCR-based Jnr3.2 are given in Fig. 7. For the neat binders, it can be clearly observed the more CH2 and CH3 contents resulted higher Jnr3.2 values. However, the binder rutting resistance is not sensitive to the IB and CH2/CH3 parameters. In future study, the structure properties of asphalt binder should be further addressed and characterized to reveal the macroscale rheological performance.

4. Fatigue performance at intermediate temperature The fatigue performance of asphalt binders are firstly evaluated through the LAS-based fatigue modeling approach at a typical intermediate temperature of 20 °C in Beijing area. The stress–strain response curves of all binders during the standard LAS test that completed within 5 min are compared in Fig. 8(a) and each curve are displayed up to the identified failure occurrence. It can be seen that the three neat binders show much higher peak stress and smaller failure strain levels whereas the two modified binders present much more ductile failure behaviour that would be more fatigue resistant. The LAS test data under three loading rates are modeled to simulate the strain-controlled fatigue life by means of AsphaFATTM 1.0 software. Fig. 8 (b) compares the fatigue life results of all tested binders and the two modified binders show

30000

30000

Neat Binders Modified Binders

25000

25000

20000

20000 Nf

Nf

y = 2E-08x-14.43 R² = 0.8892

15000

15000

10000

10000

5000

5000

0 14%

15%

(a)

30000 25000

16% LMS

17%

0 65%

18%

30000

Neat Binders Modified Binders

25000

69% MMS

71%

73%

Neat Binders Modified Binders

20000 Nf

Nf

15000

15000

10000

10000

5000

5000

(c)

67%

(b)

20000

0 10%

Neat Binders Modified Binders

15% SMS

0 0.00

20%

(d)

y = 3.556e8.53x R² = 0.8419

0.50

1.00 SMS/LMS

Fig. 11. Comparison of GPC parameters to LAS-based Nf: (a) LMS (b) MMS (c) SMS (d) SMS/LMS.

1.50

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4.1. Physico-rheological properties The asphalt binder physical properties of penetration and ductility are respectively compared to the binder fatigue life at 3% strain in Fig. 9. It is observed that the penetration results merely distinguish well the fatigue performance of neat binders in Fig. 9(a), implying that the softer neat binder is expected to be more fatigue resistant. The ductility is a physical property that normally associated with the cracking potential at intermediate and low temperature. In Fig. 9(b) it is seen that the ductility demonstrate well the fatigue resistance improvement from asphalt modification, however, the two neat binders with similar fatigue life exhibit distinguished ductility property. Therefore, it is not adequately reasonable to reveal the fatigue performance of neat and modified asphalt binders from physical properties based on the limited tested materials in this study.

binders, it can be generally observed that the fatigue life increase with increasing the contents of oil phases of saturates and aromatics. Meanwhile, the higher weight percents of resins and asphaltenes negatively impact the fatigue resistance. However, none conclusive results can be made here regarding to the SARA fractionation influence on fatigue performance of two modified binders as shown in Fig. 10. How the modifier additives impact the SARA analysis and the composition form of the modifier display within the asphalt binder is beyond the scope of this study but indeed to be addressed in the future study. Though the chemical properties of the modifiers may introduce complex impact on asphalt binder compositions, the molecular

3.0 N-1 2.5

Strain (mm/mm)

clearly advanced fatigue resistance than the neat binders, which is consistent to the field pavement practice experiences. It can be also observed that the fatigue laws of tested binders shown in Fig. 8 (b) are approximately parallel to each other; therefore, the binder fatigue life at 3% strain amplitude is utilized as the fatigue performance index in this study to compare with physical and chemical properties in the following sections.

N-2

2.0 1.5

N-3

1.0

M-1

0.5 M-2 0.0

4.2. Chemo-rheological properties

0

500

The comparison of SARA fractionation results to corresponding binder fatigue life at 3% strain is given in Fig. 10. For the neat

30000 25000

Nf

Nf

20000

15000

15000

10000

10000

5000

5000

0 0.014

0.015 IB

(a)

30000

0 0.060

0.016

20000

30000

0.064 ICH2

0.066

0.068

4.4 CH2/CH3

4.6

4.8

Neat Binders Modified Binders

25000

Nf

20000 Nf

15000

15000

10000

10000

5000

5000

(c)

0.062

(b)

Neat Binders Modified Binders

25000

0 0.0140

2000

Neat Binders Modified Binders

25000

20000

1500

Fig. 13. DSR-ER test results of all tested binders.

30000

Neat Binders Modified Binders

1000 Time (s)

0

0.0144

0.0148 ICH3

0.0152

0.0156

4.0 (d)

4.2

Fig. 12. Comparison of FTIR parameters to LAS-based Nf: (a) IB (b) ICH2 (c) ICH3 (d) CH2/CH3.

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80%

80%

Neat Binders

Neat Binders

Modified Binders

Modified Binders

60%

ER

ER

60%

40%

40%

20%

20%

0%

0% 0

10000

(a)

20000

30000

Nf

0%

20%

(b)

40% R3.2

60%

80%

Fig. 14. Comparison of binder performance index to DSR-ER: (a) Nf vs. ER (b) R3.2 vs. ER.

weight distribution measured from GPC test seems a more sample way to reveal the microscale characteristics of asphalt binders. The four GPC parameters are respectively compared to the binder fatigue life as given in Fig. 11. Generally, it can be clearly demonstrated that the fatigue resistance increases with lower LMS and MMS levels and higher SMS values. In other words, the more small molecules within asphalt are favorable for improving the fatigue performance whereas bigger molecules generate negative effects. This is consistent to previous studies that LMS can play a significant role in cracking and that low LMS is desired to reduce cracking [52]. In addition, the effects of MMS and SMS on binder fatigue life are still dependent on asphalt modification. However, the LMS and SMS/LMS parameters are found to be monotonically corresponded to the fatigue life of both neat and modified binders, respectively. Therefore, LMS or SMS/LMS can be potentially utilized as a microscale chemical index to select a fatigue resistant asphalt binder. Also, the LMS and SMS/LMS levels are critical indices for designing an asphalt binder with excellent fatigue performance. The function group properties from FTIR test are also compared with asphalt binder fatigue performance as shown in Fig. 12. For neat binders, higher contents of large molecules of benzene ring as indicated by IB decrease the binder fatigue life and more small molecules as identified from ICH2 and ICH3 improve the fatigue resistance. Additionally, a higher CH2/CH3 represents a lower content of branched-chain in asphalt molecules, suggesting a longer and thinner molecular structure. In Fig. 12(d), the CH2/CH3 parameter distinguish well the modification effect on binder molecular structure and thus, the improvements on binder fatigue performance from longer and thinner molecular structure. However, in this study more details on molecular structure properties are limited and need further advanced characterization. 4.3. Elastic recovery performance The elastic recovery performance of all binders measured from DSR-ER test at 20 °C is summarized in Fig. 13. It is seen that the two modified binders display much better recovery potential than neat binders. Fig. 14(a) compares the quantified ER parameters to the LAS-based binder fatigue life and the improved binder fatigue resistance from asphalt modification can also be clearly observed. In addition, the binder ER properties that measured at intermediate temperature are further compared with the percent recovery of R3.2 from the MSCR test at high temperature as shown in Fig. 14 (b). A better strain recovery potential of polymer modified binders is verified under both two temperature conditions that independent of loading modes and loading histories.

5. Conclusions This paper presents a comprehensive laboratory investigation on physico-chemo-rheological performance of neat and polymermodified asphalt binders. The specific findings of this study are summarized as follows: (1) The penetration, softening point and ductility were found to effectively distinguish the rheological performance for unmodified neat asphalt binders. However, one cannot accurately identify the binder performance ranking merely from physical properties when asphalt modification information is unknown. (2) The aromatic composition was demonstrated to correlate to MSCR-based Jnr3.2 results, in which lower aromatics contents would improve the binder rutting resistance. A unified relationship between aromatic contents and Jnr3.2 was clearly obtained for both neat and modified binders. In addition, GPC-based molecular weight distribution indicated that increasing the amount of small asphalt molecules (SMS) decreased the resistance to permanent deformation respectively for neat and modified binders. (3) The fatigue resistance of asphalt binders were increased with lower LMS, MMS levels and higher SMS, SMS/LMS values, suggesting that small asphalt molecules is favorable for improving the fatigue performance. Especially, both LMS and SMS/LMS parameters were monotonically correlated to the fatigue life of both neat and modified binders, indicating a unified relationship as a chemical index to select a fatigue resistant asphalt binder. Generally, it is recommended that the aromatics contents and SMS, SMS/LMS parameters could be further implemented as a principle to respectively select and design a rutting and fatigue resistant asphalt binder from a microscale perspective. In the future study, more types of asphalt binder materials and long-term aging effects should be included and validated for the findings in this study. Conflict of interest Any findings and conclusions in this study are those of the authors and do not reflect the views of the funding organizations. The authors declare that they do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.

C. Wang, Y. Wang / Construction and Building Materials 199 (2019) 471–482

Acknowledgements The authors would like to gratefully acknowledge the sponsorship from National Natural Science Foundation of China (51608018), Beijing Natural Science Foundation (8174059) and Beijing Municipal Education Commission (KM201810005020).

References [1] J.S. Miller, W.Y. Bellinger, Distress identification manual for the long-term pavement performance program, Publication No. FHWA-RD-03-031, June 2003. [2] D.A. Anderson, T. Kennedy, Development of SHRP binder specification, J. Asphalt Paving Technol. 62 (1993) 481–507. [3] D.A. Anderson, D.W. Christensen, H.U. Bahia, R. Dongre, et al., Binder characterization and evaluation Volume 3: Physical characterization SHRP-A369, National Research Council, 1994. [4] H.U. Bahia, H. Zhai, K. Bonnetti, S. Kose, Non-linear viscoelastic and fatigue properties of asphalt binders, J. Assoc. Asphalt Paving Technol. 68 (1999) 1–34. [5] H.U. Bahia, H. Zhai, M. Zeng, Y. Hu, P. Turner, Development of binder specification parameters based on characterization of damage behavior, J. Assoc. Asphalt Paving Technol. 70 (2001) 442–470. [6] H.U. Bahia, D.I. Hanson, M. Zeng, et al., Characterization of modified asphalt binders in superpave mix design. NCHRP Report 459, Transportation Research Board, National Research Council, 2001. [7] D.A. Anderson, Y.M.L. Hir, M.O. Marasteanu, J.-P. Planche, D. Martin, G. Gauthier, Evaluation of fatigue criteria for asphalt binders, Trans. Res. Rec.: J. Trans. Res. Board 1766 (2001) 48–56. [8] K.S. Bonnetti, K. Nam, H.U. Bahia, Measuring and defining fatigue behavior of asphalt binders, Trans. Res. Rec.: J. Trans. Res. Board 1810 (2002) 33–43. [9] W. Martono, H.U. Bahia, J. D’Angelo, Effect of testing geometry on measuring fatigue of asphalt, ASCE J. Mater. Civil Eng. 19 (9) (2007) 746–752. [10] Transportation Research Circular E-C147, Development in asphalt binder specifications, Papers from a Workshop, Papers from a Workshop, January, 2008, Washington, D.C. [11] AASHTO, Determining the rheological properties of asphalt binder using a dynamic shear rheometer (DSR), AASHTO T315, 2008, Washington D.C. [12] AASHTO, Standard method of test for multiple stress creep recovery (MSCR) test of asphalt binder using a dynamic shear rheometer (DSR), AASHTO TP70, 2010, Washington D.C. [13] J. D’Angelo, The relationship of the MSCR test to rutting, Road Mater. Pavement Des. 10 (S1) (2009) 61–80. [14] J. D’Angelo, R. Dongré, Practical use of multiple stress creep and recovery test, Transp. Res. Rec. 2126 (2009) 73–82. [15] AASHTO, Standard method of test for estimating damage tolerance of asphalt binders using the linear amplitude sweep, AASHTO TP101, 2014, Washington, DC. [16] Y.R. Kim, D.N. Little, One-dimensional constitutive modeling of asphalt concrete, ASCE J. Eng. Mech. 116 (4) (1990) 751–772. [17] Y.R. Kim, H.J. Lee, D.N. Little, Fatigue characterization of asphalt concrete using viscoelasticity and continuum damage theory, J. Assoc. Asphalt Paving Technol. 66 (1997) 520–569. [18] J.S. Daniel, Y.R. Kim, Development of a simplified fatigue test and analysis procedure using a viscoelastic damage model, J. Assoc. Asphalt Paving Technol. 71 (2002) 619–650. [19] B.S. Underwood, Multiscale Constitutive Modeling of Asphalt Concrete (Ph.D. dissertation), North Carolina State University, Raleigh, N.C., 2011. [20] C.M. Johnson, Estimating Asphalt Binder Fatigue Resistance using an Accelerated Test Method (Ph.D. Dissertation), University of WisconsinMadison, Madison, WI, 2010. [21] C. Hintz, H. Bahia, Simplification of linear amplitude sweep test and specification parameter, Transp. Res. Rec. 2370 (2013) 10–16. [22] C. Wang, C. Castorena, J. Zhang, Y.R. Kim, Unified failure criterion for asphalt binder under cyclic fatigue loading, J. Assoc. Asphalt Paving Technol. 84 (2015) 269–299 (Republished at Road Materials and Pavement Design, 2015, 16(S2): 125–148.). [23] C. Wang, W. Xie, Y. Chen, A. Diab, Z. You, Refining the calculation method for fatigue failure criterion of asphalt binder using the linear amplitude sweep test, ASCE J. Mater. Civ. Eng. 30 (2) (2018). [24] C. Wang, C. Castorena, J. Zhang, Y.R. Kim, Application of time-temperature superposition principle on fatigue failure analysis of asphalt binder, ASCE J. Mater. Civ. Eng. 29 (1) (2017). [25] C. Wang, H. Wang, L. Zhao, D. Cao, Experimental study on rheological characteristics and performance of high modulus asphalt binder with different modifiers, Constr. Build. Mater. 155 (2017) 26–36. [26] W. Xie, C. Castorena, C. Wang, Y.R. Kim, A framework to characterize the healing potential of asphalt binder using the linear amplitude sweep test, Constr. Build. Mater. 154 (2017) 771–779. [27] AASHTO, Measuring asphalt binder yield energy and elastic recovery using the dynamic shear rheometer, AASHTO TP123, 2016, Washington D.C. [28] C.S. Clopotel, H. Bahia, Importance of elastic recovery in the DSR for binders and mastics, Eng. J. 16 (4) (2012) 99–106.

481

[29] H.A. Tabatabaee, C. Clopotel, A. Arshadi, H. Bahia, Critical problems with using the asphalt ductility test as a performance index for modified binders, Transp. Res. Rec. 2370 (2013) 84–91. [30] C. Wang, L. Zhao, W. Cao, D. Cao, B. Tian, Development of paving performance index system for selection of modified asphalt binder, Constr. Build. Mater. 153 (2017) 695–703. [31] Y. Wang, C. Wang, H. Bahia, Comparison of the fatigue failure behaviour for asphalt binder using both cyclic and monotonic loading modes, Constr. Build. Mater. 151 (2017) 767–774. [32] P. Cong, J. Wang, K. Li, S. Chen, Physical and rheological properties of asphalt binders containing various antiaging agents, Fuel 97 (2012) 678–684. [33] M. Jasso, D. Bakos, D. MacLeod, L. Zanzotto, Preparation and properties of conventional asphalt modified by physical mixtures of linear SBS and montmorillonite clay, Constr. Build. Mater. 38 (2013) 759–765. [34] F. Zhang, C. Hu, Physical and rheological properties of crumb rubber/styrene– butadiene–styrene compound modified asphalts, Polym. Compos. (2017), https://doi.org/10.1002/pc.23762. [35] L. Zhang, T. Li, F. Gao, Y. Tan, Rheological and physical properties of asphalt mixed with warm compaction modifier, Constr. Build. Mater. 123 (2016) 309– 316. [36] W. Luo, Y. Zhang, P. Cong, Investigation on physical and high temperature rheology properties of asphalt binder adding waste oil and polymers, Constr. Build. Mater. 144 (2017) 13–24. [37] J.B. Wei, J.C. Shull, Y. Lee, M.C. Hawley, Characterization of asphalt binders based on chemical and physical properties, J. Polym. Anal. Charact. 3 (1) (1996) 33–58. [38] Y. Wang, Y. Wen, K. Zhao, D. Chong, J. Wei, Connections between the rheological and chemical properties of long-term aged asphalt binders, J. Mater. Civ. Eng. 27 (9) (2015). [39] D. Sun, F. Yu, L. Li, T. Lin, X.Y. Zhu, Effect of chemical composition and structure of asphalt binders on self-healing, Constr. Build. Mater. 133 (2017) 495–501. [40] J. Wang, T. Wang, X. Hou, F. Xiao, Modelling of rheological and chemical properties of asphalt binder considering SARA fraction, Fuel 238 (2019) 320– 330. [41] J. Wang, J. Yuan, K.W. Kim, F. Xiao, Chemical, thermal and rheological characteristics of composite polymerized asphalts, Fuel 227 (2018) 289–299. [42] V. Venudharan, K. Prapoorna Biligiri, N.C. Das, Investigations on behavioral characteristics of asphalt binder with crumb rubber modification: rheological and thermo-chemical approach, Constr. Build. Mater. 181 (2018) 455–464. [43] X. Cao, H. Wang, X. Cao, W. Sun, H. Zhu, B. Tang, Investigation of rheological and chemical properties asphalt binder rejuvenated with waste vegetable oil, Constr. Build. Mater. 180 (2018) 455–463. [44] L.W. Corbett, Composition of asphalt based on generic fractionation, using solvent deasphaltening, elution-adsorption chromatography, and densimetric characterization, Anal. Chem. 41 (1969) 576–579. [45] P. Michalica, I.B. Kazatchkov, J. Stastna, L. Zanzotto, Relationship between chemical and rheological properties of two asphalts of different origins, Fuel 87 (2008) 3247–3253. [46] E. Santagata, O. Baglieri, D. Dalmazzo, L. Tsantilis, Rheological and chemical investigation on the damage and healing properties of bituminous binders, J. Assoc. Asphalt Paving Technol. 78 (2009) 567–596. [47] S. Sultana, A. Bhasin, Effect of chemical composition on rheology and mechanical properties of asphalt binder, Constr. Build. Mater. 72 (2014) 293–300. [48] J. Lin, J. Hong, J. Liu, S. Wu, Investigation on physical and chemical parameters to predict long-term aging of asphalt binder, Constr. Build. Mater. 122 (2016) 753–759. [49] S. Mangiafico, H. Di Benedetto, C. Sauzéat, F. Olard, S. Pouget, L. Planque, Effect of colloidal structure of bituminous binder blends on linear viscoelastic behaviour of mixtures containing reclaimed asphalt pavement, Mater. Des. 111 (2016) 126–139. [50] S. Weigel, D. Stephan, Modelling of rheological and ageing properties of bitumen based on its chemical structure, Mater. Struct. 50 (2017) 83, https:// doi.org/10.1617/s11527-016-0957-7. [51] M. Liang, S. Liu, W. Fan, X. Xin, H. Luo, B. Xing, Rheological and chemical characterization of deoiled asphalt modified with FCC slurry, Mater. Struct. 49 (2016) 3607–3617. [52] P.W. Jennings, J.A.S. Pribanic, K.R. Dawson, C.E. Bricca, Use of HPLC and NMR spectroscopy to characterize asphaltic materials, ACS Div. Pet. Chem. 26 (4) (1981) 915–922. [53] E.V. Churchill, S.N. Amirkhanian, J.L. Burati Jr., HP-GPC characterization of asphalt aging and selected properties, J. Mater. Civ. Eng. 7 (1) (1995). [54] H.I.A. Wahhab, I.M. Asi, F.M. Ali, I.A. Al-Dubabi, Prediction of asphalt rheological properties using HP-GPC, J. Mater. Civ. Eng. 11 (1) (1999) 6–14. [55] K.W. Kim, K. Kim, Y.S. Doh, S.N. Amirkhanian, Estimation of RAP’s binder viscosity using GPC without binder recovery, J. Mater. Civ. Eng. 18 (4) (2006) 561–567. [56] H. Kim, S. Lee, S.N. Amirkhanian, K. Jeong, Quantification of oxidative aging of polymer-modified asphalt mixes made with warm mix technologies, J. Mater. Civ. Eng. 25 (1) (2013) 1–8. [57] S. Zhao, B. Huang, X. Shu, M.E. Woods, Quantitative evaluation of blending and diffusion in high RAP and RAS mixtures, Mater. Des. 89 (2016) 1161–1170. [58] G. Hao, W. Huang, J. Yuan, N. Tang, F. Xiao, Effect of aging on chemical and rheological properties of SBS modified asphalt with different compositions, Constr. Build. Mater. 156 (2017) 902–910.

482

C. Wang, Y. Wang / Construction and Building Materials 199 (2019) 471–482

[59] Y.R. Kim, D.N. Little, F.C. Benson, Chemical and mechanical evaluation of healing mechanism of asphalt concrete, J. Assoc. Asphalt Paving Technol. 59 (1990) 240–275. [60] J. Lamontagnea, P. Dumasb, V. Mouilletb, J. Kistera, Comparison by Fourier transform infrared (FTIR) spectroscopy of different ageing techniques: application to road bitumens, Fuel 80 (2001) 483–488. [61] A.R. Abbas, U.A. Mannan, S. Dessouky, Effect of recycled asphalt shingles on physical and chemical properties of virgin asphalt binders, Constr. Build. Mater. 45 (2013) 162–172. [62] N. Tang, W. Huang, F. Xiao, Chemical and rheological investigation of highcured crumb rubber-modified asphalt, Constr. Build. Mater. 123 (2016) 847– 854. [63] Z. Feng, H. Bian, X. Li, J. Yu, FTIR analysis of UV aging on bitumen and its fractions, Mater. Struct. 49 (2016) 1381–1389.

[64] T. Nian, P. Li, Y. Mao, G. Zhang, Y. Liu, Connections between chemical composition and rheology of aged base asphalt binders during repeated freeze-thaw cycles, Constr. Build. Mater. 159 (2018) 338–350. [65] H. Zhang, Z. Chen, G. Xu, C. Shi, Physical, rheological and chemical characterization of aging behaviors of thermochromic asphalt binder, Fuel 211 (2018) 850–858. [66] AASHTO, Standard method of test for effect of heat and air on a moving film of asphalt binder (rolling thin-film oven test), AASHTO T240, Washington, DC. [67] ASTM, Standard test method for penetration of bituminous materials, ASTM , 2013. [68] ASTM, Standard test method for softening point of bitumen (Ring-and-Ball Apparatus), ASTM , 2014. [69] ASTM, Standard test method for ductility of asphalt materials. ASTM, 2017. [70] ASTM. Standard test method for separation of asphalt into four fractions. ASTM, 2009.