Performance of hot mix epoxy asphalt binder and its concrete ...

Materials and Structures (2015) 48:3825–3835 DOI 10.1617/s11527-014-0442-0

ORIGINAL ARTICLE

Performance of hot mix epoxy asphalt binder and its concrete Haiyan Yin • Yuge Zhang • Yifan Sun Wei Xu • Dier Yu • Hongfeng Xie • Rongshi Cheng

•

Received: 25 March 2014 / Accepted: 3 October 2014 / Published online: 11 October 2014 Ó RILEM 2014

Abstract Hot mix epoxy asphalt (HMEA) binders have been widely used on the pavement of orthotropic steel bridge decks. In present paper, rotational viscosity, glass transition temperature, damping properties, mechanical properties, and morphology of HMEA were investigated using Brookfield rotational viscometer, differential scanning calorimetry, dynamic mechanical analysis (DMA), universal material tester, laser scanning confocal microscopy. Furthermore, the high temperature deformation resistance, rutting resistance, and fatigue cracking resistance of HMEA concretes (HMEACs) were evaluated using Marshall, wheel tracking, and three-point bending tests. Results

H. Yin Y. Zhang Y. Sun H. Xie (&) R. Cheng Key Laboratory of High Performance Polymer Materials and Technology, School of Chemistry and Chemical Engineering, Nanjing University, Ministry of Education, Nanjing 210093, China e-mail: [email protected] W. Xu Road Engineering Institute, South China University of Technology, Guangzhou 510641, China D. Yu National Engineering Laboratory for Advance Road Materials, Jiangsu Transportation Institute, Nanjing 211112, China R. Cheng College of Material Science and Engineering, South China University of Technology, Guangzhou 510641, China

show that the addition of asphalts postpones the cure reaction of epoxy resin. The rotational viscosity of HMEA binder keeps low enough to meet the demands of asphalt mixture mixing and paving at 160 °C. DMA results show that HMEA exhibits excellent damping properties. The addition of asphalts lowers the tensile strength and modulus of epoxy resin. However, the elongation at break of HMEA increases with the increase of asphalt contents. HMEACs exhibit good resistance to high temperature deformation, rutting, and fatigue cracking performances. All these results show that HMEA binder exhibits excellent performance in the steel bridge pavement. Keywords Epoxy asphalts Polymer modified asphalts Binder Epoxy asphalt concretes Mechanical properties Morphology

1 Introduction Asphalt is an important thermoplastic which finds many applications as a building and engineering material. However, asphalt has poor mechanical properties as it is hard and brittle in cold environments and soft and fluid in hot environments [1]. One of the many ways of toughening asphalt is by blending it with synthetic polymers, which can be either virgin or waste polymer. A large number of polymers have been used for asphalt modification, including polyethylene,

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most extensively styrene homopolymers and copolymers, ethylene vinyl acetate and acrylic copolymers, and many other polymeric materials [2–6]. More recently, there has been intense interest in the use of recycled or scrap plastic, including tire rubber crumb to modify asphalt [7]. Orthotropic deck bridges have been built worldwide because of their low cost and good performance. However, the condition such as temperature and deformation at the steel bridge deck is much severer than that of common highway. Compared with the general asphalt pavement, the paving layer on steel bridge deck should deform with the steel bridge deck synchronously. Furthermore, it should have a better stability at high temperature, a better crack resistance at lower temperature and a better fatigue resistance [8]. At the same time, the pavement must be equipped with better waterproof and good adhesion to the deck. The afore-mentioned polymer-modified asphalt cannot change the thermoplastic nature of asphalt, which means that asphalt flow easily at high temperature. Therefore, the above mentioned polymer modified asphalt can not satisfy the rigorous demands of the steel deck bridge surface paving. Epoxy asphalt (EA), a thermosetting asphalt, has attracted considerable interest for better thermal stability, skid resistance, a uniform riding surface and steel deck waterproofing for extended years even under severe ambient and load conditions during recent years [9]. Yu and Cong et al. reported the effects of epoxy resin on the mechanical and rheological properties of SBS modified asphalts with methyl tetrahydro phthalic anhydride as curing agent [10, 11]. In addition, the effects of epoxy resin contents on the fatigue life and creep properties of epoxy asphalt concrete were also investigated [12]. Kang et al. [13] explored the glass transition and mechanical properties of rubber-like thermosetting EA with maleated petroleum asphalt, adipic acid, and methylhexahydrophthalic anhydride as curing agents. In addition, the reaction mechanism between asphalt and anhydride was revealed by FTIR and chemical titration [14]. The results show that the epoxy asphalt concrete (EAC) has a good resistance to moisture damage, permanent deformation, and lowtemperature cracking and is a good material for protective course of railway bridge deck [15, 16]. Yao et al. [17] compared the dynamic modulus and the flexural stiffness of three typical concrete types on orthotropic steel bridge decks, including polymer-

Materials and Structures (2015) 48:3825–3835 Table 1 Properties of epoxy resin Property Viscosity (23 °C, mPa s) 3

Measured value

Test method

3,142

ASTM D445

Specific gravity (23 °C, g/cm )

1.15

ASTM D1475

Epoxide equivalent weight (g/eq)

203

ASTM D1652

Table 2 Properties of cure agents Property

Measured value

Test method

Viscosity (23 °C, mPa s)

472

ASTM D445

Specific gravity (23 °C, g/cm3)

0.86

ASTM D1475

Acid value (mg KOH/g)

174

ASTM D664

modified asphalt concrete, gussasphalt concrete and EAC. The EAC shows the highest dynamic modulus and flexural stiffness. Xiao et al. [18] characterized the two-component epoxy modified bitumen. They concluded that this type of epoxy modified bitumen can be promising as a binder in anti-skid layers. EAC has been widely used on the pavement of orthotropic deck bridges. Previous researches have focused on the properties of the EACs. However, there were few reports on the difference between pure epoxy resin (EP) and EA binders [19]. The aim of the present work is to investigate the properties of hot mix EP binder and its concrete with different asphalt contents. The rotational viscosity, thermal, damping, mechanical properties, and morphology of EP binders with different asphalt contents were determined. In addition, the high temperature deformation, rutting, and fatigue cracking performances of EP concrete (EPC) and hot mix EA concretes (HMEACs) were evaluated.

2 Experimental 2.1 Materials 2.1.1 Binder The HMEA binder has three components before use. Part A (used at 56 % by mass) consists of an epoxy

Materials and Structures (2015) 48:3825–3835

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Table 3 Properties of the base asphalt Property

Value

Penetration (25 °C, 100 g, 5 s), 0.1 mm

63.0

Softening point (R&B), °C

48.5

Ductility (15 °C, 5 cm/min), cm Density (15 °C), g/cm3

[200 1.035

Viscosity (60 °C), Pa s

173

Wax contain, %

1.83

Table 4 Properties of the basalt aggregate Property

Measured value

Test method

Specific gravity (g/cm3)

2.91

ASTM C127

Water absorption (%)

0.65

ASTM C127

Abrasion loss (%)

11.5

ASTM C131

Polish value (%)

0.62

ASTM D3319

Sand equivalent value

78

ASTM D2419

a 13.2 mm nominal maximum size aggregate was used for the concrete testing. The properties of aggregate are summarized in Table 4. The optimum binder content of EPC and HMEAC was chosen at 6.5 % based on the Marshall concrete design using the densegraded aggregate gradation given in Fig. 1. 2.2 HMEA preparation Epoxy resin was mixed with cure agents at 80 °C. Afterward, the mixture of epoxy and curing agent (epoxy binder) was stirred by magnetic force for 5 min. Asphalt preheated at 160 °C in an oven for 1 h was added to the epoxy binder with continuous mechanical stirring, until a homogeneous mixture (HMEA binder) was observed. The HMEA binder was immediately poured into polytetrafluoroethylene molds and cured for 1 h at 150 °C and subsequently for 3 d at 60 °C. The asphalt contents were 0, 44, 50, and 55 % by mass of HMEA binders, which were denoted as EP, HMEA44, HMEA50, and HMEA55, respectively. 2.3 Characterization 2.3.1 Rotational viscosity

Fig. 1 Aggregate gradation curve

resin. Part B (used at 44 % by mass) is a cure agent. Both epoxy resin and cure agent were provided by Taiyu Kensetsu Co., Ltd. Japan. Part C is an AH-70 paving asphalt obtained from China Offshore Bitumen (Taizhou) Co., Ltd. (Taizhou, China). Details of the properties of the Part A, Part B and Part C are presented in Tables 1, 2, and 3. 2.1.2 Aggregates The normal aggregates used are the basalt aggregates for EPC and HMEACs. A typical dense gradation with

Brookfield rotational viscometer (RV, Model NDJ1C, Shanghai Changji Instrument Co., Ltd., China) was used to measure the rotational viscosity of HMEA binder referring to ASTM D4402. The appropriate amounts of HMEA binder were poured into the sample chamber, and immediately placed in the thermo container to decrease the reaction between epoxy resin and curing agents. Afterward, the spindle was lowered into the chamber that had been preheated to 160 °C to test the rotational viscosity. 2.3.2 Differential scanning calorimetry Differential scanning calorimetry (DSC) measurements were performed using a Perkin-Elmer Pyris 1 DSC system under a 20 mL/min argon flow. Approximately 5 mg sample was tested using two cycles with a temperature range of 50–200 °C at a heating rate of 20 °C/min. DSC results were presented as curves of heat flow versus temperature, in which Tg was defined as the inflection point in the second heating cycle according to ASTM D7426.

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2.3.3 Dynamic mechanical analysis

2.3.7 Wheel tracking test

Dynamic mechanical analysis (DMA) was carried out on a DMA ? 450 (01 dB-Metravib, France) according to ASTM D7028. The dimensions of samples were 20 mm 9 18 mm 9 2 mm. The measurements were obtained under tension mode from -100 to 100 °C with a 1 Hz frequency at a heating rate of 2 °C/min.

To evaluate the rutting resistance performance of the HMEAC, wheel tracking tests were conducted at 60 °C according to JTG E20-2011. The 300 mm 9 300 mm 9 50 mm HMEA slab specimens with different asphalt contents were compacted using a rolling compactor. A 700 kPa contact pressure was applied to the slab specimens, and the wheel passed 42 times/ min at the center of the specimen using the wheel tracking tester [20].

2.3.4 Tensile test All tensile tests were performed on an Instron 4466 universal material tester (Norwood, MA, USA) at room temperature at a 500 mm/min strain rate according to ASTM D638. The results were averaged over at least six samples. 2.3.5 Laser scanning confocal microscopy The morphology of cured HMEA binders was observed using a Zeiss LSM710 laser scanning confocal microscope (LSCM, Jena, Germany) in the reflection mode. The samples were excited at 488 nm (blue light) with Ar? laser light. Fluorescence light emitted (from 560 to 615 nm) from the sample was detected using a photomultiplier tube. Microscope slides were prepared by heating HMEA binder to a fluid state and placing a small drop in a concave well in the slide. A cover slip was placed over the drop of HMEA binder before the slide was placed in an oven at 150 °C until the HMEA binder was fluid enough to allow the cover slip to be pressed flat against the slide. Slides of samples were then cured in the oven at 150 °C for 1 h and 60 °C for 3 d. 2.3.6 Marshall test HMEA binders, aggregates, and fillers were heated, mixed, and agitated by following the procedures mentioned above; afterwards, the HMEA binders were mixed with the specific gradation aggregates for 60 min [13]. The HMEAC was placed in the Marshall mold. After both slides of samples had been blown 50 times, the samples were placed in the oven at 60 °C for 4 d to prepare the Marshall compaction sample. Subsequently, Marshall test was performed according to ASTM D1559.

2.3.8 Three-point bending test Three-point bending tests (JTG E20-2011) were carried out to evaluate fatigue cracking resistance performance of HMEACs. The specimens with 300 mm 9 300 mm 9 50 mm were prepared. The tests were carried on at 15 °C with a loading rate of 50 mm/min. Stress–strain curve was obtained during the loading process. Critical flexural strain energy density (Gcf ) was calculated to evaluate the fatigue cracking resistance of HMEAC. Gcf is the absorbed energy per unit projected area of the fracture zone during the complete fracture process. The relevant equation was shown as following: Z ec Gcf ¼ rde ð1Þ 0

where r is the stress fraction, e is the strain fraction, and ec is the strain at maximum stress.

3 Results and discussions 3.1 Rotational viscosity The effect of rotational viscosity on asphalt binder’s workability is very important in selecting proper mixing and compacting temperature. HMEA binder is a thermosetting material, i.e., the cure reaction proceeds as long as the epoxy is in contact with the curing agents. Therefore, to guarantee pavement completion, the reaction rate of HMEA binder should be carefully controlled. In this case, the viscosity of HMEA binder could be low enough to obtain a uniform coating of HMEA binder to all aggregates and compact all these materials during the pavement. Figure 2 shows the effect of curing time on rotational


3829 Table 5 The rotational viscosity of the neat EP and HMEA binders Sample

Rotational viscosity (mPa s) 0 min

150 min

EP

144

3,063

HMEA45

167

1,360

HMEA50

175

1,473

HMEA55

205

1,234

Fig. 2 Rotational viscosity-time curves of the neat epoxy and HMEAs at 160 °C

viscosity of EP binder with different asphalt contents at 160 °C. The rotational viscosity of the neat EP and HMEA binders at 0 and 150 min is listed in Table 5. It can be seen that the rotational viscosity of HMEA binders increase with the increase of asphalt contents in the initial stage of cure reaction. However, with the cure reaction proceeding, the rotational viscosity of HMEA binders is found to be lower than that of the neat EP binder, thereby indicating that the addition of asphalt hinders the cure reaction of epoxy resin. For HMEAs, the rotational viscosity increases with the increase of asphalt contents and reaches a highest value at the loading of 50 % by mass asphalt. When the asphalt content above 50 % by mass, the rotational viscosity of HMEA binder decreases slightly. It is known that the optimum rotational viscosity range for HMEA binder is found to be 2,000–3,000 mPa s for compacting EACs [11]. If the rotational viscosity of EA binder exceeds 3,000 mPa s, the concrete becomes very hard to compact. As shown in Table 5, the rotational viscosity of the neat EP binder is 3,060 mPa s at the curing time of 150 min at 160 °C, whereas the rotational viscosity of HMEA45, HMEA50, and HMEA55 is 1,360, 1,473, and 1,234 mPa s, respectively, which is much lower than 2,000 mPa s. It was reported that the time to reach 2,000 mPa s for warm mix epoxy asphalt curing at 110, 120 and 130 °C is approximately 48 min, 56 min and 69 min, respectively, which is much shorter than that of HMEA [21]. Therefore, the HMEA viscosity is low enough to satisfy the requirement of concrete pavement at high temperature.

Fig. 3 DSC curves of the cured neat epoxy and HMEAs

3.2 Glass transition temperature Figure 3 shows the DSC curves of the EP and HMEAs. Only one Tg appears for all HMEAs, which suggests good compatibility between epoxy resin and asphalts. Moreover, the Tgs of HMEAs are much higher than that of neat asphalt, which Tg determined by DSC is ca. -20 °C [22]. Similar result was also reported by Çubuk et al. [23]. Tg of modified asphalt with 2 % epoxy increases from -22.50 to -13.85 °C. DMA is also used to evaluate the Tg of asphalt or polymer modified asphalt [24, 25]. The temperature dependence of the loss tangent tan d for the samples is shown in Fig. 4. As compared with the neat EP, a broad and intense tan d peak has been obtained, corresponding to the glass transition of each HMEA. Similar to our previous work [26], at low temperatures, the tan d curves of HMEAs reveal a broad peak centered at ca. -10 °C, identified as the b relaxation of the neat asphalt (Tb) [27]. The double glass transitions in Fig. 4 indicate that phase separation exists in the

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HMEAs, as demonstrated by a broad peak centered at ca. -10 °C, indicating an asphalt-rich phase, and a larger peak around 30 °C, corresponding to epoxyrich phases. Similar phenomena were also reported by Wise et al. [28] for carboxyl-terminated butadieneacrylonitrile (CTBN) rubber in aromatic amine cured epoxy. The Tg and Tb values are summarized in Table 6. Although the Tg data given by DSC and DMA are different, the variation tendency of Tg is consistent, i.e., the Tg of HMEAs is slightly higher than that of the neat epoxy resin. The increase of Tg may be attributed to the decrease of crosslinking density of epoxy resin with the addition of asphalt. Similar results were also reported by Kang et al. [14]. Tb of HMEAs decrease with the increase of asphalt contents, which implies that HMEA has better performance at lower temperature.

tan d intensity is essential for good damping materials [29, 30]. In present work, the damping property of HMEAs is quantitatively evaluated by the loss tangent maximum [(tan d)max], the loss tangent at room temperature [(tan d)rt], the temperature range (DT) for efficient damping (tan d [ 0.3), and the area under the tan d versus temperature curve (TA) [31–33]. All these parameters for the neat EP and HMEAs are listed in Table 6. The (tan d)max of the neat EP is 0.99, which is even higher than those of thermosetting copolymer and polyurethane-based interpenetrating polymer network (IPN) damping materials [34, 35]. More specifically, the neat epoxy exhibits high damping at room temperature ((tan d)rt = 0.95), but shows efficient damping (tan d [ 0.30) over a narrow temperature range from 9.8 to 50.9 °C (DT = 41.1 °C) and low TA value (26.9). The addition of asphalts increases (tan d)max, (tan d)rt, DT, and TA of the neat epoxy. Furthermore, the damping properties of the resulting epoxy resin have obviously been improved by increasing the asphalt content. For example, HMEA55 not only shows highest (tan d)max (1.18), (tan d)rt (1.08), and TA value (58.8), but also possesses efficient damping (tan d [ 0.3) over a much broader temperature range from -5.6 to 76.8 °C (DT = 82.4 °C), which is much higher than that of rubber modified asphalt [36]. Hence, HMEA appears to be a good damping material [37]. Metallic plates of orthotropic steel bridge deck are very flexible and asphalt surfacings applied to such supports are submitted to very high levels of strain [38]. Thus, a HMEAC pavement with excellent damping behavior is needed to obtain better durability of the pavement.

3.3 Damping properties

3.4 Mechanical properties

The loss factor tan d, which indicates the damping ability of the material, is the ratio of the mechanical dissipation energy to the storage energy. Hence, a high

To evaluate the effects of asphalt contents on the mechanical properties of the epoxy resin, tensile tests were performed, as shown in Fig. 5. With the addition

Fig. 4 Temperature dependence of tan d for the neat epoxy and HMEAs

Table 6 Tg and damping properties of the neat EP and HMEAs

Sample

DSC Tg (°C)

DMA Tg (°C)

Tb (°C)

(tan d)max

(tan d)rt

DT at tan d [ 0.3 (K)

TA (K)

EP

11.3

27.4

–

0.99

0.95

41.1 (9.8 to 50.9)

26.9

HMEA45

13.1

27.6

-10.6

1.09

0.99

74.1 (-1.6 to 72.5)

44.0

HMEA50

13.2

31.2

-11.3

1.16

1.03

85.3 (1.8 to 87.1)

56.8

HMEA55

12.5

29.9

-11.4

1.18

1.08

82.4 (-5.6 to 76.8)

58.8


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modified asphalts [41, 42]. Epoxy resin is known to strongly fluoresce when illuminated with blue light (488 nm), thereby revealing the size and distribution of epoxy constituent in epoxy composite [26, 43]. The LSCM images of the cured neat epoxy and HMEAs are shown in Fig. 6. As mentioned above, HMEAs have two distinct phases: the larger phase is the base resin and the other phase consists of a large number of small (on the order of microns in diameter), distributed spherical asphalt particles acting as stress concentrators as compared with uniform dispersion of the neat epoxy. The spherical asphalt particles are suspected to cause some localized plastic shear yielding, resulting in the observed increase in toughness. Similar phase separations have been reported by other researchers in rubber toughened epoxy resins [44–46]. In addition, the diameters of spherical asphalt particles increase with increasing asphalt contents. With 55 % by mass asphalt, the asphalt particles aggregate into bigger particles, thereby suggesting that the compatibility between asphalt and epoxy resin becomes worse. In this case, two glass transitions appear in the tan dtemperature curve, as shown in Fig. 4. Fig. 5 Mechanical properties of the neat epoxy and HMEAs: tensile strength and elongation at break (a), tensile modulus (b)

of asphalts, the tensile strength and tensile modulus of epoxy resin decrease, whereas the elongation at break increases. Generally, the tensile strength improvement is always accompanied by a sacrifice in the toughness. For HMEAs, with the increase in asphalt contents, the tensile strength and elongation at break decreases and increases, respectively. This indicates that the toughness of HMEAs increases with the increase of asphalt contents. For tensile modulus, HMEA50 has a maximum tensile modulus. Notably, a dramatic increase of three-fold for elongation at break of HMEA with 55 % by mass content is observed. The magnitude of this optimal value is expected to depend on the compatibility between base asphalt and epoxy resin. A decrease in tensile strength and modulus and increase in elongation at break may be caused by the soft segment structure of asphalt, which is in agreement with studies of rubber toughened epoxy systems [39, 40]. 3.5 Morphology Laser scanning confocal microscope is a powerful imaging tool to observe the morphology of polymer

3.6 Marshall stability Marshall stability is defined as the maximum load carried by a compacted specimen tested at 60 °C at a loading rate of 50 mm/min. This stability is generally a measure of the mass viscosity of the aggregateasphalt concrete and is affected significantly by the angle of internal friction of the aggregate and the viscosity of the asphalt concrete at 60 °C. The Marshall test results of HMEACs are listed in Table 7. The Marshall stability of the neat EPC is more than 90 kN, which attributes to the high cohesion and shear stress introduced by the crosslinking reaction between epoxy and cure agents. The Marshall stability of HMEACs is lower than that of the neat EPC. It means that epoxy resin gives the contribution of the high temperature deformation resistance to the asphalt concrete. With increasing asphalt contents, Marshall stabilities of HMEACs slightly increase, whereas flow values decrease. Similar results were also reported in epoxy modified asphalt without cure agents [23]. The Marshall stability of HMEACs is much greater than that of the neat asphalt concrete ad styrene–butadiene– styrene (SBS) copolymer modified asphalt concrete, which are 5.6 and 10.8 kN, respectively [13, 47].

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Fig. 6 LSCM images in the reflection mode for cured neat epoxy (a) and HMEAs: HMEA45 (b); HMEA50 (c); HMEA55 (d). Images were taken at 920 magnification

Table 7 Marshall test results of EPC and HMEACs Sample

Marshall stability (kN)

Flow value (0.1 mm)

EP

[90

NA

HMEA45

63.1

53.3

HMEA50

64.1

49.5

HMEA55

64.4

44.6

These results indicate that HMEACs have good temperature deformation resistance performance.

evaluate the rutting resistance of HMEAC. The dynamic stability for the neat EPC and HMEACs is presented in Table 8. The dynamic stability for the neat epoxy and HMEACs varies from 14,000 to 21,000 cycles/mm, which is much greater than those of the neat asphalt concrete and SBS modified asphalt concrete, which is 2,193 and 5,465 cycles/mm, respectively [13, 48]. These results suggest that both EPC and HMEACs have a good rutting resistance performance. In addition, HMEA50 concrete has the maximum dynamic stability, which is 20 % higher than that of the neat EPC.

3.7 Rutting resistance 3.8 Fatigue cracking resistance The wheel tracking test with a solid rubber-faced tire is often used to provide the permanent deformation (rutting) evolution with the repetitions of loading. Therefore, the wheel tracking test was employed to

Critical flexural strength and critical deflection are used to characterize the brittleness, fatigue, and toughness for the asphalt concrete. However, the


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Table 8 Dynamic stabilities of EPC and HMEACs Sample

Dynamic stability (cycles/mm)

EP

17,560

HMEA45

16,520

HMEA50

21,032

HMEA55

14,367

(3)

Table 9 The ec and Gcf of EPC and HMEACs

(4)

Sample

ec

Gcf (kJ/m3)

EP

0.023

31.4

HMEA45

0.017

17.2

HMEA50 HMEA55

0.012 0.009

12.7 7.9

variation tendencies of two parameters are paradoxical and one-sided. For the critical condition, it is more effective to evaluate the flexural performance of asphalt concrete by critical flexural strain energy density [49]. The critical deflection (ec) and Gcf of the neat EPC and HMEACs are shown in Table 9. It can be seen from Table 9 that both ec and Gcf decrease with the increase of asphalt contents, which indicates that the addition of asphalt decreases the fatigue cracking performance of EPC. With 55 % by mass asphalt, ec and Gcf of the EP decrease ca. 250 and 400 %, respectively. However, it is worthy to note that even the lowest Gcf of HMEAC (7.9 kJ/m3) is much greater than that of the neat asphalt concrete (ca. 4 kJ/m3) [50]. This indicates that HMEACs have good fatigue cracking resistance.

4 Conclusions From the RV, DSC, DMA, LSCM, Marshell, wheel tracking and three-point bending tests results of HMEA and HMEAC, the following items can be concluded. (1)

(2)

The addition of asphalt hinders the cure reaction of epoxy resin. The rotational viscosity of HMEA binder is low enough to satisfy the requirement of concrete pavement at high temperature.

(5)

The Tg of HMEA is much higher than that of neat asphalt, implies that HMEAC has better resistance to high temperature deformation. HMEAs have excellent damping properties, which suggest that HMEACs can serve better durability on the pavement of flexible orthotropic steel bridge deck. The tensile strength and modulus of HMEA decrease with the increase of asphalt contents. However, the elongation at break of HMEAs increases, which indicates better toughness. HMEAs exhibit phase separation, which can be attributed to the improved toughness of epoxy resin with asphalts. This property gives better performance at lower temperature. HMEACs exhibit good resistance to high temperature deformation, rutting, and fatigue cracking.

These results show that HMEA binder exhibits excellent performance in the orthotropic steel bridge deck pavement. Acknowledgments The authors are grateful to the financial support from Opening Funds of National Engineering Laboratory for Advance Road Materials, Jiangsu Province Natural Science Foundation (BK2011085), Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT) and the Fundamental Research Funds for the Central Universities (20620140066). The authors are also grateful to Dr. Sunjie Ye for language help.

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