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Study on cohesion and adhesion of high-viscosity modified asphalt
International Journal of Transportation Science and Technology xxx (xxxx) xxx
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Study on cohesion and adhesion of high-viscosity modified asphalt Yourong Tan a,b,c, Zhang Haiyan b,c,⇑, Cao Dongwei b,c, Xia Lei b,c, Du Rongjie d, Shi Zhaoqiang b,c,e, Dong Rui d, Wang Xianhe b,c a
Chongqing Jiaotong University, Chongqing 400074, China Research Institute of Highway Ministry of Transport, Beijing 100088, China c Zhong Lu Gao Ke (Beijing) Road Technology Co. Ltd, Beijing 100088, China d Qilu Transportation Development Group Co., Ltd, Shandong Ji’nan 250000, China e Hebei University of Engineering, Hebei Handan 056038, China b
a r t i c l e
i n f o
Article history: Received 2 September 2018 Received in revised form 18 March 2019 Accepted 1 April 2019 Available online xxxx Keywords: Pavement engineering High-viscosity modified asphalt Cohesion and adhesion Permeable asphalt pavement
a b s t r a c t High-viscosity modified asphalt (T-HVA) specifically used for drainage/permeable asphalt pavement was prepared by composite modification of matrix asphalt using a thermoplastic elastomer (TPE) and SBS particles. The performance of the high-viscosity modified asphalt (T-HVA) was characterized by conventional tests, and compared with the performance of 70# asphalt, SBS modified asphalt and engineering high-viscosity asphalt. The results show that all the indicators of the modified asphalt are better than that of the matrix asphalt, and the dynamic viscosity of the T-HVA is greater than one million Pa.s, which is much higher than that of the engineering high-viscosity asphalt and SBS modified asphalt. The segregation test shows that the compatibility and stability of T-HVA asphalt are better than others. Cohesion test shows that the cohesion of the modified asphalt is obviously better than that of the matrix asphalt at different temperatures, and the higher the temperature, the better the cohesion, and the cohesion of the T-HVA before and after aging is relatively stable. The result of the peeling rate measured by ultraviolet spectrophotometry shows that: the peeling rate of the T-HVA is the smallest, i.e., the adhesion is the best, and is consistent with the dynamic viscosity, i.e., the greater the dynamic viscosity, the better the adhesion. Based on the comprehensive analysis of various indicators. The results of Performance Grade (PG) grading test show that T-HVA has good high and low temperature performance. The modified materials with good dispersion in asphalt and the TPE particles as high elastic interlocking units are uniformly distributed in the network structure; The T-HVA has relatively strong aggregate adhesion and cohesiveness, exhibits good high temperature stability and low temperature flexibility, and is suitable for drainage/permeable asphalt pavement. Ó 2019 Tongji University and Tongji University Press. Publishing Services by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).
Peer review under responsibility of Tongji University and Tongji University Press. ⇑ Corresponding author. https://doi.org/10.1016/j.ijtst.2019.04.001 2046-0430/Ó 2019 Tongji University and Tongji University Press. Publishing Services by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Please cite this article as: T. Yourong, H. Zhang, D. Cao et al., Study on cohesion and adhesion of high-viscosity modified asphalt, International Journal of Transportation Science and Technology, https://doi.org/10.1016/j.ijtst.2019.04.001
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1. Introduction The drainage asphalt pavement adopts large-void asphalt mixture as a surface layer, which makes the rain water penetrate into a drainage function layer and discharges the rain water laterally through the layer. Under different rainfall conditions, the influence on surface runoff reduction and urban rainwater control (Wu et al, 2019), which eliminates many adverse effects of surface water film, and significantly improves the safety and comfort of driving in rainy days. At the same time, due to the porous characteristics of the drainage asphalt pavement, traffic noise can be greatly reduced. For conventional pavement, water damage is a common problem at present and has seriously affected the service performance of the pavement. It is generally believed that the water damage of the asphalt surface layer is caused by the loss of the adhesion between the asphalt and aggregate and the loss of the cohesion of the asphalt (Yao et al., 2009; Lin et al., 2009). For the drainage asphalt pavement, since the rain water will enter the drainage asphalt concrete structure, the adhesion and cohesion are the important technical indicators for the interaction between the asphalt and aggregate. At present, the evaluation methods of the asphalt cohesion mainly include force-ductility test method, stretching method, and atomic force microscope method. Chen et al. (2005) proposed the force-ductility evaluation indicator of matrix asphalt and modified asphalt. Zhou et al. (2012) conducted a force-ductility test on different modified asphalts, and verified the reasonableness for evaluating the low-temperature performance of the modified asphalt by the tensile flexibility. Ma et al. (2018) applied DSR direct tensile test to study the high-temperature cohesion of different asphalts; Yu et al. (2013) applied AFM to measure the adhesion of asphalt on a microscopic scale. At present, there are many evaluation methods for the adhesion between asphalt and aggregate, such as water boiling method and water immersion method, but these methods can not quantitatively evaluate the adhesion of asphalt; there are also some quantitative evaluation methods, mainly including water boiling method, peeling rate method (improved water boiling method), photoelectric colorimetry, agitated water net adsorption method, solvent elution method, etc (Song et al., 2005). In recent years, there have been more and more methods for evaluating the adhesion properties of stones and asphalt, and many new methods have been proposed at home and abroad. Xiao et al. (2007) proposed adhesion work as the characterization indicator of adhesion between asphalt and mineral materials based on the wetting-adsorption theory. Yu et al. (2011) tested the contact angle between asphalt and stone, and verified the correctness of the measurement method by water boiling method so as to evaluate the adhesion between asphalt and stone. Wang et al. (2017), Zhanf et al. (2008) used a modified pull-out test method to evaluate the adhesion by the pulling force loss rate and the peeling rate. Ahmed et al. (2018) introduced the feasibility of a test method of a new bonding strength test device (ABS) and applied it to the evaluation method of a PE wax-based warm-mix asphalt mixture. Zhu et al. (2000) proposed ultraviolet spectrophotometry to measure the adhesion between asphalt and stone. It can be seen that some test methods have been used to evaluate the studies on cohesion of asphalt and the adhesion between asphalt and aggregate; however, there are few studies on high-viscosity asphalt for drainage asphalt pavement, and most of them are qualitative analysis, and there is no quantitative analysis. This article mainly introduces a special high-viscosity asphalt (hereinafter referred to as T-HVA) self-made in the laboratory, and a performance comparison is made with a high-viscosity asphalt (Cao et al., 2017) (hereinafter referred to as engineering high-viscosity asphalt), SBS modified asphalt and matrix asphalt, in order to study the cohesion and adhesion of the high-viscosity modified asphalt, so as to meet the use of the surface structure of drainage asphalt pavement. 2. Test 2.1. Test materials The asphalt is Esso 70# pavement petroleum asphalt, SBS is 791H linear type purchased from Yueyang Petrochemical, and TPE is a thermoplastic elastomer material. The main performance indicators of the 70# pavement petroleum asphalt and SBS are shown in Tables 1 and 2. 2.2. Preparation of high viscosity modified asphalt (1) Preparation of SBS modified asphalt: 1) 70# asphalt was heated to 180–185 °C; 2) swelling oil was added, and stirred at low speed to a uniform state; 3) 6% by mass of SBS was doped, and sheared with a high-speed shearing machine (3000 r/ min) to a state without obvious particles; and 4) a stabilizer was slowly added at 175 °C, stirred and developed for 3 h to form a stable system.
Table 1 Performance indicators of 70# pavement petroleum asphalt. Penetration (25 °C)/ 0.1 mm
Softening point/°C
Ductility (10 °C)/cm
Dynamic viscosity (60 °C)/Pas
Residue after TFOT Quality change rate/%
Penetration ratio (25 °C)/%
Ductility (10 °C)/cm
63
46.5
58
185
0.073
66
7.0
Please cite this article as: T. Yourong, H. Zhang, D. Cao et al., Study on cohesion and adhesion of high-viscosity modified asphalt, International Journal of Transportation Science and Technology, https://doi.org/10.1016/j.ijtst.2019.04.001
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T. Yourong et al. / International Journal of Transportation Science and Technology xxx (xxxx) xxx Table 2 Performance indicators of SBS. Type
S/B ratio
Oil filling amount
300% Stress at a definite elongation (MPa)
Tensile strength (MPa)
Elongation at break (%)
791H
30/70
0
2.2
16.0
700
(2) Preparation of T-HVA: 1) 70# asphalt was heated to 180–185 °C; 2) swelling oil was added, and stirred at low speed to a uniform state; 3) 5% SBS + 3% TPE particles was doped, and sheared with a high-speed shearing machine (3500 r/min) for 30 min; 4) a stabilizer was slowly added at 175–180 °C, stirred and developed for 2 h to form a stable system. 3. Test method 3.1. Conventional performance indicators Performance test (JTG E20-2011) of 70# pavement petroleum asphalt, SBS modified asphalt, engineering high-viscosity asphalt and T-HVA were performed according to the relevant provisions in ‘‘Standard Test Methods of Bitumen and Bituminous Mixtures for Highway Engineering” (JTG E20-2011). 3.2. Cohesion test The adhesion of asphalt was tested using a COOPER-Vialit cohesion pendulum (BS EN 13588, 2004). In this test, the kinetic energy principle is used to calculate the cohesion of the asphalt based on the measured peak angle. The calculation formula is as follows:
Cohesion C ¼ E E0 =S ¼ mgr ðcosa cosa0 Þ=S In the formula, C is the cohesion of the asphalt material; E is the energy of the pendulum when the angle of the pendulum is a; E0 is the energy of the pendulum when the angle of the pendulum is a0 ; S is the smear area of the asphalt material; m is the mass of the pendulum; g is the gravitational acceleration; r is the radius of the pendulum center of gravity; a is the first peak angle of the pendulum; and a0 is the second peak angle of the pendulum. 3.3. Peeling rate test The adhesion between asphalt and aggregate was measured by ultraviolet spectrophotometry. In order to have a relatively obvious distinction, the aggregate used in this test comprises 2.36–4.75 mm limestone and basalt rock material. A full-wavelength scan was performed on a Shimadzu UV-2550 ultraviolet spectrophotometer with an asphalt-toluene solution having a formulated solution concentration of 0.04 g/L, so as to determine the maximum absorption wavelength, and Aa, Ab and Ac were measured by the obtained maximum absorption wavelength, thus the peeling rate can be calculated (Zhu et al., 2000). 3.4. Rheological test of asphalt In this paper, the Dynamic Shear Rheometer (DSR) was used to grade asphalt at high temperature, and bending creep stiffness test was used to grade asphalt at low temperature. The experimental parameters are as follows: the strain value of the original asphalt is 12%, the angular frequency is 10 rad/s; the strain value of the aged asphalt is 10%, the angular frequency is 10 rad/s; the strain value of the aged asphalt is 1%, and the angular frequency is 10 rad/s. 3.5. Fluorescence dispersion observation The dispersion of modifier in asphalt was observed by fluorescence microscopy. The 0.5 g sample was placed on the slide and heated on the heating table at 100 C. The sample was evenly spread out. The slide was placed under the objective lens to observe the dispersion of the sample. 4. Test results and analysis 4.1. Conventional performance indicators The conventional performances of 70# pavement petroleum asphalt, SBS modified asphalt, engineering high-viscosity asphalt and T-HVA were tested. The results are shown in Table 3. Please cite this article as: T. Yourong, H. Zhang, D. Cao et al., Study on cohesion and adhesion of high-viscosity modified asphalt, International Journal of Transportation Science and Technology, https://doi.org/10.1016/j.ijtst.2019.04.001
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Table 3 Asphalt conventional performance indicators. Asphalt types
Penetration (25 °C)/ 0.1 mm
Softening point/°C
Ductility (5 °C)/cm
Rotational viscosity (175 °C)/Pas
Dynamic viscosity (60 °C)/Pas
Segregation/ °C
70# Asphalt SBS modified asphalt engineering highviscosity asphalt T-HVA
63 48.4 41.4
46.5 89.4 103.8
0 29.9 38.9
1.12 1.08
185 123,070 824,768
– 0.3 24.1
50.5
102.3
39.4
1.03
1,107,362
0.8
It can be seen from Table 3 that the high and low temperature properties of the three types of modified asphalts are significantly improved compared with the matrix asphalt. The penetration of the engineering high-viscosity asphalt is slightly lower than that of the T-HVA. The dynamic viscosity at 60 °C of the engineering high-viscosity asphalt is lower than that of the T-HVA, but both are greater than 600,000 Pas, and other indicators have little difference. The softening point, ductility and dynamic viscosity at 60 °C of the two types of high-viscosity asphalts are obviously better than that of the SBS modified asphalt. The penetration is slightly reduced, but it has little effect on the consistency, softness and hardness of the asphalt. It can be seen from Table 3 that the order of dynamic viscosity is: T-HVA > engineering high-viscosity asphalt > SBS modified asphalt > 70# asphalt. According to the preparation process analysis, due to the modification effect of SBS, the fluidity of the three types of modified asphalts decreased, becoming more viscous, and the dynamic viscosity increased greatly. The TPE particles in T-HVA have the effect of tackifying and improving adhesion, therefore, the dynamic viscosity of T-HVA increased significantly. There is a certain correlation between the dynamic viscosity and asphalt adhesion, i.e., the greater the dynamic viscosity, the stronger the adhesion between the asphalt and aggregate. The Brookfield viscosity is used to characterize the viscosity of the asphalt, and the higher the Brookfield viscosity, the higher the construction temperature of the mixture. It can be seen from Table 3 that the SBS modified asphalt has the highest Brookfield viscosity, but it is also similar to that of the engineering high-viscosity asphalt. Since high-viscosity modified asphalt is mainly used for permeable/drainage asphalt pavement, the use of asphalt binder with high dynamic viscosity can significantly improve the anti-stripping ability and water damage resistance of the mixture. T-HVA has relatively high dynamic viscosity and larger bonding strength with aggregate, and is suitable for permeable/drainage asphalt pavement, so as to ensure the durability and water damage resistance of the pavement. The asphalt has relatively low viscosity, good fluidity, and moderate mixing temperature and compaction temperature during construction, and thus it can reduce energy consumption and reduce exhaust emissions. Table 3 shows that the segregation value of engineering high-viscosity asphalt is the largest, and its compatibility and storage stability are very poor. SBS modifier has good compatibility with base asphalt, and the system is uniform and stable. There is almost no segregation phenomenon in the test, and the storage stability is good. The segregation value of T-HVA is higher than that of SBS modified asphalt, but it is also less than 1.0 °C. The main reason is that medium T-HVA contains solvents. A small part of T-HVA will deposit at the bottom of the sample tube after long storage at high temperature, resulting in high softening point at the bottom and small softening point of upper asphalt. However, the difference of segregation softening point is much smaller than that of general engineering application, which still meets the requirements and has good storage stability. Separation test of modified asphalt is an effective measure to evaluate the descriptive stability of modified asphalt and base asphalt. Good compatibility between modified asphalt and base asphalt is a prerequisite for the stability of modified asphalt. The asphalt with good compatibility will not precipitate or degrade the modifier during production and transportation. The properties of modifier and the preparation process of modified asphalt have a very important influence on the asphalt’s descriptivity (Kang et al., 2007). 4.2. Cohesion test According to the formula in (2.2), the cohesion of different asphalt materials at different temperatures was calculated. The results are shown in Fig. 1. It can be seen from Fig. 1 that, as to the original asphalt, the order of cohesion at both 5 °C and 25 °C is: engineering highviscosity asphalt > SBS modified asphalt > T-HVA > 70# asphalt, and the order of cohesion at 60 °C is: T-HVA > engineering high-viscosity asphalt > SBS modified asphalt > 70# asphalt. As to the aged asphalt, the order of cohesion at both 5 °C and 25 °C is: T-HVA > engineering high-viscosity asphalt > SBS modified asphalt, and the difference of the cohesion among the three types of asphalts is little; and the order of cohesion at 60 °C is: SBS modified asphalt > engineering high-viscosity asphalt > T-HVA. No matter before aging or after aging, the cohesion increases with increasing temperature. As to the cohesion before aging and after aging of the asphalt, the cohesion before aging is less than that after aging both for the SBS modified asphalt and THVA at 5 °C, and it is opposite for the engineering high-viscosity asphalt; the cohesion before aging is greater than that after aging for all the three types of modified asphalts at 25 °C; and the cohesion before aging is less than that after aging both for the SBS modified asphalt and the engineering high-viscosity asphalt at 60 °C, and it is opposite for the T-HVA. The cohesion C measured by the cohesion pendulum impact test can reflect the cohesion of the asphalt to a certain extent, and further reflects the shear resistance of the asphalt at different temperatures. Overall, compared with the matrix asphalt, Please cite this article as: T. Yourong, H. Zhang, D. Cao et al., Study on cohesion and adhesion of high-viscosity modified asphalt, International Journal of Transportation Science and Technology, https://doi.org/10.1016/j.ijtst.2019.04.001
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T. Yourong et al. / International Journal of Transportation Science and Technology xxx (xxxx) xxx
Fig. 1. Comparison of cohesion between the original asphalt and the asphalt after aging (TFOT (163 °C, 5 h)).
the cohesion of the modified asphalt increased significantly, and the cohesion of the T-HVA was relatively stable before aging and after aging, and the cohesion at 5 °C was higher than 0.5 J/mm2, which is greater than that of other asphalt materials. This is due to the good low-temperature flexibility of the thermoplastic elastomer TPE material in T-HVA, thereby providing the modified asphalt with better resistance to deformation at low temperature; and certain cohesion at low temperature provides resistance to aging problem in actual application. 4.3. Peeling rate test Since the adhesion between the modified asphalt obtained by the water boiling method and the stone is 5 grade, and the adhesion between the matrix asphalt and stone is generally 1–2 grade, the adhesion between the asphalt and aggregate cannot be quantitatively analyzed. The adhesion between the asphalt and stone can be quantitatively analyzed by the test method in item 2.3, and the results of the asphalt peeling rate of the basalt and granite thus obtained are shown in Table 4. In order to compare the dynamic viscosity with peeling rate, the dynamic viscosity value is now divided by one million, and the results are shown in Fig. 2. It can be seen from Table 4 that before aging, the order of peeling rate of basalt and limestone with several types of asphalt measured by ultraviolet spectrophotometry is: 70# asphalt > SBS modified asphalt > engineering high-viscosity asphalt > T-HVA. After aging, the order of peeling rate of basalt and limestone with several types of asphalts measured by this method is: 70# asphalt > engineering high-viscosity asphalt > SBS modified asphalt > T-HVA. It can be known that, the T-HVA has the best adhesion; and it can be seen from Fig. 2 that, the larger the dynamic viscosity, the smaller the peeling rate; i.e., the adhesion is related to the dynamic viscosity. Literature studies show that the adhesion between asphalt and aggregate is mainly accomplished by intermolecular forces, which are mainly divided into physical effects and chemical effects (Kang et al., 2007). The physical effects mainly depend on van der Waals forces, mainly including molecular orientation force, induction force, and dispersion force, and the effect is weak. The chemical effects include ionic bonds, covalent bonds, and metal bonds, and the effect is very strong. Compared with the matrix asphalt, various modified asphalts cause redistribution of the asphalt components due to the doping of modifiers, usually the polar components increase, and the saturated components and the aromatic components decrease relatively (Zhou et al., 2005), and thus the physical effects and chemical effects with the stone are enhanced. In this experiment, basalt and limestone are used, which belong to neutral or alkaline stone; meanwhile, chemical adsorption occurs between the stone material and surface active substance in the asphalt, so as to form a new water-insoluble
Table 4 Peeling rate of different stones with asphalt. Asphalt types
70#
SBS modified asphalt
Engineering high-viscosity asphalt
T-HVA
basalt limestone TFOT (163 °C, 5 h) basalt limestone
0.745 0.453
0.307 0.294
0.296 0.290
0.248 0.225
0.542 0.407
0.232 0.193
0.284 0.216
0.189 0.161
Please cite this article as: T. Yourong, H. Zhang, D. Cao et al., Study on cohesion and adhesion of high-viscosity modified asphalt, International Journal of Transportation Science and Technology, https://doi.org/10.1016/j.ijtst.2019.04.001
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Fig. 2. Diagram of relation between dynamic viscosity and stripping rate.
compound, so that the asphalt layer formed on the surface of the mineral material has relatively strong resistance to water damage. Especially for T-HVA, the introduced thermoplastic elastomer contains a reactive double-bond structure, which can react with SBS and asphalt to form a new polar group in the preparation process of modified asphalt, therefore, the T-HVA has the best adhesion with stone. The peeling rate of the modified asphalt with stone is much smaller than that of the matrix asphalt, reflecting that water has the greatest influence on the matrix asphalt, and has the least influence on the T-HVA. Although the peeling rates of the modified asphalt with the stones are similar, it also reflects that the T-HVA has sufficient cohesion to resist water damage. Since the selected stone has a relatively high internal void ratio and a surface with a large number of micropores, it has a great adsorption potential to asphalt (Chen et al., 2010); and the greater the alkalinity of the stone, the better its adhesion to asphalt. For the two different types of stones in this article, the limestone is a carbonate rock, and is an alkaline rock; while the basalt is a medium-alkaline rock, and its alkalinity is lower than that of limestone rock, so its adhesion with asphalt is weaker than that of limestone. Since the selected stone has a relatively high internal void ratio and a surface with a large number of micropores, it has a great adsorption potential to asphalt and can adsorb most of the surface active components (Na, 2009). 4.4. Rheological test of asphalt American SHRP research program specification stipulates that the high temperature grade of asphalt samples is determined by G*/sin d (>1.0 kPa) of original asphalt, G*/sin_d (>2.2 kPa) of TFOT residual asphalt, and |G*|sin d (<5000 kPa) of asphalt after pressure aging (PAV); and the low temperature grade of asphalt samples is determined by creep stiffness modulus S not more than 300 MPa and creep rate m not less than 0.3. The results of PG grading of different asphalt materials are shown in Table 5. Table 5 shows that the rutting factor G*/sin (d) of modified asphalt is higher than that of base asphalt at the same test temperature. The high temperature deformation resistance and low temperature bending ability of modified asphalt are greatly improved. Compared with the base asphalt, the high temperature grade of modified asphalt is improved. SBS modified asphalt has a high temperature grade of 70 °C, which is 1 higher grading than the base asphalt, while the engineering high-viscosity asphalt has a high temperature grade of 88 °C, which is 5 higher grading than the original Binder. The high temperature grade of T-HVA is 82 °C, which is 4 higher grading than the base asphalt. The high temperature grade of modified asphalt after film aging generally decreases, because the modified asphalt is more viscous, it can not flow smoothly like the base asphalt during the aging process in the film oven, and it is difficult to form uniform asphalt film. The temperature of modified asphalt after pressure aging is higher than that of base asphalt, and the degree of improvement of self-made highviscosity asphalt is more obvious than that of SBS modified asphalt and the engineering high-viscosity asphalt. In addition, the asphaltene content increases and the content of gum, aromatics and saturates decreases with the increase of asphaltene in the long-term high temperature environment (Li et al., 2005). The more the irrecoverable viscous component increases under repeated loads, the easier the permanent deformation will occur. According to the low temperature classification results in Table 5, the low temperature grades of base asphalt, SBS modified asphalt and engineering high-viscosity asphalt are 12 °C. The low temperature grades of T-HVA can reach 18 °C. The creep stiffness modulus S and creep rate M are better than other asphalts. The lower the temperature, the greater the stiffness modulus and the smaller the creep rate, which accords with the rheological and stress relaxation characteristics of asphalt materials under low temperature and fixed load pressure characterized by stiffness modulus and creep rate. With Please cite this article as: T. Yourong, H. Zhang, D. Cao et al., Study on cohesion and adhesion of high-viscosity modified asphalt, International Journal of Transportation Science and Technology, https://doi.org/10.1016/j.ijtst.2019.04.001
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T. Yourong et al. / International Journal of Transportation Science and Technology xxx (xxxx) xxx Table 5 Performance-graded asphalt binder specification. Asphalt types
70#
SBS modified asphalt
Engineering high-viscosity asphalt
T-HVA
2.73 1.25 0.606
7.58 4.25 2.49 1.55 1.04
22.7 15.6 11.8 9.24 7.59 6.19
14.5 8.5 5.25 3.61 2.79 2.34
TFOT (163 °C, 5 h) (|G*|/sin (d) (kPa)) 58 °C 64 °C 70 °C 76 °C 82 °C 88 °C
5.03 2.15 — — — —
12 6.47 3.64 2.14 — —
22.9 13.3 7.89 4.89 3.21 2.2
13.8 8.11 4.89 3.08 2.21 —
Pressurized Aging Vessel Residue PAV aging temperature/°C
100
100
100
100
|G*|sin (d) (kPa) 28 °C 25 °C 22 °C
— 4950 7900
1750 2810 4460
1820 2830 —
1180 1870 —
Creep stiffness S (12 °C)/MPa m (12 °C) S (18 °C)/MPa m (18 °C) S (24 °C)/MPa m(-24 °C) Performance-Graded
247 0.331 562 0.246 — — 58–16
0.159 0.362 209 0.269 — — 70–22
142 0.332 359 0.278 — — 88–22
— — 257 0.31 405 0.231 82–28
Original Binder (|G*|/sin (d) (kPa)) 58 °C 64 °C 70 °C 76 °C 82 °C 88 °C
the change of temperature, the stiffness modulus of T-HVA is smaller than that of base asphalt, which reflects that T-HVA has stronger stress relaxation performance, shows more flexibility at low temperature, and thus has better crack resistance at low temperature. Under the combined modification of tackifier and solvent, the T-HVA exerts the excellent performance of two materials, effectively improves the low temperature performance of asphalt, and thus improves the low temperature performance of asphalt. The durability of pavement is improved. 4.5. Microstructure analysis The asphalt was magnified 100 times by fluorescence microscope to observe the microstructures of 70# asphalt, SBS modified asphalt, Engineering high-viscosity asphalt and T-HVA asphalt, as shown in Fig. 3.
Fig. 3. Microscopic morphologies of different asphalts.
Please cite this article as: T. Yourong, H. Zhang, D. Cao et al., Study on cohesion and adhesion of high-viscosity modified asphalt, International Journal of Transportation Science and Technology, https://doi.org/10.1016/j.ijtst.2019.04.001
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Microscopic photography can be used to directly study the distribution and interfacial behavior of polymer in asphalt system. It is an effective method for microscopic analysis of the mechanism of polymer modified asphalt modification (Zhang et al., 2013; Huang, 2003). From Fig. 1, it can be seen that the modified materials are uniformly dispersed in the base asphalt without obvious agglomeration and obvious phase interface, forming a homogeneous stable system. Fig. 3(a) is the microstructure of the base asphalt. It can be seen that there are no impurities. Fig. 3(b) The SBS fine particles after long time and high speed shearing are evenly dispersed in the base asphalt. Through swelling and adsorption, the SBS fine particles are crosslinked with the base asphalt to form a uniform network structure, which improves the cohesion inside the asphalt structure, reduces the flowability of the asphalt and improves the high and low temperature stability of the asphalt. The change of asphalt microstructure is the essence of asphalt performance change. Fig. 3(c) shows that SBS particles in engineering high-viscous asphalt form dense and stable network structure with asphalt formation system. Fig. 3(d) is the microstructure of T-HVA asphalt. SBS particles and asphalt form a dense and stable network structure. TPE particles are evenly distributed in the network structure as high elastic embedding units, increasing the contact area with asphalt molecules, thereby improving the cohesion and viscoelasticity between asphalt molecules. 5. Conclusion In this paper, a special asphalt material for drainage/permeable asphalt pavement was prepared, wherein the thermoplastic elastomer TPE as high-elasticity embedded unit was uniformly distributed in the cross-linked network structure formed by SBS after swelling, forming a stable continuous phase, thereby effectively improving the high and low temperature performance of the asphalt. Comparing the dynamic viscosity of different asphalts, the dynamic viscosity of T-HVA is much larger than that of the engineering high-viscosity asphalt and SBS modified asphalt, other indicators of T-HVA are similar to that of the engineering high-viscosity asphalt, the low-temperature ductility of T-HVA is higher than that of the SBS modified asphalt, and the softening point is greater than 100 °C, and the dynamic viscosity reaches one million Pas or higher, and thus the asphalt concrete with large pores can be effectively wrapped and adsorbed. For the storage stability and compatibility of asphalt, the performance of T-HVA asphalt is also better. The cohesion C measured by the cohesion pendulum impact test can reflect the cohesion of the asphalt material to a certain extent, and comprehensively speaking, the cohesion of the modified asphalt is significantly better than that of the matrix asphalt at different temperatures, and the higher the temperature, the better the cohesion. Moreover, the T-HVA has good cohesion at low temperature. The T-HVA has the lowest peeling rate measured by ultraviolet spectrophotometry, and the best adhesion to stones, and can effectively coat aggregate to ensure the durability and water damage resistance of the pavement. From the classification of pavement performance of different asphalt materials, T-HVA has better high and low temperature performance. Generally speaking, the T-HVA can meet the performance requirements of the permeable/drainage asphalt pavement and large-pore permeable asphalt concrete. It has excellent high temperature performance and excellent low temperature performance, and is more suitable for colder areas Acknowledgements The research is supported by National Key R&D Program of China grants by the from Ministry of Science and Technology of China, ‘‘Research and Implementation of Pervious Pavement for Low Impact Development Sponge Cites”, (No. 2016YFE0108200), and Science and Technology Project of Shandong Provincial Communications Department, ‘‘Research and Application of New Thermo-Plastic-Elastor (TPE) Alloy Modified Asphalt Technology”, (No. 2017B83). All the sponsorships are gratefully acknowledged. Meanwhile, we sincerely appreciate the editors and reviewers helping to revise the paper writing and grammar very carefully. References: Ahmed, T.A., Lee, H.D., Christopher Williams, R., 2018. Using a modified asphalt bond strength test to investigate the properties of asphalt binders with poly ethylene wax-based warm mix asphalt additive. Int. J. Pavement Res. 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Study on storage stability of waste rubber powder modified asphalt. China Foreign Highway 27 (3), 205–207. Li, N., Huang, X., Zeng, F., 2005. Analysis and evaluation of aging behavior of road asphalt. Highway Transport. Sci.: Nat. Sci. Ed. 22 (4), 5–8. Lin, Y., 2009. Cause of formation of water damage on asphalt pavement and its protective measures. China Water Transport (second half of the month) 9 (4), 234–235. Ma, X., Chen, H., Xing, M., 2018. Analysis of high-temperature cohesiveness of asphalt based on DSR direct tensile test. J. Mater. Sci. Eng. 36 (2), 223–228. Na, Li, 2009. Study on the interfacial adsorption between asphalt and aggregate. Northern Traffic 2009 (1), 42–44.
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International Journal of Transportation Science and Technology journal homepage: www.elsevier.com/locate/ijtst
Study on cohesion and adhesion of high-viscosity modified asphalt Yourong Tan a,b,c, Zhang Haiyan b,c,⇑, Cao Dongwei b,c, Xia Lei b,c, Du Rongjie d, Shi Zhaoqiang b,c,e, Dong Rui d, Wang Xianhe b,c a
Chongqing Jiaotong University, Chongqing 400074, China Research Institute of Highway Ministry of Transport, Beijing 100088, China c Zhong Lu Gao Ke (Beijing) Road Technology Co. Ltd, Beijing 100088, China d Qilu Transportation Development Group Co., Ltd, Shandong Ji’nan 250000, China e Hebei University of Engineering, Hebei Handan 056038, China b
a r t i c l e
i n f o
Article history: Received 2 September 2018 Received in revised form 18 March 2019 Accepted 1 April 2019 Available online xxxx Keywords: Pavement engineering High-viscosity modified asphalt Cohesion and adhesion Permeable asphalt pavement
a b s t r a c t High-viscosity modified asphalt (T-HVA) specifically used for drainage/permeable asphalt pavement was prepared by composite modification of matrix asphalt using a thermoplastic elastomer (TPE) and SBS particles. The performance of the high-viscosity modified asphalt (T-HVA) was characterized by conventional tests, and compared with the performance of 70# asphalt, SBS modified asphalt and engineering high-viscosity asphalt. The results show that all the indicators of the modified asphalt are better than that of the matrix asphalt, and the dynamic viscosity of the T-HVA is greater than one million Pa.s, which is much higher than that of the engineering high-viscosity asphalt and SBS modified asphalt. The segregation test shows that the compatibility and stability of T-HVA asphalt are better than others. Cohesion test shows that the cohesion of the modified asphalt is obviously better than that of the matrix asphalt at different temperatures, and the higher the temperature, the better the cohesion, and the cohesion of the T-HVA before and after aging is relatively stable. The result of the peeling rate measured by ultraviolet spectrophotometry shows that: the peeling rate of the T-HVA is the smallest, i.e., the adhesion is the best, and is consistent with the dynamic viscosity, i.e., the greater the dynamic viscosity, the better the adhesion. Based on the comprehensive analysis of various indicators. The results of Performance Grade (PG) grading test show that T-HVA has good high and low temperature performance. The modified materials with good dispersion in asphalt and the TPE particles as high elastic interlocking units are uniformly distributed in the network structure; The T-HVA has relatively strong aggregate adhesion and cohesiveness, exhibits good high temperature stability and low temperature flexibility, and is suitable for drainage/permeable asphalt pavement. Ó 2019 Tongji University and Tongji University Press. Publishing Services by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).
Peer review under responsibility of Tongji University and Tongji University Press. ⇑ Corresponding author. https://doi.org/10.1016/j.ijtst.2019.04.001 2046-0430/Ó 2019 Tongji University and Tongji University Press. Publishing Services by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Please cite this article as: T. Yourong, H. Zhang, D. Cao et al., Study on cohesion and adhesion of high-viscosity modified asphalt, International Journal of Transportation Science and Technology, https://doi.org/10.1016/j.ijtst.2019.04.001
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1. Introduction The drainage asphalt pavement adopts large-void asphalt mixture as a surface layer, which makes the rain water penetrate into a drainage function layer and discharges the rain water laterally through the layer. Under different rainfall conditions, the influence on surface runoff reduction and urban rainwater control (Wu et al, 2019), which eliminates many adverse effects of surface water film, and significantly improves the safety and comfort of driving in rainy days. At the same time, due to the porous characteristics of the drainage asphalt pavement, traffic noise can be greatly reduced. For conventional pavement, water damage is a common problem at present and has seriously affected the service performance of the pavement. It is generally believed that the water damage of the asphalt surface layer is caused by the loss of the adhesion between the asphalt and aggregate and the loss of the cohesion of the asphalt (Yao et al., 2009; Lin et al., 2009). For the drainage asphalt pavement, since the rain water will enter the drainage asphalt concrete structure, the adhesion and cohesion are the important technical indicators for the interaction between the asphalt and aggregate. At present, the evaluation methods of the asphalt cohesion mainly include force-ductility test method, stretching method, and atomic force microscope method. Chen et al. (2005) proposed the force-ductility evaluation indicator of matrix asphalt and modified asphalt. Zhou et al. (2012) conducted a force-ductility test on different modified asphalts, and verified the reasonableness for evaluating the low-temperature performance of the modified asphalt by the tensile flexibility. Ma et al. (2018) applied DSR direct tensile test to study the high-temperature cohesion of different asphalts; Yu et al. (2013) applied AFM to measure the adhesion of asphalt on a microscopic scale. At present, there are many evaluation methods for the adhesion between asphalt and aggregate, such as water boiling method and water immersion method, but these methods can not quantitatively evaluate the adhesion of asphalt; there are also some quantitative evaluation methods, mainly including water boiling method, peeling rate method (improved water boiling method), photoelectric colorimetry, agitated water net adsorption method, solvent elution method, etc (Song et al., 2005). In recent years, there have been more and more methods for evaluating the adhesion properties of stones and asphalt, and many new methods have been proposed at home and abroad. Xiao et al. (2007) proposed adhesion work as the characterization indicator of adhesion between asphalt and mineral materials based on the wetting-adsorption theory. Yu et al. (2011) tested the contact angle between asphalt and stone, and verified the correctness of the measurement method by water boiling method so as to evaluate the adhesion between asphalt and stone. Wang et al. (2017), Zhanf et al. (2008) used a modified pull-out test method to evaluate the adhesion by the pulling force loss rate and the peeling rate. Ahmed et al. (2018) introduced the feasibility of a test method of a new bonding strength test device (ABS) and applied it to the evaluation method of a PE wax-based warm-mix asphalt mixture. Zhu et al. (2000) proposed ultraviolet spectrophotometry to measure the adhesion between asphalt and stone. It can be seen that some test methods have been used to evaluate the studies on cohesion of asphalt and the adhesion between asphalt and aggregate; however, there are few studies on high-viscosity asphalt for drainage asphalt pavement, and most of them are qualitative analysis, and there is no quantitative analysis. This article mainly introduces a special high-viscosity asphalt (hereinafter referred to as T-HVA) self-made in the laboratory, and a performance comparison is made with a high-viscosity asphalt (Cao et al., 2017) (hereinafter referred to as engineering high-viscosity asphalt), SBS modified asphalt and matrix asphalt, in order to study the cohesion and adhesion of the high-viscosity modified asphalt, so as to meet the use of the surface structure of drainage asphalt pavement. 2. Test 2.1. Test materials The asphalt is Esso 70# pavement petroleum asphalt, SBS is 791H linear type purchased from Yueyang Petrochemical, and TPE is a thermoplastic elastomer material. The main performance indicators of the 70# pavement petroleum asphalt and SBS are shown in Tables 1 and 2. 2.2. Preparation of high viscosity modified asphalt (1) Preparation of SBS modified asphalt: 1) 70# asphalt was heated to 180–185 °C; 2) swelling oil was added, and stirred at low speed to a uniform state; 3) 6% by mass of SBS was doped, and sheared with a high-speed shearing machine (3000 r/ min) to a state without obvious particles; and 4) a stabilizer was slowly added at 175 °C, stirred and developed for 3 h to form a stable system.
Table 1 Performance indicators of 70# pavement petroleum asphalt. Penetration (25 °C)/ 0.1 mm
Softening point/°C
Ductility (10 °C)/cm
Dynamic viscosity (60 °C)/Pas
Residue after TFOT Quality change rate/%
Penetration ratio (25 °C)/%
Ductility (10 °C)/cm
63
46.5
58
185
0.073
66
7.0
Please cite this article as: T. Yourong, H. Zhang, D. Cao et al., Study on cohesion and adhesion of high-viscosity modified asphalt, International Journal of Transportation Science and Technology, https://doi.org/10.1016/j.ijtst.2019.04.001
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T. Yourong et al. / International Journal of Transportation Science and Technology xxx (xxxx) xxx Table 2 Performance indicators of SBS. Type
S/B ratio
Oil filling amount
300% Stress at a definite elongation (MPa)
Tensile strength (MPa)
Elongation at break (%)
791H
30/70
0
2.2
16.0
700
(2) Preparation of T-HVA: 1) 70# asphalt was heated to 180–185 °C; 2) swelling oil was added, and stirred at low speed to a uniform state; 3) 5% SBS + 3% TPE particles was doped, and sheared with a high-speed shearing machine (3500 r/min) for 30 min; 4) a stabilizer was slowly added at 175–180 °C, stirred and developed for 2 h to form a stable system. 3. Test method 3.1. Conventional performance indicators Performance test (JTG E20-2011) of 70# pavement petroleum asphalt, SBS modified asphalt, engineering high-viscosity asphalt and T-HVA were performed according to the relevant provisions in ‘‘Standard Test Methods of Bitumen and Bituminous Mixtures for Highway Engineering” (JTG E20-2011). 3.2. Cohesion test The adhesion of asphalt was tested using a COOPER-Vialit cohesion pendulum (BS EN 13588, 2004). In this test, the kinetic energy principle is used to calculate the cohesion of the asphalt based on the measured peak angle. The calculation formula is as follows:
Cohesion C ¼ E E0 =S ¼ mgr ðcosa cosa0 Þ=S In the formula, C is the cohesion of the asphalt material; E is the energy of the pendulum when the angle of the pendulum is a; E0 is the energy of the pendulum when the angle of the pendulum is a0 ; S is the smear area of the asphalt material; m is the mass of the pendulum; g is the gravitational acceleration; r is the radius of the pendulum center of gravity; a is the first peak angle of the pendulum; and a0 is the second peak angle of the pendulum. 3.3. Peeling rate test The adhesion between asphalt and aggregate was measured by ultraviolet spectrophotometry. In order to have a relatively obvious distinction, the aggregate used in this test comprises 2.36–4.75 mm limestone and basalt rock material. A full-wavelength scan was performed on a Shimadzu UV-2550 ultraviolet spectrophotometer with an asphalt-toluene solution having a formulated solution concentration of 0.04 g/L, so as to determine the maximum absorption wavelength, and Aa, Ab and Ac were measured by the obtained maximum absorption wavelength, thus the peeling rate can be calculated (Zhu et al., 2000). 3.4. Rheological test of asphalt In this paper, the Dynamic Shear Rheometer (DSR) was used to grade asphalt at high temperature, and bending creep stiffness test was used to grade asphalt at low temperature. The experimental parameters are as follows: the strain value of the original asphalt is 12%, the angular frequency is 10 rad/s; the strain value of the aged asphalt is 10%, the angular frequency is 10 rad/s; the strain value of the aged asphalt is 1%, and the angular frequency is 10 rad/s. 3.5. Fluorescence dispersion observation The dispersion of modifier in asphalt was observed by fluorescence microscopy. The 0.5 g sample was placed on the slide and heated on the heating table at 100 C. The sample was evenly spread out. The slide was placed under the objective lens to observe the dispersion of the sample. 4. Test results and analysis 4.1. Conventional performance indicators The conventional performances of 70# pavement petroleum asphalt, SBS modified asphalt, engineering high-viscosity asphalt and T-HVA were tested. The results are shown in Table 3. Please cite this article as: T. Yourong, H. Zhang, D. Cao et al., Study on cohesion and adhesion of high-viscosity modified asphalt, International Journal of Transportation Science and Technology, https://doi.org/10.1016/j.ijtst.2019.04.001
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Table 3 Asphalt conventional performance indicators. Asphalt types
Penetration (25 °C)/ 0.1 mm
Softening point/°C
Ductility (5 °C)/cm
Rotational viscosity (175 °C)/Pas
Dynamic viscosity (60 °C)/Pas
Segregation/ °C
70# Asphalt SBS modified asphalt engineering highviscosity asphalt T-HVA
63 48.4 41.4
46.5 89.4 103.8
0 29.9 38.9
1.12 1.08
185 123,070 824,768
– 0.3 24.1
50.5
102.3
39.4
1.03
1,107,362
0.8
It can be seen from Table 3 that the high and low temperature properties of the three types of modified asphalts are significantly improved compared with the matrix asphalt. The penetration of the engineering high-viscosity asphalt is slightly lower than that of the T-HVA. The dynamic viscosity at 60 °C of the engineering high-viscosity asphalt is lower than that of the T-HVA, but both are greater than 600,000 Pas, and other indicators have little difference. The softening point, ductility and dynamic viscosity at 60 °C of the two types of high-viscosity asphalts are obviously better than that of the SBS modified asphalt. The penetration is slightly reduced, but it has little effect on the consistency, softness and hardness of the asphalt. It can be seen from Table 3 that the order of dynamic viscosity is: T-HVA > engineering high-viscosity asphalt > SBS modified asphalt > 70# asphalt. According to the preparation process analysis, due to the modification effect of SBS, the fluidity of the three types of modified asphalts decreased, becoming more viscous, and the dynamic viscosity increased greatly. The TPE particles in T-HVA have the effect of tackifying and improving adhesion, therefore, the dynamic viscosity of T-HVA increased significantly. There is a certain correlation between the dynamic viscosity and asphalt adhesion, i.e., the greater the dynamic viscosity, the stronger the adhesion between the asphalt and aggregate. The Brookfield viscosity is used to characterize the viscosity of the asphalt, and the higher the Brookfield viscosity, the higher the construction temperature of the mixture. It can be seen from Table 3 that the SBS modified asphalt has the highest Brookfield viscosity, but it is also similar to that of the engineering high-viscosity asphalt. Since high-viscosity modified asphalt is mainly used for permeable/drainage asphalt pavement, the use of asphalt binder with high dynamic viscosity can significantly improve the anti-stripping ability and water damage resistance of the mixture. T-HVA has relatively high dynamic viscosity and larger bonding strength with aggregate, and is suitable for permeable/drainage asphalt pavement, so as to ensure the durability and water damage resistance of the pavement. The asphalt has relatively low viscosity, good fluidity, and moderate mixing temperature and compaction temperature during construction, and thus it can reduce energy consumption and reduce exhaust emissions. Table 3 shows that the segregation value of engineering high-viscosity asphalt is the largest, and its compatibility and storage stability are very poor. SBS modifier has good compatibility with base asphalt, and the system is uniform and stable. There is almost no segregation phenomenon in the test, and the storage stability is good. The segregation value of T-HVA is higher than that of SBS modified asphalt, but it is also less than 1.0 °C. The main reason is that medium T-HVA contains solvents. A small part of T-HVA will deposit at the bottom of the sample tube after long storage at high temperature, resulting in high softening point at the bottom and small softening point of upper asphalt. However, the difference of segregation softening point is much smaller than that of general engineering application, which still meets the requirements and has good storage stability. Separation test of modified asphalt is an effective measure to evaluate the descriptive stability of modified asphalt and base asphalt. Good compatibility between modified asphalt and base asphalt is a prerequisite for the stability of modified asphalt. The asphalt with good compatibility will not precipitate or degrade the modifier during production and transportation. The properties of modifier and the preparation process of modified asphalt have a very important influence on the asphalt’s descriptivity (Kang et al., 2007). 4.2. Cohesion test According to the formula in (2.2), the cohesion of different asphalt materials at different temperatures was calculated. The results are shown in Fig. 1. It can be seen from Fig. 1 that, as to the original asphalt, the order of cohesion at both 5 °C and 25 °C is: engineering highviscosity asphalt > SBS modified asphalt > T-HVA > 70# asphalt, and the order of cohesion at 60 °C is: T-HVA > engineering high-viscosity asphalt > SBS modified asphalt > 70# asphalt. As to the aged asphalt, the order of cohesion at both 5 °C and 25 °C is: T-HVA > engineering high-viscosity asphalt > SBS modified asphalt, and the difference of the cohesion among the three types of asphalts is little; and the order of cohesion at 60 °C is: SBS modified asphalt > engineering high-viscosity asphalt > T-HVA. No matter before aging or after aging, the cohesion increases with increasing temperature. As to the cohesion before aging and after aging of the asphalt, the cohesion before aging is less than that after aging both for the SBS modified asphalt and THVA at 5 °C, and it is opposite for the engineering high-viscosity asphalt; the cohesion before aging is greater than that after aging for all the three types of modified asphalts at 25 °C; and the cohesion before aging is less than that after aging both for the SBS modified asphalt and the engineering high-viscosity asphalt at 60 °C, and it is opposite for the T-HVA. The cohesion C measured by the cohesion pendulum impact test can reflect the cohesion of the asphalt to a certain extent, and further reflects the shear resistance of the asphalt at different temperatures. Overall, compared with the matrix asphalt, Please cite this article as: T. Yourong, H. Zhang, D. Cao et al., Study on cohesion and adhesion of high-viscosity modified asphalt, International Journal of Transportation Science and Technology, https://doi.org/10.1016/j.ijtst.2019.04.001
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Fig. 1. Comparison of cohesion between the original asphalt and the asphalt after aging (TFOT (163 °C, 5 h)).
the cohesion of the modified asphalt increased significantly, and the cohesion of the T-HVA was relatively stable before aging and after aging, and the cohesion at 5 °C was higher than 0.5 J/mm2, which is greater than that of other asphalt materials. This is due to the good low-temperature flexibility of the thermoplastic elastomer TPE material in T-HVA, thereby providing the modified asphalt with better resistance to deformation at low temperature; and certain cohesion at low temperature provides resistance to aging problem in actual application. 4.3. Peeling rate test Since the adhesion between the modified asphalt obtained by the water boiling method and the stone is 5 grade, and the adhesion between the matrix asphalt and stone is generally 1–2 grade, the adhesion between the asphalt and aggregate cannot be quantitatively analyzed. The adhesion between the asphalt and stone can be quantitatively analyzed by the test method in item 2.3, and the results of the asphalt peeling rate of the basalt and granite thus obtained are shown in Table 4. In order to compare the dynamic viscosity with peeling rate, the dynamic viscosity value is now divided by one million, and the results are shown in Fig. 2. It can be seen from Table 4 that before aging, the order of peeling rate of basalt and limestone with several types of asphalt measured by ultraviolet spectrophotometry is: 70# asphalt > SBS modified asphalt > engineering high-viscosity asphalt > T-HVA. After aging, the order of peeling rate of basalt and limestone with several types of asphalts measured by this method is: 70# asphalt > engineering high-viscosity asphalt > SBS modified asphalt > T-HVA. It can be known that, the T-HVA has the best adhesion; and it can be seen from Fig. 2 that, the larger the dynamic viscosity, the smaller the peeling rate; i.e., the adhesion is related to the dynamic viscosity. Literature studies show that the adhesion between asphalt and aggregate is mainly accomplished by intermolecular forces, which are mainly divided into physical effects and chemical effects (Kang et al., 2007). The physical effects mainly depend on van der Waals forces, mainly including molecular orientation force, induction force, and dispersion force, and the effect is weak. The chemical effects include ionic bonds, covalent bonds, and metal bonds, and the effect is very strong. Compared with the matrix asphalt, various modified asphalts cause redistribution of the asphalt components due to the doping of modifiers, usually the polar components increase, and the saturated components and the aromatic components decrease relatively (Zhou et al., 2005), and thus the physical effects and chemical effects with the stone are enhanced. In this experiment, basalt and limestone are used, which belong to neutral or alkaline stone; meanwhile, chemical adsorption occurs between the stone material and surface active substance in the asphalt, so as to form a new water-insoluble
Table 4 Peeling rate of different stones with asphalt. Asphalt types
70#
SBS modified asphalt
Engineering high-viscosity asphalt
T-HVA
basalt limestone TFOT (163 °C, 5 h) basalt limestone
0.745 0.453
0.307 0.294
0.296 0.290
0.248 0.225
0.542 0.407
0.232 0.193
0.284 0.216
0.189 0.161
Please cite this article as: T. Yourong, H. Zhang, D. Cao et al., Study on cohesion and adhesion of high-viscosity modified asphalt, International Journal of Transportation Science and Technology, https://doi.org/10.1016/j.ijtst.2019.04.001
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Fig. 2. Diagram of relation between dynamic viscosity and stripping rate.
compound, so that the asphalt layer formed on the surface of the mineral material has relatively strong resistance to water damage. Especially for T-HVA, the introduced thermoplastic elastomer contains a reactive double-bond structure, which can react with SBS and asphalt to form a new polar group in the preparation process of modified asphalt, therefore, the T-HVA has the best adhesion with stone. The peeling rate of the modified asphalt with stone is much smaller than that of the matrix asphalt, reflecting that water has the greatest influence on the matrix asphalt, and has the least influence on the T-HVA. Although the peeling rates of the modified asphalt with the stones are similar, it also reflects that the T-HVA has sufficient cohesion to resist water damage. Since the selected stone has a relatively high internal void ratio and a surface with a large number of micropores, it has a great adsorption potential to asphalt (Chen et al., 2010); and the greater the alkalinity of the stone, the better its adhesion to asphalt. For the two different types of stones in this article, the limestone is a carbonate rock, and is an alkaline rock; while the basalt is a medium-alkaline rock, and its alkalinity is lower than that of limestone rock, so its adhesion with asphalt is weaker than that of limestone. Since the selected stone has a relatively high internal void ratio and a surface with a large number of micropores, it has a great adsorption potential to asphalt and can adsorb most of the surface active components (Na, 2009). 4.4. Rheological test of asphalt American SHRP research program specification stipulates that the high temperature grade of asphalt samples is determined by G*/sin d (>1.0 kPa) of original asphalt, G*/sin_d (>2.2 kPa) of TFOT residual asphalt, and |G*|sin d (<5000 kPa) of asphalt after pressure aging (PAV); and the low temperature grade of asphalt samples is determined by creep stiffness modulus S not more than 300 MPa and creep rate m not less than 0.3. The results of PG grading of different asphalt materials are shown in Table 5. Table 5 shows that the rutting factor G*/sin (d) of modified asphalt is higher than that of base asphalt at the same test temperature. The high temperature deformation resistance and low temperature bending ability of modified asphalt are greatly improved. Compared with the base asphalt, the high temperature grade of modified asphalt is improved. SBS modified asphalt has a high temperature grade of 70 °C, which is 1 higher grading than the base asphalt, while the engineering high-viscosity asphalt has a high temperature grade of 88 °C, which is 5 higher grading than the original Binder. The high temperature grade of T-HVA is 82 °C, which is 4 higher grading than the base asphalt. The high temperature grade of modified asphalt after film aging generally decreases, because the modified asphalt is more viscous, it can not flow smoothly like the base asphalt during the aging process in the film oven, and it is difficult to form uniform asphalt film. The temperature of modified asphalt after pressure aging is higher than that of base asphalt, and the degree of improvement of self-made highviscosity asphalt is more obvious than that of SBS modified asphalt and the engineering high-viscosity asphalt. In addition, the asphaltene content increases and the content of gum, aromatics and saturates decreases with the increase of asphaltene in the long-term high temperature environment (Li et al., 2005). The more the irrecoverable viscous component increases under repeated loads, the easier the permanent deformation will occur. According to the low temperature classification results in Table 5, the low temperature grades of base asphalt, SBS modified asphalt and engineering high-viscosity asphalt are 12 °C. The low temperature grades of T-HVA can reach 18 °C. The creep stiffness modulus S and creep rate M are better than other asphalts. The lower the temperature, the greater the stiffness modulus and the smaller the creep rate, which accords with the rheological and stress relaxation characteristics of asphalt materials under low temperature and fixed load pressure characterized by stiffness modulus and creep rate. With Please cite this article as: T. Yourong, H. Zhang, D. Cao et al., Study on cohesion and adhesion of high-viscosity modified asphalt, International Journal of Transportation Science and Technology, https://doi.org/10.1016/j.ijtst.2019.04.001
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T. Yourong et al. / International Journal of Transportation Science and Technology xxx (xxxx) xxx Table 5 Performance-graded asphalt binder specification. Asphalt types
70#
SBS modified asphalt
Engineering high-viscosity asphalt
T-HVA
2.73 1.25 0.606
7.58 4.25 2.49 1.55 1.04
22.7 15.6 11.8 9.24 7.59 6.19
14.5 8.5 5.25 3.61 2.79 2.34
TFOT (163 °C, 5 h) (|G*|/sin (d) (kPa)) 58 °C 64 °C 70 °C 76 °C 82 °C 88 °C
5.03 2.15 — — — —
12 6.47 3.64 2.14 — —
22.9 13.3 7.89 4.89 3.21 2.2
13.8 8.11 4.89 3.08 2.21 —
Pressurized Aging Vessel Residue PAV aging temperature/°C
100
100
100
100
|G*|sin (d) (kPa) 28 °C 25 °C 22 °C
— 4950 7900
1750 2810 4460
1820 2830 —
1180 1870 —
Creep stiffness S (12 °C)/MPa m (12 °C) S (18 °C)/MPa m (18 °C) S (24 °C)/MPa m(-24 °C) Performance-Graded
247 0.331 562 0.246 — — 58–16
0.159 0.362 209 0.269 — — 70–22
142 0.332 359 0.278 — — 88–22
— — 257 0.31 405 0.231 82–28
Original Binder (|G*|/sin (d) (kPa)) 58 °C 64 °C 70 °C 76 °C 82 °C 88 °C
the change of temperature, the stiffness modulus of T-HVA is smaller than that of base asphalt, which reflects that T-HVA has stronger stress relaxation performance, shows more flexibility at low temperature, and thus has better crack resistance at low temperature. Under the combined modification of tackifier and solvent, the T-HVA exerts the excellent performance of two materials, effectively improves the low temperature performance of asphalt, and thus improves the low temperature performance of asphalt. The durability of pavement is improved. 4.5. Microstructure analysis The asphalt was magnified 100 times by fluorescence microscope to observe the microstructures of 70# asphalt, SBS modified asphalt, Engineering high-viscosity asphalt and T-HVA asphalt, as shown in Fig. 3.
Fig. 3. Microscopic morphologies of different asphalts.
Please cite this article as: T. Yourong, H. Zhang, D. Cao et al., Study on cohesion and adhesion of high-viscosity modified asphalt, International Journal of Transportation Science and Technology, https://doi.org/10.1016/j.ijtst.2019.04.001
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Microscopic photography can be used to directly study the distribution and interfacial behavior of polymer in asphalt system. It is an effective method for microscopic analysis of the mechanism of polymer modified asphalt modification (Zhang et al., 2013; Huang, 2003). From Fig. 1, it can be seen that the modified materials are uniformly dispersed in the base asphalt without obvious agglomeration and obvious phase interface, forming a homogeneous stable system. Fig. 3(a) is the microstructure of the base asphalt. It can be seen that there are no impurities. Fig. 3(b) The SBS fine particles after long time and high speed shearing are evenly dispersed in the base asphalt. Through swelling and adsorption, the SBS fine particles are crosslinked with the base asphalt to form a uniform network structure, which improves the cohesion inside the asphalt structure, reduces the flowability of the asphalt and improves the high and low temperature stability of the asphalt. The change of asphalt microstructure is the essence of asphalt performance change. Fig. 3(c) shows that SBS particles in engineering high-viscous asphalt form dense and stable network structure with asphalt formation system. Fig. 3(d) is the microstructure of T-HVA asphalt. SBS particles and asphalt form a dense and stable network structure. TPE particles are evenly distributed in the network structure as high elastic embedding units, increasing the contact area with asphalt molecules, thereby improving the cohesion and viscoelasticity between asphalt molecules. 5. Conclusion In this paper, a special asphalt material for drainage/permeable asphalt pavement was prepared, wherein the thermoplastic elastomer TPE as high-elasticity embedded unit was uniformly distributed in the cross-linked network structure formed by SBS after swelling, forming a stable continuous phase, thereby effectively improving the high and low temperature performance of the asphalt. Comparing the dynamic viscosity of different asphalts, the dynamic viscosity of T-HVA is much larger than that of the engineering high-viscosity asphalt and SBS modified asphalt, other indicators of T-HVA are similar to that of the engineering high-viscosity asphalt, the low-temperature ductility of T-HVA is higher than that of the SBS modified asphalt, and the softening point is greater than 100 °C, and the dynamic viscosity reaches one million Pas or higher, and thus the asphalt concrete with large pores can be effectively wrapped and adsorbed. For the storage stability and compatibility of asphalt, the performance of T-HVA asphalt is also better. The cohesion C measured by the cohesion pendulum impact test can reflect the cohesion of the asphalt material to a certain extent, and comprehensively speaking, the cohesion of the modified asphalt is significantly better than that of the matrix asphalt at different temperatures, and the higher the temperature, the better the cohesion. Moreover, the T-HVA has good cohesion at low temperature. The T-HVA has the lowest peeling rate measured by ultraviolet spectrophotometry, and the best adhesion to stones, and can effectively coat aggregate to ensure the durability and water damage resistance of the pavement. From the classification of pavement performance of different asphalt materials, T-HVA has better high and low temperature performance. Generally speaking, the T-HVA can meet the performance requirements of the permeable/drainage asphalt pavement and large-pore permeable asphalt concrete. It has excellent high temperature performance and excellent low temperature performance, and is more suitable for colder areas Acknowledgements The research is supported by National Key R&D Program of China grants by the from Ministry of Science and Technology of China, ‘‘Research and Implementation of Pervious Pavement for Low Impact Development Sponge Cites”, (No. 2016YFE0108200), and Science and Technology Project of Shandong Provincial Communications Department, ‘‘Research and Application of New Thermo-Plastic-Elastor (TPE) Alloy Modified Asphalt Technology”, (No. 2017B83). All the sponsorships are gratefully acknowledged. Meanwhile, we sincerely appreciate the editors and reviewers helping to revise the paper writing and grammar very carefully. References: Ahmed, T.A., Lee, H.D., Christopher Williams, R., 2018. Using a modified asphalt bond strength test to investigate the properties of asphalt binders with poly ethylene wax-based warm mix asphalt additive. Int. J. Pavement Res. 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Please cite this article as: T. Yourong, H. Zhang, D. Cao et al., Study on cohesion and adhesion of high-viscosity modified asphalt, International Journal of Transportation Science and Technology, https://doi.org/10.1016/j.ijtst.2019.04.001