1 Introduction
2 Materials
2.1 Asphalt binders (conventional and modified)
Test items | A-type SBS | B-type SBS |
---|---|---|
25 °C penetration (0.1 mm) | 49.9 | 48.3 |
5 °C ductility (cm) | 21 | 32 |
Softening point (°C) | 87 | 84 |
60 °C dynamic viscosity (Pa · s) | 16,343 | 16,819 |
Sticky toughness (N · m) | 30.8 | 38.1 |
Toughness (N · m) | 19.5 | 30 |
Elastic recovery (25 °C) | 93 | 95.6 |
2.2 High-viscosity asphalt binder modifiers
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Japan high-viscosity modifier TPS. It is a kind of asphalt viscosity modifier, which is the main component of asphalt pavement in Japan. The basic physical properties of TPS modifier are illustrated in Table 2 [20].Table 2Physical properties of TAFPACK-Super (TPS) asphalt modifierItemPropertiesShapeGranular (2–3 mm)ColorYellowProportion (specific gravity or specific weight)0.98Weight per volume0.6 ton/m3
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RST is the second type of viscosity modifier used in this study. It is a kind of thermal plastic polymer, which is added to the plant mixer asphalt. Its properties are listed in Table 3 [18]. RST at about 170 °C can modify the straight asphalt and completely melt and be delivered directly to the aggregates and asphalt in the mix, in a relatively short period of time. Moreover, it can be uniformly distributed in the asphalt and its modified effect is significant. RST modifier asphalt has excellent high-temperature resistance and moisture damage resistance, also greatly reduces the cost and simplifies the operation process. It is also suitable for drainage pavement (RST-P), steel deck (RST-B), asphalt concrete pavement stress-absorbing structure layer (RST-G) and other pavement structures.Table 3Properties of road-science-technology (RST) asphalt modifierItemPropertiesSignificationAppearanceWell distributed sizeSeparating properties within mixtureDensity (g/cm3)0.95–1.02SmellNo irritant smellEnvironmental and safety propertiesMelt index (g/10 min)>10Separation properties within mixture
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HVA modifier is a comprehensive performance high-viscosity modifier and has laid a solid foundation for the high-viscosity asphalt brand localization. This product performance reaches the international advanced level of similar products and is significantly reduced by about 30% the cost of similar imported products. The basic physical properties of HVA modifier are illustrated in Table 4.Table 4Properties of high-viscosity additive (HVA) asphalt modifierItemTechnical requirementsAppearanceGranular, uniform, fullUnit particle quality (g)≯0.03Density (g/cm3)0.90–1.00Melt flow index (g/10 min)≮2.0
2.3 High-viscosity modified asphalt binder preparation method
3 Test methods
3.1 Sticky toughness and toughness test
3.2 Elastic recovery test
3.3 Dynamic viscosity test
Items | Unit | Test conditions | Target | Methods |
---|---|---|---|---|
Penetration | 0.1 mm | 25 °C, 100 g, 5 s | >40 | T0604-2011 |
Softening point | °C | >80 | T0606-2011 | |
Ductility | cm | 5 °C, 5 cm/min | ≥30 | T0605-2011 |
Film heat quality change rate | % | <0.6 | T0609-2011 | |
Sticky toughness | N · m | 25 °C | >20 | T0624-2011 |
Toughness | N · m | 60 °C | >15 | T0624-2011 |
Dynamic viscosity | Pa · s | 60 °C | ≥20,000 | T0620-2000 |
Elastic recovery | (%) | 25 °C | T0662-2000 |
Variables | Level of each variable | |||||
---|---|---|---|---|---|---|
Level 1 | Level 2 | Level 3 | Level 4 | Level 5 | Level 6 | |
Asphalt type (A) | Local #70 grade asphalt | High rich #70 grade asphalt | A-type SBS | B-type SBS | ||
TPS percentage (B) | 0 | 8 | 10 | 12 | 14 | 16 |
HVA percentage (C) | 8 | 12 | – | – | – | – |
RST percentage (D) | 8 | 12 | – | – | – |
4 Results and analysis
4.1 Effect of different percentages of TPS on local #70 grade asphalt binder
Test item | TPS content (%) | |||||
---|---|---|---|---|---|---|
0 | 8 | 10 | 12 | 14 | 16 | |
25 °C penetration (0.1 mm) | 62 | 53.3 | 62.0 | 44.7 | 47.1 | 49.0 |
5 °C ductility (cm) | 4 | 11 | 15 | 21 | 26 | 29 |
Softening point (°C) | 48 | 54.5 | 71 | 78 | 87 | 91 |
60 °C dynamic viscosity (Pa · s) | 248 | 721 | 1,695 | 10,592 | 21,599 | 30,914 |
Sticky toughness (N · m) | – | – | – | 22.7 | 26.5 | 30.4 |
Toughness (N · m) | – | – | – | 13.8 | 16.3 | 17.0 |
Elastic recovery 25 °C (%) | – | – | – | 98 | 98.7 | 99.6 |
RTFOT residue | ||||||
Loss of mass (%) | – | – | – | – | 0.24 | 0.25 |
Penetration 25 °C (0.1 mm) | – | – | – | – | 37.0 | 41.4 |
Ductility (5 °C) | – | – | – | – | 14.2 | 26.7 |
Softening point (°C) | – | – | – | – | 72.1 | 89 |
4.2 Effect of different percentages of viscosity modifier (HVA and TPS) on two conventional asphalt binders
Item | High rich #70 grade asphalt | High rich #70 grade asphalt +12% TPS | High rich #70 grade asphalt +12% HVA | Local #70 grade asphalt + 12% TPS | Local #70 grade asphalt + 12% HVA |
---|---|---|---|---|---|
25 °C penetration (0.1 mm) | 65 | 54.4 | 43 | 44.7 | 38.1 |
5 °C ductility (cm) | 3 | 10 | 14 | 21 | 21 |
Softening point (°C) | 47 | 75 | 78 | 78 | 93 |
60 °C dynamic viscosity (Pa · s) | 207 | 12,367 | 13,609 | 10,592 | 14,566 |
Sticky toughness (N · m) | – | 17.4 | 25.6 | 22.7 | 39.7 |
Toughness (N · m) | – | 0.2 | 16 | 13.8 | 26.1 |
Elastic recovery (25 °C) | – | 95.1 | 94.8 | 98 | 99.5% |
4.3 Effect of different percentages of modifier viscosity (HVA, TPS and RST) modifiers on A-type and B-type modified SBS asphalt binders
Tests items | 8% TPS | 8% HVA | 8% RST | 12% RST |
---|---|---|---|---|
25 °C penetration (0.1 mm) | 44 | 39.9 | 40.4 | 39.8 |
5 °C ductility (cm) | 27 | 30 | 28 | 34 |
Softening point (°C) | 93.5 | 95.5 | 96 | 95 |
60 °C dynamic viscosity (Pa · s) | 68,215 | 45,683 | 48,599 | 142,854 |
Sticky toughness (N · m) | 35.8 | 35.5 | 36.5 | 33.2 |
Toughness (N · m) | 23.8 | 23.4 | 23.3 | 16.2 |
Elastic recovery (25 °C) | 98.5 | 98.5 | 98 | 99.8 |
Tests items | 8% TPS | 8% HVA | 8% RST | 12% RST |
---|---|---|---|---|
25 °C penetration (0.1 mm) | 44.9 | 42.9 | 41.3 | 46.7 |
5 °C ductility (cm) | 42 | 37 | 37 | 47 |
Softening point (°C) | 91.5 | 99 | 95.5 | 99 |
60 °C dynamic viscosity (Pa · s) | 169,298 | 180,131 | 291,057 | >360,000 |
Sticky toughness (N · m) | 32.8 | 35.5 | 38 | 28.1 |
Toughness (N · m) | 20.9 | 19.5 | 25.9 | 14.6 |
Elastic recovery (25 °C) | 100 | 100 | 100 | 100 |
5 Conclusion
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The results of physical properties test of local #70 asphalt binder with different contents of TPS showed that TPS modifier can significantly improve low-temperature properties of binders (ductility at 5 °C) and resistance to permanent deformation of asphalt mixes (softening point). The rate of increase in asphalt ductility at 5 °C and softening point gives an indication of the stiffening influence of TPS modification. Also, test results show that only a percentage greater or equal to 14% TPS can achieve the 60 °C dynamic viscosity of 20,000 Pa · s, which is the standard requirement. Furthermore, local #70 grade asphalt has a poor compatibility with TPS modifier.
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Both conventional asphalt binders have not met the requirements of the 60 °C dynamic viscosity which is 20,000 Pa · s, when 12% of TPS or HVA modifiers are used.
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The addition of 8% of the three different kinds of viscosity modifiers into A-type SBS modified asphalt resulted in a certain degree of improvement in its performance. The 60 °C dynamic viscosity is improved at the same percentage of different modifiers and meets the standard requirement of 20,000 Pa · s.
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When 8% of the three different kinds of viscosity modifiers are added into B-type SBS modified asphalt, the physical properties (25 °C penetration, 5 °C ductility and softening point) improvement is not significant. The same effect has been witnessed with its sticky toughness and toughness properties. Regarding the 60 °C dynamic viscosity, the B-type SBS modified asphalt binder has better viscosity balance than the A-type SBS modified one, and thus, it is a better option to use in the bus rapid transit asphalt mixture.