rap with fiber

Performance Evaluation of High RAP Asphalt Mixture with Fiber and Warm Mixing Agent

Shifa Xu1, Zhenpeng Wu1, Ying Xu1, and Shaokun Chen1

1 Department of Transportation Engineering, Beijing University of Civil Engineering and Architecture, Beijing, China

ABSTRACT The WRAM (warm recycled asphalt mixture) is a new type bituminous

material for the green environmental friendly pavement construction. The WRAM technology combines the benefits of hot recycled and warm mix. It significantly reduces energy consumption and gas effusion due to lower mixing and compact temperature. However, related research indicated that low temperature and water stability of WRAM with high RAP content (more than 30% by weight) cannot meet the requirements of the specification. In this research, the fiber was applied to improve the performance of AC-20 WRAM with 40% and 50% RAP content. The composition design was carried out using Marshall Test. The optimum bitumen content is 4.9% and 5.1%, respectively. A series of laboratory tests, such as wheel tracking before and after conditioning, and beam bending at low temperature, were carried out to evaluate the performance properties of AC-20 WRAM with reinforcing fiber. It was shown that this method can effectively improve the low temperature and water stability of asphalt concrete pavement. The properties of WRAM meet the requirements of the specification. INTRODUCTION

At present, due to pavement repair and maintenance, a large number of road reconstruction produce huge amount of waste asphalt in China. Reclaimed asphalt pavement (RAP) contains aged bitumen (approximately 5% by weight) and variety of particle size aggregates (about 95%). If the RAP cannot be recycled, it not only cause huge waste of resources, but also pollute to the environment. It does not meet the basic national policy of sustainable development (Qin 2006). The hot mix plant recycling technology is popularly used in China. However, the content of RAP is 10 -30% in recycled asphalt mixture, while consuming a lot of fuel and emit large quantities of gas (Qin et al. 2006).Warm mix asphalt technology is a new type of asphalt technology. It mainly reduces the viscosity of the asphalt and improves asphalt high temperature fluidity by adding warm mix material. It makes asphalt and mineral aggregate to be mixed at a lower temperature, named as warm mixing asphalt (WMA). Because of its lower mixing and compaction temperatures, its fuel

343

Challenges and Advances in Sustainable Transportation Systems

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consumption decreases by 20% to 50%. It also effectively reduces the aging of asphalt and enhances the life of the road compared to hot mix asphalt (Malliek et al. 2007). In addition, it reduces emissions and pollution to improve the working environment, especially the working environment of tunnels and underground transportation and other enclosed spaces. Warm mix asphalt can substantially all exist equipment of hot mix asphalt, without transformation of production machinery and equipment.

WMA technology combines warm mix with renewable technologies to make up the traditional hot asphalt recycling technology insufficiency, achieve the recycling of waste asphalt and energy saving double effect, and extend the pavement life. It is a revolutionary asphalt pavement materials technology, which epitomizes the advantages of the use of waste and energy conservation. It was found that if AC-20-type warm mix recycled asphalt mixture contains more than 30% the amount of aged material at low temperature, water stability and other road performance do not meet the regulatory requirements. Lignin fibers can have effect on asphalt toughening, thickening effect, enhance bond strength of aggregate particles, mortar shear, tensile strength, and improve low temperature properties and water stability of mixed families. Therefore, this study improved road performance of AC-20-type warm mix recycled mixtures containing 40% and 50% aged material by adding fiber in order to improve the ratio of aged material blending.

RAW PERFORMANCE TEST Mineral aggregate

This test used mineral aggregate 0 ~ 4.75mm diameter of limestone, 4.75 ~ 19mm diameter of basalt. Aggregates requires clean, dry, rough surface, In accordance with the test method in "Highway Engineering Aggregate testing procedures" (JTG E42-2005), the densities of mineral aggregate were tested (JTJ058 2010). To reduce errors, the asphalt mixture gradation was closer to synthesize gradation. The mineral aggregate were stored according to each sieve for screening. Asphalt

Penetration grade 70 # virgin asphalt was applied in this research. According to "technical specification for construction of highway asphalt pavement (JTG F40-2004)" and "regulations of highway engineering asphalt and asphalt mixture test (JTJ 052-2000) to evaluate the properties asphalt and its conventional index test results are listed in Table 1-1. Table 1-1. 70 # bitumen properties test results

Item Unit Requirements Results Test method

Penetration25,5s,100g 0.1mm 6080 74 T 06042000

Softening point TR&B 46 50.2 T 06062000

344 CHALLENGES AND ADVANCES IN SUSTAINABLE TRANSPORTATION SYSTEMS


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Ductility15,5cm/min cm 100 100 T 06051993 Fiber

In this study the lignin fibers, lignin fiber reinforced the role played in the mixture to improve high-temperature mixture rutting resistance and fatigue resistance capability, so that the road of high temperature stability and fatigue durability is improved. Lignin fibers continued to show flexibility at low temperatures, which can effectively resist thermal stress, reduce temperature shrinkage cracks and improve the pavement temperature crack resistance. Different types of asphalt mixture, lignin fiber content in 0.25% ~ 0.4% can effectively improve road performance.

According to experience, the study selected lignin fiber content is 0.3%. This study used loose lignin fibers, performance testing indicators in Table 1-2. Table 1-2. Lignin fibers test results

Indicators Unit Test results Technical requirements

Ash content 20.1 185,No volatiles

PH value -- 7.5 7.51.0

Absorption rate 5.0 Mass of fiber 5.0 1.0-fold

Moisture 3.0

Table 1-3. LTR physical performances Items Unit results

Physical state20 Liquid state Freezing point -10

Flash point 178 Density25 g/cm3 1

Solubility Soluble in aromatic, alcohol insoluble in water

MIXTURE DESIGN

This paper used the Marshall Mix design method of recycling temperature and mixture ratio design, Marshall Compaction method for molding specimens for research related to performance. According to the selected grading type, we determine the scope of mineral aggregate gradation. Selecting the appropriate grading scale, according to the Marshall specimen volume parameters, determine warm mix asphalt recycling mixture of the best proportion, warm mix asphalt recycled asphalt amount includes new asphalt and old aged asphalt compound the original two-part . Aggregate gradation

According to "asphalt pavement construction specifications" (JTG F40-2004) coupled with lower-level requirements, this article uses the coarse and fine aggregate sieve into a file by size, for aggregate gradation design. AC-20 asphalt mixture composed of aggregate gradation shown in Figure 1 AC-20 asphalt mixture aggregate gradation

Figure 1. AC-20 synthetic grading curve

AC-20 Warm Mix Asphalt with 40% RAP Optimum asphalt content

Preparing Marshall Specimens, based on past experience, an initial 3.5%, 4%, 4.5%, 5%, 5.5% five kinds of Binder content, lignin fiber content is 0.3%. Accordance with the ordinary hot-mix asphalt request preparing specimen volume



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determination Marshall specimens for Marshall test parameters and determine its stability and flow values, the results shown in Table 2-1. Table 2-1. AC-20 test results

AC - 20 calculated from above, the optimum proportion of asphalt mixture is

4.9%, the ratio of the Marshall test results are shown in Table 2-2. Table 2-2. The optimum proportion corresponding index test results

Temperature mixing materials performance test (1)High temperature stability performance test

According to the above test to determine the optimum proportion of high temperature stability performance inspection, test results such as Table 2-3. Table 2-3. High temperature stability test results

(2)Water stability performance test

According to the above test to determine the optimum proportion of preparing Marshall Specimen, water stability test, freeze-thaw splitting test and immersion Marshall test, test results such as Table 2-4.

Binder content

% Bulk density

g/cm3 stability

KN Flow value

mm Air void

% VMA% VFA%

3.5 2.39 5.92 2.11 9.26 16.40 43.56

4.0 2.41 7.06 2.55 7.92 15.97 50.42

4.5 2.43 8.07 2.64 6.28 15.54 59.60

5.0 2.45 8.27 3.12 4.50 15.44 70.86

5.5 2.45 7.47 3.27 2.75 15.87 78. 05

specification 8 1.54 46 13 6575

Binder content

% bulk density

g/cm3 stability

kN flow value

mm Air Void

% VMA

% VFA

% 4.9 2.45 8.83 3.0 4.88 15.53 68.57


Binder content % Dynamic stabilitypass /mm specification

4.9 3319 1000

CHALLENGES AND ADVANCES IN SUSTAINABLE TRANSPORTATION SYSTEMS 347


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Table 2-4. Water stability test results

Binder content% 4.9

test item The soaking stability% Freeze-thaw splitting strength ratio%

87.2 77.5

Specification values 80 75

(3)Low temperature performance test

According to the above test to determine the optimum proportion of the molding plate specimen with wheel grinding method, and cut into trabecular, the UTM - 25 material testing machine for testing, test temperature for - 10 , the results in Table 2-5.

Table 2-5. Low temperature bending test results

Mixture type Binder type

Failure strain

Measured Specification

AC-20 70# 2326.5 2000 AC-20 Warm Mix Asphalt with 50% RAP Optimum asphalt content

Molding Marshall Specimen, based on past experience, the initial 3.5%, 4%, 4.5%, 5%, 4.5%, five kinds of binder content, lignin fiber content is 0.3%. Molding according to the requirements of ordinary hot mix asphalt mixture specimen, determine the volume parameter Marshall specimen and Marshall test to determine the degree of stability and flow values, the results in Table 2-6. Table 2-6. Adding 50% RAP AC - 20 test results

Binder content

% Bulk density

g/cm3 stability

KN flow value

mm

Void

fraction

%

VMA

% VFA

%

3.5 2.38 7.28 2.29 9.86 16.49 40.20

4.0 2.42 8.11 2.67 8.08 15.72 48.59

4.5 2.42 9.02 2.81 6.76 15.89 57.45

5.0 2.45 12.46 3.16 4.75 15.51 69.37

5.5 2.44 9.77 3.24 4.50 16.09 72. 04




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AC - 20 calculated from above, the optimum proportion of asphalt mixture is 5.2%, the ratio of the Marshall test results are shown in Table 2-7.

Table 2-7. The optimum proportion corresponding index test results

Temperature mixing materials performance test

(1)High temperature stability performance test According to the above test to determine the optimum proportion of high

temperature stability performance inspection, test results such as Table 2-8. Table 2-8. High-temperature stability test results

(2) The water stability performance test

According to the above test to determine the optimum proportion of preparing Marshall specimen, water stability test, freeze-thaw splitting test and immersion Marshall test, test results such as Table 2-9.

Table 2-9. Water stability test results

Binder content% 5.2

test item The soaking stability% Freeze-thaw splitting strength ratio%

86.8 75.7

Specification values 80 75

(3)The low temperature performance test According to the above test to determine the optimum proportion of the

molding plate specimen with wheel grinding method, and cut into trabecular, the UTM - 25 material testing machine for testing, test temperature for - 10 , the results in Table 2-10.

Binder content

% Bulk density

g/cm3 stability

kN flow value

mm

Void

fraction

%

VMA

% VFA

%

5.2 2.47 8.9 3.6 4.13 14.91 72.82


Binder content % Dynamic stability times/mm Specification

5.2 4000 1000



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Table 2-10. Low temperature bending test results

The mixture type Asphalt type

Failure strain The measured

values Specification values

AC-20 70# 2219 2000 CONCLUSIONS

This paper studied the performance properties of fiber reinforcing WRAM with 40% and 50% RAP contents, such as high temperature stability, water stability performance, and low temperature crack resistance, etc.. Following conclusions were obtained:

(1) With the increase of the proportion of aged material, mixing temperature of recycled asphalt mixture, Marshall Stability and dynamic stability are increased. The fiber added can effectively improve the rutting resistance of the mixture.

(2) The freeze-thaw splitting strength ratio and Marshall stability of WRAM can satisfy the requirements of the specification. Warm mix of recycled asphalt mixture water stability was improved with fiber.

(3) Lignin fiber increased the optimum asphalt content of mixture and the ductility of the mixture. The WRAM with lignin fiber has same cracking resistance as virgin materials at low temperatures.

(4) Mixed with 40% of RAP, the optimum binder content was 4.9% for WRAM. It was 5.2% for WRAM with 50% RAP. It means that the optimum binder content increases with the increasing of the proportion of RAP.

ACKNOWLEDGMENTS

This research was supported by a Grant from the National Natural Science Foundation of China (Grant No.51178024 and 51078017). REFERENCES Chen, Huaxin, Strife, Zhang, and Hu, Changshun (2002). Fiber with the

Performance of the Asphalt Research. Journal of Chang'an University (Natural Science Edition), 22 (6): 5-71.

JTJ052 (2000). The Highway Engineering Asphalt and Asphalt Mixture Test Regulation JTJ052-2000. People's Traffic Press, Beijing.

JTJ058 (2000). The Aggregate for Highway Engineering Test Procedures JTJ058-2000. People's Traffic Press Specification for Design of Highway Modified Asphalt Pavement Construction Traffic Press JTJ036-98, Beijing.

Larsen, O. R., and Robertus, C. (2005). Process and System for Production of a Warm Foam Mix Asphalt. US Patent 6846354.

Li, Zhen (2010). Mix Recycled Asphalt Mixture Performance Evaluation Research.



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Master thesis. Beijing Institute of Civil Engineering and Building, 12. Lv, Weimin (2001). Design Principle and Method of Asphalt Mixture. Tongji

University Press. 1, Shanghai. Malliek, R. B., Bradley, J. E., and Bradbury, R. L. (2007). Evaluation of Heated

Reclaimed Asphalt Pavement Material and Wax-Modified Asphalt for Use in Recycled Hot-Mix Asphalt. Journal of the Transportation Research Board.

Qin, Jun (2006). Warm mix asphalt paved road to environmental protection and energy saving. Transportation World (Mechanical) Built, (9).

Qin, Yongchun, Huang, Songchang, Xu, Jian, Xu, Changkui, and Su, Yukun (2006). "Warm mix asphalt mixture technology and the latest research. Asphalt, 8, 20 (4).



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rap with fiber

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