Performance evaluation and field application of hard asphalt concrete under heavy traffic conditions

Construction and Building Materials 228 (2019) 116729

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Performance evaluation and field application of hard asphalt concrete under heavy traffic conditions Guoping Qian a,b, Ding Yao a, Xiangbing Gong a,b,⇑, Huanan Yu a,b, Ningyuan Li c a

School of Traffic and Transportation Engineering, Changsha University of Science & Technology, Changsha 410114, China Key Laboratory of Special Environment Road Engineering of Hunan Province, Changsha University of Science & Technology, Changsha 410114, China c Department of Civil and Environmental Engineering, University of Waterloo, Waterloo N2L 3G1, Canada b

h i g h l i g h t s
Hard asphalt concrete significantly improves high temperature performance.
Hard asphalt concrete can be used as a pavement under heavy traffic conditions.
Hard asphalt concrete has remarkable long-term performance.

a r t i c l e

i n f o

Article history: Received 23 April 2019 Received in revised form 9 August 2019 Accepted 14 August 2019

Keywords: Heavy traffic Hard asphalt mixture Design Performance Field application Structural integrity

a b s t r a c t In order to improve the service performance of asphalt pavement under high temperature and rain during summer under heavy traffic conditions, this research compared the pavement performance of hard, heavy-duty AH-70, and Styrene Butadiene Styrene (SBS) polymer-modified asphalt mixtures through high temperature performance, low temperature crack resistance, fatigue resistance, and water stability tests. Results indicate that 30# hard asphalt mixture remarkably improves high temperature performance compared with 70# and 70# SBS asphalt mixtures. Moreover, the water stability of these asphalt mixtures is comparable. The fatigue performance of 30# hard asphalt mixture is comparable with that of 70# asphalt mixture. Finally, after 10 years of pavement performance, the hard asphalt concrete pavement structure achieved the best road conditions. Ó 2019 Elsevier Ltd. All rights reserved.

1. Introduction Heavy duty traffic asphalt pavement causes rutting, pitting, cracking, and other disasters. Among all distresses, rutting is the most common form of damage [1]. Therefore, scholars have given substantial attention in investigating the rutting resistance of asphalt mixture under heavy traffic condition. Currently, many studies focused on improving the fatigue, rutting, and water resistances of asphalt pavement by using modified asphalt. However, modified asphalt is expensive, and its manufacture and preservation technology are complex [2,3]. Hard asphalt concrete can achieve the same effect as modified asphalt in heavy duty areas. The asphalt concrete structure layer, which uses hard asphalt as binder, has high modulus, strong resistance to high temperature rutting, and load transfer ability to the lower layer, which is suit⇑ Corresponding author at: School of Traffic and Transportation Engineering, Changsha University of Science & Technology, Changsha 410114, China. E-mail address: [email protected] (X. Gong). https://doi.org/10.1016/j.conbuildmat.2019.116729 0950-0618/Ó 2019 Elsevier Ltd. All rights reserved.

able for high-grade highway pavement structure under heavy traffic conditions [4–7]. Hard asphalt and aggregate also have good bonding performance that effectively improves asphalt mixture bonding, water damage resistance, and fatigue resistance [8–14]. Moreover, compared with modified asphalt, hard asphalt can reduce construction cost and mitigate construction difficulties [3,15]. Therefore, highway engineers, scientists, and technicians focus on finding an economic and effective method of solving the main problems of asphalt pavements in high temperature, rainy, and heavy-duty traffic areas. The author begins by investigating the contents of hard asphalt to solve the problems of high temperature stability, resistance to water ingress damage, and rutting of asphalt pavements in China by utilizing the high viscosity of hard asphalt and the high strength and modulus characteristics of the mixture. This study also attempts to enable the high modulus asphalt concrete pavement to reach the level equivalent to SBS-modified asphalt pavement in terms of high temperature stability and water damage resistance, thereby avoiding the early damage of asphalt pavements,

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G. Qian et al. / Construction and Building Materials 228 (2019) 116729

solving the key technical problems in highway pavement construction, and improving highway construction techniques through the advancement of highway engineering. Furthermore, the application prospect of hard asphalt is verified by 10 years of actual highway engineering and road condition data analysis. 2. Materials and tests 2.1. Asphalt Through the primary selection of raw materials, the asphalt used in this test including CNOOC Taizhou 30# asphalt, SBS (I-D) modified 70# asphalt, and 70# asphalt. The test results are shown in Table 1. Table 1 shows that the ductility of 30# asphalt at 10 °C and 15 °C is 6 cm and 13 cm, respectively, indicating that the current specification requirements are met. At present, the ductility at 10 °C is used as an index to evaluate the low temperature performance of asphalt pavement in China. However, 10 °C cannot certainly represent the low temperature environment of asphalt pavement. Although the low temperature performance of 30# hard asphalt is poor according to the current standards of China, reasonable tests should be carried out to verify the low temperature performance of hard asphalt. The SHRP asphalt test method was used to test the rheological properties of asphalt in different temperature ranges based on the rheology.

for 20 s. After 20 s, 100 g load was applied, 240 s was maintained, the deflection of asphalt trabecula was recorded, the curve of deflection versus time was drawn by the computer, and the creep stiffness (S) and m-value were calculated (See Table 3). Low temperature stiffness and crack resistance are good. Three kinds of original and PAV residual asphalt can meet the requirements of bending stiffness modulus S not exceeding 300 MPa, and creep curve slope m not less than 0.30 at 6 °C. At 12 °C. Although the m-values of the three asphalt can still meet the requirements, the bending stiffness modulus of 30# PAV residual asphalt is already greater than 300 MPa, and that of the 70# PAV residual asphalt is also close to 300 MPa. Thus, 30# can no longer meet the specification requirements. 70# and SBS-modified asphalt still cannot meet the specification requirements at 18 °C. Many scholars emphasized that the loading time of the low temperature stiffness of asphalt binder should be 7200 s [16–18]. Such test conditions are not only very low temperature, but also long and relatively difficult. However, according to the basic principle of the rheology of asphalt materials, the load action time can be shortened to 60 s, and the test temperature can be decreased by 10 °C according to the time and temperature change algorithm. Therefore, the low temperature level of 30# is 16 °C, and the low temperature grades of 70# and SBS-modified asphalts are both 22 °C. In summary, the PG grades of 30#, SBS-modified, and 70# asphalt are PG88-16, PG82-22, and PG70-22, respectively.

2.2. Asphalt mixture grading 2.1.1. PG grading of asphalt materials (1) Dynamic shear rheology (DSR) test results and analysis Three dynamic shear tests were carried out on three kinds of original and Rotary Thin Film Oven Test (RTFOT) residual asphalt samples, and rutting resistance factor G*/sind was obtained. The initial test temperature was 64 °C and then increased to 94 °C at intervals of 6 °C. The angular velocity of the test was 10 rad/s. The DSR test results of the three asphalt specimens are shown in Table 2. Table 2 shows that the rutting resistance factor of the three asphalts decreases with the increase in temperature, indicating the reduction in the asphalts’ high temperature resistance. The virgin asphalt values of the three specimens reached more than 1.0 kPa at 70 °C, and 30# and modified asphalts remained at more than 1.0 kPa at 88 °C. This result indicates that the high temperature performance of 30# asphalt is similar to that of modified asphalt and slightly better than that of 70# asphalt. At 88 °C, the residual asphalt after the RTFOT of 30# asphalt is still higher than 2.2 kPa. Therefore, the partial replacement of modified asphalt with 30# asphalt in appropriate layers of pavement structure is of practical significance under the premise of meeting relevant requirements in areas with high temperature performance requirements. According to the DSR test results of the original and RTFOT residual asphalts, the high temperature grade of 30# asphalt is the highest at 88 °C; SBS-modified asphalt is second at 82 °C; and 70 # asphalt is the lowest at 70 °C. (2) Test results and analysis of bending beam rheology (BBR) The BBR tests were carried out at three different temperatures for three kinds of original asphalt and its Pressure Ageing Vessel (PAV) residual asphalt. The asphalt trabecula with the size of 125  12.5  6.25 mm was placed on two supports and artificially preloaded by 3–4 g to ensure the close contact between the trabecula and the support. The specimen was positioned on the computer by applying 100 g load for 1 s. Then, the specimen was unloaded to preload and let it restore

To ensure rutting resistance at high temperature and crack resistance at low temperature, the dosage of coarse aggregate near nominal maximum particle size should be appropriately reduced, and the dosage of fine powder less than 0.6 mm should also be reduced in mixture proportion design. Therefore, additional medium-sized aggregates can be obtained, and the S-shaped compactness gradation curve can be formed. Furthermore, intermediate or advanced aggregate design voids should be selected [19,20]. Coarse dense graded asphalt mixture should be selected for sections with high temperature, long duration of high temperature, and heavy traffic during summer. Therefore, the mixing ratio of the surface layer AC-20C and the lower layer AC-25C in the test section was designed in accordance with the indoor test results of several kinds of asphalts, and the aggregates were limestone gravel. The recommended grading of high modulus asphalt mixtures AC-20C and AC25C is shown in Fig. 1, both within the scope of the standard engineering grading, respectively. Bailey method refers to a set of methods that determine the gradation of asphalt mixtures [21,22]. It was invented by Robert D. Bailey of Illinois Department of Transportation. The main characteristic of Bailey method is that it controls the ratio of the size of key sieve holes between coarse and fine aggregates, so that the aggregate gradation of asphalt mixture can obtain a good skeleton structure. In this study, when using Marshall method to design high modulus asphalt mixture, the gradation selection is made by Bailey method to make gradation design convenient to operate. The designed gradation not only has good construction performance, but also meets the compaction requirements. Table 4 illustrates the controlled mesh openings for the two asphalt mixes, namely, AC-20C and AC-25C. Table 5 presents the calculation method, technical requirements, and calculation results of the two grading parameters of the Bailey method. The two gradations meet the requirements of the Bailey method. According to the Marshall method, the mix design of AC-20C and AC-25C was presented in Fig. 1, and the mix design test was completed. The test proved that both grades met the test requirements, and the two types were finally selected. The optimum asphalt to stone ratio for the mixture was 4.6–4.0%.

Table 1 Test results of asphalt conventional properteis. Item

AH-30

Specification

SBS (AH-70)

Specification

AH-70

Specification

Penetration (25 °C, 100 g, 5 s, 0.1 mm) Ductility (5 cm/min, 5 °C, cm) (5 cm/min, 10 °C, cm) (5 cm/min, 15 °C, cm) Softening point (Ring-and-ball method, °C)

26 – 6 13 60

20–40 – 10 50 55

56 34 – – 79

30–60 20 – – 60

65 – 86 >100 50

60–80 – 20 100 46

Penetration index RTFOT (163 °C, 5 h)

0.99 0.0 85 –

1.5 to +1.0 ±0.8 65 –

0.533 R = 0.99 0.1 73 16

0 ±1.0 65 15

0.476 R = 0.99 0.026 63 7

1.5 to +1.0 ±0.8 61 6

Mass loss (%) Residual penetration ratio (%) Residual ductility (10 °C, cm)

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G. Qian et al. / Construction and Building Materials 228 (2019) 116729 Table 2 DSR test results of asphalt specimens. Item

Test temperature/°C

AH-30

SBS (AH-70)

AH-70

Virgin

RTFOT

Virgin

RTFOT

Virgin

RTFOT

G*/kPa

64 70 76 82 88 94

19 7.17 3.67 1.89 1.01 –

– – 9.25 4.73 2.54 1.48

5.85 3.4 2.16 1.4 0.96 –

– 6.63 4.06 2.57 1.63 –

2.6 1.34 0.7 – – –

4.43 2.25 1.13 – – –

d/°

64 70 76 82 88 94

77.7 78.2 79.2 81 82.3 –

– – 72.6 74.9 77.1 79.0

64.1 64.1 62.6 60 55.2 –

– 62.5 62 61.9 62.3 –

86.4 87.2 87.4 – – –

84 85.6 86.6 – – –

G*/sind/kPa

64 70 76 82 88 94

19.45 7.32 3.74 1.91 1.02 –

– – 9.69 4.9 2.6 1.51

6.5 3.77 2.43 1.62 1.17 –

– 7.48 4.6 2.92 1.84 –

2.61 1.34 0.7 – – –

4.46 2.26 1.13 – – –

Table 3 Summary of bending creep test results. 6 °C

Temperature

12 °C

18 °C

S (MPa)

m

S (MPa)

m

S (MPa)

m

AH-30

Virgin PAV

80.8 142.0

0.445 0.360

222.0 354.0

0.375 0.319

481.0 599.0

0.274 0.256

SBS (AH-70)

Virgin PAV

– 48.4

– 0.486

90.7 115.0

0.466 0.421

265.0 348.0

0.380 0.287

AH-70

Virgin PAV

26.8 72.2

0.696 0.444

146.0 265.0

0.480 0.350

339.0 499.0

0.420 0.325

Fig. 1. Gradation curves of AC-20C and AC-25C.

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G. Qian et al. / Construction and Building Materials 228 (2019) 116729 method: rutting by wheel and rolling using universal material testing machine for testing. The test temperature was 10 °C. The bending strength at break can be obtained as RB, which is the maximum bending strain at the bottom of the beam.

Table 4 Control screen holes for two mixtures. Key sieve

D/2

[PCS]

[SCS]

[TCS]

AC-20C AC-25C

9.5 mm 13.2 mm

4.75 mm 4.75 mm

1.18 mm 1.18 mm

0.30 mm 0.30 mm

2.3. Test methods 2.3.1. Rutting test The rutting test can well reflect the process of permanent deformation of asphalt mixture with time and temperature. This test is in line with the actual stress of the road surface. Three rutting tests on asphalt mixture were carried out in accordance with the Standard Test Methods of Bitumen and Bituminous Mixtures for Highway Engineering. The wheel mill was used to form a 300  300  50 mm plate. Under the pressure of 0.7 MPa ± 0.05 MPa tire at 60 °C, the running distance of the wheel was 230 mm ± 10 mm, and the running speed was 42 times/min (21 roundtrips/min). The running direction was consistent with the rolling direction of the specimen, and the dynamic stability was determined. The dynamic stability calculation method is presented as follows:

DS ¼

ðt60  t 45 Þ  N  C1  C2 d60  d45

ð1Þ

where: DS is the dynamic stability of asphalt mixture, time/mm; t60, d60 is the test time (e.g., 60 min) and the deformation of specimen, respectively; t45, d45 is the test time (e.g., 45 min) and the deformation of specimen, respectively; C1 is the correction coefficient of test machine; it is equivalent to 1.0 in the variable speed running mode of crank connecting rod for driving the specimen, and is 1.5 in the constant speed mode of chain-driving test wheel; C1 = 1 in this test; C2 is the specimen coefficient; it is equivalent to 1.0 for the 300-mm wide specimen that has been prepared in the laboratory and is 0.8 for 150-mm wide specimen sampled from the pavement; C2 = 1 in this test. 2.3.2. Repeated shear tests at a constant height (RSTCH) To quantitatively study the high-temperature shear performance of highmodulus asphalt mixture, three parallel RSTCH were carried out for each group by using SHRP’s SST shear tester with reference to the AASHTO TP7-94 specification. During the test, the test temperature was selected at 60 °C, a void ratio of 4% ± 0.5%, and a repeated half-sinusoidal shear stress of 69 ± 5 kPa (approximately 1220 N shear load for a 150 mm diameter test piece). The load time is 0.1 s, the unloading time is 0.6 s, and the frequency is 1.43 Hz, so that one circle is called one cycle. The permanent shear strain is calculated by the following formula:

c ¼ dshearfinal  dshearinitial

ð2Þ

where: c is Permanent shear strain, %; dshear-initial is Initial shear deformation, mm; dshear-final is Final shear deformation, mm.

c ¼ kn þ b

ð3Þ

2.3.4. Fatigue test Two parallel bending fatigue tests on asphalt mixture were carried out for each group with reference to Specification [23]. Three-point loading test was used, and the test used 50  50  250 mm trabecula; the loading mode is stress control and three-point loading; the loading waveform and frequency is 10 Hz continuous half-vector waveform; the stress ratios are 0.1, 0.2, 0.3, 0.4, and 0.5; the test temperature is 15 °C ± 1 °C; and the test equipment is MTS-810 material testing machine. 2.3.5. Residual stability test The residual stability test was carried out according to Specification [23], that is, a set of Marshall test pieces were tested for stability after being kept at 60 °C for 30 min in hot water, and another condition of Marshall test pieces was measured at 60 °C lasting for 48 h. Then, the two test pieces were compared to evaluate the water stability of the mixture. 2.3.6. Freeze-thaw splitting test The inundate Marshall residual stability test cannot evaluate the water stability of asphalt mixture after freeze-thaw cycles in winter and summer. Thus, freezethaw splitting test was added for comparison. This test refers to the immersion Marshall test in Specification [23]. The test specimen was formed in accordance with Marshall’s method. The positive and negative sides were hit 50 times each. The two groups were saturated with water. One group was immersed in water at 25 °C for 2 h before testing. The other group’s water soaking process is conducted as follows: (1) Immersion in water at room temperature (25 °C) for 20 min; (2) 0.09 MPa immersion in water for 15 min; (3) in  18 °C refrigerator for 16 h; (4) in 60 °C water bath for 24 h; and (5) in 25 °C water for 2 h. 2.3.7. Test road performance test 2.3.7.1. Pavement structure program. To compare the field performance of 30# hard, SBS-modified, and 70# mixtures, three test sections (e.g., Pavement Structures A, B, and C) were established on a highway in Henan Province, China. Pavement Structure A refers to a high modulus asphalt concrete in the middle and lower surface coats of K9 + 500–K10 + 591. Pavement Structure B refers to a high modulus asphalt concrete in the lower surface coat of K8 + 500–K9 + 500. The K7 + 500–K8 + 500 is the same as the main body Pavement Structure C (Table 6). The design speed is 120 km/h, and the roadbed is 28 m wide. In addition, the highway along the line locates in the north warm temperate monsoon climate zone. It is generally warm in spring, hot in summer, cool and rainy in autumn, and cold in winter. 2.3.7.2. Axle load spectrum. The traffic condition investigation of this section is shown in Figs. 3–5. 2.3.7.3. Pavement performance index. Investigating the 10 years using test road, this research studied and analyzed the pavement damage index PCI (Pavement Surface Condition Index), the international roughness index IRI (m/km), and the rutting depth index (RDI) of the test section.

where: c is the repeated shear strain for the second stage; and k and b are the regression coefficients (Fig. 2). The three indices obtained from the tests, namely, c, dshear-initial, and dshear-final, which reflect the high temperature shear resistance of asphalt mixtures at the beginning, and at the end of repeated shear tests, respectively. It aims to satisfactorily evaluate the whole process of high temperature permanent deformation of asphalt mixtures. 2.3.3. Low temperature bending test of trabecula Flexural strength refers to the ability of the mixture to resist bending stress. The resistance of the material to damage is stronger, the ability to resist shrinkage stress at low temperatures is more robust, and the low temperature crack resistance of the pavement is better when the bending strength is higher. Three parallel bending tests on asphalt mixture were carried out for each group with reference to Specification [23]. The test size shall be based on the length requirements, that is, 250 mm ± 2 mm length, 30 mm ± 2 mm width, and 35 mm ± 2 mm height. Forming

Fig. 2. Relationship between shear strain and repeated shear time.

Table 5 Technical requirements and calculated values of parameters. Item

[CA] ratio

[FAc] ratio

[FAf] ratio

Calculation method Specification Results

(PD/2–P PCS)/(100–PD/2) 0.4–0.8 0.47 0.72

PSCS/P PCS 0.25–0.50 0.46 0.47

PTCS/P SCS 0.25–0.50 0.48 0.40

AC-20C AC-25C

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G. Qian et al. / Construction and Building Materials 228 (2019) 116729 Table 6 Pavement structure scheme relying on engineering. Pavement structure

Thickness (mm)

Pavement structure A

Surface course Upper binder course Lower binder course Base course Subbase course Subgrade

40 60 80 360 180 –

AC-13 (70#SBS) AC-20C (30#) AC-25C (30#) 5% Cement stabilized macadam 4% Cement stabilized aggregate Compacted subgrade

Pavement structure B

Pavement structure C

AC-20C (70#SBS) AC-25C (30#)

AC-20C (70#SBS) AC-25C (70#)

Fig. 3. Single-axle and single-wheel axle load spectra.

Fig. 4. Single-axle and double-wheel axle load spectra.

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G. Qian et al. / Construction and Building Materials 228 (2019) 116729

Fig. 5. Dual-axle and double-wheel axle load spectra.

PCI is expressed as follows:

PCI ¼ 100  a0 DRa1

3. Results and discussion ð4Þ

3.1. Performance evaluation of asphalt mixture

where: the specified parameter a0 is 15, and the parameter a1 is 0.412. DR is expressed as follows:

DR ¼ 100

Pi0

i¼1 wi Ai

ð5Þ

A

where: A is the total area of the road section; Ai is the area of a certain disease; and wi is the weight divided according to the severity of the disease. IRI is expressed as follows:

IRI ¼ a þ b  BI

ð6Þ

where: BI is the test result of the flatness test equipment, and a, b is the calibration coefficient. RDI is expressed as follows:

RDI ¼

8 RD  RDa > < 100  a0 RD; 60  a1 ðRD  RDa Þ; RDa < RD  RDb > : 0 RD > RDb

ð7Þ

where: RD is the rut depth, mm; RDa is 20 mm; RDb is 35 mm; the specified parameter a0 is 2; and parameter a1 is 4.

Fig. 6. Comparison of rutting test.

3.1.1. High temperature performance Fig. 6 shows the AC-20C high modulus asphalt mixture (dynamic stability of 5457 times/mm) or AC-25C high modulus asphalt mixture (dynamic stability of 6565 times/mm). It has better anti-rutting performance than 70# SBS modified asphalt mixture and far exceeds the specification limitation of 3000 times. In comparison, the ordinary 70# asphalt mixture has relatively lower rutting resistance. The rutting test results imply that the hard asphalt AC-20C mixture and the hard asphalt AC-25C mixture meet the specification requirements, and have good high temperature anti-rutting performance. That is, the order of anti-rutting ability of each asphalt mixture is: AC-25C (30#) > AC-20C (30#) > AC20C (70#SBS) > AC-25C (70#). The test was stopped when the RSTCH reached cycles or when the shear strain reached 5%. The test results are shown in Fig. 7 and Table 7. The linear correlation among the three indicators, namely, c, k, and b, reflects the consistency of the shear resistance of the asphalt mixture. The test results imply that the shear resistance of different asphalt mixtures from large to small is AC-20C (30#) > AC25C (30#) > AC-20C (70#SBS) > AC-25C (70#). The shear resistance

Fig. 7. Relationship between repeated shear number and strain.

G. Qian et al. / Construction and Building Materials 228 (2019) 116729

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Table 7 Regression results of RSTCH test parameters. Mixture type

c (%)

k

b

AC-20C AC-25C AC-20C AC-25C

0.292 0.309 0.617 1.181

2.0 2.0 3.0 9.0

0.176 0.229 0.637 0.777

(30#) (30#) (70#SBS) (70#)

of the hard 30# asphalt mixture is very good and superior to the performance of the SBS-modified asphalt. The high temperature shear resistance of the 70# asphalt mixture is poor. In the asphalt pavement structure, the middle and lower layers are generally subjected to large shear resistance, and an asphalt mixture that is superior in high temperature resistance is required. Therefore, the use of 30# asphalt mixture in the middle and lower layers of the road surface is advantageous. 3.1.2. Low temperature performance The test results in Figs. 8 and 9 show that the tensile strength of SBS-modified asphalt mixture is 12.755 MPa, which indicate a strong resistance to bending and tensile stresses. The mixture has strong resistance to damage and shrinkage stress at low temperature, so that the pavement has good low temperature crack resistance. The tensile strength of the 30# high modulus AC-20C mixture is 10.714 MPa, and the bending strength of AC-25C mixture is 9.225 MPa, which also indicates strong low temperature crack resistance. This asphalt mixture has a bending strength of 8.776 MPa or better. 30# high modulus asphalt mixture AC-20C and AC-25C, the ultimate failure strain at low temperature is 4843 le and 6602 le, respectively. The flexural tensile strain of high modulus asphalt mixture at low temperature is smaller, and its low temperature resistance is weaker compared with AC-25C (70#) and AC20C (70#SBS) asphalt mixtures. However, this mixture can still meet the requirements of low temperature flexural-tensile failure strain of ordinary asphalt mixtures in Henan Province (2000 le). The damage strain of the modified asphalt mixture under low temperature bending and tension is not less than 2500 le, and the mixture is located in the middle and lower layers of the pavement, which is in a favorable pavement structure level. 3.1.3. Fatigue performance Through a large number of asphalt mixture trabecula bending fatigue tests, the test results are provided in Fig. 10:

Fig. 8. Low temperature bending strength results of different mixtures.

Fig. 9. Low temperature bending strain failure results of different mixtures.

Fig. 10. Stress levels and fatigue life times of different mixtures.

For AC-20C (30#), AC-25C (30#), and AC-25C (70#) asphalt mixtures, asphalt mixing is at high stresses of 0.3, 0.4, and 0.5P, respectively. The average fatigue life of the materials is relatively close. In the low stresses of 0.1P and 0.2P, AC-20C (30#) mixture showed greater fatigue life than the two other asphalt mixtures because of the different types of mixture gradation. During the whole fatigue test process, AC-25C (30#) and AC-25C (70#) asphalt mixtures have relatively close fatigue life. Moreover, when these mixtures are in the same pavement structure, they have the same ability to support repeated loads. Therefore, the use of AC-20C (30#) and AC-25C (30#) asphalt mixtures is suitable in the lower layer of the pavement structure. AC-20C (70#SBS) asphalt mixture has higher fatigue life in 0.1, 0.2, 0.3, 0.4, 0.5P states than other asphalt mixture materials. Fatigue life reaches approximately 1.0  106 times, which fully reflects the superior performance of the modified asphalt mixture, especially under low stress conditions. 3.1.4. Water stability energy The test results in Fig. 11 exhibit that the residual stability of AC-20C (30#) and AC-25C (30#) is higher than AC-20C (70#SBS) and AC-25C (70#), indicating that the high modulus asphalt mixture has strong water damage resistance and can meet the loadbearing capacity for pavements.

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G. Qian et al. / Construction and Building Materials 228 (2019) 116729

Fig. 11. Results of Marshall residual stability of different mixtures.

Fig. 13. Test road section road damage status index from 2009 to 2018.

Fig. 12. Residual strength ratio of freeze-thaw splitting of different mixtures.

Fig. 14. International road flatness index of test road sections from 2009 to 2018.

Fig. 12 shows that AC-20C (30#) and AC-20C (70#SBS) asphalt mixtures have high freeze-thaw splitting strength ratios at 96.1% and 94%, respectively. The results illustrate that the water stability of asphalt mixture is very good after freeze-thaw cycles in winter and summer, whereas the water stability of AC-25C (30#) asphalt mixture decreases. The results also show that the water stability of mixtures is not only related to the type of asphalt, but also to the gradation type of mixtures.

3.2. Test road performance evaluation According to the PCI curve on the test road, the PCI decay rate of Pavement Structure A is slow during the first four years, thereby reflecting the high load capacity of the high modulus asphalt pavement structure during the initial use of pavement under the actions of traffic load and nature factors. Two other structural schemes have fast PCI reduction rates [24]. The hard asphalt concrete achieves the same effect as the modified asphalt concrete or even better without affecting the low temperature performance. The structural load capacity gradually decreases as the road service time increases, so that various diseases are produced on the pavement, and the PCI decay rate also gradually increases. However, the PCI decay rate of Pavement Structure A is the smallest among the three structures, followed by Pavement Structures B and C, indicat-

Fig. 15. Test section road rut depth index from 2009 to 2018.

ing that the different pavement structures vary greatly with the increase in long-term performance (Fig. 13). Fig. 14 shows that the IRI decay rates of the three pavement structures during the initial use are slow. The decay rate accelerates as the road service

G. Qian et al. / Construction and Building Materials 228 (2019) 116729

time increases. However, the difference of those three pavement structures indicating that the hard asphalt pavement structure in the middle and lower surface coats achieves the same effect as the modified asphalt pavement structure. The test results in Fig. 15 show that the RDI decay rates of the Pavement Structures A, B, and C are relatively slow, middle, and large, respectively. That is, the hard asphalt concrete has good high temperature stability and is superior to the SBS-modified asphalt in terms of deformation resistance. After 10 years of pavement performance, Pavement Structure A achieved the best road conditions. Therefore, Pavement Structure A should be prioritized when constructing the asphalt pavement under heavy load traffic conditions in Henan area.

4. Conclusions In this study, the material design of high modulus asphalt mixture is carried out by improving the Marshall method. Moreover, the pavement performance of high modulus asphalt mixture, such as high temperature, low temperature, fatigue, and water damage resistance, is systematically analyzed. The PCI, IRI, and RDI of pavement test sections were investigated in a real engineering project after 10 years of use. The following conclusions can be drawn: (1) According to the conventional index and rheological performance test results of asphalt, 30# hard asphalt can meet the requirements of local traffic conditions and climatic conditions, considering the reality of heavy traffic and high temperature during summer. (2) The road performance evaluation of hard asphalt mixture meets the design requirements. Cost effectiveness is the major advantage of replacing SBS-modified asphalt by hard asphalt. (3) According to the long-term road performance of the asphalt pavement of the project, the pavement performance of the middle and lower layers with hard asphalt concrete structure is worth promoting.

Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments The research was supported by National Key R&D Program of China (grant No.: 2018YFB1600100) and National Natural Science Foundation of China (grant No.: 51778071, 51808058).

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