Research Article  Open Access
Changqing Deng, Yingjun Jiang, Zhanchuang Han, Hongwei Lin, Jiangtao Fan, "Effects of Paving Technology, Pavement Materials, and Structures on the Fatigue Property of DoubleLayer Pavements", Advances in Materials Science and Engineering, vol. 2020, Article ID 5038370, 15 pages, 2020. https://doi.org/10.1155/2020/5038370
Effects of Paving Technology, Pavement Materials, and Structures on the Fatigue Property of DoubleLayer Pavements
Abstract
Doublelayer paving technology, which is a new technology for construction asphalt pavements, has received increasing research attention for several years. However, few studies have focused on the effect of asphalt pavement layer thickness and mixturetype combinations on the fatigue properties of a doublelayer pavement. Therefore, the fatigue properties of the doublelayer and traditionally paved asphalt pavements were studied in this work. The effects of two paving technologies, three mixture combinations, and two asphalt layer thickness combinations on the fatigue properties of asphalt pavements were studied through bending beam tests, and a fatigue equation of different asphalt pavements was established using the twoparameter Weibull distribution. Subsequently, the fatigue lives of different pavements were compared and analyzed under the same cyclic load. Results indicate that the flexural strength and fatigue life of the doublelayer pavement increased by at least 10% and 54%, respectively, compared with those of a traditionally paved pavement structure. The goodness of fit of the equation established using the Weibull distribution exceeded 0.90. For the traditional paving technology, compared with the pavement structure combination of 4cm AC13 surface layer/6cm AC20 bottom layer, the fatigue life of a 3cm AC13 surface layer/7cm AC20 bottom layer can be increased by at least 8%, while the fatigue lives of other pavement structures are reduced significantly. The results also indicate that the fatigue life of the doublelayer pavement structure with the 3cm AC13 surface layer/7cm AC20 bottom layer can be increased by at least 114% compared with that of the traditionally paved pavement structure (4cm AC13 surface layer/6cm AC20 bottom layer). Additionally, the fatigue lives of other pavement structures can be improved. To effectively improve the fatigue life of an asphalt pavement, a doublelayer pavement structure with the 3cm AC13 surface layer/7cm AC20 bottom layer combination is recommended.
1. Introduction
Pavement structures and material types significantly affect the fatigue life of an asphalt pavement [1–4]. The surface layer (4cm AC13), middle layer (6cm AC20), and lower layer (8–12cm AC25, ATB25, or ATB30) constitute the primary asphalt pavement structure of China’s highgrade highways [5, 6]. In addition, the 5cm AC13 surface layer/67cm AC20 bottom layer combination is primarily used as the typical structure of the National Trunk Highway System of China [5, 6]. Most asphalt pavements were constructed using traditional paving technology, i.e., stratified spreading and layerbylayer compaction because of the scarcity of construction machineries. In the field, a tacky coat oil is typically sprinkled between the asphalt structural layers to improve the adhesion force between the asphalt concrete layers [7, 8]. However, although the tacky coat oil can improve the adhesion between two structural layers to some extent, the upper layer of a hot paving asphalt mixture cannot be embedded into the lower layer that has been cooled and compacted. Consequently, the extrusion effect of the aggregates between the two structural layers is poor, and their bonding action is weak. The poor “aggregatebinder” and “aggregateaggregate” interfaces result in poor mechanical strength, moisture susceptibility, and poor high and lowtemperature performance of asphalt concrete [9–11]. This seriously affects the reliability of the pavement design and the durability of the asphalt pavement [12], thereby increasing the cost of pavement construction and maintenance. In addition, many drawbacks such as rapid heat dissipation, long construction periods, and low work efficiency of construction machineries are difficult to avoid during traditional paving.
Doublelayer paving technology for asphalt pavements, which is a new construction technology, simultaneously completes the paving and rolling of two structural layers [13, 14]. The primary advantage of this paving technology is that the simultaneous paving and rolling of the twolayer asphalt structure, which can effectively avoid the “cold and hot combination” contact between two structural layers constructed by traditional paving, ensures that the two layers of asphalt concrete are simultaneously paved and compacted with the condition of the “hot and hot” contact. Thus, the asphalt in the upper and lowerlayer mixtures can be completely in contact with each other, and the aggregates in the upper and lowerlayer mixtures can be extruded together during the construction, thereby resulting in good adhesion and extrusion between the mixture layers [15, 16]. Moreover, interlayer treatment is not applied during doublelayer paving, which not only saves the use of the tacky coat oil and shortens the construction period but also fundamentally solves the interlayer discontinuity problem of a traditionally paved pavement, thus ensuring a good bonding effect between the layers [15, 16]. Other advantages, such as a reduction in the temperature loss of the asphalt mixture during construction and not being limited to the principle of 2.5–3.0 times between the pavement structure thickness and nominal maximum particle size of the aggregate in the asphalt mixture, are also significant [15–17]. At present, Sweden, the Netherlands, and Germany have mastered advanced doublelayer paving technology. In Germany, the highgrade road surface with doublelayer paving construction has reached ∼4 million m^{2}, and the road surface has been used well. The doublelayer paving process has also been approved by the construction regulations of European countries such as Germany [18].
Recently, with the development and application of doublelayer paving equipment, road construction researchers have conducted some studies on asphalt mixtures with doublelayer paving technology. Großmann et al. considered that doublelayer paving technology aids to improve the interlayer bonding effect of the asphalt layers [19]. Mueller found that doublelayer paving technology fully utilized the thermal capacity stored in the lowerlayer asphalt mixture, thereby allowing the upper layer asphalt mixture to easily reach a good compact state [20]. Morgan et al. explored the feasibility of applying doublelayer paving technology to a doublelayer largegap asphalt pavement. The results indicated that it was feasible and more economical to apply this paving technology in constructing a largegap asphalt pavement. Moreover, this technology not only improved the construction speed and reduced the temperature loss but also ensured that the asphalt mixture achieved better compactness [21]. Füleki considered that a doublelayer asphalt pavement is advantageous for improving the aggregate interlocking effect between layers, thereby helping to resist the relative displacement between the layers caused by the shear stress generated by the traffic load [22]. Kuennan reported that the twolift asphalt paving technology not only helps us to improve the durability of the asphalt pavement but also enhances its ability to resist traffic load and pavement distress [23]. Wang compared the interlaminar shear properties of field cores drilled from the traditional and doublelayer paving pavements using the oblique shear test. The results indicated that the shear performance of the field cores drilled from the doublelayer asphalt pavement increased significantly compared with that of the traditionally constructed pavement, and the test data were more stable. Moreover, a laboratory rutting test also indicated that the deformation resistance of the doublelayer paved specimens was clearly better [24]. Gharabaghy et al. found that compared with the conventional asphalt pavements, the doublelayer asphalt pavements showed better rutting resistance and shear strength [25]. Using field testing and laboratory analyses, Li demonstrated that doublelayer paving can slow down the temperature reduction process and improve the compaction effect of asphalt pavements [26]. Liu et al. found that compared with the pavements constructed using conventional construction technology, the shear strength of the doublelayer asphalt pavements was improved and the effective compaction time was extended [27]. Wang et al. established a finite element prediction model of mixture temperature loss based on heat conduction theory to study the effective rolling time and rolling temperature of the asphalt mixture with doublelayer paving technology. Moreover, a test section was constructed to verify the model. The results indicated that the asphalt mixture with doublelayer paving required a longer effective rolling time [28]. Yang et al. analyzed the interlayer stress distribution law of the doublelayer pavement using a finite element and studied the fatigue performance of the doublelayer pavement through laboratory tests. The results indicated that doublelayer paving technology facilitated a reduction in the interlayer horizontal stress and improved the fatigue resistance of the asphalt pavement [29]. Jiang et al. studied the effect of paving technology, pavement materials, and structures on the rutting resistance of doublelayer pavements through laboratory tests. The results showed that the 3cm AC16 surface layer/7cm AC20 bottom layer combination could improve the hightemperature rutting resistance of asphalt pavements [30].
The abovementioned studies have undoubtedly promoted the understanding of doublelayer paving technology and the development of such technologies. However, related studies that were confined to the existing pavement structures and mixturetype combinations primarily investigated the effects of this paving technology on the bonding between the asphalt layers, temperature dispersion law during construction, shear performance, road performance, etc. Moreover, studies related to the effects of asphalt pavement layer thickness and mixturetype combinations on the fatigue properties of a doublelayer pavement are scarce.
Fatigue life is the key performance parameter for asphalt pavements [31, 32]. Asphalt pavement fatigue cracks due to insufficient fatigue life will gradually develop into cracks throughout the pavement structure. Furthermore, it will reduce the water damage resistance, road comfort, and safety of the asphalt pavement; shorten the service life of the road surface; increase the frequency of road surface maintenance and major and medium repair time; and increase the road life cycle cost [33–35]. At present, no standardized laboratory tests for fatigue cracking have been universally adopted for routine mix design or screening purposes for hotmix asphalt crack resistance [36]. Globally, the commonly employed test methods are mainly the indirect tensile method, trapezoidal cantilever beam bending method, and bending beam method. The indirect tensile method is the most common in the early fatigue test of asphalt mixtures. However, owing to some shortcomings of its test mode, it is gradually being abandoned by asphalt mixture fatigue researchers. Trapezoidal cantilever beam bending and bending beam fatigue tests are the more popular fatigue test methods for small specimens. The former is mainly employed in Europe, while the latter has been the basis of numerous experimental studies and applications in the United States, South Africa, and Australia. The bending beam test piece is easy to manufacture, and the test operation is simple compared with that in the trapezoidal cantilever beam bending fatigue test. In addition, the bending beam fatigue test has excellent sensitivity in terms of testing influencing factors and reliability [37]. Therefore, in this study, the bending beam fatigue test is used to investigate the effects of structural asphalt layer thickness and mixturetype combinations on the fatigue properties of a doublelayer paving pavement. The effects of two thickness combinations (3cm surface layer/7cm bottom layer and 4cm surface layer/6cm bottom layer) and three mixturetype combinations (AC13 surface layer/AC20 bottom layer, AC16 surface layer/AC20 bottom layer, and AC16 surface layer/AC25 bottom layer) on the fatigue properties of the doublelayer paving pavement were studied through laboratory tests. Subsequently, based on the optimal fatigue performance with doublelayer paving technology, the mixturetype combination and pavement layer thickness are recommended.
2. Materials and Methods
2.1. Materials
2.1.1. Asphalt
In this study, Singapore Esso A70 road petroleum asphalt, which was obtained from Shangluo City, Shaanxi Province, China, was used in the asphalt mixture. Moreover, the styrenebutadienestyrene (SBS) (IC) modified asphalt, which was collected from Karamay City, Xinjiang Uygur autonomous region, China, was used as the gluing material between two asphalt layers. The technical properties of the asphalt used in this study are listed in Table 1.

2.1.2. Aggregate
The coarse aggregate of the surface layer asphalt mixture used in this study was amphibolite obtained from Shangluo City, Shaanxi Province, China, while the coarse aggregate of the bottom layer asphalt mixture was limestone from Luonan City, Shaanxi Province, China. The fine aggregate of the surface and bottom layers’ asphalt mixture was limestone from Luonan City, Shaanxi Province, China. The mineral powder used in this study was limestone ore powder from Luonan County, Shaanxi Province, China. All aggregates used in this study satisfied the technical specifications for the construction of highway asphalt pavements (JTG F402004) [17], and their technical indicators were omitted.
2.2. Research Programs
2.2.1. Test Plan
To study the effects of different mixture types on the fatigue properties of asphalt pavements, four types of asphalt mixtures were selected: AC13, AC16, AC20, and AC25. The AC13 or AC16 asphalt mixture was used in the surface layer, whereas the AC20 or AC25 asphalt mixture was used in the bottom layer. Table 2 gives the gradations of the asphalt mixtures used in this study. Moreover, Table 3 gives the design data of the asphalt mixtures, in which VV, VFA, VMA, MS, and FL are defined as the air void volume, volume of the voids filled with asphalt, voids in mineral aggregate, Marshall stability, and flow value of the asphalt mixture, respectively. It is noteworthy that all types of asphalt mixtures used in this study were designed by the standard Marshall procedure.


To study the effects of different pavement structure combinations on the fatigue properties of asphalt pavements, the total thickness of the asphalt pavement was set to 100 mm, and two types of pavement structure combinations with different thicknesses of the surface and bottom layers were selected: 3cm surface layer/7cm bottom layer and 4cm surface layer/6cm bottom layer.
To study the effects of different paving technologies on the fatigue properties of asphalt pavements, two paving technologies were compared: the traditional and doublelayer paving technology.
2.2.2. Specimen Preparation Methods
The process of preparing mixture specimens by traditional paving technology for fatigue tests in the laboratory was divided into four primary stages:(1)Mold the bottom layer cut board: a cut board of size 300 mm × 300 mm × 60/70 mm (length × width × height) was produced by a rolling compaction machine with its own optimal asphalt content. The rolling compaction machine stopped when the density of the cut board specimens and that of the standard cylindrical specimens were similar. Subsequently, the cut board specimens were kept at room temperature for at least 24 h (Figure 1(a)).(2)Spray the sticky layer oil: the prepared bottom layer cut board was placed into a 300 mm × 300 mm × 100 mm (length × width × height) cut board mold. Subsequently, the SBSmodified asphalt of 0.45 kg/m^{2} was sprayed evenly on the cut board surface, with curing for at least 2 h (Figure 1(b)).(3)Mold the surface layer cut board: a certain weight of the surface layer asphalt mixture was placed into the cut board mold and compacted by the rolling compaction machine until the height of the board was 100 mm (Figure 1(c)).(4)Produce the beam specimen: the prepared cut board (300 mm × 300 mm × 100 mm) was cut into beam specimens of size 250 mm × 100 mm × 100 mm (length × width × height (Figure 1(d)).
(a)
(b)
(c)
(d)
The preparation process of the mixture specimens produced by the doublelayer paving technology for the fatigue test in the laboratory was divided into three primary stages:(1)Spread the bottom layer mixtures: a certain weight of the bottom layer asphalt mixture was placed into the cut board mold (300 mm × 300 mm × 100 mm) and subsequently placed into a 165°C oven after it was originally pressed using a hammer (Figure 2(a))(2)Spread the surface layer mixtures and compaction: a certain weight of the surface layer asphalt mixture was placed into the cut board mold and compacted by the rolling compaction machine until the height was 100 mm (Figures 2(b) and 2(c))(3)Produce the beam specimen: the prepared cut board (300 mm × 300 mm × 100 mm) was cut into beam specimens of size 250 mm × 100 mm × 100 mm (length × width × height), as shown in Figure 2(d)
(a)
(b)
(c)
(d)
2.2.3. Fatigue Test Method
The fatigue tests used to evaluate the fatigue property of asphalt mixtures in the laboratory primarily included the bending beam fatigue, indirect tension, and semicircular bending fatigue test [38, 39]. Compared with the indirect tension and semicircular bending fatigue test, the specimen preparation process of the bending beam fatigue test is more complicated and the experiment data dispersion is more significant. Moreover, the bending test could simulate the stress conditions of the actual pavement structures better and the experiment results could be directly used for asphalt pavement structure design. However, as the total thickness of the asphalt pavement structure was 100 mm, it was difficult to perform the fatigue test using the indirect tension or semicircular bending fatigue test. Furthermore, the overlay test can be used to evaluate cracking resistance of asphalt overlays, but the overlay test device is scarce in China [33–36]. Therefore, the bending beam fatigue test was adopted to study the fatigue property of asphalt pavements. Figure 3 shows the fatigue test model used in this study.
Generally, two primary control modes exist for fatigue testing: the controlledstrain and controlledstress. For the controlledstrain fatigue test, the fatigue life of materials is defined as the number of load cycles corresponding to a 50% reduction in stiffness; meanwhile, for the controlledstress test, the fatigue life of materials is defined as the number of load cycles corresponding to a fracture of specimens [40, 41]. Because of beam inhomogeneity, the modulus of the beam could not be computed from the fatigue tests. Therefore, the controlledstress test was used in this study, and the fatigue life of the beam was obtained according to the number of load cycles corresponding to the fracture of the specimens.
The bending beam fatigue test was divided into two primary stages:(1)Bending beam test The flexural strength of the beam specimen (250 mm × 100 mm × 100 mm) produced by the doublelayer and traditional paving technologies was measured using a material test system (MTS). The test temperature was 15°C, and the loading rate was 50 mm/min.(2)Bending fatigue test The fatigue test was conducted on the MTS at 15°C. Sine wave loading was used. The loading waveform diagram used in this study is shown in Figure 4. To maintain the contact between the indenter of the MTS and the specimens during the fatigue test, only vertical pressure (and no tension) was applied by the indenter. The loading frequency of the sine wave was 10 Hz. The circulation characteristic value (R) (defined as the ratio of the maximum stress to the minimum stress) was 0.1, and five stress levels were selected: 0.3, 0.4, 0.5, 0.6, and 0.7. It is noteworthy that the failure criteria adopted for fatigue testing correspond to the fracture of the specimens.
3. Results and Discussion
3.1. Bending Beam Test
Flexural strength is the basic parameter used to establish the bending fatigue equation. The bending beam test was repeated six times; subsequently, Grubbs’ method was used to examine and obtain the average of the test results [42, 43]. Hoe beam replicates were used per material per test condition. The results of the bending beam test of asphalt pavements with different paving technologies, mixture types, and pavement structural thicknesses are given in Table 4, where P_{d} and P_{t} represent the flexural strength of the beam specimen produced by the doublelayer and traditional paving technologies, respectively. In addition, P_{d}/P_{t} represents the ratio of the flexural strength of the beam specimen produced by the two paving technologies.

As presented in Table 4, the bending resistance of the doublelayer paved specimens with the same mixture types and pavement structure thicknesses increased by at least 10% compared with that of the traditionally paved specimens.
The interlayer contact of the traditionally paved specimens exhibits the “cold and hot combination.” In this case, the interlayer bonding effect is provided primarily by the tacky coat oil; thus, achieving good extrusion effect of the aggregate between asphalt layers is difficult. In contrast, the interlayer contact of the doublelayer paved specimens exhibits the “hot and hot combination.” In this case, the extrusion effects between the asphalt layers are significant, merging the surface and bottom layers’ asphalt mixtures into one and facilitating the formation of a structural skeleton. These are the primary reasons for the better bending resistance of the doublelayer paved specimens.
3.2. Bending Fatigue Test
Figure 5 shows the fatigue test process for doublelayer paved beam specimens.
(a)
(b)
(c)
(d)
The maximum and minimum load stresses were calculated based on the data presented in Table 4. Subsequently, the fatigue life of the specimens was tested. Table 5 gives the results of the bending fatigue test of specimens produced with different paving technologies, mixture types, and pavement structure thicknesses. Note that the hoe beam replicates were used per material per test condition.

Table 5 reveals that the coefficient of variation () of the fatigue test results is around 10%, which indicates that the test results are stable and reliable. Moreover, Table 5 also shows that the fatigue life of doublelayer paved or traditionally paved beam specimens decreases as the stress levels increase. Furthermore, it is noteworthy that the fatigue test results of the specimens are not the same even when the stress levels are the same. In this case, it is difficult to analyze the fatigue data and accurately evaluate which pavement structure combination or paving technology is better.
Recently, some road researchers have successfully applied the Weibull distribution to the fatigue life analysis and observed that such distribution was particularly useful for analyzing the reliability of fatigue life [44, 45]. Therefore, the Weibull distribution was used to analyze the fatigue test data of doublelayer beam specimens in this study.
The equivalent fatigue life and failure probability (P) conform to the following equation [38, 39, 46]:
Equation (1) can be transformed into the following equation after using the logarithmic transformation:where m_{0} is the shape parameter, , and u is the scale parameter.
Substituting the fatigue test results that are presented in Table 5 into the Weibull distribution model (equation (2)), its coefficients such as m_{0}, ln u, and R^{2} are as given in Table 6.

From Table 6, it is observed that the values of R^{2} of the Weibull distribution model are greater than 0.90. These observations indicate that the fatigue test results examined by the Weibull distribution model are reliable.
3.3. Fatigue Equation
Table 7 shows the equivalent fatigue life () of the doublelayer beam specimens under different stress levels (S) and failure probabilities (P) after substituting the coefficients (given in Table 6) into the Weibull distribution model (equation (2)).
The relation between the fatigue life and stress level is shown as follows [38, 39, 46]:where N is the fatigue life of the specimens, S is the stress level used in the fatigue test, and a and b are the coefficients of the fatigue equation.
The value of a represents the intercept on the longitudinal axis of the fatigue equation coordinate axis, reflecting the fatigue performance of the specimens; the larger the value of a, the better the fatigue performance of the specimens. The value of b represents the absolute value of the slope of the fatigue equation, reflecting the sensitivity of the fatigue performance of the specimens to the change in the stress level; the smaller the value of b, the lower the sensitivity of the fatigue performance of the specimens to the change in the stress level [39, 46].
From equation (3) and combinations using the values in Table 7, the fatigue equations of the doublelayer beam specimens were established using regression analysis. Table 8 lists regression coefficients a, b, and R^{2} of equation (3).


Table 8 reveals that the correlation coefficients R^{2} of the fatigue equations of the specimens produced with different structure combinations and paving technologies are not less than 0.97. These results indicate that a good double logarithmic linear relationship exists between the stress level and fatigue life.
3.4. Analysis of Influence Factors of Fatigue Property
3.4.1. Fatigue Life Analysis
Various studies indicate that the tensile stress level generated by the traffic load appearing on an asphalt pavement is generally less than 0.45 [47]. Therefore, in this study, the fatigue life of the specimens was analyzed under the stress level of 0.45. However, the ratio of the applied load to the material failure strength is defined as the stress level. Therefore, a comparison between fatigue lives under the same stress level cannot accurately reveal the fatigue properties of different materials.
Table 4 reveals that when the stress level is 0.45, the load (F) of the traditionally paved combination of 4cm AC13 surface layer/6cm AC20 bottom layer is 4.15 kN (F = 0.45 × 9.23 kN = 4.15 kN). Therefore, the evaluation of the fatigue life of specimens with different paving technologies, mixture types, and pavement structure thicknesses under the same load of 4.15 kN is more reasonable. Table 9 gives the results of the fatigue life of specimens based on the same load.

3.4.2. Effects of Paving Technology
The ratio (N_{d}/N_{t}) of the fatigue life of the specimens with the same mixture types and structure thicknesses produced by the doublelayer and traditional paving technologies is plotted in Figure 6.
(a)
(b)
Figure 6 indicates that under the load of F = 4.15 kN, the fatigue life of the specimens produced by the doublelayer paving technology is increased by at least 54% compared with that produced by the traditional paving technology. This is because for the doublelayer paving technology, the surface and bottom layers’ asphalt mixture is the “hot and hot combination” during compaction. In this case, the aggregate between the surface and bottom layers’ asphalt mixture can form an interlocking joint to avoid discontinuity between the asphalt layers. Thus, the integrity of this pavement structure is better, the stress concentration generated by the wheel load is reduced, and the fatigue property of the asphalt pavement is improved.
3.4.3. Effects of Mixture Types and Structural Thicknesses
Figure 7 shows the ratio (N_{t}/N_{c}) of the fatigue life of specimens with different pavement structure combinations produced by the traditional paving technology to that of the pavement structure combination of the 4cm AC13 surface layer/6cm AC20 bottom layer produced by the same paving technology.
(a)
(b)
Figure 7 shows that compared with that of the traditionally paved typical pavement structure (4cm AC13 surface layer/6cm AC20 bottom layer), the fatigue life of the traditionally paved pavement structure combination of 3cm AC13 surface layer/7cm AC20 bottom layer can be increased by at least 8%, whereas the fatigue lives of other traditionally paved pavement structures are reduced significantly.
Furthermore, the ratio (N_{d}/N_{c}) of the fatigue life of specimens with different pavement structure combinations produced by the doublelayer paving technology to that of the pavement structure combination of 4cm AC13 surface layer/6cm AC20 bottom layer produced by the traditional paving technology, is shown in Figure 8.
(a)
(b)
Figure 8 shows that compared with that of the pavement structure combination of 4cm AC13 surface layer/6cm AC20 bottom layer produced by the traditional paving technology, the fatigue life of all doublelayer pavement structures is improved. The fatigue life of the doublelayer pavement structure of the 3cm AC13 surface layer/7cm AC20 bottom layer combination can be increased by at least 114%.
Figure 8 also shows that under the same structural thickness and with the doublelayer paving technology, the fatigue life of the pavement structure combination of AC13 surface layer/AC20 bottom layer is higher than those of the AC16 surface layer/AC20 bottom layer and AC16 surface layer/AC25 bottom layer pavement structure combinations. Under the same test conditions, the fatigue life of the asphalt mixture decreases with an increase in the VV of the asphalt mixture; the larger the VV, the smaller the fatigue life of the asphalt mixture [48–50]. The surface layer of the combination of the AC13 surface layer/AC20 bottom layer is the AC13 asphalt mixture, whereas the bottom layer is the same as that in the AC16 surface layer/AC20 bottom layer combination. Thus, the relatively smaller VV (Table 3) of the AC13 asphalt mixture compared with that of the AC16 asphalt mixture can effectively hinder the expansion of cracks, thereby improving the fatigue properties of the mixtures [48, 49]. Moreover, the VVs of the surface layer and bottom layers’ asphalt mixtures of the AC13 surface layer/AC20 bottom layer combination are smaller than those the pavement structure combination of the AC16 surface layer/AC25 bottom layer, thereby relieving the stress concentration of the asphalt pavement and the development of cracks and indicating better fatigue properties [48, 49].
Furthermore, as shown in Figure 8, for the mixturetype combination of AC13 surface layer/AC20 bottom layer, the fatigue life of the thickness combination of 3cm surface layer/7cm bottom layer is longer than that of the thickness combination of the 4cm surface layer/6cm bottom layer. The thickness values of the bottom layer asphalt mixture affect the antifatigue cracking ability of the pavement [51, 52]. When the mixture types are the same, increasing the thickness of the bottom layer can effectively improve the fatigue performance of the doublelayer pavement [52]. This is the primary reason why the pavement structure combination of 3cm surface layer/7cm bottom layer demonstrates better fatigue resistance than that of the 4cm surface layer/6cm bottom layer structure combination.
4. Conclusions
In this study, the effects of paving technologies, pavement materials, and structures on the fatigue properties of a doublelayer asphalt pavement were investigated. The following conclusions are obtained from the results:(1)The asphalt mixture specimens produced by the doublelayer paving technology with the same mixture types and pavement structure thicknesses exhibit higher flexural strength and fatigue life than those produced by the traditional paving technology.(2)The bending beam fatigue test shows high practicality, repeatability, and data consistency. The fatigue life of the doublebeam mixture specimens obeys the Weibull distribution and the fatigue equations with different paving technologies, mixturetype combinations, and pavement structural thicknesses effectively reflect the fatigue life of the combination specimens.(3)The fatigue life of the 3cm surface layer/7cm bottom layer pavement structure combination is better than that of the pavement structure combination of 4cm surface layer/6cm bottom layer when the mixturetype combinations are identical.(4)The doublelayer pavement with 3cm AC13 surface layer and 7cm AC20 bottom layer combination is applicable to the field and industry and will be effective in improving the fatigue property of asphalt pavements.
Compared with the traditionally paved typical pavement structure (4cm AC13 surface layer/6cm AC20 bottom layer), the 3cm AC13 surface layer/7cm AC20 bottom layer with doublelayer paving technology not only saves the asphalt binder (the asphalt content used in AC13 is higher than that of the AC20) and tacky coat oil but also improves the durability of asphalt pavements. Thus, the cost of construction and maintenance of asphalt pavements are obviously lower. Finally, the current study was focused primarily on the effects of paving technologies, pavement materials, and structures on the fatigue properties of doublelayer asphalt pavements. Accordingly, our future study will explore their effects on the lowtemperature anticracking performance of asphalt pavements.
Data Availability
The data used to support the findings of this study are included within the article.
Conflicts of Interest
The authors declare that they have no conflicts of interest.
Acknowledgments
This research was supported by the Scientific Project from Zhejiang Provincial Communication (Grant No. 2015J23), Scientific Project from Henan Provincial Communication (Grant No. 2020J22), and Scientific Research of Central Colleges of China for Chang’an University (Grant No. 300102218212).
References
 J. B. Sousa, J. C. Pais, M. Prates, R. Barros, P. Langlois, and A.M. Leclerc, “Effect of aggregate gradation on fatigue life of asphalt concrete mixes,” Transportation Research Record: Journal of the Transportation Research Board, vol. 1630, no. 1, pp. 62–68, 1998. View at: Publisher Site  Google Scholar
 S. Bhattacharjee, J. S. Gould, R. B. Mallick, and F. Hugo, “An evaluation of use of accelerated loading equipment for determination of fatigue performance of asphalt pavement in laboratory,” International Journal of Pavement Engineering, vol. 5, no. 2, pp. 61–79, 2004. View at: Publisher Site  Google Scholar
 D. H. Timm and D. E. Newcomb, “Perpetual pavement design for flexible pavements in the US,” International Journal of Pavement Engineering, vol. 7, no. 2, pp. 111–119, 2006. View at: Publisher Site  Google Scholar
 J. Žák, C. L. Monismith, and D. Jarušková, “Consideration of fatigue resistance tests variability in pavement design methodology,” International Journal of Pavement Engineering, vol. 16, no. 1, pp. 91–96, 2015. View at: Publisher Site  Google Scholar
 F. Tang, T. Ma, Y. Guan, and Z. Zhang, “Parametric modeling and structure verification of asphalt pavement based on BIMABAQUS,” Automation in Construction, vol. 111, Article ID 103066, 2020. View at: Publisher Site  Google Scholar
 F. Tang, T. Ma, J. Zhang, Y. Guan, and L. Chen, “Integrating threedimensional road design and pavement structure analysis based on BIM,” Automation in Construction, vol. 113, Article ID 103152, 2020. View at: Publisher Site  Google Scholar
 Y. Chen, G. Tebaldi, R. Roque, and G. Lopp, “Effects of trackless tack interface on pavement topdown cracking performance,” Procedia—Social and Behavioral Sciences, vol. 53, no. 3, pp. 432–439, 2012. View at: Publisher Site  Google Scholar
 J. Wang, F. Xiao, Z. Chen, X. Li, and S. Amirkhanian, “Application of tack coat in pavement engineering,” Construction and Building Materials, vol. 152, pp. 856–871, 2017. View at: Publisher Site  Google Scholar
 T. Chen, Y. Luan, T. Ma, J. Zhu, X. Huang, and S. Ma, “Mechanical and microstructural characteristics of different interfaces in cold recycled mixture containing cement and asphalt emulsion,” Journal of Cleaner Production, vol. 258, Article ID 120674, 2020. View at: Publisher Site  Google Scholar
 T. Chen, T. Ma, X. Huang, S. Ma, F. Tang, and S. Wu, “Microstructure of synthetic composite interfaces and verification of mixing order in coldrecycled asphalt emulsion mixture,” Journal of Cleaner Production, vol. 263, Article ID 121467, 2020. View at: Publisher Site  Google Scholar
 J. Zhu, T. Ma, J. Fan, Z. Fang, T. Chen, and Y. Zhou, “Experimental study of high modulus asphalt mixture containing reclaimed asphalt pavement,” Journal of Cleaner Production, vol. 263, Article ID 121447, 2020. View at: Publisher Site  Google Scholar
 H. Ziari and M. M. Khabiri, “Interface condition influence on prediction of flexible pavement life,” Journal of Civil Engineering and Management, vol. 13, no. 1, pp. 71–76, 2007. View at: Publisher Site  Google Scholar
 S. Shieldscook and P. C. Taylor, “Working a double life: twolift paving makes a comeback in the US,” Roads Bridges, vol. 47, pp. 32–35, 2009. View at: Google Scholar
 J. Hu, D. W. Fowler, M. S. Siddiqui, and D. P. Whitney, “Feasibility study of twolift concrete paving,” Tech. Rep., US Department of Transportation, Washington, DC, USA, 2014, Technical report FHWA/TX14/067491. View at: Google Scholar
 Y. L. Wang, Z. Q. Zhang, and B. G. Wang, “Performance of asphalt concrete pavement with doublelayer paving technology,” Journal of China and Foreign Highway, vol. 27, no. 6, pp. 66–70, 2007, in Chinese. View at: Google Scholar
 Y. Q. An, “The technology of double deck paving of asphalt pavement,” in Proceedings of the 2nd International Conference on Material Engineering and Application (ICMEA), Wuhan, China, 2015. View at: Google Scholar
 China Communications Press, Ministry of Transport of the People’s Republic of China, Technical Specifications for Construction of Highway Asphalt Pavements (JTG F402004), China Communications Press, Beijing, China, in Chinese.
 F. Z. Shi, “Study on the double layer continuous paving technology of Asphalt pavement,” Chang’an University, Xi’an, China, 2006, Ph.D. dissertation. View at: Google Scholar
 S. Großmann, T. Weyrauch, S. Saal, and W. Haase, “Internal electrical field distribution in double layer polymer stacks as studied by electroabsorption,” Optical Materials, vol. 9, no. 1–4, pp. 236–239, 1998. View at: Publisher Site  Google Scholar
 S. Mueller, “Compact asphalt–advantages and disadvantages of a new technology, choice for sustainable development,” in Proceedings of the 23rd PIARRC World Road Congress, Paris, France, September 2007. View at: Google Scholar
 P. A. Morgan, R. E. Stait, S. Reeves, and M. Clifton, The Feasibility of Using TwinLayer Porous Asphalt Surfaces on England’s Strategic Road Network, Transport Research Laboratory, Wokingham, UK, 2007.
 T. P. Füleki, “Improving pavement performance by compactasphalt technology,” Pollack Periodica, vol. 4, no. 3, pp. 111–120, 2009. View at: Publisher Site  Google Scholar
 T. Kuennan, “One and one is one,” Better Roads, vol. 80, no. 9, pp. 12–21, 2010. View at: Google Scholar
 L. F. Wang, “Study on shear performance of double pavement pavement,” Highway Automotive and Applation, vol. 4, pp. 82–85, 2010, in Chinese. View at: Google Scholar
 C. Gharabaghy, P. Arnold, K. Scharnigg, and C. Schulze, StateoftheArt Experience in the Use of the Compact Asphalt Paver for the Construction of ThinBed Low Noise OpenPored 2course Asphalt Surfacings: StateoftheArt Technology and Practice in the Netherlands and Germany, Aachen Institute for Highway/RWTH Aachen, Aachen, Germany, 2010.
 Y. Li, “Analysis of economy of heattoheat paving technique for asphalt pavement,” Road Machinery and Construction Mechanization, vol. 28, no. 8, pp. 54–60, 2011, in Chinese. View at: Google Scholar
 J. Liu, S. Saboundjian, P. Li, B. Connor, and B. Brunette, “Laboratory evaluation of sasobitmodified warmmix asphalt for alaskan conditions,” Journal of Materials in Civil Engineering, vol. 23, no. 11, pp. 1498–1505, 2011. View at: Publisher Site  Google Scholar
 C. H. Wang, K. Mu, J. J. Zhao, and X. C. Wang, “Heat losing and effective compacting time of double layer spreading pavement,” Journal of Chang’an University (Natural Science Edition), vol. 33, no. 5, pp. 7–12, 2013, in Chinese. View at: Google Scholar
 Y. H. Yang, Y. P. Ren, and X. C. Wang, “Fatigue performance of asphalt surface layers in doublelayer paving system,” Journal of Building and Materials, vol. 18, no. 3, pp. 458–463, 2015, in Chinese. View at: Google Scholar
 Y. J. Jiang, H. W. Lin, J. S. Xue, Z. C. Han, and Z. J. Chen, “Influences of pavement material and structure on the hightemperature stability of doublelayer pavements,” Journal of Materials in Civil Engineering, vol. 32, no. 3, Article ID 4020020, 2020. View at: Publisher Site  Google Scholar
 L. F. Walubita, “Comparison of fatigue analysis approaches for predicting fatigue lives of hotmix asphalt concrete (HMAC) mixtures,” Texas A&M University, College Station, TX, USA, 2006, Ph.D. dissertation. View at: Google Scholar
 L. F. Walubita, G. S. Simate, E. OforiAbebresse, A. E. Martin, R. L. Lytton, and L. E. Sanabria, “Mathematical formulation of HMA crack initiation and crack propagation models based on continuum fracturemechanics and workpotential theory,” International Journal of Fatigue, vol. 40, pp. 112–119, 2012. View at: Publisher Site  Google Scholar
 L. F. Walubita, “The overlay tester: a sensitivity study to improve repeatability and minimize variability in the test results,” Tech. Rep., Texas Transportation Institute, College Station, TX, USA, 2012, Technical Research Report# FHWA/TX12/066071. View at: Google Scholar
 L. F. Walubita, A. N. Faruk, and Y. Koohi, “The overlay tester (OT): comparison with other crack test methods and recommendations for surrogate crack tests,” Tech. Rep., TTI—Texas A&M University System, College Station, TX, USA, 2013, Technical Research Report# FHWA/TX12/066072. View at: Google Scholar
 L. F. Walubita, A. N. M. Faruk, A. E. Alvarez, and T. Scullion, “The Overlay Tester (OT): using the fracture energy index concept to analyze the OT monotonic loading test data,” Construction and Building Materials, vol. 40, pp. 802–811, 2013. View at: Publisher Site  Google Scholar
 L. F. Walubita, B. P. Jamison, G. Das et al., “Search for a laboratory test to evaluate crack resistance of hotmix asphalt,” Transportation Research Record: Journal of the Transportation Research Board, vol. 2210, no. 1, pp. 73–80, 2011. View at: Publisher Site  Google Scholar
 L. F. Walubita and A. E. Martin, “Laboratory fatigue characterization of asphalt mixtures using the flexural bending beam fatigue test,” in Proceedings of the Athens 2007 International Conference: Advanced Characterization of Pavements and Soil Engineering Materials, Athens, Greece, 2007. View at: Google Scholar
 J. Xue and Y. Jiang, “Analysis on the fatigue properties of vertical vibration compacted limefly ashstabilized macadam,” Construction and Building Materials, vol. 155, pp. 531–541, 2017. View at: Publisher Site  Google Scholar
 Y. Jiang, C. Deng, J. Xue, H. Liu, and Z. Chen, “Investigation of the fatigue properties of asphalt mixture designed using vertical vibration method,” Road Materials and Pavement Design, vol. 21, no. 5, pp. 1454–1469, 2020. View at: Publisher Site  Google Scholar
 A. A. Tayebali, J. A. Deacon, and C. L. Monismith, “Development and evaluation of dynamic flexural beam fatigue test system,” Transportation Research Record: Journal of the Transportation Research Board, vol. 1545, no. 1, pp. 89–97, 1996. View at: Publisher Site  Google Scholar
 X. Shu, B. Huang, and D. Vukosavljevic, “Laboratory evaluation of fatigue characteristics of recycled asphalt mixture,” Construction and Building Materials, vol. 22, no. 7, pp. 1323–1330, 2008. View at: Publisher Site  Google Scholar
 L. F. Fan, L. N. Y. Wong, and G. W. Ma, “Experimental investigation and modeling of viscoelastic behavior of concrete,” Construction and Building Materials, vol. 48, no. 48, pp. 814–821, 2013. View at: Publisher Site  Google Scholar
 L. F. Fan, Z. J. Wu, Z. Wan, and J. W. Gao, “Experimental investigation of thermal effects on dynamic behavior of granite,” Applied Thermal Engineering, vol. 125, pp. 94–103, 2017. View at: Publisher Site  Google Scholar
 B. W. Jo, S. Chakraborty, M. A. Sikandar, and Y. S. Lee, “Prediction of the failure stress of hydrogenrich water based cement mortar using the Weibull distribution model,” KSCE Journal of Civil Engineering, vol. 22, no. 5, pp. 1827–1839, 2018. View at: Publisher Site  Google Scholar
 G. Murali, R. Gayathri, V. R. Ramkumar, and K. Karthikeyan, “Two statistical scrutinize of impact strength and strength reliability of steel fibrereinforced Concrete,” KSCE Journal of Civil Engineering, vol. 22, no. 1, pp. 257–269, 2017. View at: Publisher Site  Google Scholar
 Y. Jiang, C. Deng, J. Xue, and Z. Chen, “Investigation into the performance of asphalt mixture designed using different methods,” Construction and Building Materials, vol. 177, pp. 378–387, 2018. View at: Publisher Site  Google Scholar
 J. Sun, “Research on fatigue cracking prediction model of asphalt mixture based on stress control model,” South China University of Technology, Guangzhou, China, 2010, M.D. thesis. View at: Google Scholar
 S. AboQudais and I. Shatnawi, “Prediction of bituminous mixture fatigue life based on accumulated strain,” Construction and Building Materials, vol. 21, no. 6, pp. 1370–1376, 2007. View at: Publisher Site  Google Scholar
 G. Valdés, F. PérezJiménez, and A. Martínez, “Effect of temperature and asphalt mixture type on the fatigue behaviour of flexible pavements,” Revista de la construcción, vol. 11, no. 1, pp. 87–100, 2012. View at: Publisher Site  Google Scholar
 D. Han, L. Wei, and J. Zhang, “Experimental study on performance of asphalt mixture designed by different method,” Procedia Engineering, vol. 137, pp. 407–414, 2016. View at: Publisher Site  Google Scholar
 B. Radovskiy, “Analytical formulas for film thickness in compacted asphalt mixture,” Transportation Research Record, vol. 1829, no. 1, pp. 26–32, 2003. View at: Publisher Site  Google Scholar
 H. Wen, “Development of a damagebased phenomenological fatigue model for asphalt pavement,” Journal of Materials in Civil Engineering, vol. 25, no. 8, pp. 1006–1012, 2012. View at: Google Scholar
Copyright
Copyright © 2020 Changqing Deng et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.