Construction and Building Materials 25 (2011) 3117–3122

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Construction and Building Materials

journal homepage: www.elsevier .com/locate /conbui ldmat

Performance evaluation of a lightweight epoxy asphalt mixture for basculebridge pavements

Zhendong Qian a,⇑, Leilei Chen a, Chenlong Jiang b, Sang Luo a

a Intelligent Transport System Research Center, Southeast University, Nanjing 210096, Chinab T.Y.Lin International Engineering Consulting (China) Co., Ltd., Chongqing 401121, China

a r t i c l e i n f o a b s t r a c t

Article history:Received 11 July 2010Received in revised form 13 November 2010Accepted 20 December 2010

Keywords:Lightweight epoxy asphalt mixtureBascule bridgePerformance evaluationLaboratory testsFinite element modelMaterial propertiesStructural performance

0950-0618/$ - see front matter � 2010 Elsevier Ltd. Adoi:10.1016/j.conbuildmat.2010.12.030

⇑ Corresponding author. Tel./fax: +86 25 83792868E-mail addresses: qianzd@seu.edu.cn (Z. Qian), Ch

jcdragon123@163.com (C. Jiang), luosangseu@gmail.c

This paper proposes a lightweight epoxy asphalt mixture (LEAM) for pavement on bascule bridges. Thematerial properties of LEAM are evaluated with the Marshall test, indirect tensile test, wheel trackingtest, and bending beam test. Moreover, the structural performance of LEAM is evaluated by a finite ele-ment numerical analysis for a bascule bridge with LEAM pavement. Test results show that the LEAM has agood resistance to moisture damage, permanent deformation, and low-temperature cracking. The LEAMwith a 70% lightweight aggregate replacement percentage has been found to have the best effect on dead-weight reduction as well as the other performance measures. Moreover, the analytical result shows thatLEAM can reduce pavement stress significantly when compared to an epoxy asphalt mixture, which indi-cates that the LEAM has a good structural performance.

� 2010 Elsevier Ltd. All rights reserved.

1. Introduction

The bascule bridge is considered to be one of the most appropri-ate bridges for ports and inland rivers from a structural and an eco-nomic viewpoint, therefore many have been built all over theworld [1]. However, the bridge’s opening process puts its pave-ment in a critical stress state, this may lead to a service life de-crease of the bridge, for the pavement is a key structural layerthat protects the bridge deck against moisture and provides highservice quality and skid resistance [2]. In this case, certain mea-sures should be taken to keep the pavement healthy, among whichthe adopting of new pavement material is an effective way. Epoxyasphalt concrete has been proven to be a good material for steeldeck pavements [3], and an initial analysis of bascule bridge pave-ment shows that reducing the deadweight of the bascule bridgepaving material can lead to an improved stress state [1]. Therefore,lightweight epoxy asphalt concrete is under consideration as a bas-cule bridge pavement material.

Lightweight asphalt concrete was first studied in the 1950s inthe USA [4–5], and the first lightweight asphalt concrete designguide was established for highway pavement in 1998 [6]. It iswidely acknowledged that lightweight asphalt concrete has good

ll rights reserved.

.enleilei@seu.edu.cn (L. Chen),om (S. Luo).

skid resistance and durability. However, there is no report of light-weight asphalt concrete having been used in steel bridge pavementbecause of its high requirements for the material performancewhen compared to the highway pavement. However, it was re-cently shown that epoxy asphalt concrete was used successfullyas steel deck pavement material in China. Moreover, many studiesof the performance of epoxy asphalt mixture (EAM), where it wastested and evaluated in different ways, have proven it to be a betterpavement material than conventional asphalt mixture [7–8].Therefore, the lightweight aggregate (LWA) was mixed with epoxyasphalt and normal weight aggregate to produce a new lightweightasphalt mixture for bascule bridge pavement.

Previous research has focused on either normal epoxy asphaltconcrete or lightweight aggregate concrete and few studies canbe found on the lightweight epoxy asphalt mixture (LEAM). There-fore, the primary objective of this study is to develop and evaluatea LEAM for bascule bridge pavement. First, the development of theLEAM is proposed, and then a series of laboratory tests are pre-sented to evaluate its material properties. A finite element numer-ical analysis for a typical bascule bridge with a LEAM pavement isfollowed to evaluate the structural performance of the LEAM.

2. Development of the LEAM

The normal epoxy asphalt mixture is produced by mixing theepoxy asphalt and the normal weight aggregate. The LEAM used

3118 Z. Qian et al. / Construction and Building Materials 25 (2011) 3117–3122

in this study is developed by replacing part of the normal weightaggregate in the EAM with lightweight aggregate.

The normal weight aggregate in the epoxy asphalt mixture usu-ally uses basalt. However, the aggregate is mined from a mountain,which is an environmentally destructive process. Therefore,ceramisite was selected as the LWA used in the LEAM because, inaddition to its light weight and good performance, it is an eco-friendly material produced from industrial waste.

2.1. Raw materials

As mentioned above, the LEAM is composed of epoxy asphaltbinders, fillers, and graded aggregates, which include the normalaggregates and LWA. The binder used here is the 2910-typedomestic epoxy asphalt, the fillers and normal aggregate are thelimestone powder and basalt aggregate for steel bridge pavement,and the LWA is ceramisite. Details of the materials are presented inTables 1–4.

2.2. Replacement percentage

In order to determine the optimum replacement percentage ofLWA in the LEAM, LEAM with 0%, 15%, 25%, 40%, and 70% LWAs

Table 1Technical index of 2910-type domestic epoxy asphalt.

Technical indexes Measured value Criteria Test method

Mass ratio (A:B) 100:290 100:290Tensile strength (23 �C, Mpa) 3.26 P2.0 ASTM D 638Fracture elongation (23 �C, %) 242 P200 ASTM D 638Viscosity from 0 to 1 Pa s (min) 110 P50 JTJ052–2000

Table 2Technical index of the basalt aggregate.

Technical indexes Measuredvalue

Criteria Test method

Compressive strength(MPa)

140 P120 JTG E41-2005(T0221-2005)

Los Angeles abrasionvalue (%)

11.5 622.0 JTG E42-2005(T0317-2005)

Crushing value (%) 8.9 612 JTG E42-2005(T0316-2005)

Apparent density (g/cm3) 2.91 P2.65 JTG E42-2005(T0304-2005)

Table 3Technical index of the limestone powder.

Technical indexes Measuredvalue

Criteria Test method

Density (g/cm3) 2.703 P2.500 JTG E42-2005(T0352-2005)

Hydrophilic coefficient(%)

0.63 61 JTG E42-2005(T0353-2005)

Plasticity index (%) 3.2 4.0 JTG E42-2005(T0354-2005)

Table 4Technical index of the lightweight aggregate.

Technical Indexes Measured value Criteria

Particle size range (mm) 5–10 –Density degree (kg/m3) 890 600–900Cylinder compressive strength (Mpa) 7.3 P6.5Water absorption (%) 3.6 68Mud content (%) 1.2 62

by weight were prepared for tests, based on the properties ofceramisite and the earlier research with lightweight asphalt con-crete [9–10], where it was shown that 70% LWA was the largestpercentage that could be reached due to the particle size of ceram-isite. The LEAM with 0% LWA is actually the normal epoxy asphaltmixture for comparison.

3. Experimental programs

3.1. Asphalt content

The Marshall mix design procedure was employed to design the LEAM. Theoptimum asphalt contents of LEAM with different LWA replacement percentagesare listed in Table 5. It was found that the asphalt absorption ratio increases withthe increased replacement percentage. The reason is that with the LWA replace-ment percentage increasing, the filler decreases and the air void of the mixture en-larges, and more binder is needed to fill the void. Based on the optimum asphaltcontent selected, the performances of the LEAM were tested through the followingexperimental programs.

3.2. Marshall test

Air void, strength, and flow value are three main indices of steel bridge deckpaving materials [3]. In this sense, the Marshall test was adopted to test the mainindices of LEAM and the results are reported in Table 5. It was observed that theflow value of LEAM decreases with increasing LWA replacement percentage, indi-cating that the LEAM is more brittle than the EAM and that the LEAM becomes morebrittle with a larger LWA replacement percentage. On the other hand, stability doesnot vary a lot among the LEAM specimens with different LWA replacement percent-ages. It is also observed that with the growing LWA replacement percentage, thedensity of the LEAM decreases. What is more, the LEAM with a 70% LWA replace-ment percentage has the smallest density, which is only about 70% of EAM’sdensity.

3.3. Indirect tensile test

One of the major distresses observed in bridge deck pavements is moisture-induced cracking. Considering that tensile strength is an important measure toevaluate the cracking resistance of paving material, general principles in ASTMD4867-92 [11] were followed and indirect tensile tests were conducted to evaluatethe moisture susceptibility of the LEAM. Two subsets cylindrical specimens of LEAMwith different LWA replacement percentages were shaped using the Marshall com-pactor. One subset was tested in the indirect tensile mode after a 2 h preservationperiod at 25 �C, and the other was tested after frozen at �18 �C for 16 h, moisture-conditioned for 24 h at 60 �C, and then preserved at 25 �C for 2 h.

The indirect tensile tests of LEAM specimens with and without freeze–thawwere conducted respectively, and the results are presented in Fig. 1, where theresistance of the asphalt mixture to moisture is expressed as a tensile strength ratio(TSR) defined as the tensile strength ratio between specimens with and withoutfreeze–thaw. It is well known that a higher TSR value indicates better resistanceto moisture damage. Departments of Transportation in most countries recommenda TSR value greater than 80%. As shown in Fig. 1, the TSR values of LEAM with dif-ferent LWA replacement percentages do not vary a lot and are all greater than 80%,indicating that the LEAM has a good resistance to moisture.

3.4. Wheel tracking test

In order to evaluate the high temperature performance of the LEAM, wheeltracking tests were conducted at 60 �C. The 300 mm � 300 mm � 50 mm LEAM slabspecimens with different LWA replacement percentages were compacted by a roll-ing compactor. A contact pressure of 700 kPa was applied to the slab specimens,and the wheel passed 42 times per minute at the center of the specimen usingthe wheel tracking tester [12].

Table 5The basic parameters of LEAM.

Replacementpercentage(%)

Asphaltcontent(%)

Asphaltabsorption(%)

Density(kg/m3)

Airvoid(%)

Stability(kN)

Flowvalue(0.1 mm)

0 6.2 0.28 2569 2.5 60.78 47.715 6.3 0.46 2472 2.7 60.82 42.225 7.1 0.75 2316 1.9 60.09 39.140 7.7 0.94 2150 2.4 60.06 40.170 8.6 1.03 1807 2.5 60.46 32.4Criteria – – – 63.0 P40 20�50

50

60

70

80

90

100

0 15 25 40 70Ten

sile

Str

engt

h R

itio

(%

)

LWA Replacing Percentage (%)

Fig. 1. The indirect tensile test result of LEAM.

10000

12000

14000

16000

18000

20000

0 15 25 40 70Dyn

amic

Sta

bilit

y (C

ycle

s/m

m)

LWA Replacing Percentage (%)

Fig. 2. The dynamic stability of LEAM.

Table 6The bending beam test results of LEAM.

Replacementpercentage (%)

Bending strength(Mpa)

Maximumstrain (e)

Bendingmodulus (Mpa)

0 28.5 5.32 � 10�3 535715 23.9 6.20 � 10�3 385825 22.4 8.26 � 10�3 271240 19.3 7.99 � 10�3 241570 16.1 5.84 � 10�3 2757Criteria P10 P2 � 10�3 –

Z. Qian et al. / Construction and Building Materials 25 (2011) 3117–3122 3119

The permanent deformation of the asphalt mixtures were tested and recordedin Fig 2, where dynamic stability (DS) is the index for evaluating the rutting resis-tance of the asphalt mixture, and the rutting resistance is considered to be goodwhen the DS is greater than 3000 cycles/mm. It can be observed that the DSs ofall the LEAM specimens are much larger than 15,000 cycles/mm, and increase withthe LWA replacement percentage, indicating that the LEAM had rather good ruttingresistance. Therefore, the permanent deformation of LEAM can be neglected.

3.5. Bending beam test

To evaluate the resistance to low-temperature cracking, the three-point bend-ing beam test was conducted at �15 �C. The 300 mm � 300 mm � 50 mm LEAMslab specimens with different LWA replacement percentages were compacted usinga wheel tracking compactor and then cut into beams with a size of250 mm � 30 mm � 35 mm. The strain value and bending strength were measuredand recorded by the UTM-25, as shown in Fig. 3 and Table 6.

The data in Table 6 show that the bending strength of LEAM is lower than thatof normal EAM, but the bending strength and maximum strain are much higherthan the criteria for steel bridge deck paving material [13]. This means that theLEAM can meet the resistance to low-temperature cracking of paving material.

(a) The beam specimens (b) The ben

Fig. 3. The bending beam

3.6. Result discussion

The test results show that with increasing LWA replacement percentage, theLEAM becomes more and more brittle, and the dynamic stability becomes greater,while the bending strength become smaller. However, the Marshall strength andthe TSR of the LEAM are not significantly affected by the LWA replacementpercentages.

The test results also show that the LEAM with LWA replacement percentagesfrom 0% to 70% all perform well and satisfy the requirements for steel bridge pave-ments. Since the LEAM with an LWA replacement percentage of 70% has the small-est density, which can reduce deadweight of the pavement about 30% whencompared to EAM, the LEAM with 70% LWA replacement percentage isrecommended.

4. Numerical analysis

4.1. Structure of the model

To investigate the structural performance of the LEAM, a full-scaled three dimensional (3D) finite element model of a 76 m bas-cule bridge paving with LEAM was built using the ADINA program.The dynamic responses of the LEAM pavement during the openingprocess of the bascule bridge were studied. Because of its struc-tural symmetry, a quarter of the bridge was modeled. In order tosimulate the deck pavement precisely, an 8-note 3D solid elementwas employed to model the asphalt pavement, and the steel bridgedeck was simulated by a shell element. Between the shell and solidelements, the rigid links were used to make the pavement and steeldeck deform together. A sensitivity analysis of stress response wasthen conducted to determine the FE mesh size by reducing theelement size gradually until the difference of the calculated stres-ses in the two processes was within 5% [14]. As a result, the criticalstress positions such as ribs were meshed with a fine size of2 cm � 2 cm � 2 cm for each element, and the regions located farfrom critical positions were meshed with coarse element sizes. Inall 21546 elements were used in the FE model as shown in Fig 4.

ding beam test device (c) Fracture section of the LEAM and the EAM

test of the LEAM.

Pavement

Steel DeckU-shaped

rib

Diaphragms

Steel box

Fig. 4. FE model of the quarter bascule bridge.

3σ3σ

1σ

Fig. 5. Dynamic modulus test of the LEAM.

Table 7Geometry and material parameters.

Parameter (mm) Value Parameter Value

Deck thickness 20 Poisson’s ratio of steel 0.3Diaphragms space 3000 Steel elastic modulus (MPa) 210,000Diaphragms thickness 16 Poisson’s ratio of asphalt

concrete0.25

U-shaped Stiffening ribthickness

6 Pavement modulus (MPa) 2000

U-shaped Stiffening rib topwidth

294 Steel density (kg/m3) 7830

U Stiffening rib bottomwidth

171 EAM density (kg/m3) 2620

U Stiffening rib height 251 LEAM density (kg/m3) 1800Distance between U-ribs 500 Damping coefficient a 0.03436Pavement thickness 40 Damping coefficient b 0.00290

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4.2. Material model

4.2.1. Stiffness modulusThe LEAM is a viscoelastic–plastic material, similar with most

other asphalt mixture, and its stiffness modulus is affected signif-icantly by temperature and loading frequency. In order to simulatethe behavior of the pavement more accurately, the dynamic mod-ulus of the LEAM was tested for the dynamic opening process forthe bascule bridge.

The Simple Performance Test was employed to determine thedynamic modulus of the LEAM [15–16]. The test was conductedat four different temperatures (4 �C, 20 �C, 40 �C, 60 �C) and nine

(1) Frequency 3.279HzVertical bending

(2) Frequency 3.609H

Fig. 6. The vibration beha

different frequencies (0.1 Hz, 0.2 Hz, 0.5 Hz, 1 Hz, 2 Hz, 5 Hz,10 Hz, 20 Hz, 25 Hz) respectively, following the procedure as sta-ted in NCHRP 1–37A [17], as shown in Fig. 5.

The bascule bridge is required to open to an 85�angle at a con-stant speed within five minutes, so the rotation velocity is about0.3�/s. According to the relationship between the frequency f andangular frequency x, i.e., x = 2pf, the loading frequency is about8.333 � 10�4 Hz.

To obtain the stiffness modulus of the LEAM under the actual fre-quency, the master curve of the dynamic modulus at a reference tem-perature of 20 �C was constructed using the time–temperaturesuperposition principle based on the Williams–Landel–Ferry equation[18]. The data at different temperatures can be shifted with respect totime until the curves merge into single smooth function. Mathemati-cally, the master curve can be modeled by a sigmoidal function as

log jE�j ¼ dþ a=½1þ ebþcðlog xcÞ� ð1Þ

where xr is the reduced time of loading at the reference frequency(Hz); d is the minimum value of E�; d + a is the maximum value ofE�; b and c are the parameters describing the shape of the sigmoidalfunction.

The shift factor could be rewritten in the following form [19]:

logðxrÞ ¼ logðaðTÞÞ þ logðxÞ ð2Þ

where a(T) is the shift factor as a function of temperature; x is thefrequency of loading at desired temperature (Hz); xr is the reducedfrequency of loading at the reference temperature (Hz); and T is thetemperature of interest (K).

The frequency shift factor is a function of temperature and canbe approximated by a quadratic relationship as:

logðaðTÞÞ ¼ aT2 þ bT þ c ð3Þ

where a (K�2), b (K�1) and c are the coefficients of the second orderpolynomial.

z Rotation (3) Frequency 4.896Hz Rotation

vior of the FE model.

(a) Maximum transversal tensile stress due to different opening angle

(b) Maximum interfacial shear stress due to different opening angle

Fig. 7. Peak stresses in the opening process of the bascule bridge.

Z. Qian et al. / Construction and Building Materials 25 (2011) 3117–3122 3121

A nonlinear optimization was conducted in Matlab software tofind the optimal solutions by minimizing the sum of squares of theerrors between the fitted model and the experimental data [20]. Amaster curve of the LEAM dynamic modulus resulting from the testdata is expressed as follows and depicted in Fig. 5:

log jE�j ¼ 4:5309� 2:4861=½1þ e1:5371þ0:4973ðlog xcÞ� ð4Þ

Based on Eq. (4), the stiffness modulus of the LEAM used in the FEmodel at 20 �C and 8.333 � 10�4 Hz can be estimated, and the resultis 1956.59 MPa. For convenience in calculations, the stiffness mod-ulus can be taken as 2000 Mpa.

4.2.2. Damping parameterRayleigh damping was adopted in this study. The damping ma-

trix can be expressed as a linear combination of the mass and stiff-ness matrices as C = a M + b K. The coefficients a and b areparameters that can be estimated from the equations (5) whentwo mode-damping ratios ni and nj are available.

a ¼ 2ðnixj�njxiÞðx2

j�x2

iÞ xixj

b ¼ 2ðnjxj�nixiÞðx2

j�x2

iÞ

8><>:

ð5Þ

where xi and xj are the frequencies of two known vibration modes(Hz).

In civil engineering, the damping ratio of a bridge is normallyselected in the range from 0.01 to 0.2. To find the natural frequen-cies for a bascule bridge, a modal analysis was conducted using theLanczos iteration method. The analytical results of the first threeorder vibration mode are presented in Fig. 6, in which the large fre-quencies are due to the small main-span and the large stiffness ofthe bascule bridge.

The damping ratio is assumed as 0.01 for the bascule bridge inthe study. Then the damping coefficients a and b can be obtainedaccording to Eq. (6) as 0.03436 and 0.00290, respectively.

4.3. Analytical result

The dynamic analysis during the opening process of the basculebridge was conducted using the FE model. In addition to the LEAMpavement, the EAM pavement was also analyzed for comparison.The structure and the material parameters used in the FE modelare listed in Table 7.

The tensile stress is an important control parameter in the anti-crack design for the steel bridge pavement. The result of the

dynamic analysis indicates that the transversal tensile stress is lar-ger than the vertical tensile stress. The transversal tensile stressesof the LEAM pavement and the EAM pavement are plot in Fig. 7a.The shear stress is another important parameter for pavement de-sign, especially in the design of the bascule bridge. The result of theinterfacial shear stress between the pavement and the bridge deckduring the opening process is present in Fig. 7b.

From the Fig. 7, it can be found that the LEAM pavement and theEAM pavement present similar changing rules in both the maxi-mum transversal tensile stress and the maximum interfacial shearstress due to the increasing opening angles. Meanwhile, both themaximum transversal tensile stress and the maximum interfacialshear stress of the LEAM pavement are smaller than those of theEAM pavement, indicating that the LEAM has a good impact onthe reduction of the pavement stress. Specifically, at the largestopening angle (85�), the maximum transversal tensile stress andthe maximum interfacial shear stress of the LEAM pavement de-crease 12.7% and 15.2%, respectively, when compared to those ofthe EAM pavement.

5. Conclusion

This paper proposes a new asphalt mixture for pavement onbascule bridges, i.e., lightweight epoxy asphalt mixture, and pre-sents a performance evaluation program for the LEAM based onthe laboratory tests and a 3D FE numerical analysis. From thestudy, several conclusions can be drawn as follows.

� The LEAM can be developed by replacing part of the normalaggregate with the lightweight aggregate, and the best impactson the dead weight reduction can be obtained with a LWAreplacement percentage of 70% in weight.� When the LWA replacement percentage increases, the LEAM

becomes more brittle, the dynamic stability becomes greater,while the bending strength becomes smaller. Meanwhile, theMarshall strength and the TSR of the LEAM are not affected sig-nificantly by the LWA replacement percentages.� The LEAM has a good resistance to moisture, permanent defor-

mation and low-temperature cracking, and it can meet therequirements of the steel bridge deck pavement very well.� It is observed from the numerical analysis that the maximum

transversal tensile stress and the maximum interfacial shearstress of the LEAM pavement are significantly smaller thanthose of the EAM pavement, indicating that the LEAM canreduce the pavement stress efficiently.

3122 Z. Qian et al. / Construction and Building Materials 25 (2011) 3117–3122

Acknowledgment

The authors would like to thank the financial support to thisresearch from the Chinese Western Transportation ConstructionTechnology Project of Transportation Ministry (No. 2009318000086)and Specialized Research Fund for the Doctoral Program of HigherEducation (No. 20090092110049).

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