Table 2 Characteristics of Coarse aggregate, Fine aggregate and Filter 300 mm wide, 300 mm long, but vary thichness according to Coarse Fine three times of norminal dimensions of gradation. And for the Items of test Aggregate Aggregate Filter double-deck asphalt concrete, all specimen dimensions are Crushed index values % 20.3 300 mm wide, 300 mm long,but total thichness for each a Los Angeles abrasion loss % 24.1 specimen is the sum combined by the up-layer plus the down-layer respectively according to three times of norminal Specific gravity (20 20 ) 2.732 2.693 2.713 dimensions of gradation. The specimens were maintanced a Water absorption % 1.5 1.9 contant temperatures at 60°C above 5 hours and then tested. Robustness % 9.8 12 Test samples are loaded for a hour at tire contact pressures of 0.7MPa. The travel speed of the wheel move back and forth Contents of soft rock % 3 approximately 42 times per 60 second. Data, which is the Contents of flat and slender particles % 15 average value of four specimens tested, is automatically Contents of less than 0.075mm % 1 2.5 collected and calculated by the computer.The dynamic stability(DS) of samples for asphalt mixtures was calculated by Sand equivalences % 66 62 the formula (1): (t 2 − t1 ) × N × C Sand flow s 31.5 The graphs of three types of aggregate gradation, which meet DS= × C2 (1) d 2 − d1 1requirements of China’s Techincal specifications forconstruction of highway asphalt pavementsare shown in fig.1. Where is DS- the dynamic stability of asphalt mixtures times/mm. d1-deformations corresponding with time t1 =45min mm. d2- deformations corresponding with time t2 =60min mm. C1-revise coefficient for type of tester.It is applied to 1.0 when the tester is droven by the crank and connecting rod mechanism; It is applied to 1.5 when the tester is droven by the chain mechanism. C2- sample coefficient.It is1.0 for the sample being prepared by 300 mm wide, 300 mm long. N- The travel speed of the wheel, it is approximately 42 times /min.2.2 Description of Symbols Used in Paper 3 EXPERIMENTAL RESULTS AND DISCUSSION In order to have a simple and clear description symbols forgrading types, binder types and types of mixtures are defined 3.1 Experimental Resultsrespectively in table 3 and table 4. Experimental results for monolayer and double-deck asphalt Table 3 Types of Gradations and Binders and all their Symbols concrete are respectively shown in Table 5 and Table 6. Grading Types Symbols Binder Types Symbols Table 4 Types of the Mixtures and the Composite Structures and their Symbols Coarse Grading Maximum Conventional Monolayer Asphalt Combination of Double-deck Asphalt Size 31.5mm Gc Bitumen60/80 CB Concrete Structures Concrete Structures Middle Grading Maximum Types of Size 26.5mm Gm Modified Bitumen MB Mixtures Symbols Types of Mixtures Symbols Fine Grading Maximum Super-Viscous Gc with Gc CB Up-layer: Gm CB(60/80) plus Size 16mm Gf Modified Bitumen SVMB CB(60/80) Down-Layer: Gc CB(60/80)2.3 Test Methods Gm CB Up-layer:Gm MB plus Down-Layer: Gc CB(60/80) For simulating research of rut resistance behavior of Gf with Gf CB CB(60/80)HMA the most common type of laboratory equipment to be Gc withused is generally a Loaded wheel testers (LWT).They include MB Gc MBthe Georgia Loaded Wheel Tester (GLWT), Asphalt PavementAnalyzer (APA), Hamburg Wheel Tracking Device(HWTD), Gm MBLCPC (French) Wheel Tracker, Purdue University LaboratoryWheel Tracking Device(PURWheel), and one-third scale Model Gf with MB Gf MBMobile Load Simulator (MMLS3) . In the paper China’sWheel Tracking Tester (Accuracy of deformation sensor is up to Gc SVMB0.01%) similar to GLWT was used. All test was carried out Gm with Gm SVMBaccording to the Standard Specification’s SVMB Gf withmethod,T0719-1993,Standard test Methods of Bitumen and SVMB Gf SVMBBituminous Mixtures for Highway Engineering. All specimendimensions for the monolayer asphalt concrete are respectively Authorized licensed use limited to: IEEE Xplore. Downloaded on April 30,2011 at 20:19:33 UTC from IEEE Xplore. Restrictions apply.
Table 5 Experimental Results for the Monolayer Asphalt Concrete structures 1 s1 t1 y1 Types of Asphalt 1 s2 t2 y2 Concrete Gc CB 1087 3.86 0.0386 5.2 1 s3 t3 y3 Gc MB 4400 9.6 0.0096 6.7 1 s4 t4 ˆ k0 y4 Gc SVMB 4440 10.5 0.0095 5.65 Gm CB 1189 6.53 0.0353 5.4 1 s5 t5 ˆ ˆ y5 Gm MB 3280 12.8 0.0128 7.84 X= k = k1 Y= Gm SVMB 4200 10.55 0.01 6.75 1 s6 t6 y6 ˆ k2 Gf CB 868 4.84 0.0484 7.9 1 s7 t7 y7 Gf MB 2832 14.8 0.0148 12.18 Gf SVMB 3360 12.55 0.0125 4.76 1 s8 t8 y8Table 6 Experimental Results for the Double-deck Asphalt Concrete structures 1 s9 t9 y9 Combined by the Different Asphalt Mixtures 1 s10 t10 y10 Combination of Asphalt Concrete Structures ˆ ˆ k =X/Y; Y=X k . Gm CB+ Gc CB 630.5 6.67 0.0667 12.4 Y =the DS’s or the RD’s of double-deck asphalt concrete. Gm MB+ Gc CB 1832 12.9 0.0229 3.6 X1 =the DS’s or the RD’s of the monolayer down-layer Gm SVMB+ Gc CB 1890 8.22 0.0222 4.3 asphalt concrete. Gm MB+ Gc SVMB 2102 12.5 0.02 7.2 X2 =the DS’ s or the RD’s of the monolayer up-layer asphalt Gm SVMB+ Gc SVMB 2044 12.04 0.0205 4.1 concrete. Calculations based upon experimental data in table 5 and Gf CB+ Gc CB 541.5 7.76 0.0776 14.7 table 6 by (2) can be obtained respectively: Gf MB+ Gc CB 1339 13.1 0.0314 8.1 DSdouble=120.15+0.0501x1+0.4214x2 (3) Gf SVMB+ Gc CB 1443 12.91 0.0291 14.5 RDdouble=4.4447×10-3+0.0896x1+1.5133x2 (4) Gf MB+ Gc SVMB 1451 10.29 0.029 4.8 Gf SVMB+ Gc SVMB 1535 11.28 0.0275 11.2 Where DSdouble =the DS of double-deck asphalt concrete. RDdouble= the RD of double-deck asphalt concrete. 3.2 Discussion The relationship between the experimental value and the 3.2.1 Correlation of the DS or the RD calculating value for the DS’s and for the RD’s obtained respectively by the (3) and the (4) and their residuals are shown Comparing the data in table 5 and in table 6 can know that respectively in fig.2 and in fig. 3.The results indicated that thethe rut resistance behavior of all double-deck asphalt concrete values predicted by the (3) or the (4) have a good linearstructures whether they made up of different HMA or same, are relationship with experimental value whether is for the DS’s orconsiderably poor than that of monolayer asphalt concrete for the RD’s. So we recognize that the (3) and the (4) predictingstructures, for example, the former the DS almost had only half the DS’s or the RD’s of double-deck asphalt concrete with theof that of the latter but the former the RD had an increase of monolayer DS’s or RD’s are reliable and accurate.about 50% than that of the latter, and no exception even though Relationship between experimental value and calculating value for DS (Model A)for a combination of SVMB with coarse aggregate gradation. 2500Results also indicated that if the HMA of upper-layer of 2000 Experimental valuedouble-deck asphalt concrete is same type, using the MB or 1500 y = 1*x - 1.2e-013SVMB binder substituting the CB binder in the lower layer of 1000double-deck asphalt concrete, rut resistance property notimproved markedly. From the data in the table mentioned 500 data 1 linearabove,we can build the relationships of the DS or the RD 0 400 600 800 1000 1200 1400 1600 1800 2000 2200between the double-deck asphalt concrete structures and the Calculating valuedifferent monolayer asphalt concrete structures as the following residualsmodel: 300 Linear: norm of residuals = 554.5275 200 y=k0+k1x1+k2x2 (2) 100 0 -100 ˆ The matrix X, k Y: -200 -300 Where 600 800 1000 1200 1400 1600 1800 2000 Figure 2 The relationship between experimental value and calculating value for the DS and residuals Authorized licensed use limited to: IEEE Xplore. Downloaded on April 30,2011 at 20:19:33 UTC from IEEE Xplore. Restrictions apply.
Relationship between experimental value and calculating value for RD (Model A) but a considerable improvement for the MB or the SVMB. 0.08 Experimental value y = 1*x - 2.7e-017 0.06 0.04 data 1 0.02 linear 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 Calculating value residuals 0.05 Linear: norm of residuals = 0.010101 0 -0.05 0.03 0.04 0.05 0.06 0.07 0.08Figure 3 The relationship between experimental value and calculating value for the RD and residuals3.2.2 Influence of the combination of different asphaltmixtures on rut resistance behavior As showed in Fig.4 and in Fig.5, in the same group whetherit is for the Down-layers or for the up-layers only the types ofbinders change the DS of the pavement structures combined bydifferent asphalt mixtures have quite evident difference. In thesame group when keeping the mixtures of the Down-layers arethe same and the binders of the Up-layer’s mixtures use the 4 SUMMARY AND CONCLUSIONSmodified asphalt substituting the conventional asphalt, the Evaluating the rutting resistance behavior of theenhancement of the DS’s for the double-deck asphalt concrete HMA using the results of wheel tracking test, the DS’s ofare the more evident than that of the DS’s for the double-deck the monolayer asphalt concrete are the evident large thanasphalt concrete when keeping the mixtures of the Up-layers are that of the composite double-deck layer asphalt concrete.the same then using the modified asphalt substitute the This state that the deformation of asphalt concreteconventional asphalt of the Down-layers. This showed that pavement increase with the increase of asphalt concreteusing the high-quality binder in asphalt concrete of the thickness and the DS’s of asphalt concrete pavementUp-layers will develop most-effeteness than that of using the decrease with the decrease of asphalt concrete thickness.high-quality binder in the Down-layers. However, the results in Hence not using the DS’s of the monolayer asphaltFig.6 showed that in the same group when keeping every concrete structures substitutes that of the compositecombination of the double-deck asphalt concrete in the grade multi-layer asphalt concrete as a criterion of controlling rutare the same, the DS’s improvement for the high property binder, of multi-layer asphalt concrete pavement.MB or SVMB, used in the Up-layers and the Down-layers arenot evident than that of only the high property binder, MB or However, utilizing the rutting experimentalSVMB, used in the Up-layers but the CB used in the result of the different types of monolayer asphalt concreteDown-layers . structure we can build a relationship of the differently composite multi-layers asphalt concrete structure with thatFurthermore, as showed in Fig. 7,when in the same group of the different types of monolayer asphalt concretekeeping the mixtures of the Down-layers and the binders of the structure to evaluate the rutting resistance behavour ofUp-layers are the same, only changing the fine grade in the composite multi-layers asphalt concrete structure.Up-layer’s into the middle grade, the DS’s for the double-deckasphalt concrete only have a limited improvement for the CB The high property binder used in Up-layer of Authorized licensed use limited to: IEEE Xplore. Downloaded on April 30,2011 at 20:19:33 UTC from IEEE Xplore. Restrictions apply.
pavement can play the more-effective rutting resistance behavior than used in the Down-layer of pavement. However For all using the high property binder in the Up- layer and the Down-layer at the same time, the rutting resistance property of asphalt concrete structure can not greatly get increasing at a direct proportion to the DS’s of the monolayer asphalt concrete structures . When the fine grade in the Up-layer’s be substituted by the middle grade, the DS’s for the double-deck asphalt concrete can evidently improve for the MB or the SVMB but only have a limited improvement for the CB. Using the asphalt concrete structure of the CB plus course gradation in the Down-layer of pavement,there is a equivalent rutting resistance property but the most cost-effective than using the asphalt concrete structure of the MB or the SVMB plus course gradation in the Down-layer of pavement. References Parker Jr., F., and E. R. Brown, “A Study of Rutting of Alabama Asphalt Pavements” [R],Alabama Department of Transportation,final report for Project 2019-09, Bureau of Research and Development, Montgomery, Alabama, November 1993. Thomas D. White, John E. Hadock, Adam J. T. Hand, Hongbing Fang, “Contributions of Pavement Structional Layers to Rutting of Hot Mix Asphalt Pavements” [R], NCHRP Report 468, Transportation Research Board, National Academy Press, Whashington D.C-2002:1-164. Brown, S. F., and J. M. Gibb, “Validation Experiments for Permanent Deformation Testing of Bituminous Mixtures” [J], Journal of the Association of Asphalt Paving Technologists,Association of Asphalt Paving Technologists, St. Paul, Minnesota,1996,65. Brown, E. R., and S. A. Cross. “A National Study of Rutting in Hot Mix Asphalt (HMA)Pavements ” (R). NCAT Report 92-05, 1992:1-38. L. Allen Cooley Jr.Prithvi S. Kandhal M. Shane Buchanan Frank Fee Amy Epps ,“Loaded Wheel Testers in the UNITED STATES: State of the Practice”[R], Transportation Research E-Circular No. E-C016, NCAT,July 2000:1-12. Chen, D.-H., J. Bilyeu, D. Walker, and M. Murphy, Study of Rut-Depth Measurements[J],Transportation Research Record: Journal of the Transportation Research Board, Washington, D.C., 2001,1764. 78-88. Techincal specifications for construction of highway asphalt pavements (JTG F40-2004) [S] Publishing House of People’s Communication, Pejing, China, 2004:9-10, 15-21. Standard test Methods of Bitumen and Bituminous Mixtures for Highway Engineering(JTG 052-2000) [S] Publishing House of People’s Communication, Pejing, China, 2000:345-351. Authorized licensed use limited to: IEEE Xplore. Downloaded on April 30,2011 at 20:19:33 UTC from IEEE Xplore. Restrictions apply.