SPENS D10 WP3 Mix Design F

EUROPEAN COMMISSION

DG RESEARCH

SIXTH FRAMEWORK PROGRAMME

Sustainable Surface Transport

Sustainable Pavements for European New Member State s

Practical mix design model for asphalt mixture

Deliverable no. D10

Dissemination level Public

Work Package WP3 Task 3.3 “Optimisation of asphalt mixture design to ensure favourable behaviour at low and high air temperatures”

Editor I. Pap

Author(s) U. Tatić , A. Ipavec, B. Kalman, B. Palković, A. Strineka,

I. Marukić, F. Schlosser, B. Nemec, J. Šrámek, K. Mirski,

Status (F: final, D: draft) Date Final

File Name SPENS_D10_WP3_Mix_design_F.doc

Project Contract No. Contract No. 031467 (STREP, Priority 1.6.2)

Project Start Date and Duration 01 September 2006, 36 months


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TABLE OF CONTENTS

FOREWORD VI

EXECUTIVE SUMMARY VIII

1 INTRODUCTION 10

1.1 Goals and objectives 10

1.2 Optimisation procedure of asphalt mixes to ensure satisfactory behaviour at low and high air temperature 10

1.3 Experimental program 10

2 METHODS OF ASPHALT MIX DESIGN 12

2.1 Analytical design of asphalt mixture composition using PRADO software 12

2.2 Design of asphalt mixture composition using Marshall method 14

3 ASPHALT MIXTURE DESIGN USING PRADO SOFTWARE 15

4 ASPHALT MIXTURE DESIGN USING MARSHALL METHOD 17

4.1 History 17

4.2 Procedure 17

4.2.1 Aggregate Evaluation and Selection 17 4.2.2 Asphalt Binder Evaluation and Selection 18 4.2.3 Sample Preparation 18 4.2.4 The Marshall Stability and Flow Test 18 4.2.5 Density and Voids Analysis 19 4.2.6 Selection of Optimum Asphalt Binder Content 19

4.3 Summary 19

5 PREPARATION OF ASPHALT SAMPLES 25

5.1 Introduction 25

5.2 Types and marking of asphalt mixtures 25

5.3 Design and production of asphalt mixtures 25

5.4 Preparation of specimens 28

5.4.1 Mixing of asphalt mixtures and preparation of specimens 28 5.4.2 Final preparation, selection and transportation of asphalt specimens 30 5.4.3 Properties of prepared asphalt specimens 32

6 RESULTS OF LABORATORY TESTS 33

6.1 Dynamic testing using NAT 33

6.1.1 Determination the indirect tensile stiffness modulus (ITSM) 33 6.1.2 Determination the permanent deformation (VRLT- Vacuum Repeated Load Test ) 35 6.1.3 Determination the resistance to fatigue (ITFT - Indirect Tensile Fatigue Test ) 37

6.2 Rutting resistance using WTT 39

6.3 Testing and evaluation of fatigue 40

6.4 Thermal stress restrained specimen testing 42

7 CONCLUSIONS AND FUTURE RESEARCH 44


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7.1 Binder test results 44

7.2 Marshall test results 47

7.3 Asphalt mixture composition designed using PRADO 48

7.4 Dynamic test results using NAT 48

7.5 Testing rutting resistance 53

7.6 Testing and evaluation of fatigue – 2PBT 55

7.7 Thermal stress restrained specimen test 56

8 KEY FINDINGS AND RECOMMENDATIONS 58

9 SOURCES 60

9.1 Reference List 60

TABLES Table 3-1 Basic mineral mixture composition AB-11s, % (m/m) ............................................15

Table 3-2 Grading of the mineral mixture AB-11s, passing % (m/m) .....................................15

Table 3-3 Volumetric characteristics of asphalt mixtures AB-11s with different binders .........16

Table 4-1 Final grading of the mineral mixture for AC 11.......................................................20

Table 5-1 “A category types of asphalt mixtures ...................................................................25

Table 5-2 Densities of used bitumen types ...........................................................................26

Table 5-3 Grain size distribution of AC 11 aggregate mixtures ..............................................26

Table 5-4 AC 11 asphalt mixture properties (Marshall method) for WP 3 programs...............27

Table 5-5 Properties of AC 11 asphalt mixture (PRADO method)..........................................27

Table 5-6 Types of asphalt mixture and number of prepared plates in “A” category ..............30

Table 5-7 Properties of specimens prepared from AC 11 asphalt-concrete plates (Marshall method) for WP 3 programs ..........................................................................................32

Table 5-8 Properties of specimens prepared from AC 11 asphalt-concrete plates (PRADO method) for WP 3 program ............................................................................................32

Table 7-1 Comparison the dynamic characteristics of asphalt mixtures with conventional binders performed on NAT (Marshall design) and PRADO (PRADO) ............................52

Table 7-2 Comparison the dynamic characteristics of asphalt mixtures with polymer-modified binders performed on NAT (Marshall design) and PRADO ............................................52

Table 7-3 Criteria according to experiences in Serbia for dynamic characteristics of asphalt mixture tested on NAT...................................................................................................52

Table 7-4 Criteria according to experience in Serbia for axial-micro strain of asphalt mixture tested on NAT at different temperatures ........................................................................53

FIGURES Figure 2-1 Correlation between measured and calculated stiffness modules by PRADO [] ..14

Figure 3-1 Grading of mineral mixture AC-11........................................................................16

Figure 6-1 Scheme of complex modulus ..............................................................................41


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Figure 7-1 Penetration at 25°C and softening point. .............................................................44

Figure 7-2 Dynamic and kinematic viscosity Figure 7-3 Dynamic viscosity and softening point ..............................................................................................................................45

Figure 7-4 Complex modulus (logarithm of) versus temperature. .........................................46

Figure 7-5 Phase angle versus temperature.........................................................................46

Figure 7-6 Correlation between stability of asphalt mixture and penetration of binder ..........47

Figure 7-7 Correlation between stiffness of asphalt mixture and penetration of binder .........47

Figure 7-8 Comparison the stiffness modulus of asphalt mixture at 200C with different binders designed by Marshall and PRADO method.......................................................48

Figure 7-9 Correlation between the Sm of asphalt mixtures and the penetration of binders..49

Figure 7-10 Correlation between the Sm designed by PRADO and Marshall methods.........49

Figure 7-11 Resistance to deformation of AC-11 with different binders performed on NAT....50

Figure 7-12 The accession of strain vs. temperature with B 50/70 and PmB 50/90 []............50

Figure 7-13 Number of cycles to fatigue of asphalt mixtures with different binders ..............51

Figure 7-14 Rutting resistance of AC-11 with different binders tested on WTT......................53

Figure 7-15 Proportional rut depth and rutting slope of AC 11 with different binders .............54

Figure 7-16 Correlation between rut depth of AC-11 and viscosity, penetration of binders....54

Figure 7-17 Rut depth and rut slope of AC-11 v.s. softening point of binders ........................54

Figure 7-18 Comparison the test results of AC-11 obtained on VRLT and WTT....................55

Figure 7-19 Comparison of fatigue lines for the frequency of 20Hz.......................................56

Figure 7-20 Mean stress at failure for all tested mixtures......................................................57

Figure 7-21 Mean cracking temperature for all tested mixtures ............................................57

Figure 7-22 Mean cracking temperature versus mean stress at failure for all mixtures.........57

PICTURES Picture 4-1 Laboratory mixing and Marshall specimen preparation.......................................20

Picture 5-1 Laboratory mixer for preparation of asphalt mixtures..........................................28

Picture 5-2 Roller compactor ................................................................................................29

Picture 5-3 Prepared plate specimens of asphalt..................................................................29

Picture 5-4 Laboratory drill ...................................................................................................30

Picture 5-5 Cores drilled from plate samples ........................................................................31

Picture 5-6 Packaging of specimens for transportation .........................................................32

Picture 6-1 NAT with ITSM Tester........................................................................................34

Picture 6-2 VRLT Tester........................................................................................................35

Picture 6-3 ITF Tester ...........................................................................................................37

Picture 6-4 Wheel tracker COOPER-CRT-WTEN1 ...............................................................39

Picture 6-5 Test sample in the climatic chamber ...................................................................42

Picture 6-6 Instrumented specimen at the temperature chamber..........................................43


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GLOSSARY AC Asphalt-Concrete type of asphalt mixture B Road bitumen BBR Bending beam rheometer D Marshall flow value Fraass Breaking point of binder according to Fraass ITSM Indirect Tensile Stiffness Modulus test ITFT Indirect Tensile Fatigue Test HMA Hot Mix Asphalt 2PBT Two Point fatigue Bending Test NAT Nottingham Asphalt Tester PA Porous Asphalt PMB Polymer-Modified Binder (PmB) PRADO Programme for Asphalt Mix Design and Optimization RSD Relative Standard Deviation

σn-1 Standard Deviation S Marshall Stability value Sm Stiffness modulus of asphalt mixture SBS Styrene-Butadiene-Styrene block copolymer SMA Split Mastic Asphalt TSRST Thermal Stress Restrained Specimen Test Vm Voids content in asphalt sample VMA Voids in Mineral Mixture VFB Voids in mineral mixture Filled with Bitumen VRLT Vacuum Repeated Load Test WTT Wheel Tracking Test


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FOREWORD This report is the final report of the Work Package 3, Task Group 3.3 in the EU-project SPENS – Sustainable Pavements for European New Member States. The objective of this research project is to develop appropriate tools and procedures for the rapid and cost-effective rehabilitation and maintenance of roads. The overall objective is to search for materials and technologies for road pavement construction and rehabilitation that would behave satisfactorily, have an acceptable environmental impact and be cost-effective. A consortium of the following partners has conducted the SPENS project.

Partner Partner acronym Country Slovenian National Building and Civil Engineering Institute

Co-ordinator ZAG Slovenia

Institute for Transport Sciences KTI Hungary

The Swedish National Road and Transport Research Institute VTI Sweden

arsenal research arsenal Austria

Transport Research Centre CDV Czech Rep.

Road and Bridge Research Institute IBDiM Poland

Zilina University TUZA Slovakia

Europe’s National Road Research Centres with ** FEHRL Belgium

DDC Consulting & Engineering Ltd. DDC Slovenia

Ferriere Nord SpA FENO Italy

** TECER- Transport and Road Research Institute (Estonia)

IGH - Civil Engineering Institute of Croatia (Croatia)

IP - Institut za puteve (Serbia)

CRBL - (Bolgaria)

List of participating organizations in Task Group 3.3

• IP - Institut za puteve, Kumodraska 257, 11000 Belgrade, SERBIA

• ZAG - Zavod za gradbeništvo Slovenije, Dimičeva 12, Ljubljana, SLOVENIA

• IGH - Institut grañevinarstva Hrvatske d.d., Janka Rakuše 1, PO Box 283, 10000 Zagreb, CROATIA

• TUZA - Zilinská univerzita v Ziline, Univerzitna 8215/1, 01026 Zilina, SLOVAKIA

• IBDiM - Instytut Badawczy Dróg i Mostów, Jagiellonska 80, 03-301, Warsaw, POLAND

• VTI - Statens väg-och transportforskningsinstitut, Olaus Magnus väg 35, SE-58195 Linköping, SWEDEN

The EC, participating partners and national organisation have funded this project, which is gratefully acknowledged.


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Members of Work Task listed:

Imre Pap, IP, Serbia Aleksander Ipavec, ZAG, Slovenia Branislav Palković, IGH, Croatia Branislav Nemec, TUZA, Slovakia Krzysztof Mirski, IBDiM, Poland Björn Kalman, VTI, Sweden Other contributors who provided additional input: Uroš Tatić, IP, Serbia Andrea Strineka, IGH, Croatia Ivana Marukić, IGH, Croatia František Schlosser, TUZA, Slovakia Juraj Šrámek, TUZA, Slovakia We thank the following reviewer:

Aleksandar Ljubič, IGMAT (Inštitut za gradbene materiale - Building Materials Institute Ljubljana), Slovenia Bojana Lukač, ZAG Ljubljana (Zavod za gradbeništvo - Slovenian National Building and Civil Engineering Institute), Slovenia

for all his valuable comments on the contents of this report. We hope that this report will be of great assistance both to the individual and to those responsible for construction and maintenance of flexible roads. Mojca Ravnikar Turk

Project Co-ordinator


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EXECUTIVE SUMMARY The research in WP 3, Task 3.3 “Optimisation of asphalt mixture design to ensure favourable behaviour at low and high air temperatures” is aimed to find a practical model for the optimisation of asphalt mixture composition which will be related to the target functional properties of asphalt pavement relevant for various climate and traffic conditions in the field. Two different mix design methods (Marshall method and PRADO software), one silicate aggregate fractions “Hruškovec” and four binders: B 50/70, B 70/100, PmB 50/90 and PmB 25/55-55 were used for evaluation the optimal composition of asphalt concrete type of mixture (AC-11). By variation mineral grading of AC-11 and binder contents using two mix design methods the optimal volumetric composition of asphalt mixtures were established in a way that ensured favourable functional properties of asphalt mixtures: stiffness modulus, permanent deformation and fatigue. Comparing the methods of mix design there were found minor differences in mix compositions between Marshall and PRADO design only with binder contents (between 0,1 to 0,2%) for the same bulk characteristics of asphalt mixture (Vm, VMA and VFB). Although Marshall test is the most used method for mix design, PRADO software is a good method for analytical study of asphalt mixture composition and for prediction mechanical properties and performance of a mix.

Studding the results on testing dynamic characteristics of asphalt mixtures AC-11 with four different binders, performed on NAT, there were found that asphalt mixtures designed by PRADO software has lower stiffness modulus than asphalt mixtures designed by Marshall method. Binders with lower penetration (harder bitumen) showed higher stiffness modulus than binders with higher penetration (softer binder), i.e AC-11 with B 50/70 and PmB 50/90 and PmB 25/55-55) has higher stiffness modulus than AC-11 with B 70/100. The resistance to permanent deformation (rutting) of asphalt mixtures AC-11 with harder type of binder (higher viscosity, higher softening point and higher deformation energy at 250C) showed better resistance to permanent deformation, lower value of rutting depth and smaller rutting slope which mean better resistance to rutting than asphalt mixtures with softer type of binder, i.e AC-11 with B 50/70, PmB 50/90 and PmB 25/55-55 better than AC-11 with B 70/100. That was confirmed through VRLT and WTT tests. The viscosity of binder, softening point as well as deformation energy at 250C was appeared as a good parameter for predicting rutting resistance of asphalt mixture. Testing resistance to permanent deformation there were found good correlation between results of axial micro-dilatation obtained in VRLT at 300C and proportional rut depth from WTT at 600C for asphalt mixtures AC-11 with different types of binders. Although this correlation are valid only for this asphalt mixture AC-11 with silicate aggregate and one grading it would be interesting to investigate in future research is it valid for other types of asphalt mixtures, other grading, other aggregates and binders and at different test temperatures. Results of VRLT tests showed that asphalt mixtures with modified binders PmB 50/90 has lower resistance to permanent deformation at 300C than at higher temperature (400C, 500C) due to elastic deformation of SBS-polymer in comparison to the asphalt mixture with conventional bitumen B 50/70. Conclusion was that the test temperature of 300C is not convenient for PmB and recommendation would be at least 500C. Further research is need to highlight this observation.


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The resistance to fatigue and longer fatigue life are found to be with asphalt mixture AC-11 containing polymer-modified binder PmB 25/55-55 and softer bitumen B 70/100 than with harder type of bitumen B 50/70. This was confirmed thorough ITFT and 2PBT tests. Resistance to thermal cracks of asphalt mixtures AC-11 testing with TSRST showed that asphalt mixture AC-11 with B 70/100 has the lowest cracking temperature whilst AC-11 with B 50/70 has the highest cracking temperature. Mixture with polymer binder can resist higher stress then mixture with road binder. Test results confirmed that cracking temperature mainly depend on properties of binder. Thorough research performed in Task 3.3 there were shown that application of conventional binders (B 50/70, B 70/100) in asphalt mixture depends of which dynamic parameters are needed to be emphasized, because none of them could satisfy the all performance criteria. For higher stiffness modulus and resistance to permanent deformation it is better to use harder type of bitumen (B 50/70) while for better resistance to fatigue softer bitumen is recommended (B 70/100). Among binder properties penetration, softening point, elastic recovery and phase angle with PmB are the most promising characteristics which influence to the dynamic parameters of asphalt mixture. It is worth to highlight that asphalt mixture AC-11 with PmB 25/55-55 showed the highest resistance to fatigue despite of the highest stiffness and good creep deformation. The recommendation would be that asphalt mixtures with softer type of binder (B 70/100) can be used for regions with lower temperature and traffic volume where it is important for asphalt pavement to has good resistance to fatigue and thermal cracks while in regions with higher temperature and higher traffic volume it is recommended to use harder type of binder (B 50/70). These binders can’t be used for asphalt pavements in regions with extreme daily temperatures changes and roads with heavy traffic. Polymer-modified binders, especially PmB 25/55-55, due to considerable amount of elasticity at low and even at high temperatures, in same time are resistant to rutting, fatigue and thermal cracking. Asphalt mixtures with these binders can be mainly used for application in asphalt pavement exposed to heavy traffic and extreme climate changes. It is important to say that the results of research and conclusions in this WP3 Task 3.3 are valid only for asphalt mixture AC-11 with silicate aggregate “Hruškovec” and binders B 50/70, B 70/100, PmB 50/90 and PmB 25/55-55. For validation of asphalt mix design model it is necessary to test other types of asphalt mixtures with other aggregates and binders, which is recommendation for the future research work.


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1 INTRODUCTION

1.1 Goals and objectives

The research in WP 3, Task 3.3 “Optimisation of asphalt mixture design to ensure favourable behaviour at low and high air temperatures” is aimed to find a practical model for the optimisation of asphalt mixture design which will be related to the target functional properties relevant for various climate and traffic conditions in the field (performance indicator, rutting, cracking, ravelling, etc). The objective of this task is to evaluate a practical mix design model for asphalt concrete type of mixtures by comparing two different methods of design (Marshall and PRADO) which are based on physical and functional properties so that can be related to the performance of bituminous pavement for various climate and traffic conditions. The goal of this task is optimization of asphalt mixture design using different types of binders to ensure favourable behaviour at low and high air temperatures.

1.2 Optimisation procedure of asphalt mixes to ensu re satisfactory behaviour at low and high air temperature

To ensure satisfactory behaviour of asphalt mixes at low and high air temperature it is necessary to follow the next optimisation procedure:

• Selection of mineral materials (aggregate, sand, filler),

• Selection of binder (B or PmB ),

• Selection of asphalt mixture (AC, HMA, SMA, PA),

• Design of mineral mixture,

• Selection volumetric characteristics of asphalt mixture (Vm, VMA and VFB) and

• Verification composition of asphalt mixture - mechanical tests (S, D, WTT, ITSM, 2PBT, TSRST)

During the above procedure of asphalt mix optimisation, criteria must be used to assess whether the result obtain is adequate and meet the requirements, which are in essence compromise between different and sometimes conflicting requirements, such as resistance to fatigue and resistance to rutting.

1.3 Experimental program

In Task 3.3 are presented two methods of designing the composition of asphalt-concrete type of mixtures 0/11 (AC-11):

• Analytical design using PRADO software and

• Marshall method.

For both methods were used the same componential materials:

• Binders:

− Bitumen B 50/70 (INA-Rijeka, Croatia) − Bitumen B 70/100 (INA-Rijeka, Croatia) − Polymer-bitumen PmB 50/90 (MODIBIT, Croatia) − Polymer-bitumen PmB 25/55-55 STARFALT (OMV, Austria)

• Limestone filler “Očura” (Croatia) and

Crushed silicate aggregate “Hruškovec”, fractions 2/4, 4/8 and 8/11 mm (Croatia),

Experimental program are comprised of the following tests:



• Binder testing (EN 13808 and EN 14023)

• Filler, sand and aggregate testing (EN 13108-1),

• Testing dynamic characteristics with Nottingham Asphalt Tester (NAT)

− ITSM (Indirect Tensile Stiffness Modulus Test), − VRLT (Vacuum Repeated Load Test) and − ITFT (Indirect Tensile Fatigue Test).

• Rutting resistance – wheel tracking test (EN 12697-22),

• Low temperature resistance - TSRST test and

• Fatigue test 2PBT (EN 12697-24 Annexe A).

The results from the experimental program are compared in relation to the design methods and the types of binder used in asphalt mixture.



2 METHODS OF ASPHALT MIX DESIGN

Asphalt mix design model is the process of determining what mineral filler, sand and aggregate to use, what asphalt binder to use and what the optimum combination of these ingredients ought to be to satisfy the performance based criteria. The asphalt mixture with optimum composition and physical-mechanical properties shall ensured following requirements which depend of:

• Resistance to deformation (stability)

− Grain angularity and aggregate texture − Grading of mineral mixture − Binder content − Viscosity of binder at high temperatures − Air void content − Maximum aggregate size

• Resistance to fatigue (binder content, voids)

• Resistance to thermal cracks at low temperatures (type of binder)

• Durability

− Thickness of bitumen film around aggregate grain − Voids in asphalt

• Resistance to water influence

− Chemical and mineralogical composition of aggregates − Voids in asphalt − Specific area of aggregate (fine material)

• Resistance to wearing

− Texture, grain angularity, aggregate size and abrasion properties − Binder content

• Workability

− Size, angularity and texture of aggregates − Grading of mineral mixture − Binder content − Binder viscosity during mixing and compacting

There are several methods which are used for designing optimal asphalt mixture composition of which the Marshall, PRADO, SUPERPAVE and Gyratory methods are the most common. In case of lack of appropriate equipment the Marshall method and PRADO software are most practical for optimisation of asphalt mixture design with contribution of dynamic testing of performance based parameters [1].

2.1 Analytical design of asphalt mixture compositio n using PRADO software

The software package “Programme for Asphalt Mix Design and Optimization” (PRADO) developed by Belgian Road Research Centre and distributed under the form of “Code of good practise for bituminous mix design” (CRR-R 61/87) is a good method for analytical study of asphalt mixture composition by volumetric calculation [2]. This programme can be used for prediction of complex modulus of asphalt mixture from rheological properties of pure binder and prediction of mechanical properties and performance of a mix, based on its composition and on the properties of the binder as well.



The PRADO method is consists of several phases:

1. Selection of materials (aggregate, sand, filler and binder);

2. Testing base characteristics of materials

• aggregate: density, grading, grain angularity

• filler: density, grading, Rigden voids

• bitumen: density, viscosity, penetration, softening point, break point (Fraass)

3. Analytical volumetric design

• selection of asphalt mixture,

• design of mineral mixture,

• determination of max. VMA available for mastic,

• determination the characteristics of mastic (k=f/b, ∆SP),

• determination the basic composition of asphalt mixture,

4. Verification of composition – mechanical tests

• Marshall test (bitumen variation ± 0.3%) (S, D, S/D, V, VMA, VFB),

• wheel test, Schelenberg test (SMA) and Cantabrio cohesion test (PA),

• complex modulus and master curve,

• parameters of fatigue law,

• parameters of permanent deformation law,

• thermal dilatation and ageing properties

5. Evaluation and verification of preliminary asphalt mixture composition according to technical specification.

The above mentioned phases of the mix design method are logically connected. During the process, criteria must be used to assess whether the result obtain is adequate and what should be done if it fails to meet the requirements. The analytical study aims at designing a mix that offers the best possible compromise between different and sometimes conflicting requirements, such as resistance to fatigue and to rutting. In this approach, the stability of the mix can be ensured by making use of intergranular friction while avoiding overfilling the mineral skeleton with mastic (filler + binder). This mastic should only fill part of the voids in the mineral aggregate and should also have the right consistency (that is, the right proportion between filler and binder). The following diagram (Figure 2-1) presented the correlation between measured and calculated stiffness modules by PRADO programme at different temperatures and for a frequency of 10Hz for different bituminous mixtures, so it seems that there are good prediction between PRADO modulus and laboratory tests. The use of an analytical mix design method is no guarantee that a bituminous mix has a good mechanical behaviour. In order to obtain this guarantee one must verify the mix formula by using one or more mechanical laboratory tests which can be empirical or even better performance related. However such test methods do not quickly and directly lead to the optimal mix design formula and very often require preliminary studies. The analytical design approach is of paramount importance since when applied, besides avoiding serious design mistakes, it enables the number of preliminary studies as well as the number of mechanical tests to reduced, i.e. by estimation of the volume available for the mastic. Moreover, when requirements for the mechanical test are not met, the analytical method allows one to identify the cause more quickly. PRADO software is one of the most essential tools needed to fulfil this aim [3].



Figure 2-1 Correlation between measured and calcula ted stiffness modules by PRADO [4]

2.2 Design of asphalt mixture composition using Ma rshall method

Optimum composition and physical-mechanical properties of asphalt mixture shall be determined according to Marshall test (EN 12697-34) namely by producing a asphalt mix formula (JMF-Job Mix Formula), although Marshall test is not quite proper method for testing asphalt mixture with modified binders. Stone material and binder selection shall enable mineral proportions and binder quantity to be designed so that physical and mechanical properties of asphalt mixtures can meet the certain criteria’s in technical specifications. Optimum binder content shall be based on optimum voids in asphalt sample, voids in stone materials, bitumen filled voids, stability and flow values and should be a compromise between stability and durability. Optimum binder content in asphalt mixture is calculated as a average value between following data’s and shall satisfy the requirements for certain asphalt layer and traffic condition given in technical specification:

• binder content at maximum density,

• binder content at maximum Marshall stability,

• binder content at optimum air voids and

• binder content at optimum filled voids in mineral mixture.



3 ASPHALT MIXTURE DESIGN USING PRADO SOFTWARE

The optimisation of asphalt mixture design using PRADO software consist of input the characteristics of basic materials:

• Binder (pen, R&B, density, Fraass point, viscosity) - given in Appendix A1,

• Filler (density, grading, Rigden voids) - given in Appendix A2,

• Sand 0/2 mm (grading, density, sand equivalent, angularity) see Appendix A2,

• Aggregate 2/4, 4/8, 8/11 mm (grading, density, angularity), see Appendix A2,

• Mineral mixture 0/11 mm (grading curve),

• Asphalt mixture (target air voids, compaction rate).

After volumetric design of mineral mixture by combination of fines, sand and coarse aggregate > 2.0 mm and determination of voids in mineral aggregate available for mastic, characteristics of mastic (mixture of binder and fines), target air voids and compaction rate, software PRADO calculate the basic composition of asphalt mixture and mix characteristics (aggregate volume, binder volume, voids, maximum density, bulk density, voids in mineral aggregate VMA and voids filled with binder VFB). Evaluation and verification the composition of asphalt mixture is done by calculating complex modulus and master curve, parameters of fatigue law, parameters of permanent deformation law, thermal dilatation and ageing properties. The final mineral mixture composition of AC-11 are shown in Table 3-2, granulometric composition in Table 3-2 and in diagram, Figure 3-1. .

Table 3-1 Basic mineral mixture composition AC-11, % (m/m)

Materials Mineral Mixture

K.B. “Očura” 8,1

0/2 mm "Hruškovec" 26,8




T O T A L: 100,0

Table 3-2 Grading of the mineral mixture AC-11, pas sing % (m/m)

Sieves (mm) 0,09 0,25 0,71 2,0 4,0 8,0 11,2 16,0

Design 7,1 13,4 21,6 37,8 55,4 79,9 99,9 100

Spec.* 3-11 8-18 16-30 31-48 49-65 75-87 97-100 100

*SRPS U.E4.014/90 [5]



GRADING OF MINERAL MIXTURE AB 11s

0.09

0.25

0.71 2 4 8

11.2 16 22

.431

.5 45

0

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90

100

sieve size d 0.45 [mm]

pass

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reta

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Designed

SRPS U.E4.014

Figure 3-1 Grading of mineral mixture AC-11

In Table 3-3 are presented the volumetric characteristics of asphalt mixtures with optimum content of four different binders.

Table 3-3 Volumetric characteristics of asphalt mix tures AC-11 with different binders

Volumetric characteristics B 70/100 B 50/70 PmB 50/90S PmB 25/55-55

Voids in mineral aggregate filled with binder, % (v/v)

73,2 73,2 73,2 73,2

Voids in mineral aggregate, %(v/v) 18.7 18.7 18.7 18.7

Bulk density, (Mg/m3) 2,438 2,435 2,437 2,438

Maximum density, (Mg/m3) 2,567 2,564 2,566 2,566

Binder content in asphalt mixture, %(m/m)

5,73 5,61 5,69 5,70

Volume of binder, %(v/v) 13,7 13,7 13,7 13,7

Volume of stone aggregate (aggregat+sand+filler), %(v/v)

81,3 81,3 81,3 81,3

Void content, % (v/v) 5,00 5,00 5,00 5,00

In Appendixes A3-A6 are shown the listing of PRADO software with calculation of optimal asphalt mixture compositions for 4 binders as well as mechanical characteristics of designed mixtures.



4 ASPHALT MIXTURE DESIGN USING MARSHALL METHOD

The basic concepts of the Marshall asphalt mix design method were originally developed by Bruce Marshall of the Mississippi Highway Department around 1939 and then refined by the U.S. Army. The Marshall method seeks to select the asphalt binder content at a desired density that satisfies minimum stability and range of flow values (White, 1985).

4.1 History

During World War II, the U.S. Army Corps of Engineers (USCOE) began evaluating various HMA mix design methods for use in airfield pavement design. Motivation for this search came from the ever-increasing wheel loads and tire pressures produced by larger and larger military aircraft. Early work at the U.S. Army Waterways Experiment Station (WES) in 1943 had the objective of developing "...a simple apparatus suitable for use with the present California Bearing Ratio (CBR) equipment to design and control asphalt paving mixtures...". The most promising method eventually proved to be the Marshall Stability Method developed by Bruce G. Marshall at the Mississippi Highway Department in 1939. WES took the original Marshall Stability Test and added a deformation measurement (using a flow meter) that was reasoned to assist in detecting excessively high asphalt contents. This appended test was eventually recommended for adoption by the U.S. Army because:

• it was designed to stress the entire sample rather than just a portion of it

• it facilitated rapid testing with minimal effort

• it was compact, light and portable

• it produced densities reasonably close to field densities.

WES continued to refine the Marshall method through the 1950s with various tests on materials, traffic loading and weather variables. Today the Marshall method, despite its shortcomings, is probably the most widely used mix design method in the world.

4.2 Procedure

The Marshall mix design method consists of 6 basic steps [6]:

• Aggregate selection

• Asphalt binder selection

• Sample preparation (including compaction)

• Stability determination using the Marshall stability and flow test

• Density and voids calculations

4.2.1 Aggregate Evaluation and Selection

A typical aggregate evaluation for use with Marshall asphalt mix design method includes three basic steps (Roberts et al., 1996): Determine aggregate physical properties. This consists of running various tests to determine properties such as toughness and abrasion, durability and soundness, cleanliness and deleterious materials, particle shape and surface texture. Determine other aggregate descriptive physical properties. If the aggregate is acceptable according to step #1, additional tests are run to fully characterize the aggregate. These tests determine gradation and size, specific gravity and absorption. Perform blending calculations to achieve the mix design aggregate gradation. Often, aggregates from more than one source or stockpile are used to obtain the final aggregate gradation used in a mix design. Trial blends of these different gradations are usually



calculated until an acceptable final mix design gradation is achieved. Typical considerations for a trial blend include:

• All gradation specifications must be met. Typical specifications will require the percent retained by weight on particular sieve sizes to be within a certain band.

• The gradation should not be too close to the FHWA's 0.45 power maximum density curve. If it is, then the voids in the mineral aggregate (VMA) is likely to be too low. Therefore, gradation should deviate from the FHWA's 0.45 power maximum density curve.

4.2.2 Asphalt Binder Evaluation and Selection

The Marshall test does not have a common generic asphalt binder selection and evaluation procedure. Each specifying entity uses their own method with modifications to determine the appropriate binder and, if any, modifiers. Binder evaluation can be based on local experience, previous performance or a set procedure. Once the binder is selected, several preliminary tests are run to determine the asphalt binder's temperature-viscosity relationship.

4.2.3 Sample Preparation

The Marshall method, like other mix design methods, uses several trial aggregate-asphalt binder blends (typically 5 blends with 2 or 3 samples each for a total of 10 or 15 specimens), each with a different asphalt binder content. Then, by evaluating each trial blend's performance, an optimum asphalt binder content can be selected. In order for this concept to work, the trial blends must contain a range of asphalt binder contents both above and below the optimum asphalt binder content. Therefore, the first step in sample preparation is to estimate an optimum asphalt binder content. Trial blend asphalt contents are then determined from this estimate.

Optimum Asphalt Binder Content Estimate The Marshall mix design method can use any suitable method for estimating optimum asphalt content and usually relies on local procedures or experience.

Sample Asphalt Binder Contents Based on the results of the optimum asphalt binder content estimate, samples are typically prepared at 0.5 or 0.4 percent by weight of mix increments, with at least two samples above the estimated asphalt binder content and two below.

Compaction with the Marshall hammer Each sample is then heated to the anticipated compaction temperature and compacted with a Marshall hammer, a device that applies pressure to a sample through a tamper foot. Some hammers are automatic and some are hand operated. Key parameters of the compactor are: sample size, tamper foot, compaction pressure and number of blows. The tamper foot strikes the sample on the top and covers almost the entire sample top area. After a specified number of blows (typically 50) the sample is turned over and the procedure repeated.

4.2.4 The Marshall Stability and Flow Test

The Marshall stability and flow test provides the performance prediction measure for the Marshall mix design method. The stability portion of the test measures the maximum load supported by the test specimen at a specified loading rate. Basically, the load is increased until it reaches a maximum then when the load just begins to decrease, the loading is stopped and the maximum load is recorded.

During the loading, an attached dial gauge measures the specimen's plastic flow as a result of the loading. The flow value is recorded in specified increments at the same time the maximum load is recorded.



4.2.5 Density and Voids Analysis

All mix design methods use density and voids to determine basic HMA physical characteristics. Two different measures of densities are typically taken:

• bulk specific gravity (bulk density of Marshall specimen - using EN terms)

• theoretical maximum specific gravity (maximum density of asphalt mixture - using EN terms)

These densities are then used to calculate the volumetric parameters of the HMA. Measured void expressions are usually:

• air voids content in asphalt mixture (Vm)

• voids content in the mineral aggregate (VMA)

• voids in the mineral aggregate filled with bitumen (VFB)

Generally, these values must meet local or national criteria.

4.2.6 Selection of Optimum Asphalt Binder Content

The optimum asphalt binder content is finally selected based on the combined results of Marshall stability and flow, density analysis and voids analysis. Optimum asphalt binder content can be arrived at in the following procedure:

- Plot the following graphs:

• Asphalt binder content vs. bulk density. Density will generally increase with increasing asphalt content, reach a maximum, then decrease. Peak density usually occurs at a higher asphalt binder content than peak stability.

• Asphalt binder content vs. air voids content Vm. Percent air voids should decrease with increasing asphalt binder content.

• Asphalt binder content vs. VMA. Percent VMA should decrease with increasing asphalt binder content, reach a minimum, then increase.

• Asphalt binder content vs. VFB. Percent VFB increases with increasing asphalt binder content.

• Asphalt binder content vs. Marshall stability. This should follow one of two trends:

• Stability increases with increasing asphalt binder content, reaches a peak, then decreases.

• Stability decreases with increasing asphalt binder content and does not show a peak. This curve is common for some recycled HMA mixtures.

• Asphalt binder content vs. flow.

- Determine the asphalt binder content that corresponds to the required air voids content. This is the optimum asphalt binder content.

- Determine properties at this optimum asphalt binder content by referring to the plots. Compare each of these values against specification values and if all are within specification, then the preceding optimum asphalt binder content is satisfactory. Otherwise, if any of these properties is outside the specification range the mixture should be redesigned.

4.3 Summary

The Marshall mix design method was developed to address specific mix design issues confronting the USCOE during World War II. Therefore, it was developed to be simple, light, quick and reasonably accurate for the wheel loading of the time. Since then it has been



modified and supplemented to address new concerns but the basic testing apparatus and selection criteria remain the same.

The biggest differentiating aspects of the Marshall method are the Marshall hammer and the Marshall stability and flow apparatus. Both are probably overly simplistic for high-end or high-load pavements but they are simple, light, portable and inexpensive.

List of EN standards which were used for designing and testing:

EN 12697-35: Laboratory mixing EN 12697-5: Determination of the maximum density EN 12697-6: Determination of bulk density of bituminous specimens EN 12697-8: Determination of void characteristics of bituminous specimens EN 12697-29: Determination of the dimensions of a bituminous specimen EN 12697-30: Specimen preparation by impact compactor EN 12697-34: Marshall test

Table 4-1 Final grading of the mineral mixture for AC 11

Sieve (mm) 0.063 0.09 0.25 0.71 2.0 4.0 8.0 11.2 16.0

Passing % (m/m) 5.7 7.7 14.2 21.6 38.3 55.6 80.0 99.9 100

Required air voids content Vm : 5.0 % (v/v)

Picture 4-1 Laboratory mixing



Binder: PAVING GRADE BITUMEN B 70/100

Mixing temperature: 155oC

Temperature for Marshall specimen compaction: 145oC

optimum

Characteristic unit A B C D E

Binder content % (m/m) 5.0 5.4 5.8 6.2 6.6

Density of bitumen at 25oC kg/m3 1014 1014 1014 1014 1014

Density of aggregate (calculated) kg/m3 2830 2830 2830 2830 2830

Maximum density of AM (calculated) kg/m3 2597 2580 2564 2547 2531

Bulk density of Marshall specimen kg/m3 2406 2429 2438 2447 2458

Air voids content Vm % (v/v) 7.4 5.9 4.9 3.9 2.9

Voids content in the aggregate VMA % (v/v) 19.2 18.8 18.8 18.9 18.9

Voids filled with bitumen VFB % (v/v) 61.7 68.8 74.0 79.2 84.8

Stability at 600C kN 10.1 10.7 11.6 11.5 10.3

Flow at 600C mm 2.9 3.0 3.2 3.4 3.7

Marshall stiffness at 600C kN/mm 3.5 3.6 3.6 3.4 2.8

2400

2410

2420

2430

2440

2450

2460

2470

5,0 5,4 5,8 6,2 6,6

Binder content %(m/m)

Bul

k de

nsity

(kg

/m3)

2,0

3,0

4,0

5,0

6,0

7,0

8,0

5,0 5,4 5,8 6,2 6,6


Air

void

s co

nten

t Vm

%(v

/v)

18,7

18,8

18,9

19,0

19,1

19,2

19,3

19,4

5,0 5,4 5,8 6,2 6,6


Voi

ds in

the

aggr

egat

e V

MA

%(v

/v)

55,0

60,0

65,0

70,0

75,0

80,0

85,0

90,0

5,0 5,4 5,8 6,2 6,6


Voi

ds fi

lled

with

bitu

men

VF

B %

(v/v

)

9,0

9,5

10,0

10,5

11,0

11,5

12,0

5,0 5,4 5,8 6,2 6,6


Sta

bilit

y (k

N)

2,6

2,8

3,0

3,2

3,4

3,6

3,8

5,0 5,4 5,8 6,2 6,6


Flo

w (

mm

)



Binder: PAVING GRADE BITUMEN B 50/70



optimum



Density of bitumen at 25oC % (m/m) 1017 1017 1017 1017 1017




Air voids content Vm kg/m3 7.4 6.1 5.1 4.2 2.9



Stability at 600C % (v/v) 14.3 14.5 14.7 14.9 14.5

Flow at 600C kN 3.3 3.5 3.7 3.9 4.4

Marshall stiffness at 600C mm 4.3 4.1 4.0 3.8 3.3

2400

2410

2420

2430

2440

2450

2460

2470

5,0 5,4 5,8 6,2 6,6


Bul

k de

nsity

(kg

/m3)

2,0

3,0

4,0

5,0

6,0

7,0

8,0

5,0 5,4 5,8 6,2 6,6


Air

void

s co

nten

t Vm

%(v

/v)

18,7

18,8

18,9

19,0

19,1

19,2

19,3

5,0 5,4 5,8 6,2 6,6


Voi

ds in

the

aggr

egat

e V

MA

%(v

/v)

55,0

60,0

65,0

70,0

75,0

80,0

85,0

90,0

5,0 5,4 5,8 6,2 6,6


Voi

ds fi

lled

with

bitu

men

VF

B %

(v/v

)

13,8

14,0

14,2

14,4

14,6

14,8

15,0

5,0 5,4 5,8 6,2 6,6


Sta

bilit

y (k

N)

3,1

3,4

3,7

4,0

4,3

4,6

5,0 5,4 5,8 6,2 6,6


Flo

w (

mm

)



Binder: POLYMER MODIFIED BITUMEN PmB 50-90S



optimum










Stability at 600C % (v/v) 12.1 12.3 12.9 13.7 13.0

Flow at 600C kN 3.3 3.5 3.7 4.1 4.4


2400

2410

2420

2430

2440

2450

2460

2470

5,0 5,4 5,8 6,2 6,6


Bul

k de

nsity

(kg

/m3)

2,0

3,0

4,0

5,0

6,0

7,0

8,0

5,0 5,4 5,8 6,2 6,6


Air

void

s co

nten

t Vm

%(v

/v)

18,7

18,8

18,9

19,0

19,1

19,2

19,3

5,0 5,4 5,8 6,2 6,6


Voi

ds in

the

aggr

egat

e V

MA

%(v

/v)

55,0

60,0

65,0

70,0

75,0

80,0

85,0

90,0

5,0 5,4 5,8 6,2 6,6


Voi

ds fi

lled

with

bitu

men

VF

B %

(v/v

)

11,8

12,1

12,4

12,7

13,0

13,3

13,6

13,9

5,0 5,4 5,8 6,2 6,6


Sta

bilit

y (k

N)

3,1

3,3

3,5

3,7

3,9

4,1

4,3

4,5

5,0 5,4 5,8 6,2 6,6


Flo

w (

mm

)



Binder: POLYMER MODIFIED BITUMEN PmB 25/55-55



optimum










Stability at 600C % (v/v) 17.4 18.2 19.0 18.6 17.9

Flow at 600C kN 3.4 3.6 3.8 4.2 4.7


2400

2410

2420

2430

2440

2450

2460

2470

5,0 5,4 5,8 6,2 6,6


Bul

k de

nsity

(kg

/m3)

2,0

3,0

4,0

5,0

6,0

7,0

8,0

5,0 5,4 5,8 6,2 6,6


Air

void

s co

nten

t Vm

%(v

/v)

18,7

18,8

18,9

19,0

19,1

19,2

19,3

5,0 5,4 5,8 6,2 6,6


Voi

ds in

the

aggr

egat

e V

MA

%(v

/v)

55,0

60,0

65,0

70,0

75,0

80,0

85,0

90,0

5,0 5,4 5,8 6,2 6,6


Voi

ds fi

lled

with

bitu

men

VF

B %

(v/v

)

17,0

17,3

17,6

17,9

18,2

18,5

18,8

19,1

5,0 5,4 5,8 6,2 6,6


Sta

bilit

y (k

N)

3,1

3,4

3,7

4,0

4,3

4,6

4,9

5,0 5,4 5,8 6,2 6,6


Flo

w (

mm

)



5 PREPARATION OF ASPHALT SAMPLES

5.1 Introduction

This chapter describes types and marking of designed and produced asphalt mixtures (hot mixed asphalt–HMA), asphalt specimens production and preparation processes and properties of prepared asphalt specimens to be subjected to laboratory testing within the planned WP3 programs.

5.2 Types and marking of asphalt mixtures

The prepared production plan anticipated production of eight (8) different asphalt mixtures in total, composed of one type of aggregate and four types of bitumen. The mixtures were grouped into “A” category:

• “A” category (HRUSKOVEC silicate aggregate),

A” category includes 8 different types of HMA, made of HRUSKOVEC silicate aggregate, as follows:

• 8 HMA - Asphalt-concrete (AC 11),

Table 5-1 presents all 8 types of HMA, taking into consideration the type of used bitumen, i.e. the applied asphalt-concrete designing method (Marshall method, PRADO method).

Table 5-1 “A category types of asphalt mixtures

Category HMA Designation HMA Design Binder 1 AC 11 Marshall B 50/70 (Croatia) 2 AC 11 PRADO B 50/70 (Croatia) 6 AC 11 Marshall PmB SBS 50/90 (Croatia) 7 AC 11 PRADO PmB SBS 50/90 (Croatia)

13 AC 11 Marshall B 70/100 (Croatia) 14 AC 11 PRADO B 70/100 (Croatia) 16 AC 11 Marshall PmB 25/55-55 (Austria)

“A” category

HRUSKOVEC silicate aggregate

17 AC 11 PRADO PmB 25/55-55 (Austria)

5.3 Design and production of asphalt mixtures

Four types of asphalt mixture of AC 11 asphalt-concrete type of “A” category were designed in ZAG-Ljubljana using Marshall method, for the application of WP 3 program (asphalt mixtures designated “1”, “6”, “13” and “16”) and in IP-Beograd they were designed using PRADO method, for the purpose of the same application (asphalt mixtures designated “2”, “7”, “14” and “17”). Four types of bitumen were used for preparation of all the types of asphalt mixtures. Density of each of the four bitumen types was determined at the temperature of 25°C for the purpose of designing all the types of asphalt mixtures. The results of determining density of all the types of used bitumen are presented in Table 5-2.



Table 5-2 Densities of used bitumen types

Binder Test methods Density @25 °C,

ρρρρB, Mg/m 3

Road construction bitumen 50/70 (Croatia) EN ISO 3838 1.001

Road construction bitumen 70/100 (Croatia) EN ISO 3838 1.022

Polymer modified bitumen SBS 50/90 (Croatia) EN ISO 3838 1.014

Polymer modified bitumen PmB 25/55-55 (Austria) EN ISO 3838 1.017

The design of asphalt mixtures required preparation of laboratory specimens using impact compactor (EN 12697-30) and applying 2×50 impacts, resulting in the following void values:

• AC 11 – approximately 5 % (v/v) (Marshall method and PRADO method),

Asphalt mixtures are designed so that all the asphalt mixtures of the same type have the same share of bitumen, regardless the type of used bitumen. Furthermore, all the asphalt mixtures of the same type share the same grain size distribution. All the asphalt mixtures made of AC 11 asphalt-concrete belonging to “A” category are made of HRUSKOVEC silicate aggregate. Four asphalt mixtures with four types of bitumen were designed using the standard Marshall method for application within WP 3 programs. Furthermore, four asphalt mixtures with four types of used bitumen were designed using PRADO method for application of WP 3 program. Grain size distribution of aggregate mixture was the same for all the asphalt mixtures type AC asphalt–concrete 11 (Table 5-3).

Table 5-3 Grain size distribution of AC 11 aggregat e mixtures

Sieves (mm)

0.063 0.090 0.25 0.71 2 4 8 11.2

Design 6.5 7.8 12.2 21.6 38.3 55.6 80.0 100.0

Specification - 3 - 11 8 - 18 16 – 30 31 - 48 49 - 65 75 - 87 97 - 100

AC 11 asphalt-concrete (Marshall method) Four asphalt mixtures type AC 11 asphalt-concrete were designed and prepared with four different bitumen types for the purpose of application of WP 3 and WP 4 programs, using Marshall method (Table 5-4).



Table 5-4 AC 11 asphalt mixture properties (Marshal l method) for WP 3 programs

1 13 6 16 Mix designation 50/70

Croatia 70/100 Croatia

PmB 50-90 Croatia

PmB 25/55-55 Austria

Aggregate density

Apparent density ρa Mg/m3 2.898

Bulk density ρrd Mg/m3 2.789

Effective density ρeff Mg/m3 2.873

Mix characteristics

Maximum density ρAM Mg/m3 2.592 2.595 2.594 2.595

Bulk density ρAS Mg/m3 2.463 2.467 2.467 2.468

Total bitumen content B(AM) %(m/m) 5.80 5.92 5.87 5.89

Absorbed bitumen Bab(AM) %(v/v) 2.57

Effective bitumen Beff(AM) %(v/v) 12.45

Total bitumen content B(AM) %(v/v) 15.02

Total bitumen content B(AS) %(v/v) 14.28 14.28 14.29 14.29

Marshall specimens characteristics

Air Voids V %(v/v) 5.0 4.9 4.9 4.9

Voids in mineral aggregate* VMA %(v/v) 16.8 16.8 16.7 16.7

Voids filled with bitumen * VFB % 70.4 70.5 70.7 70.8

* effective bitumen (Beff)

AC 11 asphalt-concrete (PRADO method) Four asphalt mixtures type AC 11 asphalt-concrete were designed and prepared with four different bitumen types for the purpose of application of WP 3 program, using PRADO method (Table 5-5).

Table 5-5 Properties of AC 11 asphalt mixture (PRAD O method)

2 14 7 17 Mix designation 50/70

Croatia 70/100 Croatia

PmB 50-90 Croatia


Aggregate density

Apparent density ρa Mg/m3 2.898

Bulk density ρrd Mg/m3 2.789

Effective density ρeff Mg/m3 2.873 Mix characteristics

Maximum density ρAM Mg/m3 2.596 2.599 2.598 2.598

Bulk density ρAS Mg/m3 2.464 2.463 2.466 2.461

Total bitumen content B(AM) %(m/m) 5.70 5.82 5.77 5.79

Absorbed bitumen Bab(AM) %(v/v) 2.57

Effective bitumen Beff(AM) %(v/v) 12.22

Total bitumen content B(AM) %(v/v) 14.79

Total bitumen content B(AS) %(v/v) 14.04 14.01 14.04 14.01 Marshall specimens characteristics

Air Voids V %(v/v) 5.1 5.2 5.1 5.3

Voids in mineral aggregate* VMA %(v/v) 16.7 16.8 16.7 16.9

Voids filled with bitumen * VFB % 69.5 68.9 69.5 68.6

* effective bitumen (Beff)



5.4 Preparation of specimens

5.4.1 Mixing of asphalt mixtures and preparation of specimens

• Specimens were prepared in the Laboratory of IGH Zagreb for the following laboratory testing:

− Permanent deformity (rutting), − Behaviour at low temperatures (Thermal Stress Restrained Specimen Test-

TSRST), − Fatigue of cylindrical specimens, − Fatigue of small beams, − Stiffness, − Marshall stability and flow.

All the types of asphalt mixtures were prepared using laboratory mixer equipped with a 30 litres capacity mixing drum, automatic thermostatic heater and automatic mixing duration regulator (Picture 5-1).

Picture 5-1 Laboratory mixer for preparation of asp halt mixtures

Plate specimens were prepared for testing of permanent deformities, TSRST, fatigue and rigidity, according to EN 12697-33 standard, using roller compactor (Picture 5-2). The dimensions of specimens were 305 mm × 305 mm and thickness was 50, 60 or 80 mm, depending on the intended testing (Picture 5-3). All the asphalt samples had to be prepared as to contain voids in the range of ± 1 %(v/v) of the value defined in advance. Standard cylindrical specimens were prepared for testing of Marshall stability and flow, according to EN 12697-30 standard. The specimens were of 100 mm diameter. The preparation of cylindrical specimens for testing of stability and flow required 2 × 50 impacts.



Picture 5-2 Roller compactor

Picture 5-3 Prepared plate specimens of asphalt

Prepared plates and Marshall specimens The total of 56 asphalt plates and 72 Marshall specimens were prepared for application of WP 3 program. Designations of asphalt mixtures and number of prepared asphalt plates and Marshall specimens within the “A” category are presented in Table 5-6.



Table 5-6 Types of asphalt mixture and number of pr epared plates in “A” category

Category HMA Designation HMA Design Binder #

Plates # Marshall specimens

1 AC 11 Marshall 50/70 (Croatia) 13 18

2 AC 11 PRADO 50/70 (Croatia) 1 -

6 AC 11 Marshall SBS 50/90 (Croatia) 13 18

7 AC 11 PRADO SBS 50/90 (Croatia) 1 -

13 AC 11 Marshall 70/100 (Croatia) 13 18

14 AC 11 PRADO 70/100 (Croatia) 1 -

16 AC 11 Marshall PmB 25/55-55 (Austria) 13 18

“A” category

HRUSKOVEC silicate aggregate

17 AC 11 PRADO PmB 25/55-55 (Austria) 1 -

Total: 56 72

5.4.2 Final preparation, selection and transportati on of asphalt specimens

Final test specimens were prepared from plate specimens by sawing or drilling, depending on the type of laboratory testing they were to be subjected to (Picture 5-4 and Picture 5-5). Plates of 50 mm thickness were prepared for testing of permanent deformities by rutting; cores of 200 mm in diameter were subsequently drilled out of those plates. Plates of 80 mm thickness were prepared for TSRST, which were transported to the laboratory where the testing was to take place.

Picture 5-4 Laboratory drill



Picture 5-4 Cores drilled from plate samples

Plates of 60 mm thickness were prepared for fatigue testing on small beams, which were transported to the laboratory where the testing was to take place. Plates of 50 mm thickness were prepared for fatigue testing on cylindrical specimens and rigidity testing; cylindrical specimens were drilled subsequently, which were transported to the laboratories where the testing was to take place. The share of voids was determined on all the specimens prior to transportation. Only those specimens were approved whose share of voids was within the range of ± 1 %(v/v) of the target value. The samples were transported in appropriate wooden packaging (Picture 5-6), marked by the asphalt mixture number (A) and the number of prepared plate (B), protected and secured from damage during transportation. Note: In case the number of a prepared plate is larger than the planned number of plates for one type of asphalt mixture, it means that some plates were discarded because the share of voids did not comply with the requirements concerning the prescribed range of targeted void share.



Picture 5-5 Packaging of specimens for transportati on

5.4.3 Properties of prepared asphalt specimens

Data on values of void share in asphalt specimens prepared from AC 11 asphalt-concrete plates of “A” category (HRUSKOVEC silicate aggregate) are presented in Tables 5-7 and 5-8.

Table 5-7 Properties of specimens prepared from AC 11 asphalt-concrete plates (Marshall method) for WP 3 programs

Asphalt Mix & Plates designation 1 13 6 16

Asphalt Concrete - AC 11

HRUSKOVEC - diabas Marshall Design

50/70

Croatia

70/100

Croatia

PmB 50-90

Croatia

PmB 25/55-55

Austria

VAVERAGE %(V/V) 4.9 4.5 4.9 4.8

VMIN %(V/V) 3.9 3.7 4.0 4.2

VMAX %(V/V) 5.5 5.8 5.7 5.2

Standard Deviation %(V/V) 0.443 0.505 0.557 0.344

Air Voids

N - 33 33 33 33

Table 5-8 Properties of specimens prepared from AC 11 asphalt-concrete plates (PRADO method) for WP 3 program

Asphalt Mix & Plates designation 2 14 7 17

Asphalt Concrete - AC 11 HRUSKOVEC - diabas

PRADO Design

50/70 Croatia

70/100 Croatia

PmB 50-90 Croatia


VAVERAGE %(V/V) 5.0 5.2 5.0 5.0

VMIN %(V/V) 4.9 5.2 5.0 4.3

VMAX %(V/V) 5.1 5.3 5.1 5.3

Standard Deviation %(V/V) 0.139 0.072 0.019 0.589

Air Voids

N - 3 3 3 3



6 RESULTS OF LABORATORY TESTS

According to the Experimental program which is predicted in WP 3, Task 3.3 the aim of laboratory tests is to determine the target functional properties of asphalt mixtures which are relevant for various climate and traffic conditions, i.e. stiffness modulus, permanent deformation and fatigue. The following tests were performed:

• Testing dynamic characteristics with Nottingham Asphalt Tester (NAT)

− ITSM (Indirect Tensile Stiffness Modulus Test), − VRLT (Vacuum Repeated Load Test) and − ITFT (Indirect Tensile Fatigue Test).

• Rutting resistance – wheel tracking test – WTT (EN 12697-22),

• Low temperature resistance - TSRST test and

• Fatigue test 2PBT (EN 12697-24 Annex A).

The entire reports of laboratory tests are in the Appendices from A7 to A10.

6.1 Dynamic testing using NAT

Dynamic tests on asphalt mixture AB-11s, designed by PRADO and Marshall methods, are performed on Nottingham Asphalt Tester (NAT 14). With NAT following tests are done:

• Determination of the modulus of indirect tensile stiffness according to EN 12697-26.

• Indirect tension test is used to determine dynamic stiffness modulus at 200C and 124µs (IT-CY),

• Testing the resistance to permanent deformation according to EN 12697-25, Resistance to permanent deformation is determined with dynamic creep test with confine axial strain at 300C after 1800 cycles of load,

• Testing the resistance to fatigue in the indirect tensile test (IT-CY) at 200C and 1,28Hz, according to the EN 12697-24.

For these tests were used the cylindrical samples of diameter Φ100 mm and thickness of 50 mm, cut out from beam samples, dimensions of 50 x 50 x 410 mm which has been prepared and send by IGH. There were tested totally 108 samples.

6.1.1 Determination the indirect tensile stiffness modulus (ITSM)

Indirect Tensile Stiffness Modulus Test (ITSM) is a simple and rapid test method for measuring stiffness modulus of asphalt mixture which is the most important input for pavement design to obtain the structural behaviour in the road. Stiffness modulus is dependent on a number of factors such as: asphalt mixture composition, binder grade and level of compaction as well as of test conditions (temperature, loading time and the stress magnitude at elevated stress level) [7].

Principle of ITSM test is that cylindrical specimen is exposed to repeated sinusoidal compressive loads through the vertical diameter plane, which develops a relatively uniform tensile stress perpendicular to the direction of the applied load and along the vertical diametral plane. The resulting horizontal deformation of the specimen is measured and an assumed Poisson’s ratio is used to calculate the tensile strain at the centre of the specimen.



According to the EN 12697-26 [8], stiffness modulus are calculated using measurements from the 5 load pulses and using following formula:

( )( )hz

27,0FSm ×

+ν×= …………………………………………..(1)

Sm - stiffness modulus (MPa)

F - applied vertical load (N)

ν - Poisson`s ratio (0,35)

z - amplitude of the horizontal deformation(mm)

h - thickness of the specimen (mm)

The stiffness modulus (Sm) of asphalt samples was determined in ITSM tester (Picture 6-1) according to the standard EN 12697-26 (Annex C) and following conditions:

Test temperature 20± 0.5°C

Time of loading 124 ± 4ms

Pulse repetitions: 3.0 ± 0.1s

Number of load cycles 5

Picture 6-1 NAT with ITSM Tester

Results of testing are shown that generally asphalt mixtures designed by PRADO software has lower stiffness modulus than asphalt mixtures designed by Marshall method. Asphalt mixtures with bitumen B 50/70 and polymer-modified binder has higher stiffness modulus than asphalt mixture with bitumen B 70/100. Detailed test results are shown in Appendix A7.



6.1.2 Determination the permanent deformation (VRLT - Vacuum Repeated Load Test )

Vacuum repeated load test (VRLT) is a standard test methods to determine the resistance to permanent deformation of a bituminous mixture by cyclic compression test with confinement. The test make it possible to rank various mixes or to check on the acceptability of a give n mix. They do not allow making a quantitative prediction of rutting in the field to be made. VRLT is used for determining the creep characteristics of asphalt mixtures by means of an uniaxial cyclic compression test with some confinement present. Confinement of the sample is necessary to predict realistic rutting behaviour [9].

The method is applicable to cylindrical test specimens having a thickness between 30mm and 75 mm and nominal diameter of 100mm, 150mm or 200mm [10].

A cylindrical test specimen, maintained at elevated conditioning temperature, is placed between two plan parallel loading platens. The specimen is subjected to a cyclic axial block pressure under confine shear stress (see Picture 6-2). During the test the change in height of the specimen is measured at specified numbers of load application. From this, the cumulative axial strain (permanent deformation) of the test specimen is determined as a function of the number of load applications. The results are represented in a creep curves as given in Figure 7-6.From this, the creep characteristics of the specimens are computed.

Picture 6-2 VRLT Tester



The cumulative axial strain (εn) after n-load applications shall be calculated in percent (%) from the following equation:

100

h

h

0n ×∆=ε

……….……………………………………. (2)

where

εn is the cumulative axial strain after n load applications, (%)

h0 is the average height of specimen, (mm)

∆h is the axial deformation (h0-hn), (mm)

hn is the height of sample after n load applications, (mm)

Also, from the test results, creep rate (fc) and creep modulus (En) can be calculated from the following equations:

21

2n1nc nn

f−

ε−ε=

……………………………………………… (3)

1000E

nn ×

εσ=

……………………………...……………… (4)

where

fc is the creep rate (micro-strain/loading pulse)

εn1 ;εn2 is the cumulative axial strain after n1, n2 load applications, (micro-strain)

En is the creep modulus after n load applications, (MPa)

σ is the applied stress, (kPa)

Determination of the resistance to permanent deformation in this test is made under the cycling compression with confine shear strain according to the standard DD 226:1996, and conditions:

Test temperature 30 ± 0,5°C

Axial stress 100 ± 2kPa

Load period 1 ± 10ms

Unload period 1 ± 10ms

Number of load applications 1800

Confined shear stress 50 kPa

Results of testing are shown that the resistance to permanent deformation of asphalt mixtures with bitumen B 50/70 and polymer-modified binders are higher than with bitumen B 70/100. Detailed test results are given in Appendix A7.



6.1.3 Determination the resistance to fatigue (ITFT - Indirect Tensile Fatigue Test )

The repeated load indirect tensile test (ITFT) are simple and fast method for testing fatigue properties of asphalt mixture. The procedure is used to rank bituminous mixtures on the basis of resistance to fatigue, as a guide to relative performance in the pavement, to obtain data for estimating the structural behavior in the road in the same order as more sophisticated types of fatigue test such as two-point bending and axial-tension compression test.

Picture 6-3 ITF Tester

The principle of ITFT test, like with ITSM test, is that cylindrical specimen is exposed to repeated sinusoidal compressive loads through the vertical diameter plane, which develops a relatively uniform tensile stress perpendicular to the direction of the applied load and along the vertical diametral plane (see Picture 6-3). The resulting horizontal deformation of the specimen is measured and an assumed Poisson’s ratio is used to calculate the tensile strain at the centre of the specimen. The fatigue life is defined as the total number of load applications before fracture of the specimen occurs. There are two main types of fatigue test , namely controlled stress and controlled strain. In a controlled stress test the magnitude of the applied stress pulse is maintained constant until failure. In a controlled strain test the magnitude of the strain is maintained constant during the test. Whereas failure usually occurs relatively soon after crack initiation under controlled stress condition, the crack propagation time (the period between crack initiation and complete failure) in controlled strain is generally a considerable portion of the total test period. In controlled strain testing, therefore, the test is usually terminated when the stiffness modulus of the specimen has fallen to certain percentage (e.g. 50%) of the stiffness modulus at the start of the test. Currently, on the NAT it is only possible to carry out controlled stress testing because there is no satisfactory method of monitoring horizontal deformation. Consequently, the test involves measuring stiffness, as in the ITST, and during the fatigue test (ITFT) permanent vertical



deformation are monitored under control stress conditions (from 100 to 800 kPa) until a level of 50% of vertical deformations is reached. At this point, the specimen is considered to have failed. The results of testing are plotted as a number of load applications to failure versus horizontal strain on log-log axes and results is linear regression [11]. Number of cycles till failure (N) is than calculated at horizontal micro-dilatation of 50 x10-6 mm/mm. Results can be also expressed as a horizontal micro-dilatation after 106 cycles of load applications (ε6). According to the EN 12697-24 [12] and DD ABF [13], the maximum horizontal tensile strain and stress at the centre o the specimen shall be calculated with the following equitation’s:

hD

F20 ××π

=σ …………………………………………(5)

( )1000

S

31

m

00 ×

υ+×σ=ε …………………………………(6)

where

σ0 – is the tensile stress at specimen centre, (kPa)

ε0 – is the tensile horizontal strain at the centre of the specimen, (micro-strain)

Sm – is the stiffness modulus (MPa)

F - is the applied vertical load (N)

ν - is the Poisson’s ratio (0,35)

D - is the specimen diameter (m)

h - is the thickness of the specimen (m)

The resistance to fatigue of asphalt samples on NAT was determined in the indirect tensile fatigue test on cylindrical samples of diameter Φ100 mm and thickness of 50 mm.

The test was made at following conditions:

Test temperature 20 ± 0.5°C

Loading time 124 ± 4ms (128 Hz)

Critical horizontal strain 50 x 10-6 (mm/mm

Test are performed at constant stress level till failure and the results are expressed from linear regression ε0 = f(N) as a number of cycles (N) at horizontal micro-dilatation of 50 x10-6 mm/mm.

The resistance to fatigue and longer fatigue life are found to be with asphalt mixture containing polymer-modified binder PmB 25/55-55 and softer bitumen B 70/100 than with asphalt mixture with harder type of bitumen B 50/70. Some unexpected results arise with fatigue properties of asphalt mixture containing PmB 50/90, worse than conventional bitumen. The expectation was that polymer-modified binder PmB 50/90 will more influence to resistance to fatigue of asphalt mixture due to elastic characteristics of SBS-polymer than conventional binders B 50/70 and B 70/100. One possible reason why it not happen is potential non-homogeneity of binder during sample preparation. Analysing the test results obtained on NAT it can be concluded that only asphalt mixtures with polymer-modified binders has satisfactory stiffness, resistance to permanent deformation and resistance to fatigue, i.e. PmB 25/55-55 showed better characteristics and more influence to the performance properties of asphalt pavement than asphalt mixture with PmB 50/90. The entire report of ITFT tests can be find in the Appendix A7.



6.2 Rutting resistance using WTT

One of the major forms of distress present in HMA pavements is rutting or permanent deformation. This type of distress is characterized by longitudinal depression in wheel paths of a roadway with small upheavals to the sides. Aggregate properties, binder, and mixture properties greatly influence the permanent deformation characteristics of HMA pavements. In this part of research we investigated the influence of bitumen type on the rutting resistance of asphalt concrete with “A” types of aggregate (silicate). At the present time, a number of laboratory tests exist that are used to evaluate the resistance of HMA mixtures to permanent deformations. In this task we tested rutting resistance, using wheel tracking test, according to EN 12697-22 with small size device (procedure B, testing in air) at 60ºC (Picture 6-4).

Picture 6-4 Wheel tracker COOPER-CRT-WTEN1

According to work program, IGH prepared asphalt slabs using roller compactor with a smooth steel roller according to the EN 12697-33. We prepared 4 asphalt mixes, designed by Marshall Method, using laboratory mixer according to EN 12697-35. For each mixture were prepared 2 slabs. From each slab was drilled one cylindrical test specimen with the diameter of 200 mm. Bulk density of each specimen was determined according to EN 12697-6 (procedure B: saturated surface dry). The asphalt mixes type AC 11 with silicate aggregate (previously defined composition) were made with 4 various types of bitumen:



• AC 11 – SILICATE AGGREGATE (HRUŠKOVEC):

− Mixture “13”: with road bitumen 70/100 − Mixture “1”: with road bitumen 50/70 − Mixture “6”: with polymer modified binder PmB 50/90S − Mixture “16”: with polymer modified binder PmB 25/55-55

Total of 8 asphalt specimens were tested (2 specimens for each test). Test conditions:

• test temperature: 60 ºC;

• number of wheel passes 20 000.

According to the EN 12697-22 test results are: • wheel-tracking slope, WTSAIR, of individual test specimens;

• mean wheel-tracking slope, WTSAIR, of two test specimens;

• proportional rut depth, PRDAIR, at 10 000 cycles of individual specimens;

• mean proportional rut depth, PRDAIR, at 10 000 cycles;

• rut depth, RDAIR, at 10 000 cycles of individual specimens;

• mean rut depth, RDAIR, at 10 000 cycles.

According to the test results it was concluded that asphalt mixtures AC 11 with harder type of binder (higher viscosity, higher softening point and lower penetration value) showed lower value of rutting depth and smaller rutting slope which mean better resistance to rutting. The worst resistance to rutting showed asphalt mixture with B 70/100 and the best resistance asphalt mixtures with PmB 25/55-55 and PmB 50/90. The viscosity of binder as well as softening point is a good parameter for predicting rutting resistance of asphalt mixture. The entire report of rutting resistance are in the Appendix A8.

6.3 Testing and evaluation of fatigue

The reinforced and unreinforced materials can be used in the road and highway pavement layers. Bituminous mixtures consisting of crushed aggregate and bitumen binder are one of materials used in road building industry. They are viscoelastic and design methods of asphalt pavements use their deformation characteristics for examination of pavement proposal.

Various tests and methods are applied for testing of viscoelastic materials. These tests can be static or dynamic. The dynamic test of the complex modulus E* enables to test the bituminous mixtures in the range of frequencies from 6 Hz to 25 Hz. These frequencies express the passage of the car on a road.

The European Standard specifies the testing methods for characterizing the fatigue of bituminous mixtures. These tests are performed on compacted bituminous material under a sinusoidal loading or other controlled loading, using different types of specimens and supports. Outputs of tests can be used in different ways. They give a possibility to estimate performance of mixture in the pavement, to rank bituminous mixtures on the basis of resistance to fatigue or to judge asphalts according to specifications for bituminous mixtures.

The method of complex modulus (E*) can be used for dynamic testing of viscoelastic materials (Burgers solid). The viscoelastic characteristics of asphalt mixtures depend on sinusoidal stress which is caused by harmonic force. The deformation of the tested sample changes and there is a phase delay in relation to the harmonic force (Figure 6-1).



Im

Re

M.ω2

Po /y o

P/yo

ψ ϕϕϕϕ

E1

E2

|E*|

Figure 6-1 Scheme of complex modulus

Fatigue of bituminous mixtures is a very important indicator of quality. The Wöhler curve is used to determine parameters of fatigue. The fatigue test is similar to the complex modulus test (E*) but the time of the test is longer. Three different deviations of free end of sample have to be used during the tests. Measuring finishes when the value of complex modulus (stress amplitude) decreases (for every specimen) to one half of starting value. The deformation of free end of trapezoid is constant during the test.

The fatigue is reduction of strength of a material under repeated loading when compared to the strength under a single load. Conventional criteria of failure (constant displacement) is the number of load applications Nf/50 where the value of complex modulus is one half of its initial value. Initial complex modulus is complex stiffness modulus after 100 load applications (Smix,0). Fatigue life of a specimen is a number of cycles Ni,j,k corresponding with the conventional criteria of failure for the set of test conditions k (temperature, frequency and loading mode; e.g. constant deviation level or constant force level and/or any other constant loading condition).

The Two Point Bending Test (2 PBT) for the SPENS project were carried out according to the European standard EN 12697-24 Bituminous mixtures - Test methods for hot mix asphalt – Part 24: Resistance to fatigue, Annex A - Two-point bending test on trapezoidal shaped specimens. The slabs of asphalts (4 mixes with different binders, 2 slabs for each mix) were prepared in IGH for 2 PBT and transported to the laboratory of University of Zilina. Testing specimens (trapezoids) were sawn from the slabs of asphalts produced in IGH. The tests were carried out in the laboratory of Department of Construction Management. The equipment works with constant deviation with possible changes of frequency and temperature during tests. The temperature during fatigue tests was +10°C and the frequency of 20 Hz. Three different deviations of the free end of sample were used for each mixture. Deviations were chosen to satisfy the provision of European standard EN 12697 – 24, Annex A that require one third of results has to reach at least 1 million loading cycles. Six valid measurements were required for evaluation. Specimens were tempered 12 hours before measuring in the climatic chamber (Picture 6-5). Test procedure consisted of:

• adjusting of deviation at the head of isosceles trapezoidal console of test sample;

• recording the change of the force during the test (test was stopped when the specimen was broken or the value of complex modulus reached conventional criteria of failure);

• determination of the fatigue line of the test sample when the failure criterion is achieved.



Picture 6-5 Test sample in the climatic chamber

Test specimens were tested according to the standard EN 12697–24, Annex A (two point bending test method). Ten samples from each mixture were tested at temperature of +10°C and frequency of 20 Hz. The results of measurements were evaluated, fatigue parameters were defined and the fatigue line for each asphalt mixture was determined. Important results are following:

• the best mixture was AC-11 with binder B 70/100 (non modified);

• the mixtures with polymer modified binders have similar resistance to fatigue;

• the mixtures with polymer modified binders have slightly lower resistance to fatigue than AC-11 B 70/100, but are in the same category;

• spacing of ε6 value of B 70/100 from polymer modified binders is higher than the difference of ε6 value between B 50/70 and polymer modified binders.

The entire report of fatigue tests are in the Appendix A9.

6.4 Thermal stress restrained specimen testing

The one of the important performance parameters of asphalt pavement is low temperature cracking resistance. Evaluation of this characteristic was performed at IBDiM laboratory with use of Temperature Stress Restrained Specimen Test (TSRST) according to procedure which is given in the American Association of State Highway and Transportation Officials Method (AASHTOTP10).

Tests are performed on the MTS device (see Picture 6-6). Test specimens are rectangular shape with size of 50 x 50 x 250 mm. Test beams were sawed from the slabs delivered by IGH. Steel disks are glued to the bottom and top of specimen and enable to fix the sample to the testing device. Three strain extensometers are attached to the sides of the beam that is then put into the conditioning chamber. Initial temperature is 5˚C, which is lowered with speed of 10˚C/h. MTS device doesn’t allow to any shrinkage of the beam. There are thermal stresses induced in the specimen. The end of the test ensues after specimen crack. Cracking temperature and cracking stress are the results of the test.



Picture 6-6 Instrumented specimen at the temperatur e chamber

At the base of detailed results, for all mixtures was calculated mean stress at failure and determined the mean cracking temperature.

The mathematical analysis of received results leads to the following conclusions:

• Homogeneity of results for mixtures no. 1, 13 and 16 are higher than for mix number 6. This behaviour could be inducted by: not sufficient homogeneity of binder, low adhesion of binder or by faulty of the test samples preparing.

• Mixture 13 has the lowest cracking temperature,

• Mixture 1 has the highest cracking temperature,

• Mixture with polymer binder can resist higher stress then mixture with road binder,

• Results confirmed that cracking temperature mainly depend on properties of binder.

The entire report of TSRST are in the Appendix A10.



7 CONCLUSIONS AND FUTURE RESEARCH

7.1 Binder test results

Binder properties have a decisive influence on asphalt mix properties. At service temperatures and typical loading times in trafficked road constructions, asphalt binders display visco-elastic properties which are highly temperature dependent. Typically the complex dynamic viscosity varies over eight orders of magnitude between -20°C and 60°C. Such extreme temperature susceptibility makes it necessary to characterize the visco-elastic properties over the whole service temperature interval, and to some extent also into the mixing and laying temperatures, to fully describe the engineering properties of the binders. The entire reports of laboratory tests are presented in the Appendix A1. Four binders have been used in this study:

• 70/100 from INA, Croatia

• 50/70 from INA, Croatia

• PMB 25/55-55 from Starfalt, Austria

• PmB 50-90 S from MODIBIT, Croatia

The PmB 50-90 S binder, has according to the product specification, a penetration at 25°C between 50 and 90 dmm and a softening point of at least 65°C and thus does not fit in to the classes defined in the norm EN 14023. The other binders should conform to the European product specifications EN 12591 and EN 14023. Reference to the test results presented in table 1-1 (Appendix 1) the penetration values and softening points are according to the specifications for respective binder. The PmB 25/55-55 binder have the lowest penetration of the studied binders but the PmB 50-90 S has the highest softening point (Figure 7-1).

Penetration & softening point

0

10

20

30

40

50

60

70

80

70/100 50/70 PMB 25/55-55 PmB 50- 90 S

Pen

etra

tion

at 2

5°C

(dm

m)

0

10

20

30

40

50

60

70

80

Sof

teni

ng p

oint

(°C

)

Penetration Softening point

Figure 7-1 Penetration at 25°C and softening point.

The kinematic at 135°C and the dynamic viscosities at 60°C are presented in Figure 7-2. The two viscosities are correlated as expected.



In Figure 7-3 the softening point and the dynamic viscosity at 60°C are compared. Although the PmB 25/55-55 and PmB 50-90 S has similar softening points, 67°C and 71°C respectively the former binder has a dynamic viscosity that is more than three times higher compared to the latter binder, which illustrates that dynamic viscosity at 60°C is not applicable for binders with softening point above 60°C (EAPA, 2009).

Dynamic and kinematic viscosity

0

1000

2000

3000

4000

5000

6000

70/100 50/70 PMB 25/55-55 PmB 50- 90 S

Dyn

amic

vis

cosi

ty (

Pas

)

0

500

1000

1500

2000

2500

Kin

emat

ic v

isco

sity

(m

m2 /s

)

Dynamic viscosity (60°C) Kinematic viscosity (135°C)

Dynamic viscosity at 60°C and softening point

0

1000

2000

3000

4000

5000

6000

70/100 50/70 PMB 25/55-55 PmB 50- 90 S

Dyn

amic

vis

cosi

ty (

Pas

)

0

10

20

30

40

50

60

70

80

Sof

teni

ng p

oint

(°C

)

Dynamic viscosity (60°C) Softening point

Figure 7-2 Dynamic and kinematic viscosity Figur e 7-3 Dynamic viscosity and softening point

The Fraass breaking point values are as expected according to the specifications for the binders except for the PmB 50-90 S which according to the specification should be below -19°C, however the test has a low reproducibi lity, making it difficult to draw firm conclusions from the test. As expected the softest binder has the lowest breaking point value. The polymer modified binders were tested for elastic recovery and force ductility. The results are shown in Table 1-6 (Appendix 1). Both binders have excellent elastic recovery although somewhat higher for the PmB 50-90 S binder. The elongation at break is higher for the PmB 50-90 S than for the PmB 25/55-55 binder at 10°C bu t the order is reversed at 25°C. The deformation energy and the maximum force at elongation are approximately twice as high for the PmB 25/55-55 compared to the PmB 50-90 S at both temperatures studied

The low temperature properties were recorded on the binders with a bending beam rheometer. The temperature when the stiffness of a precisely shaped bar after 60 seconds load of 100g exceeds 300MPa is recorded as well as the temperature when the creep rate, called m, is lower than 0.3. The highest of these values are lowest temperature in where the binder will have enough flexibility to cope with temperature or load related strains. The values are presented in Table 1-7 (Appendix 1). For comparison the Fraass breaking point is also presented in the same table. In this study the Fraass breaking point and the bending beam temperatures have the same ranking. The softest conventional binder has the lowest BBR temperature and the two polymer modified binders have higher BBR temperatures than the conventional binders although the difference the conventional and the modified binders are not so large in BBR temperature as they are with respect to Fraass breaking point.

The complex modulus and phase angle were measured with a dynamic shear rheometer fitted with parallel plates between 36 and 62°C. Th e data is presented as logarithm of the complex modulus and the phase angle in Figures 7-4 and 7-5. As expected, the 70/100 binder has the lowest complex modulus over the temperature range studied. Over the whole temperature range the polymer modified binders have larger complex modulus compared to the 50/70 binder. The phase angle plot reveals completely opposite properties of the two classes of binders, see Figure 7-5. While the phase angle for the paving grade binders rapidly approaches 90° when the temperature is incr eased, the polymer modified binders have a considerable amount of elasticity even at high temperatures. This will have a great impact on the asphalt concrete properties.



Logarithm of complex modulus

3

3.5

4

4.5

5

5.5

6

32 37 42 47 52 57 62

Temperature (°C)

Log(

com

plex

mod

ulus

)

70/100

50/70

PMB 25/55-55

PmB 50- 90 S

Figure 7-4 Complex modulus (logarithm of) versus te mperature.

Phase angle v. temperature

55

60

65

70

75

80

85

32 37 42 47 52 57 62

Temperature (°C)

Pha

se a

ngle

° 70/100

50/70

PMB 25/55-55

PmB 50- 90 S

Figure 7-5 Phase angle versus temperature.



7.2 Marshall test results

Asphalt mix composition AC-11 are designed by Marshall method in a way that the optimum binder content with all asphalt mixtures would be the same 5.8% irrespectively of type of binders used for mixture designing. Due to different binders used only small changes are with bulk characteristics of asphalt mix. According to the test results for this asphalt mixtures AC-11 there were found a good correlation between Marshall stability and Marshall stiffness at 600C and penetration values at 250C of used binders (see figures 7-1 and 7-2). Poor correlation were found with stability and stiffness with softening point of binders. This conclusions are valid only for this asphalt mixtures AC-11. For the future research it would be interesting to find out correlation for other types of asphalt mixture and other aggregates.

Figure 7-6 Correlation between stability of asphalt mixture and penetration of binder

Figure 7-7 Correlation between stiffness of asphalt mixture and penetration of binder

Marshall stability & Penetration

y = 517,17x -0,8723

R2 = 0,9879

8

10

12

14

16

18

20

40 50 60 70 80

Penetration of binder at 25C (dmm)

Sta

bili

ty a

t 60

C (

kN)

Marshall stiffness & Penetration

y = 54,362x -0,6353

R2 = 0,9054

2,0

2,5

3,0

3,5

4,0

4,5

5,0

5,5

40 50 60 70 80

Penetration of binder at 25C (dmm)

Stif

fnes

s at

60C

(kN

/mm

)



7.3 Asphalt mixture composition designed using PRA DO

The asphalt mixture composition with four types of binder designed by PRADO software are almost the same as with Marshall method of design. The minor differences are with binder contents, i.e. between 0,1 to 0,2%, but the bulk characteristics of asphalt mixture (volume of voids, volume of voids in mineral mixture and volume of voids in mineral mixture filled with binder) are the same with both methods of design (see Table 3-3 and tables in Chapter 4). That was the reason to decide that there are no need to perform all dynamic tests with all asphalt mixtures (designed by PRADO and Marshall methods) than only with asphalt mixtures designed by Marshall method, so only values of stiffness modulus were determined with all asphalt mixtures, .

7.4 Dynamic test results using NAT

Dynamic stiffness modulus of asphalt mixture at same temperature and frequency highly depend of binder and aggregate quality and mix composition. By assume that the grading and quality of aggregate in asphalt mixture AC-11 are same we can analyze the test results only by binder quality. Variation of stiffness modulus values with same asphalt mixtures are due to the variation of binder characteristics, specially with PmB, and asphalt mix composition during sample preparation. The variations in mix composition as well as compaction degree of samples should significantly influence the properties of bituminous mixes such as stiffness modulus and fatigue strength. These variability’s should be taken into consideration when analysing and prediction pavement performance [14].

Studding the results on testing dynamic characteristics of asphalt mixtures AC-11 with four different binders, designed by Marshall method and PRADO software performed on NAT, following conclusions can be made:

• Results of testing showed that generally asphalt mixture AC-11 designed by PRADO software has lower stiffness modulus than asphalt mixtures designed by Marshall method, specially with mixture No.7 with PmB 50/90 probably due to binder non-homogeneity during sample preparation (Figure 7-3).

Asphalt mixtures AC-11 with bitumen B 50/70 and polymer-modified binder has higher stiffness modulus than asphalt mixture with bitumen B 70/100 which are in compliance with penetration of binders. Binders with lower penetration (harder bitumen) showed higher stiffness modulus than binders with higher penetration (softer binder) (Figure 7-4).

Figure 7-8 Comparison the stiffness modulus of asp halt mixture at 20 0C with different binders designed by Marshall and PRADO method

STIFFNESS MODULUS & BINDER TYPE(Marshall Design)

2048

1630

2112

1274

0

500

1000

1500

2000

2500

B 50/70 B 70/100 PmB 50/90 PmB 25/55-55

STIFFNESS MODULUS & BINDER TYPE(PRADO Design)

1796

932

1496

2224

1237

0

500

1000

1500

2000

2500

B 50/70 B 70/100 PmB 50/90 PmB 50/90ext.

PmB 25/55-55



Figure 7-9 Correlation between the Sm of asphalt mi xtures and the penetration of binders

Poor correlation are found between the stiffness modulus measured on NAT for

asphalt mixtures AC-11 designed by different methods with caution of very limited data. If we assumed that the value for stiffness modulus for asphalt mixture with PmB 50/90 (PRADO design) are incorrect (lower) than with asphalt mixture designed by Marshall method due to binder non-homogeneity and if we extrapolated this value the correlation in that case are better (Figure 7-5). Future research on different types of asphalt mixtures may improve this correlation.

Figure 7-10 Correlation between the Sm designed by PRADO and Marshall methods

(black line on diagram represent correlation before correction the value for stiffness modulus and red line represent correlation with corrected value)

Stiffness on NAT (PRADO & Marshall design)

y = 1,1758x - 529,16

R2 = 0,6391

Extrapolated valuey = 1,009x - 93,559

R2 = 0,868

500

1000

1500

2000

2500

1000 1500 2000 2500

Stiffness modulus (Marshall design)

Stif

fnes

s m

odul

us (

PR

AD

O d

esig

n)

y = -29.075x + 3505.4R2 = 0.9924

y = -25.675x + 3370.7R2 = 0.9075

0

500

1000

1500

2000

2500

40 50 60 70 80

Penetration 25 0C (1/10 mm)

Stif

fnes

s m

odu

lus

200 C

(M

Pa)

Marshall Design

PRADO Design



• The resistance to permanent deformation of asphalt mixtures AC-11 with bitumen B 50/70 and polymer-modified binders are higher than with bitumen B 70/100 which are in compliance with softening point of binders. Binders with higher softening point (harder bitumen) shown better resistance to permanent deformation than binders with lower softening point (softer binder).

Further research has to be done to establish correlation between axial micro-dilatation tested in VRLT on different types of asphalt mixtures and softening point of binders.

Figure 7-11 Resistance to deformation of AC-11 with different binders performed on NAT

• Asphalt mixtures with modified binders PmB 50/90 has lower resistance to

permanent deformation at 300C than at higher temperature (400C, 500C) due to elastic deformation of SBS-polymer in comparison to the asphalt mixture with conventional bitumen B 50/70. It seems that test temperature of 300C is not convenient for PmB. At lower temperatures elastic deformation of SBS-polymer is much larger than at higher temperatures due to lower accession of strain in function of temperatures than conventional bitumen B 50/70 (see Figure 7-7). Further research is need to highlight this observation.

0,0

0,5

1,0

1,5

2,0

2,5

30 40 50

Temperature (°C)

Axi

al m

icro

-str

ain

(%)

B 50/70

PmB 50/90

Figure 7-12 The accession of strain vs. temperature with B 50/70 and PmB 50/90 [15]

0,000

0,200

0,400

0,600

0,800

1,000

1,200

1,400

1,600

1,800

0 500 1000 1500 2000

Number of load cycles

Axi

al m

icro

-dila

tatio

n (%

)

B 70/100

B 50/70

PmB 50/90

PmB 25/55-55



• The resistance to fatigue and longer fatigue life are found to be with asphalt mixture AC-11 containing polymer-modified binder PmB 25/55-55 and softer bitumen B 70/100 than with same mix with harder type of bitumen B 50/70.

It is worth to highlight that asphalt mixture AC-11 with PmB 25/55-55 shows the highest resistance to fatigue despite the highest stiffness and good creep deformation (see Figures 7-3, 7-6 and 7-8).

Some unexpected results arise with fatigue properties of asphalt mixture containing PmB 50/90, worse than conventional bitumen. The expectation was that polymer-modified binder PmB 50/90 will more influence to resistance to fatigue of asphalt mixture due to elastic characteristics of SBS-polymer than conventional binders B 50/70 and B 70/100. One possible reason why it not happen is potential non-homogeneity of binder during sample preparation.

In future research it would be interesting to investigate the resistance to fatigue with other types of asphalt mixtures and binders and to find correlation between fatigue resistance and standard characteristics of binder.

1

10

100

1000

1,0E+02 1,0E+03 1,0E+04 1,0E+05 1,0E+06 1,0E+07 1,0E+08 1,0E+09

Number of cycles till failure

Hor

izon

tal m

icro

-dila

tatio

n

εε εε x

(10

-6 m

m/m

m)

B 50/70

B 70/100

PmB 50/90

PmB 25/55-55

Figure 7-13 Number of cycles to fatigue of asphalt mixtures with different binders

• The results of testing dynamic characteristics of asphalt mixtures AC-11 (Marshall

design), performed on NAT, are compared with dynamic parameters calculated in software PRADO (PRADO design) at same test conditions and shown in Table 7-1 and Table 7-2. Calculation the dynamic parameters in PRADO were done only for asphalt mixtures with conventional binders (B 50/70 and B70/100) due to restriction of software package for calculation stiffness and fatigue of asphalt mixtures with polymer modified binders [16].



Table 7-1 Comparison the dynamic characteristics of asphalt mixtures with conventional binders performed on NAT (Marshall des ign) and PRADO (PRADO)

B 50/70 B 70/100 Dynamic characteristics

NAT PRADO NAT PRADO

Stiffness modulus, 200C, 124ms (1,28Hz), (MPa) 2048 1644 1274 1120

Horizontal micro-strain ε6 after

106 cycles (200C, 1,28 Hz), (µdef) 69,3 152 120,4 162

Percent of axial micro-strain εv (%mm/mm) at 200C after 1800 loading cycle’s 0,753 0,849 1,584 1,392

Table 7-2 Comparison the dynamic characteristics o f asphalt mixtures with polymer-modified binders performed on NAT (Marshall design) and PRADO

B 50/90 PmB 25/55-55 Dynamic characteristics

NAT PRADO NAT PRADO

Stiffness modulus,200C, 124ms (1,28Hz), (MPa) 1630 - 2112 -

Horizontal micro-strain ε6 after 106 cycles (200C, 1,28 Hz), (µdef)

58,7 - 154,0 -

Percent of axial micro-strain εv (%mm/mm) at 200C after 1800 loading cycle’s

0,890 0,784 0,875 0,496

• Differences between experimental and calculated values of dynamic characteristic

at same temperature and load frequency are more obvious with fatigue resistance of asphalt mixture than with stiffness modulus. Somewhat higher stiffness modulus are obtained with NAT than with PRADO. At same time higher fatigue resistance are obtained in PRADO than through experiments on NAT. Resistance to permanent deformation are similar with both method of determination.

• The results of dynamic tests can be compared with the criteria according to test experience in Serbia for dynamic characteristics of asphalt mixtures tested on NAT (stiffness modulus, number of cycles to fatigue and axial micro-strain) which are given in Table 7-3. Also, in Table 7-4 are given the criteria for axial micro-strain from VRLT at different test temperatures depending on which binders in asphalt mixtures are used (PmB or conventional bitumen).

Table 7-3 Criteria according to experiences in Serb ia for dynamic characteristics of asphalt mixtures tested on NAT [17]

Type of binder Dynamic characteristics

PmB Conventional bitumen

Stiffness modulus, 200C, 124ms (1,28Hz), MPa) > 1.500 > 2.200

Number of cycles to fatigue (N x106) (horizontal micro-strain of 50x10-6 mm/mm), 200C, 1,28 Hz (IT-CY)

> 40 > 30

Percent of axial micro-strain εv (%mm/mm) at 300C after 1800 loading cycle’s

< 1,0 < 0,5



Table 7-4 Criteria according to experience in Serbi a for axial-micro strain of asphalt mixtures tested on NAT at different temperatures

T= 30°C T= 40°C T= 50°C Dynamic characteristics

B 50/70 PmB 50/90 B 50/70 PmB 50/90 B 50/70 PmB 50/90

Axial micro-strain after 1800 loading cycles (%mm/mm)

< 0,5 < 1,0 < 1,0 < 1,0 < 2,5 < 1,5

• Analysing the test results obtained on NAT it can be concluded that only asphalt

mixtures with polymer-modified binders fully satisfied all the criteria given in Table 7-3 and Table 7-4 for stiffness, resistance to permanent deformation and resistance to fatigue, i.e. PmB 25/55-55 showed better characteristics and more influence to the performance properties of asphalt pavement than asphalt mixture with PmB 50/90.

• The application of conventional binders (B 50/70, B 70/100) in asphalt mixture are depended of which dynamic parameters are need to be emphasized, because none of them can satisfy the all performance criteria. For higher stiffness modulus and resistance to permanent deformation it is better to use harder type of bitumen (B 50/70) while for better resistance to fatigue softer bitumen is recommended (B 70/100). Among binder properties penetration, softening point, elastic recovery and phase angle with PmB are the most promising characteristics which influence to the dynamic parameters of asphalt mixture.

7.5 Testing rutting resistance

The rutting resistance of asphalt layer under traffic and climate conditions dependence of asphalt mixture composition, quality of aggregate as well as binder quality. According to the test results it can concluded that asphalt mixtures AC-11 with harder type of binder (higher viscosity, higher softening point, higher deformation energy at 250C and lower penetration value) showed lower value of rutting depth and smaller rutting slope which mean better resistance to rutting. The worst resistance to rutting showed asphalt mixture with B 70/100 and the best resistance asphalt mixtures with PmB 25/55-55 and PmB 50/90 (Figures 7-9 and 7-10).

AC 11 - SILICA AGGREGATE

0

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0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000 16000 17000 18000 19000 20000

Number of passes

Rut

h de

pth

[mm

]

PmB 25/55-55 B 70/100 B 50/70 PmB 50/90S

Figure 7-14 Rutting resistance of AC-11 with differ ent binders tested on WTT



PROPORTIONAL RUTH DEPTH - AC 11 WITH SILICA

0

2

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14

16

B 70/100 B 50/70 PmB 50/90S PmB 25/55-55

Type of bitumen

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iona

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pth

(%)

WHEEL TRACKING SLOPE - AC 11 WITH SILICA

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B 70/100 B 50/70 PmB 50/90S PmB 25/55-55

Type of bitumen

Whe

el tr

acki

ng s

lope

(m

m/1

000

cycl

es)

Figure 7-15 Proportional rut depth and rutting slop e of AC 11 with different binders

The characteristics of binder such as viscosity and softening point more influence to the rutting resistance of asphalt mixture than penetration which are obvious from diagrams shown in Figure 7-11 and Figure 7-12. The viscosity of binder as well as softening point is a good parameter for predicting rutting resistance of asphalt mixture. More research are needed with different types of asphalt mixtures for establishing better correlations between rutting resistance and characteristics of binders.

Rut depth & Viscosity

y = 60,306x -0,3286

R2 = 0,8112

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2

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6

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14

16

0 1000 2000 3000 4000 5000 6000

Dynamic viskosity at 60 0C (Pa.s)

Pro

port

iona

l rut

dep

th (

%)

Rut depth & Penetration

y = 2,1663e0,0183x

R2 = 0,6212

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14

16

20 30 40 50 60 70 80 90

Penetration 25 0C (mm/10)

Pro

port

iona

l rut

dep

th (%

)

Figure 7-16 Correlation between rut depth of AC-11 and viscosity, penetration of

binders

Rut depth & Softening point

y = 105643x -2,3867

R2 = 0,6636

0

2

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6

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40 50 60 70 80

Softening point ( 0C)

Pro

porti

onal

rut

dep

th (

%)

Wheel tracking slope & Softening point

y = -0,0981Ln(x) + 0,4651R2 = 0,7212

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0,1

40 50 60 70 80

Softening point ( 0C)

Rut

slo

pe (

mm

/100

0 cy

cles

)

Figure 7-17 Rut depth and rut slope of AC-11 v.s. s oftening point of binders



Coincidently or not it was find good correlation between results of axial micro-dilatation obtained in VRLT at 300C and proportional rut depth from WTT at 600C for asphalt mixtures AC-11 with different types of binders (see Figure 7-13). Although this correlation are valid only for this asphalt mixture AC-11 with silicate aggregate and one grading it would be interesting to investigate in future research is it valid for other types of asphalt mixtures, other grading, other aggregates and binders and at different test temperatures.

Figure 7-18 Comparison the test results of AC-11 ob tained on VRLT and WTT

7.6 Testing and evaluation of fatigue – 2PBT

Resistance to fatigue of asphalt mixtures AC-11 with 4 types of binders were tested according to the EN 12697– 24, Annex A (two point bending test method) at temperature of +10°C and frequency of 20 Hz. The results of measur ements were evaluated, fatigue parameters were defined and the fatigue line for each asphalt mixture was determined (Figure 7-14).

Important results are following:

• the best mixture was AC-11 with binder B 70/100 (non modified);

• the mixtures with polymer modified binders have similar resistance to fatigue;

• the mixtures with polymer modified binders have slightly lower resistance to fatigue than AC-11 B 70/100, but are in the same category;

According to the categories of the resistance to fatigue described in EN 13108-1 Bituminous mixtures. Material specifications. Part 1: Asphalt Concrete the tested asphalt mixtures AC-11 can be classify as follows:

• AC with binder B 50/70 falls to the second highest category from aspect of fatigue – ε6-260.

• Other mixtures with binder PmB 50/90, PmB 25/55-55 and B 70/100 fall to the highest category – ε6-310. It means these mixtures are very suitable from the aspect of resistance to fatigue according to two point bending test method.

VRLT & WTT

0,0

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1,0

1,5

2,0

0,0 5,0 10,0 15,0 20,0

Proportional rut depth (%)

Per

cent

of a

xial

mic

ro s

train

(%

mm

/mm

)

y = 0,0743x + 0,4684 R2 = 0,9285



Figure 7-19 Comparison of fatigue lines for the fre quency of 20Hz

If the mixtures are compared each other the best mixture is AC-11 with binder B 70/100. The mixtures with polymer modified binders have slightly lower values (higher resistance to fatigue) but they are very similar. The worst resistance to fatigue has the mixture with binder B 50/70 and the spacing from polymer modified binders is lower than the difference between B 70/100 and polymer modified binders.

7.7 Thermal stress restrained specimen test

Results of TSRST of asphalt mixtures AC-11 with 4 types of binders leads to the following conclusions (Figures 7-15, 7-16 and 7-17):

• Homogeneity of results for asphalt mixtures AC-11 with B 50/70, B 70/100 and PmB 25/55-55 are higher than for asphalt mixture with PmB 50/90. This behaviour could be inducted by: not sufficient homogeneity of binder, low adhesion of binder or by faulty of the test samples preparing.

• Asphalt mixture with B 70/100 has the lowest cracking temperature,

• Asphalt mixture with B 50/70 has the highest cracking temperature,

• Mixture with polymer binder can resist higher stress then mixture with road binder,

• Results confirmed that cracking temperature mainly depend on properties of binder.

1,0E+03

1,0E+04

1,0E+05

1,0E+06

1,0E+07

1,00E-04 1,00E-03Strain - log [ εεεε]

log

(Ni)

B 50/70

B 70/100

PmB 25/55-55

PmB 50/90

B 70/100

B 50/70

PmB 25/55-55

PmB 50/90



Figure 7-20 Mean stress at failure for all tested mixtures

Figure 7-21 Mean cracking temperature for all teste d mixtures

Figure 7-22 Mean cracking temperature versus mean s tress at failure for all mixtures

1 – B 50/70

13 – B 70/100

16 – PmB 25/55-55

6 – PmB 50/90

1 – B 50/70

13 – B 70/100

16 – PmB 25/55-55

6 – PmB 50/90

1 – B 50/70

13 – B 70/100

16 – PmB 25/55-55

6 – PmB 50/90



8 KEY FINDINGS AND RECOMMENDATIONS

The aim of research which has been done in WP3 Task 3.3, according to the experimental program, was to define the optimal asphalt mixture composition AC-11 using one silicate aggregate and four different binders by comparing two different methods of designing (Marshall and PRADO) in a such way to determine the functional characteristics of asphalt mix and binder which are related to the target performance indicator of bituminous pavement for various climate and traffic conditions. According to the results of research following key findings were obtained:

• There were found minor differences in mix compositions between two methods of design (Marshall and PRADO) only with binder contents (between 0,1 to 0,2%) for the same bulk characteristics of asphalt mixture (Vm, VMA and VFB).

• For this asphalt mixtures AC-11 there were found a good correlation between Marshall stability and Marshall stiffness at 600C and penetration values at 250C of used binders. Poor correlation were found with stability and stiffness with softening point of binders.

• Generally asphalt mixture AC-11 designed by PRADO software has lower stiffness modulus than asphalt mixtures designed by Marshall method. Binders with lower penetration (harder bitumen) showed higher stiffness modulus than binders with higher penetration (softer binder), i.e AC-11 with B 50/70 and PmB 50/90 and PmB 25/55-55) has higher stiffness modulus than AC-11 with B 70/100.

• With caution of very limited data good correlation were found between the stiffness modulus measured on NAT for asphalt mixtures AC-11 designed by Marshall and PRADO methods. Future research on different types of asphalt mixtures may improve this correlation.

• The resistance to permanent deformation (rutting) of asphalt mixtures AC-11 with harder type of binder (higher viscosity, higher softening point, higher deformation energy at 250C and lower penetration value) showed better resistance to permanent deformation, lower value of rutting depth and smaller rutting slope which mean better resistance to rutting than asphalt mixtures with softer type of binder, i.e AC-11 with B 50/70, PmB 50/90 and PmB 25/55-55 better than AC-11 with B 70/100. It was confirmed through VRLT and WTT tests.

• The viscosity of binder, softening point as well as deformation energy at 250C with PmB is a good parameter for predicting rutting resistance of asphalt mixture. More research are needed with different types of asphalt mixtures for establishing better correlations between rutting resistance and characteristics of binders.

• Coincidently or not it was find good correlation between results of axial micro-dilatation obtained in VRLT at 300C and proportional rut depth from WTT at 600C for asphalt mixtures AC-11 with different types of binders. Although this correlation are valid only for this asphalt mixture AC-11 with silicate aggregate and one grading it would be interesting to investigate in future research is it valid for other types of asphalt mixtures, other grading, other aggregates and binders and at different test temperatures.

• Asphalt mixtures with modified binders PmB 50/90 has lower resistance to permanent deformation at 300C than at higher temperature (400C, 500C) due to elastic deformation of SBS-polymer in comparison to the asphalt mixture with conventional bitumen B 50/70. It seems that test temperature of 300C is not convenient for PmB. Further research is need to highlight this observation.



• The resistance to fatigue and longer fatigue life are found to be with asphalt mixture AC-11 containing polymer-modified binder PmB 25/55-55 and softer bitumen B 70/100 than with harder type of bitumen B 50/70. This was confirmed thorough ITFT and 2PBT tests.

• Resistance to thermal cracks of asphalt mixtures AC-11 testing with TSRST showed that asphalt mixture AC-11 with B 70/100 has the lowest cracking temperature whilst AC-11 with B 50/70 has the highest cracking temperature. Mixture with polymer binder can resist higher stress then mixture with road binder. Test results confirmed that cracking temperature mainly depend on properties of binder.

• The application of conventional binders (B 50/70, B 70/100) in asphalt mixture are depended of which dynamic parameters are need to be emphasized, because none of them can satisfy the all performance criteria. For higher stiffness modulus and resistance to permanent deformation it is better to use harder type of bitumen (B 50/70) while for better resistance to fatigue softer bitumen is recommended (B 70/100). Among binder properties penetration, softening point, elastic recovery and phase angle with PmB are the most promising characteristics which influence to the dynamic parameters of asphalt mixture.

• It is worth to highlight that asphalt mixture AC-11 with PmB 25/55-55 shows the highest resistance to fatigue despite of the highest stiffness and good creep deformation.

• Asphalt mixtures with softer type of binder (B 70/100) can be used for regions with lower temperature and traffic volume where it is important for asphalt pavement to has good resistance to fatigue and thermal cracks while in regions with higher temperature and higher traffic volume it is recommended to use harder type of binder (B 50/70). These binders can’t be used for asphalt pavements in regions with extreme daily temperatures changes and roads with heavy traffic.

• Polymer-modified binders, specially PmB 25/55-55, due to considerable amount of elasticity at low and even at high temperatures, in same time are resistance to rutting and fatigue and thermal cracking. Asphalt mixtures with these binders are mainly used for application in asphalt pavement exposed to heavy traffic and extreme climate changes.

It is important to say that the results of research and conclusions in this WP3 Task 3.3 are valid only for asphalt mixture AC-11 with silicate aggregate “Hruškovec” and binders B 50/70, B 70/100, PmB 50/90 and PmB 25/55-55. For validation of asphalt mix design model it is necessary to test other types of asphalt mixtures with other aggregates and binders.

For the future research it would be interesting to test other types of asphalt mixtures with other aggregates and binders to improve correlations between standard characteristics of binder (viscosity, penetration, softening point, stiffness, phase angle and elasticity) and functional characteristics of asphalt mix (stiffness modulus, resistance to permanent deformation, resistance to fatigue cracks and resistance to thermal cracks) as a performance indicator of bituminous pavement.

Also, further research are needed to verify the correlations between results of VRLT and WTT at different temperatures.



9 SOURCES

9.1 Reference List

1 PAP, I., SMILJANIC, M., TATIC, U., 2008. Evaluation of asphalt mix design methods within the framework of SPENS project, Transport Research Arena Europe 2008, Ljubljana - Slovenia, April 2008, Paper No. 0253 (12.5.14).

2 FRANCKEN, L., 1995. Formulaiton D'Enrobes Bitumeneux PRADO (version F3.95), Centre de Recherces routières, Bruxelles.

3 FRANCKEN, L., VANLESTRAETE, A., LÉONARD, D., and PILATE, D., 2003. New developments in the PRADO volumetric mix design, 6th Symposium on Performance Testing and Evaluation of Bituminous Materials, PTEBM`03, Zurich, Switzerland, pp.1-5.

4 FRANCKEN, L., VANLESTRAETE, A., 1993. New developments in analytical asphalt mix design, Proceedings of the 5th Eurobitume Symposium , Stockholm.

5 SRPS U.E4.014, 1990. Technical requirements for asphaltic concrete pavements 6 University of Washington and Washington State Department of Transportation

Website MARSHALL MIX COMPOSITION DESIGN - ASPHALT CONCRETE (AC 11 surf) http://training.ce.washington.edu/wsdot/Modules/05_mix_design

7 HAKIM, H., SAID, S.,VIMAN, L., Evaluation of indirect tensile test according to EN standard.

8 EN 12697-26 Bituminous mixture. Test methods for hot mix asphalt. Part 26: Stiffness.

9 EN 12697-25 Test methods for hot mix asphalt. Part 25: Cyclic compression test. 10 BS DD 226, 1998. Method for determining resistance to permanent deformation of

bituminous mixtures subject to unconfined repeated loading. 11 The NU-10 User manual 12 EN 12697-24 Bituminous mixture. Test methods for hot mix asphalt. Part 24:

Resistance to fatigue. 13 BS DD ABF 1997. Method for determination of the fatigue characteristics of

bituminous mixtures using indirect tensile fatigue. 14 SAID, S., 1997, Variability in roadbase layer properties conducting indirect tensile

stress, ISAP, Seatle. 15 SMILJANIC, M., PAP,I. TATIC, U., 2009, Effect of binder type on the permanent

deformation resistance of asphalt mix at different temperatures, 7th RILEM Symposium on Advanced Testing and Characterization of Bituminous Materials ATCBM 09, Rhodes, Greece, 27-29 May 2009, Loizos, Partl, Scarpes & Al-Quadi (eds) © 2009 Taylor & Francis Group, London, ISBN 978-0-415-55854-9,981-987.

16 FRANCKEN, L., PRADO Logiciel pour la formulation d`enrobes bitumineux, Manual d`utilisation, Centre de Recherches routières, Bruxelles.

17 PAP, I., 2007. Report on results of testing dynamic characteristics of asphalt mixtures from LOT’s and proposal for new method of asphalt mixture design, European Agency for Reconstruction, Project Implementation Unit of the Roads Directorate, BCEOM, Republic of Serbia, Belgrade.

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