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EU-LIFE+ Environment Policy and GovernanceLIFE 09 ENV/GR/304ROADTIRE

Integration of end-of-life tires in the life cycle of roadconstructionROADTIRE

Deliverable 4.4.1

Report on laboratory results of rubberizedasphalt mixtures made by the dry process

ByAthanasios Kalofotias, DATSE

Sofia Mavridou and Nikolaos Oikonomou, LBM

December 2011

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TABLE OF CONTENTS

1. INTRODUCTION......3

2. DRY PROCESS-GENERAL... .3

3. PRODUCTION OF ASPHALT MIXTURES......4

4. EXAMINATION OF PROPERTIES OF BITUMINOUS MIXTURES AND

EXPERIMENTAL RESULTS ...12

5. EXAMINATION OF THE MICROSTRUCTURE OF MODIFIED WITH TIRE RUBBER

BITUMINOUS MIXTURES...17

6. CONCLUSIONS...19

ACKNOWLEDGEMENTS.20

REFERENCES.20

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1. INTRODUCTION

This report is dealing with experimental results on asphalt mixtures produced by the dry process. In

the frame of LIFE+ project with Acronym ROADTIRE (Integration of end-of-life tires in the life

cycle of road construction) conventional and rubberised asphalt mixtures containing with various

percentages of tire rubber have been produced and examined as far as their basic characteristics are

concerned. Production of mixtures and examination of their properties have been conducted

according to Greek and European Standards, and according to similar activities on conventional

asphalt mixtures (with no tire rubber), while laboratory test results are presented in details below.

2. DRY PROCESS-GENERAL

Rubberized asphalt mixtures, produced by the dry process, include the addition of tire rubber

particles as substitutes for the natural aggregates of similar gradation. This technique permits the

utilization of a solid waste material that is produced worldwide annually in very large amounts.

According to former experience, tire rubber can modify the rheological properties of the bituminous

binder-wet process-, leading this way to mixtures, which are characterized by increased elasticity,

improved bonding between binder and aggregates, increased fatigue life and resistance to rutting as

well as reduced thermal and reflecting cracking of the mixtures [1-8]. However, by the use of the

dry method, mixtures perform inferior characteristics compared to the ones of the wet method. This

is attributed to the poor interaction between tire rubber particles and the bitumen, which resulted in

lower resistance to moisture, the detachment of the aggregates and the reduction in the bearing

capacity of the pavement [9]. Moreover, dry process, compared to the wet process has been far less

popular method because of the increased costs of having to use special graded aggregate to

incorporate the reclaimed tire rubber in addition to constructions difficulties and of course due to

higher cost compared to the one of natural aggregates. However, this method has the potential to

consume larger quantities of rubber from worn mobile tires while it is environmentally beneficial

compared to the wet process since it consumes less energy-there is no need for increased mixing

time, higher mixing temperatures and as a result less negative environmental effects during

production procedure. Furthermore, inclusion of tire rubber particles is much easier, since tire

rubber is added simply with the natural aggregates. In this process, the interaction between rubber

particles and bitumen starts as soon as aggregates are mixed with bitumen, so there is no time for

chemical interactions and modification of the binder.

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In the frame of the ROADTIRE project, tire rubber of max size 1mm has been added to asphalt

mixtures at percentages up to 3% w/t substituting natural aggregates and especially sand, whose

gradation is similar to the one of tire rubber particles.

3. PRODUCTION OF ASPHALT MIXTURES

The Marshall mix design procedure as specified by EN12697-34:2004 [10] was used in this study.

The produced mixtures consisted of conventional bitumen, tire rubber particles in the form of

powder (of gradation 0-2mm) supplied by Karabas S.A. [11] and natural aggregates of limestone

origin from a quarry near the city of Lamia Kaltsas Techniki S.A-. Properties of the mixtures were

tested in compliance withGreek standards A265-A[12] which are in force for conventional

bituminous mixtures and for surface bituminous layer. All mixtures were produced at the

Laboratory of the Department of Materials Control and Public Works Quality of Sterea Ellada in

cooperation with Laboratory of Building Materials of the Department of Civil Engineering of

Aristotle University of Thessaloniki. Tests on properties of raw materials (aggregates and tire

rubber) took also place at the above laboratories. Gradation curve of natural aggregates mix used is

showed in Figure 1 and main characteristics on Table 1. Aggregate mix design was 60% sand (size

0-4mm), 10% aggregates of size 4-12mm and 30% aggregates of size 12-25mm. Rubber, which

acted as substitution for part of the natural aggregates at percentages up to 3% had the gradation as

given in Figure 2.

0

20

40

60

80

100

120

1''3/4''3/8''No4No10No40No80No200

Sieves (mm )

Cummulat

ivepassing(%)

Lower limit Upper limit Mixture

Figure 1. Indicative gradation curve of aggregates used for the production of bituminous mixtures

with conventional bitumen (limits of-A265[12]).

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0

20

40

60

80

100

0,01 0,1 1 10

Siev es (mm)

Cummulativepassing(%)

Tire rubber

Figure 2. Gradation curve of rubber added to binder.

Moreover, basic properties of natural aggregates are given in Table 1.

Table 1. Main characteristics of aggregates used for the production of asphalt mixtures as well as

relevant test Specifications [13-24]

Specification

EN Property Particle size Value1367-2 Magnesium sulfate test Coarse (4-12mm) 3%

1097-2 Resistance to fragmentation (LA) Coarse (10-14mm) 20%

1097-1 MICRODEVAL Coarse (10-14mm) 12%

1367-5 Thermal shock (VLA) Coarse (10-14mm) 3%

933-8 Sand equivalent (SE) Sand (0- 4mm) 75

933-9 Methylene Blue (MBE) Sand (0- 4mm) 0,9

1097-8 PSV Coarse (4-12mm) 59

AAV Coarse (12-25mm) 8,2

933-04 Shape index Coarse (12-25mm) 10%

933-04 Shape index Coarse (4-12mm) 11% 933-03 Flakiness index Coarse (12-25mm) 14%

Flakiness index Coarse (4-12mm) 13%

1744-1:98 Loss on ignition Sand (0- 4mm) 42%

1744-1:98 Total sulfur content Sand (0- 4mm) 0,0015%

1744-1:98 Acid soluble sulfates Sand (0- 4mm) 0,001

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Bituminous binder was a typical 50/70 while its rheological characteristics are showed in table 2.

Table 2. Rheological characteristics of bituminous binder 50/70[25]

Rheological

characteristic Value

Penetration at 25oC, pen 55

Softening point, oC 46

Ductility at 25oC, cm 110

Viscosity at ~1000cps, oC 123

Elastic recovery, % 10

All specimens tested have been produced in the Laboratory of the Department of Materials Testing

and Control of Quality of Public Works of Sterea Ellada in cooperation with Laboratory of Building

Materials. Production of all samples has been conducted according to European Standards as well

as according to similar of conventional ones. The same procedure has been followed in order to be

able to examine the effect of tire rubbers inclusion into the mixes, keeping the rest of the

parameters constant.

Two series of compositions have been produced and examined in the laboratory.

The first one was a conventional mixture produced by asphalt binder 50/70 with no tirerubber.

The second one included the use of asphalt binder 50/70, containing tire rubber as fineaggregate at percentages up to 3%, which means 0,5-1-1,5-2-2,5 and 3% w/t of the total

mix.

As far as production is concerned, aggregates (including tire rubber) prior to mixing with asphalt

binder have been heated for 4 hours into an oven at temperature equals to ~160

o

C, which is theheating temperature for the binder before mixing.

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Photo 1 a,-d. Production stages of rubberized asphalt mixtures

All specimens have been compacted by 75 blows per face with the standard Marshall hammer

(photos 2 a-e).

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Photo 2 a-f. Compaction procedure of samples and samples ready for testing

Specimens were stored for 24 hours prior to testing, while the procedure for the tests of Marshall

characteristics is the following:

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Photo 3a,b. Testing for Marshall Deformation and stability

According to Marshall Procedure (based on EN12697-34:2004), deformation and stability have

been measured for all of the mixtures.

Moreover, rutting resistance has been examined through the use of the appropriate equipment, as

showed in photo 5a,b according to -5-03-11-04[26] based on EN12697:22-2003[27] after

the production of samples of specific dimensions photo 4a-e. Specimens used had dimensions of

40x30x5cm. European Standard used for this test describes test method for determining thesusceptibility of bituminous materials to deform under load. The Wheel tracking test is applicable to

mixtures with upper sieve size less than or equal to 32 mm. The tests are applicable to specimens

that have either been manufactured in a laboratory or cut from a pavement; test specimens are held

in a mould with their surface flush with the upper edge of the mould. The susceptibility of

bituminous materials to deform is assessed by the rut formed by repeated passes of a loaded wheel

at constant temperature (45oC).

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Photo 4a-e. Production of samples for rutting test

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Photo 5 a,b. Testing for rutting resistance

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4. EXAMINATION OF PROPERTIES OF ASPHALT MIXTURES AND EXPERIMENTAL

RESULTS

Experimental test results for the two series are showed in tables below.

Table 2. Marshall Characteristics of series with no rubber (conventional one)

Characteristics

Binders content

Limit according to

-265 A (standard)-

Heavy traffic

4,5 5 5,5 5-7,5

Compaction (No of hits) 75 75 75

Marshall stability at 60oC (lbs) 2900 2625 2504 1500

Deformation at 0,01'' 10,4 11,5 14,2 10-16

Specific gravity (kg/m3) 2362 2375 2390 NA

Voids on aggregates (%) 16 16,4 16,2 15

Voids on bituminous mixture (%) 5,8 5,1 3,7 3-5

Mixture -BIT-0 is the conventional mixture with no addition of tire rubber. As noted, increase on

binders content leads to decrease on Marshall stability, increase on deformation, increase on

specific gravity and voids on aggregates, while there is a decrease on voids on bituminous mixture.

Optimum percentage of binder was found to be around 5%w/t.

Results of the series with the addition of asphalt binder 50/70, containing tire rubber asfine aggregates at percentages up to 3%, which means 0,5-1-1,5-2-2,5 and 3% w/t of the

total mix.

Table 3a. Marshall Characteristics of series with tire rubber at percentage of 0,5% w/t of the total

mix

Characteristics

Binders content (%)

Limit according to

-265 A (standard)-

Heavy traffic

4,5 5 5,5 5-7,5

Compaction (No of hits) 75 75 75Marshall stability at 60

oC (lbs) 2810 2450 2412 1500

Deformation at 0,01'' 11,5 12,7 14,8 10-16


Voids on aggregates (%) 16,9 16,3 16,2 15


Mixture -BIT-0,5 is the one, containing 0,5% of tire rubber as part of the sand. As noted, increase

on binders content leads to decrease on Marshall stability, increase on deformation, increase on

specific gravity and decrease on voids on aggregates, while there is a decrease on voids onbituminous mixture. Optimum percentage of binder was found to be around 5.25%w/t.

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Table 3b. Marshall Characteristics of series with tire rubber at percentage of 1% w/t of the total

mix

CharacteristicsBinders content (%)

Limit according to

-265 A (standard)-

Heavy traffic4,5 5 5,5 5-7,5



Deformation at 0,01'' 12,7 13,5 15,3 10-16




Mixture -BIT-1 is the one, containing1% of tire rubber as part of the sand. As noted, increase on

binders content leads to a decrease on Marshall stability, increase on deformation, increase on

specific gravity and decrease on voids on aggregates, while there is a decrease on voids on

bituminous mixture. Optimum percentage of binder was found to be around 5.25%w/t.

Table 3c. Marshall Characteristics of series with tire rubber at percentage of 1,5% w/t of the total

mix


Limit according to

-265 A (standard)-




Deformation at 0,01'' 13,2 13,7 15,8 10-16



Voids on bituminous mixture

(%) 6,3 5,4 4 3-5

Mixture -BIT-1,5 is the one, containing1,5% of tire rubber as part of the sand. As noted, increase on




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Table 3d. Marshall Characteristics of series with tire rubber at percentage of 2% w/t of the total

mix


Limit according to

-265 A (standard)-




Deformation at 0,01'' 14 14 16,5 10-16




Mixture -BIT-2 is the one, containing 2% of tire rubber as part of the sand. As noted, increase on




Table 3e. Marshall Characteristics of series with tire rubber at percentage of 2,5% w/t of the total

mix

Characteristics

Binders content (%)

Limit according to

-265 A (standard)-

Heavy traffic

4,5 5 5,5 5-7,5Compaction (No of hits) 75 75 75


Deformation at 0,01'' 14,7 15,3 17,5 10-16




Mixture -BIT-2,5 is the one, containing 2,5% of tire rubber as part of the sand. As noted, increase

on binders content leads to a noticeable decrease on Marshall stability, increase on deformation-

even outside the limits set by Greek specifications for binders content 5,5%-, increase on specific

gravity and decrease on voids on aggregates, while there is a decrease on voids on bituminous

mixture. As far as voids on bituminous mixture are concerned, all values were found to be outside

the limits set by Greek specifications.

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Table 3f. Marshall Characteristics of series with tire rubber at percentage of 3% w/t of the total

mix

Characteristics

Binders content (%)

Limit according to

-265 A (standard)-Heavytraffic

4,5 5 5,5 5-7,5



Deformation at 0,01'' 15,5 16 18,4 10-16



Voids on bituminous mixture

(%) 11,3 9,7 8,3 3-5

Mixture -BIT-3 is the one, containing 3% of tire rubber as part of the sand. As noted, increase on

binders content leads to a noticeable decrease on Marshall stability, increase on deformation-even

outside the limits set by Greek specifications for binders content 5-5,5%-, increase on specific

gravity and decrease on voids on aggregates, while there is a decrease on voids on bituminous

mixture. As far as voids on bituminous mixture are concerned, all values were found to be outside

the limits set by Greek specifications.

Rutting resistance

Results of laboratory experiments concerning rutting resistance through measurement of rut depth

and rate of rutting are showed in diagram 3 for the conventional and the rubberized mixtures.

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0

1

2

3

0 500 1000 1500 2000 2500 3000 3500

Cycles (No)

Rutdepth(mm)

BIT0 BIT-0,5 BIT-1,0 BIT-1,5 BIT-2,0 BIT-2,5 BIT-3,0

Diagram 3. Rut depth of samples of the series one and two (conventional-BIT0- and with the

addition of tire rubber particles)

0

1

2

3

0 500 1000 1500 2000 2500 3000 3500

Cycles (No)

Rateofrutting(mm/h)

BIT0 BIT-0,5 BIT-1,0 BIT-1,5 BIT-2,0 BIT-2,5 BIT-3,0

Diagram 4. Rate ofrutting of samples of the series one and two (conventional-BIT0- and with the

addition of tire rubber particles)

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Photo 7. Tire rubber particles

Photo 8. Conventional bituminous mixture

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As far as microstructure of the bituminous mixture is concerned, it was found to be very solid

and concrete, while aggregates (natural and tire rubber) seemed to very well cooperate with the

bituminous binder despite the fact that tire rubber particless presence was difficult to be easily

specified due to its low percentage of use and its very fine gradation.

Photo 9. Modified with tire rubber bituminous mixture

6. CONCLUSIONS

Present report includes laboratory test results of rubberised asphalt mixtures produced by the dry

process containing various percentages of tire rubber from worn mobile tires.

Marshall Characteristics as well as rutting resistance has been studied for all of the mixtures.

General comments on the results of the research are presented below: The first series included

composition -BIT-0, which is the conventional mixture with no addition of tire rubber. Increase onbinders content leads to decrease on Marshall stability, increase on deformation, increase on

specific gravity and voids on aggregates, while there is a decrease on voids in bituminous mixture.

The second series included use of tire rubber as substitutes for the fines-natural sand- at percentages

0-3% and especially 0,5%-1%-1,5%-2%-2,5%-3%w/t of the total mix.Laboratory results showed

that, for the majority of compositions, increase on binders content leads to decrease on Marshall

stability, increase on deformation, increase on specific gravity and relative decrease on voids on

aggregates and on voids in bituminous mixture. The amount of tire rubber added, was found to be a

determining factor of the mixs resistance to rutting, since higher amounts of tire rubber improved

their response to plastic deformation. In particular, according to Marshall characteristics,

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substitution of fines by tire rubber at percentage of up to 2% w/t of the total mix is possible, leading

to mixtures with satisfactory characteristics and values inside the limits set by Greek Specifications

265. Higher percentages lead to mixtures with extremely high void content, which is far

outside limits of specifications. As far as rutting resistance is concerned addition of tire rubber

leads to a relative decrease of rut depth showing an improved performance compared to the

conventional one. This means that addition of tire rubber increase resistance to rutting. However, all

compositions behave worse than the ones produced by the wet method and which are presented in

details in deliverable 4.2.1 [28].

So, taking into account all laboratory results, it can be concluded that production of asphalt

mixtures by the dry process behave relatively well for the whole of the properties examined for

percentages of added tire rubber up to 2%w/t of the total mix. However, results are inferior to the

ones of the mixtures produced by the wet method, so for the pilot application, which took place in

the city of Lamia, second method has been suggested.

ACKNOWLEDGMENTS

This reports authors would like to thank the personnel of the Department of Materials Control and

Quality of Public Works of Sterea Ellada and especially: Mr Christos Tsimbouris, Mr Dimitrios

Tsoros and Mr Dimitrios Rizopoulos, Chemical Engineer, Electronical Engineer and Technician

respectively. Moreover, special thanks to the personnel of the Laboratory of Building Materials of

the Department of Civil Engineering of Aristotle University of Thessaloniki and especially Mrs

Stefanidou Maria, Ass. Professor.

Finally, this research has been realized with the contribution of the LIFE financial instrument of the

European Union.

REFERENCES

1. Khalid H.A., Artamendi I., 2002, Exploratory study to evaluate the properties of rubberizedasphalt modified using the wet and dry processes, 3rd International Conference Bituminus

mixtures and Pavements, pp.15-25, J&A Publishers, Thessaloniki, Greece, 21-22 Nov. 2002.

2. http://www.rubberpavements.org3. Goulias D.G. and A.H. Ali, 1998, Asphalt Rubber Mixture Behavior and Design-Wet

Process, Journal of Testing and Evaluation, Vol.26, No 4, pp.306-314, American Society of

Testing Materials, W4est Conshohocken, PA.

4.

Goulias D.G. and A.H. Ali, 1997, Use of Tire Rubber in Hot Mix Asphalt :Binder andMixture Evaluation, Journal of Solid Waste Technology and Management, Vol 24, no. 24,

pp.121-125, Philadelphia.

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5. Goulias D.G and A. Ntekim, 2001, Durability of Asphalt Mixtures with Recycled TireRubber, The Journal of Solid Waste Technology and Management, Vol 27 No 3&4, pp.170-

174, Philadelphia, PA.

6. Heitzman M.A., 1992, State of the Practice- Design and Construction of Asphalt PavingMaterials with Crumb Rubber Modifier, FHWA ReportSA-92-022, Washington D.C.

7. Fernandes Jr.J.L., Bertollo S.A.M, Bernucci L.L.B, E. de Moura, 2002, Laboratoryevaluation of dense asphalt mixtures modified with addition of rubber, 3

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Conference Bituminous Mixtures and Pavements, J&A Publishers, Thessaloniki, Greece, 21-

22 Nov.2002.

8. Mavridou S, 2010. Utilization of recycled tire rubber in mortars and concrete based oncement or asphalt for special applications, PhD Thesis, Department of Civil Engineering,

Aristotle University of Thessaloniki, Greece (in Greek).

9. F. Moreno, M.C. Rubio, M.J. Martinez-Echevarria, 2012, The mechanical performance ofdry-process crumb rubber modified hot bituminous mixes: The influence of digestion time

and crumb rubber percentage, Construction and Building Materials 26, pp.466-474.

10.EN12697-34:2004: Bituminous mixtures-Tests methods for hot mix asphalt-Part 34:Marshall test.

11.Karabas S.A, European Hellenic Recycling; http://www.karabas.gr/gr_index.html12.265-, Bituminous concrete, Greek Specifications, 196613.EN 933-01:1997 entitled: Tests for geometrical properties of aggregates Part 1.

Determination of particle size distribution - Sieving method.

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15.EN933-04:1999 entitled: Tests for geometrical properties of aggregates - Part 4:Determination of particle shape - Shape index.

16.EN 933-08:1999 entitled: Tests for geometrical properties of aggregates - Part 8:Assessment of fines Sand equivalent test.

17.EN 933-09:1999 entitled:Tests for geometrical properties of aggregates. Part 9: Assessmentof fines: Methylene blue test.

18.EN 1097-02:1998 entitled: Tests for mechanical and physical properties of aggregates - Part2: Methods for the determination of resistance to fragmentation, through the Los Angeles

method.

19.EN 1367-02:1998 entitled:Tests for thermal and weathering properties of aggregates, Part2: Magnesium sulfate test.

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20.EN 1367-05:2002 entitled: Tests for thermal and weathering properties of aggregates Part5: Determination of resistance to thermal shock.

21.EN 1097-03: 1998 entitled: Tests for mechanical and physical properties of aggregates - Part3: Determination of loose bulk density and voids.

22.EN 1097-06:2000 entitled: Tests for mechanical and physical properties of aggregates.Determination of particle density and water absorption

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24.EN 1744-01:1998 entitled: Tests for chemical properties of aggregates -Part 1: Chemicalanalysis.

25.A. Kalofotias, S. Mavridou, E. Aloupis and Nikolaos Oikonomou, Deliverable 4.2.1:Report on rheological characteristics of rubberised asphalt binder, July 2011, EU-LIFE+

Environment Policy and Governance LIFE 09 ENV/GR/304ROADTIRE, Integration of

end-of-life tires in the life cycle of road construction ROADTIRE.

26. 05-03-11-04, Bituminous layers of closed type, Edition 1, May 2006 (GreekSpecifications).

27.EN 12697-22:2003 Bituminous Mixtures-Tests methods for hot mix asphalt-Part 22:Wheel tracking.

28.A. Kalofotias, S. Mavridou and Nikolaos Oikonomou, Deliverable 4.3.1: Report onlaboratory results of rubberized asphalt mixtures made by the wet process, December

2011, EU-LIFE+ Environment Policy and Governance LIFE 09

ENV/GR/304ROADTIRE, Integration of end-of-life tires in the life cycle of road

construction ROADTIRE.

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D4.4.1 Dry Process