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Hrvatsko asfaltersko društvo Croatian asphalt association Raziličite tehonologije hladnog in-situ recikliranja u Europi i orgraničenja uvjetovana stanjima ceste Variety of cold-in-place recycling technologies within Europe and limits regarding varying road conditions Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija, 05.– 06. 04. 2017.

Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

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Page 1: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

Hrvatsko asfaltersko društvo Croatian asphalt association

Raziličite tehonologije hladnog in-situ recikliranja u Europi i orgraničenja uvjetovana

stanjima cesteVariety of cold-in-place recycling technologies

within Europe and limits regarding varyingroad conditions

Konrad Mollenhauer, Uni Kassel

Međunarodni seminar ASFALTNI KOLNICI 2017International seminar ASPHALT PAVEMENTS 2017

Opatija, 05.– 06. 04. 2017.

Page 2: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

• Cold recycling mixtures vary considerable in

Europe

• Binder types

• Bitumen emulsion

• Foamed bitumen

• Cement

• Binder contents

• Mix design procedures

• Laboratory Compaction methods

• Accelerated Curing procedures

• Mechanical test methods

• Specification values

• Project aim: Prepare harmonisation process

Cold Recycling Technologies in Europe: CoRePaSol-Project

Characterization of advanced cold

recycled bitumen stabilized

pavement solutions

Project funded by CEDR

2013-2014

Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 2

Page 3: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

• Cold Recycling-Technologies in Europe

• Construction procedure

• Variety of mix concepts

• Effect of mix composition

• Proposal for mix design

• Limits regarding varying road conditions

• Results of laboratory project

• Recommendations

Content of presentation

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 3

Page 4: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

Cold Recycling: Mix and constrcution procedures

1. Milling / Granulation of existing

pavement

2. Mixing crushed pavement

material (in situ or in plant)

• Bituminous binder (bitumenemulsion or foamed bitumen)

• Cement (mineral binder oractive filler)

• Additional aggregates toadjust grading

3. Paving

4. Compaction

5. Construction of surface layer(s)

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 4

• Mixing and compaction at ambient temperatures require addition of water

• Water results in high voids content and reduced bearing capacity after construction and

has to be removed from the layer:

Evaporation/Drainage in warm climate – Addition of cement in moist climate

Page 5: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

Cold recycled road materials: Variety of mixes

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 5

Collings et al., 2009

Page 6: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

Cold recycled road materials: Variety of mixes

Type and degree of bonding

affects:

• Visco-ealsticity / stiffness

• Curing time

• Cracking / rutting resistance

• Water sensitivity

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 6

Page 7: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

1. Pre-assessment of mix granulate

• Continuous grading (concrete type)

• Assessment of optimum moisture content (mod. Proctor)

2. Selection of binder content range

• BSM for dry climate or soft subground (only with foamed bitumen)

• CBSM for moist climate

3. Compaction of specimens for mechanical tests

4. Laboratory curing

• BSM: 3 days oven drying @ 50 °C

• CBSM: 28 days at room conditions

5. Specimen assessment

• Void content (the lower the better)

• Stiffness

• Strength (e. g. Indirect tensile tests - ITS)

both properties: higher values are better – however, not to be reached by excess addition of cement

CoRePaSol: Proposed (harmonised) mix design procedure

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 7

60 60

d0

d0

d60

d60

Page 8: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

• Homogeneity of reclaimed asphalt is a

predominating property controlling the hot

recycling process

• Nomograms for allowed RA contents are available

• RA content results of homogeneity of RA properties and allowed tolerances within mix composition (binder content, grading, …)

• For cold recycling, effects of non-homogeneious

pavements are not known

• Changing structural properties are obstancles for

Cold recycling (especially: cold-in-place)

• Research question (within CoRePaSol-project):

• What are the limits of homogeneities for cold recycling process?

• What is the effect of (aged) bitumen in recycled asphalt within cold recycling mixtures?

Limits for varying pavement conditions for cold recycling

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 8

Page 9: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

Limits for varying pavement conditions for cold recycling

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 9

• Conditions of pavement to be

rehabilitated can vary

• „grown“ road with multiple maintenances during last centuries/decades

• Road widening on one side

• Small repair sections

• Varying parameters:

• Layers (materials)

• Thickness

• Conditions

• In given milling horizon:

• Asphalt layers

• Hydraulically bound layers

• Unbound layers

• Transversal and longitudinal

differences

0

10

20

30

40

50

60

70

80

Pav

emen

t d

epth

[cm

]

SMA AC B AC T Cement Base Unbound Subbase

0

10

20

30

40

50

60

70

80

Pav

emen

t d

epth

[cm

]

BSM Unbound Subbase

Page 10: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

• Reclaimed asphalt 0/16

• Binder content: 5.4 %,

• TR&B: 63.5°C,

• Pen 23 1/10 mm

• Reclaimed road concrete 0/22

• Basaltic aggregates (to simulate reclaimed

unbound base)

• Mix design (BCSM):

• Addition of 3,6 % limestone filler to adjust grading

• 4 % added bitumen content

a) Foamed bitumen 50/70

b) Bitumen emulsion

• 2 % cement

• Moisture content: 7,8 %

Laboratory study: Effect of mix granulate composition on cold recycled material

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 10

0

10

20

30

40

50

60

70

80

90

100

0,0

62

5

0,1

25

0,2

5

0,5 1 2 4 8

16

32

pa

ssin

g [%

]sieve [mm]

Mix designReclaimed asphaltReclaimed road concrete

Page 11: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

Selection of mix variations

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 11

• 100 %

reclaimed

asphalt

• Reclaimed

asphalt +

unbound base

• Reclaimed

asphalt +

reclaimed road

concrete

• Reclaimed

asphalt +

reclaimed road

concrete +

unbound base

Page 12: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

Mix

variations

Reclaimed

asphalt

(RA)

Reclaimed

road

concrete

(RRC)

Unbound

material

(unb.)

A 100/0/0 96,4 - 3,6

B 75/0/25 77,1 22,9

C 50/25/25 48,2 25,0 26,8

D 50/0/50 48,2 - 51,8

E 40/20/40 38,6 20,0 41,4

F 0/50/50 - 50,0 50,0

G 0/25/75 25,0 75,0

H 0/0/100 - - 100,0

Laboratory study: Effect of mix granulate composition on cold recycled material

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 12

0% 50% 100%

A 100/0/0

B 75/0/25

C 50/25/25

D 50/0/50

E 40/20/40

F 0/50/50

G 0/25/75

H 0/0/100

Mix granulate compositions

Reclaimed asphalt

Reclaimed road concrete

Unbound Aggregates

Page 13: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

Cold recycling mix composition and test program

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | ‹Nr.›

Test program:

• Static compaction (30 s á 45.9 kN)

• Specimen curing:

• 1 day in mould

• 2 days in mould (~ 20 °C)

• 25 days at room conditions

• Tests

• Bulk density & void content

• Indirect tensile strength (5 °C)

• Water sensitivity (ITS dry vs. 14 days in water)

• CBRdry (California Bearing Ratio)

Mix preparation

Specimen curingITS CBR

Page 14: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

Results: Void content after 28 days of (dry) curing at room conditions

• Comparably high void contents

• Low compaction energy (lowercompared to field compaction)

• Coarse mix with low finescontent

• Mixtures containing RA are

better to compact compared to

mixtures without RA

• Little effect of reclaimed road

concrete vs. unbound

aggregates

• Similar void content for

emulsion and foamed bitumen

mixtures

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 14

0,0

5,0

10,0

15,0

20,0

25,0

30,0

A B C D E F G H

100%75% 50% 50% 40% - - -

- - 25% - 20% 50% 25% -

- 25% 25% 50% 40% 50% 75%100%

Vo

ids c

on

ten

t V

28

[%]

Bitumen emulsion

Foamed bitumen

Sample

RA

RRC

unb.

Page 15: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

Results: Indirect tensile strength ITSdry after 28 days of curing (5 °C)

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 15

Foamed bitumen

Bitumen emulsion

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

A B C D E F G H

100%75% 50% 50% 40% - - -

- - 25% - 20% 50% 25% -

- 25% 25% 50% 40% 50% 75%100%

Ind

irect

ten

sile s

tren

gth

IT

Sd

ry(5°C

) [M

Pa] Bitumen emulsion

Foamed bitumen

RA

RRC

unb.

Page 16: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

Results: Indirect tensile strength ITSdry after 28 days of curing (5 °C)

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 16

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

A B C D E F G H

100%75% 50% 50% 40% - - -

- - 25% - 20% 50% 25% -

- 25% 25% 50% 40% 50% 75%100%

Ind

irect

ten

sile s

tren

gth

IT

Sd

ry,2

8(5°C

) [M

Pa] Bitumen emulsion

Foamed bitumen

Sample

RA

RRC

unb.

• German specification:

• ITSdry,28 ≥ 0,75 MPa

• ITSdry,28 ≤ 1,2 MPa

• Mixtures with bitumen emulsion

show higher strength compared

to mixtures with foamed

bitumen

• Higher RA content results in

higher strength

• Lower void content

• Higher flexibility

• Increase of RRC compared to

unbound aggregates:

• Same strength in emulsionmixtures

• Higher strength in foamedbitumen mixtures

Page 17: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

Water sensitivity: ITSdry/ITSwet [%] – 14 days water saturation at 20 °C

• Comparison between ITS of dry

cured specimen with saturate,

wet-cured specimen

• Emulsion mixtures:

• Little strength loss (~ -10 %)

• No effect of RA or RCC content

• Foamed bitumen

mixtures:

• For most mixtures strength increase (cement hydration)

• Strength decrease for mixtures with RRC – resulting from higher dry strengths

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 17

0

20

40

60

80

100

120

140

160

A B C D E F G H

100%75% 50% 50% 40% - - -

- - 25% - 20% 50% 25% -

- 25% 25% 50% 40% 50% 75%100%

Wate

r sen

sit

ivit

y:

Resid

ual

Str

en

gth

[%

]

Bitumen emulsion

Foamed bitumen

Sample

RA

RRC

unb.

Page 18: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

Results: California Bearing Ratio CBRdry as indicator for resistance againstpermanent deformation (test temperature: 20 °C)

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 18

0

50

100

150

200

250

A B C D E F G H

100% 75% 50% 50% 40% - - -

- - 25% - 20% 50% 25% -

- 25% 25% 50% 40% 50% 75% 100%

Califo

rnia

Beari

ng

Rati

o C

BR

[%

]

Bitumen emulsion mixtures

Foamed bitumen mixtures

Sample

RA

RRC

Unb.

• Increase RA content results in

lower CBR-ratio (higher

deformation)

• RA bitumen is still „active“ in cold recycled mixtures

• RA flexibility results in deformation

• Foamed bitumen mixtures

indicate higher CBR (lower

deformation) compared to

emulsion mixtures

• Lower shear deformationbetween mix aggregates

• Better aggregate interlock

Page 19: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

Discussions on limits regarding non-homogeneities of pavement structures:Void content requirements

• German specification for in-situ

control tests:

• Tolerance for void content compared to mix design: +4%

• Required RA content in actual

mix granulate (on site):

• Bitumen emulsion: 55 %

• Foamed bitumen: 65 %

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 19

R² = 0,9328

R² = 0,9532

14

16

18

20

22

24

26

28

30

0 50 100Vo

id c

on

ten

t o

f sp

ecim

en

s V

[%

]

RA content in mix granualte [%]

Bitumeninous emuslion mixtures

Foamed bitumen mixtures

Emulsion mix tolerance

Foamed bit. tolerance

+4 %

Bituminous emulsion mixtures

Page 20: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

Discussions on limits regarding non-homogeneities of pavement structures:ITS requirements

• German specification for in-situ

control tests:

• Tolerance for ITS compared to mix design: -20 % (+ 30 %)

• Required RA content in actual

mix granulate (on site):

• Bitumen emulsion: 55 %

• Foamed bitumen: 70 %

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 20

R² = 0,9481

R² = 0,744

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

0 50 100

ITS

dry

(5 °

C)

[MP

a]

RA content in mix granualte [%]

Bitumeninous emuslion mixtures

Foamed bitumen mixtures

Emulsion mix tolerance

Foamed bit. tolerance

-20 %

Bituminous emulsion mixtures

Page 21: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

• Conclusions valid for following cold recylcing mix

properties

• CBSM (foamed bitumen and bitumen emulsion)

• Residual bitumen content: 4 %

• Cement content: 2 %

• Same grading of mix granulate

• RA content in mix granulate is predominating

property

• Limit of allowed RA-content in mix granulate

• Bitumen emulsion mix: RA ≥ 55 %

• Foamed bitumen mix: RA ≥ 70 %

• Bitumen within RA is significantly “active” within

cold recycling mixtures

Conclusions regarding allowed tolerances on structural variability

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 21

Page 22: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

• Assess pavement structure prior to recycling

works thoroughly:

• Assess structural history (locals)

• Coring for assessment of structure along the road with varying transversal positions

• Ensure best homogenisation of mix granulate:

• transversal mixing will reduce effects of varying structural properties

• Apply In-plant (cold) recycling

• In case of highly varying structural properties

• In case of high quality requirements (traffic loading)

Recommendations

Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 22

Transversal mixing

recommended

Page 23: Konrad Mollenhauer, Uni Kassel. Konrad Mollenhauer... · Konrad Mollenhauer, Uni Kassel Međunarodni seminar ASFALTNI KOLNICI 2017 International seminar ASPHALT PAVEMENTS 2017 Opatija,

Hrvatsko asfaltersko društvo Croatian asphalt association

Hvala na pažnji

Thank you very muchfor your attention