Emulsion Based Cold mix Paving Systems€¦ · ACCELERATED CURING Procedure selected : 14 days - 35°C - 20% Relative Humidity Water expulsion is relatively rapid. Ring & Ball softening

1

Emulsion Based Cold mix Paving Systems

François CHAIGNON

COLAS Inc.

C-TEP 2011

Calgary, AB

2nd of February

2

The agenda

Introduction

What are “Emulsion Based Cold Mix Paving Systems?

What are they not?

Gravel-Emulsion

Cold Bituminous Concrete

Innovations or not?

Conclusions


They are not cold mix patching

No cut-backs any more

Emulsion based mixes

Manufactured in cold mix plant

Applied with grader or paver

1M t in France

RO, IRL, UK,…

THE ULTIMATE WMA!!

3


Why cold bituminous concrete?:

Road history

Needs of our customers for low traffic roads

Reprofile needs

Knowledge of asphalt emulsion

Function of HMA plants network

4


In the 70’s:

“Grave Emulsion” = Gravel emulsion

Base coarse

Use of local aggregates

Use of Asphalt Emulsion

0/14 or 0/20 mm

5


In the 70’s:

“Grave Emulsion” = Gravel emulsion

Use for local roads

Reprofiling before surface treatments

– chip seals

– From 0 to 120mm

– f(size)

6



Cold mix plant:

Easy to move

5-6000t (European approach)

Location in local quarries


7



Cold mix plant:

Easy to move

5-6000t (European approach)

Location in local quarries


8


Main uses for local roads

4.5 % asphalt emulsion

3% water

Monitoring

Strong contact aggregates

15% Air voids

No rutting 9


Asphalt emulsion

Monitoring of the breaking

CRS 2P for chip seals

CSS for cold mix

Slow breaking

Mixing at the plant; transport on site

And laying

The emulsion should break after compaction ….

10

Les

Fon

dament

aux

de la R

oute

. M

odule 2

: L

es

émulsion

s. J

.E. Po

irier

Sept 2005 11

t = 0

Les

Fon

dament

aux

de la R

oute

. M

odule 2

: L

es

émulsion

s. J

.E. Po

irier

Sept 2005 12

t = 1 min

Les

Fon

dament

aux

de la R

oute

. M

odule 2

: L

es

émulsion

s. J

.E. Po

irier

Sept 2005 13

t = 2 min

Les

Fon

dament

aux

de la R

oute

. M

odule 2

: L

es

émulsion

s. J

.E. Po

irier

Sept 2005 14

t = 3 min

Les

Fon

dament

aux

de la R

oute

. M

odule 2

: L

es

émulsion

s. J

.E. Po

irier

Sept 2005 15

t = 4 min

Les

Fon

dament

aux

de la R

oute

. M

odule 2

: L

es

émulsion

s. J

.E. Po

irier

Sept 2005 16

t = 5 min

Les

Fon

dament

aux

de la R

oute

. M

odule 2

: L

es

émulsion

s. J

.E. Po

irier

Sept 2005 17

t = 5 min


Base layer ok

Next step:

Full cold mix structure

Gravel Emulsion

Wearing course

Different approach

Fully coated

Traffic resistance

18


Formulation

No real method

Not a behavior of an HMA

COLAS set up one…

19

SPECIFIC BEHAVIOUR FEATURES

Cohesion versus workability

Smoothness pb.

Compaction pb.

Smoothness?

Compaction?

Favourable

Case.

Early traffic

resistance pb.

Suitable.

Unfavourable

(and unlikely) case.

Acceptable.Smoothness?

Compaction?

Early traffic

resistance pb.

Cohesion

build-up

Fast

Med

ium

Slo

w

Difficult Fair Easy

Workability

VOIDS SIZE DISTRIBUTION

0/10 mm diorite

4.8% of 70/100

Air voids ~ 15%

0

5

10

15

20

25

110

0025

1263

10

1584

9

3981

1

1000

00

2511

89

6309

57

1584

893

3981

072

Area (µm2)

Per

cen

tage

(%)

0

5

10

15

20

25

Area (µm2)

Per

cen

tag

e (%

)

Hot mix

330 voids on unit area

Cold mix

7,200 voids on

same unit area

VOIDS SIZE DISTRIBUTION

Effects of compaction

0

5

10

15

20

25

30

Area (µm2)

Pe

rce

nta

ge

(%

)

0

5

10

15

20

25

30

Area (µm2)

Pe

rce

nta

ge (

%)

Grave-emulsion

0/14 mm diorite

4.0% of 70/100

Moderately compacted (air voids 21.7%)

The same

after 100,000 passages

of wheel @ 40°C

(air voids 14.4%)

VOIDS SIZE, DISTRIBUTION AND VARIATION

Tiny voids in cold mix result from globule

coalescence, are included within the coating mastic.

These features explain the lower densities of freshly

compacted cold mix, as compared with

“equivalent” hot mix.

Cold mix density (or compaction degree) increases

slowly under the prolonged action of curing and

consolidation under traffic.

NEED FOR A SPECIFIC DESIGN METHOD

Empirical approach prevailing so far.

Existing tests derived from hot mix design,

do not reflect in-place behaviour of cold mixes.

Curing issue not fully addressed.

FLOW CHART OF PROPOSED DESIGN METHOD

Preliminary

Aggregate

Water

NO

Mixing trials

- appearance

- workability

- etc.

NO

Adjust

moisture content

YES

Emulsion

Modify

emulsion

formula

FLOW CHART OF PROPOSED DESIGN METHOD

Design steps

Manufacture

Coating,

stripping,

early cohesion

Compactability

Accelerated

Curing

Modified Duriez

20 kN or 40 kN

fresh mature

Rutting

Cured state

Stiffness moduli

Cured state

MIX MANUFACTURE

COATING QUALITY

IMAGE ANALYSIS

HANDLING

Susceptibility to

mechanical stripping

RESISTANCE TO IMMEDIATE

TRAFFICKING

(fretting test)

Gyratory Shear Compactors

COMPACTABILITY OF COLD MIXES

PCG 0.9 MPa - 3° - 6 tr/mn

75

80

85

90

95

100

1 10 100 1000

Number of gyrations

Compaction degree (%)

End

K1

K2 K3

Beginning of water expulsion

FIELD COMPACTION

ACCELERATED CURING

Procedures evaluated

5°C - 50% Relative Humidity performances do not take off

18°C - 50% Relative Humidity moderate increase

35°C - 20% Relative Humidity marked increase*

50°C - 15% Relative Humidity rapid increase, but some

specimens affected by cracking

*brings the material to a mature state, corresponding approximately

to 2 - 3 years of service in situ.

ACCELERATED CURING

Procedure selected : 14 days - 35°C - 20% Relative Humidity

Water expulsion is relatively rapid.

Ring & Ball softening point of usual bitumens is not exceeded

(min. R & B of 160/220 = 35°C).

No specimen cracking is induced.

This procedure does not cause any significant ageing of bitumen.

35°C is a realistic in situ summer temperature in pavements.

Nota : This applies to temperate regions. Other climatic conditions may

require other curing procedures.

0

20

40

60

80

100

0 10 20 30 40

Curing time (days)

0

1

2

3

4

5

6humidity in chamber

large specimens

small specimens

Relative Humidity (%) Moisture content (%)

COMPRESSIVE STRENGTH AND SENSITIVITY TO WATER

- Standard Duriez : - produces too high densities,

- does not differentiate varied mixes.

Adapted Duriez (load reduced to 20 or 40 kN) : strength (18°C)

- Procedure 18 (fresh state)

. One series 14 days - 18°C - 50% RH Rf

. One series 7 days 18°C - 50%

+ 7 days immersion 18°C rf

- Procedure 35 (mature state)

. One series 14 days - 35°C - 20% RH Rm

. One series 14 days - 35°C - 20% RH

+ 7 days immersion 18°C rm

- Water sensitivity

fresh rf/Rf mature rm/Rm

RESISTANCE

TO RUTTING

WHEEL-TRACKING TESTS PROCEDURE

Rutting slab manufactured at ambient temperature.

Postcompaction after 24 hours.

Curing : 14 days - 35°C - 20% RH.

Wheel-tracking test conducted at 60°C.

TWO EXAMPLES OF WHEEL-TRACKING TESTS

1

10

100

100 1000 10000 100000

Number of gyrations

Co

mp

acti

on

deg

ree (

% G

mm

)

M3

GE

STIFFNESS MODULUS

INFLUENCE OF COMPACTNESS

ON STIFFNESS MODULUS

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

80 82 84 86 88 90

Compactness (%)

Ind

irec

t te

nsi

le m

od

ulu

s (M

Pa)

10°C - 120 ms

15°C - 120 ms

CONCLUSION

The proposed method aims at been :

- as comprehensive as possible,

- relatively simple,

- well connected to field practice.

It should help

- improve our knowledge,

- develop new products,

- support arguments in favour of emulsion cold mixes ...

… the mixes of the future.


Full range of products

Gravel Emulsion

0 / 10 mm to 0 / 31,5 mm

Reprofiling, Utility trench fill,

Residual AC: 3.0 to 3.6%

Structuring Gravel Emulsion

0/10 to 0/14 mm

100-120mm

Residual AC: 3.6 to 4.2%

Wearing cold bituminous concrete

0/10 to 0/14mm

35 to 80mm

45

Sustainable development:« development that meets the needs of the present

without compromising the ability of future generations to meet their own needs »

Mrs Harlem Brundtland

United Nations report - 1987

YORS EL KARAKSY (9 years old)

Documents

Emulsion Based Cold mix Paving Systems€¦ · ACCELERATED CURING Procedure selected : 14 days - 35°C - 20% Relative Humidity Water expulsion is relatively rapid. Ring & Ball softening