1.-kim-jenkins--ookk.pdf

Cold Recycling & Bitumen Stabilised Materials BSMs Research and Implementation? Kim Jenkins

57th Annual Illinois Bituminous Paving Conference 12th December 2016 tellenbosch tellenbosch

Outline 1. 2. 3. 4. 5.

What is BSM? Mix Design Structural Design Application Where to now?

BSM Binder Options BITUMEN EMULSION

FOAMED BITUMEN

Colloidal Mill

Expansion chamber

Acid or Caustic Soda

Hot bitumen

Surfactants

Water

Bitumen

Wat

Water

Air

Mill

5 microns

Cement %

Rigidity

4 3

Orientation on BSM

Cement stabilised

Noncontinuously Bound

Bound 2 1

BSM

0

Asphalt Granular

Bound

Unbound

0

1

2 3 4 Bitumen %

Flexibility

5

6

Influence of Active Filler Strength versus Flexibility

BSM foam

BSM

eb 800

4000 Foamed bitumen, Strain Cement, Strain* Foamed bitumen, UCS Cement, UCS*

Strain-at-break

600 500

3500 3000 2500

Cement < 1%

400

Unconfined Compressive Strength (kPa)

700

2000

300

1500

200

1000

100

500

0

0 0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

Cement : Foamed Bitumen Ratio *

CSIR

Cement treated with 2 percent cement and no foamed bitumen. Values plotted at an arbitrary ratio of 1.25 for 2 percent cement and 1.2 for 1 percent cement.

BSM Triaxial Tests Shear properties (monotonic tests at 25°C) Friction Angle f

Cohesion C

50

400 300 200 100

E E F E E F E E F

30 25

E E F E E F E E F

20

C-75M-0

B-75M-0

A-75M-0

C-75C-1

B-75C-1

25% RAP

A-75C-1

Jenkins, 1999 & Ebels, 2006

35

C-75C-0

75% RAP

40

B-75C-0

C-75M-0

B-75M-0

A-75M-0

C-75C-1

B-75C-1

A-75C-1

C-75C-0

B-75C-0

A-75C-0

25% RAP

45

A-75C-0

0

Friction angle [degrees]

Cohesion [kPa]

500

75% RAP

Resilient Modulus of BSM Resilient Modulus Mr (MPa)

Stress dependency: Foamed BC = 2% HMA > 2500 MPa BSM

1350 1150 950

s3

750

GCS

12kPa 24kPa 48kPa 72kPa

550 350 150 0.0

200.0

400.0

600.0

800.0

1000.0

Sum of Principal Stresses q (kPa)

Research: Visco-elasto-plastic & flexural properties on BSM-foam HMA/WMA

Tref = 20C

Fatigue cracks

HW BSM BSM Rutting

Equiv HOT T or Slow Traffic

Equiv COLD T or Fast Traffic

BSM test methods C,f Mix design to Performance Design BSM layers

Reality Index

h1 h2 h3

Testing

S Vl ie be rv ae t o r y H a m m e r

Compaction

1990

2000

>200 project mix designs!

Z e Sr idSo B L e tW a i o eo s e n f o e l e Md P o Re lo ul 2010 adnb d t a e s e

Years

Mix Design Flowchart Sampling Optimum bitumen addition

Blend Sample preparation

No

SUITABLE?

Determine shear properties

TRIAXIAL Yes

Effect of active filler

Specification Preliminary tests

ITS

C (kPa)

f (0)

>250

>40

Standardised Mixing Method FOAMED BITUMEN UNIT

PUGMILL MIXER

Lab Compaction: Vibratory Hammer

Vibratory hammer

Power rating (W)

Frequency (Hz)

Mass (Kg)

Point Energy (J)

Kango 637®

750

45.83

7.5

27

Bosch GSH 11E®

1500

15 - 31.5

10.1

16.8

Bosch GSH 11VC®

1700

15 - 30

11.4

23

For PI >8%, cannot achieve 100% Mod. AASHTO density

Influence of Frame FRAME TYPE

Refusal Density 2400 80% OMC, RFR, 10kg Surcharge

Density (kg/m3)

2350

Rigid

2300 80% OMC, LFR, 10kg Surcharge

2250 2200 2150 2100

Loose

80% OMC, RFR, 20kg Surcharge

Rigid

80% OMC,LFR, 20kg Surcharge

Loose

2050 G2

G4

Material Type

Comparison of refusal density for G2 and G4 material

(Stell Univ)

Inter-Layer Roughening (ILR) Device

ITS

2 layers

6 layers Triaxial X 50mm

Inventor: Wynand van Niekerk

S1A

CT Scans BSM-emulsion

85

75

Scan slice nummer (boorkern lengte in mm).

65

55

Poor attention to interlayer preps

45

35

25

15

voids Mortar stone

5

-5

0

20

40

60

Volume in %

80

100

Why is curing important? Mr (field) versus cure

PSPA

N7 PSPA Mr Analysis over 7 Months

Mr (MPa)

B1-B3

B4-B6

Poly. (B4-B6)

% OMC

4000 3500 3000 2500 2000 1500 1000 500 0

100

Mr

MC

80 60

Moisture 0

50

100

150

200

Tim e (days)

tellenbosch

New Triaxial Apply Load (stress s1)

Test at 25ºC Confining Pressure s3 (inflate tube)

40 250

Validation

1200 1000 800 600 400 200 0

RTT STT

0.0

1.0

2.0

3.0

4.0

Applied Stress [kPa]

Applied Stress [kPa]

Research Triaxial Test RTT versus Simple Triaxial Test STT

1400 1200 1000 800 600 400 200 0

RTT STT

0.0 1.0 2.0 3.0 4.0 5.0

Strain [%]

Strain [%]

BSM Crushed Hornfels with 3.3% Emulsion tellenbosch s3 =50 kPa

and 1% Cement

s3 = 200 kPa and 0% Cem

APPLY LOAD (3mm/min)

σ1

σ3

APPLY CONFINING PRESSURE (AIR)

Determine shear properties (C and φ) σ 1

BSM

t Shear stress

σ3

UNBOUND f Friction angle

σ1

σ3 Cohesion 0

50

100

s Normal stress

200

(kPa)

Durability of BSM t Shear stress

f Friction angle

Effect of Moisture Cohesion Loss = 25% max

CBSM Cohesion

Retained Cohesion CR = CR*100/CBSM

s Normal stress

Structural Design Considerations

90mm Asphalt 250mm CIPR: 2.5% Foam 1% Cem

BSM Design for Max Rut Depth (same principle as Granular Design)

Permanent deformation (rutting) design for granular material

Lab Triaxial Analysis

Design Life for 10mm rut

Design Function for BSM Plastic Strain (a/b)

Relative Density

a

b

𝑁 = 𝑓 (𝑅𝐷, 𝑅𝑒𝑡𝐶, 𝑃𝑆, 𝑆𝑅) Stress Ratio

Retained Cohesion

Mr change with trafficking (triaxial) 2000.0

BSM1-foam (2%)

1800.0

SR=49% SR=57% SR=65% SR=67%

Resilient Moduli (MPa) .

1600.0 1400.0 1200.0 1000.0 800.0 600.0 400.0 200.0 0.0 100

1,000

10,000

100,000

1,000,000

Load repetitions

Jenkins et al, IJPE

Jenkins, TU Delft, 1999

In service behaviour of Mr

Effective Stiffness (Mpa)

Influence of support & traffic 2000

Conceptual

Traffic Poor Support High sd/sd,f

1500

1000

N7

500

0 0

1

2

3

4

5

6

7

8

9

10

1% cem CTSB 1% cem G5SB 1% cem G7SB

Cem % Support BSM1 type

Years or Traffic

Effective Long Term Mr for BSM base Mr from FWD back-calcs

2%cem 2%cem 1%cem 1%cem

SAPDM - R35 : Theyse, 2015 & Lynch, 2014

Effective Long Term Mr Stiffness (MPa) for BSM base Supporting Layer BSM Class BSM (RAP + GCS) BSM

Cemented Subbase 900 – 1750

Granular Subbase

800 – 1200

600 – 900

700 – 1200

(GCS Grade Crushed Stone) ELT Mr = f (aggregate type and quality, RAP %, bitumen %, support, traffic, climate)

Case Study – Ayrton Senna Highway Brazil’s most heavily-trafficked highway 8-lanes / divided

30

Key Data AADT > 200,000vpd (15% heavy) (> 15,000 heavies / day in each direction)

Milling & Replacing 100mm HMA lasts < 3 months Lane closure only between 21:00 – 05:00

8 HOURS

Results from Pavement Investigation HMA ± 100mm

CEMENTED CRUSHED STONE ± 250mm

6% CEMENT GRADED CRUSHED STONE ± 200mm

SELECTED COARSE GRAVEL (CBR >25) ± 200mm

EMBANKMENT (RIVER LEEVEE) (CBR > 15) Semi-infinite

Rehabilitation Options??

(8-hour working window) HMA

350mm

HMA ?

BSM-b

20mm 50mm 130mm 100mm

BSM-a 200mm

?

Step 1. Mill off asphalt layers

100mm

Impact crusher (20mm setting)

Grading Correction using Single Stage Crushing

Normal CONTINUOUS RAP

Wirtgen KMA 220 plant mixer 2.0% / 2.1% Foamed Bitumen 1.0% OPC

Mixed material placed in stockpile

AFTER CRUSHING

Step 2. Mill and remove CTB layer

250mm

Step 5. Import / pave / compact 130mm BSM layer

130mm BSM (RAP / crushed stone blend)

Step 6. Import / pave / compact 20mm HMA

20mm HMA (gap-graded / fine mix) Temporary surfacing

18th November 2011

31ST January 2012

Currently (3.75 years later)

> 100 lane-km rehabilitated using this method

PROBLEM SOLVED !

Way Forward: Research Monotonic Load Cycle (triaxial)

GCS

BSM (Bredenhann & Jenkins, 2016)

Way Forward: Research Dynamic Conditioning (triaxial)

GCS

BSM (Bredenhann & Jenkins, 2016)

Way Forward: Research(2) Dynamic Triaxial – Permanent Deformation Deformation rate

(ep/N x 10-6)

0.035 0.030 0.025 0.020

GCS

0.015

BSM

0.010 0.005 0.000 0.5

0.6

0.7

0.8

0.9

1

Stress ratio

(Bredenhann & Jenkins, 2016)

Flexural Strain-at-break  All beams compacted in a mould  Testing temperature:

25°C

 LVDT on top of the beam to accurately measure displacement in the middle of the beam.

LVDT

(Campher, 2014)

Flexural Strain-at-break & DE Material parameter Average Average StrainAverage Maximum Stress at-break Dissipated (kPa) (µԐ) energy (Pa)

Specimen specification

Average stiffness (MPa)

0.9% Emulsion; 1% Cement

174.4

376.5

39.1

524.2

254.9

537.2

89.8

473.1

320.4

391.1

211.6

480.8

383.8

508.7

2.4% Emulsion; 1% Cement 2.4% Emulsion; 2% Cement 2.4% Foamed; 1% Flexibility related parameters

Average stiffness (MPa)

Cement 2.4% Foamed; 2%

821.6 Increase in 78.8 bitumen emulsion (specimens containing 1% cement) Increase in cement (stabilised with bitumen emulsion) Increase in 68.7 cement (stabilised with foamed 447.4 bitumen emulsion)

Average Dissipated energy (Pa)

Cement

151.3

761.9

Average Strain-at-break (µԐ) -40.00

-20.00

0.00

20.00

40.00

60.00

80.00

% Change in parameter value

100.00

120.00

140.00

(Campher, 2014)

Flexibility (triaxial)

(Llewellyn, 2016)

Flexibility (triaxial)

(Llewellyn, 2016)

Factors Influencing BSM Flexibility Analysis of Variance Summary of P values for variables in ANOVA analysis 0.85 0.8 0.75 0.7 0.65 0.6 0.55 0.5 P- 0.45 value 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0

Strain at Break Dissipated Energy

Significant Variables <0.05 Fenton, 2013

Conclusions • Mix design system in place – Aim for flexibility not high strength – Update of equipment (vib hammer & triax)

• Pavement design – New ME design function – Link of mix- and pavement-design (C & f)

• Application (field performance data) • Way forward: flexibility focus tellenbosch

tellenbosch

Pavement Balance BSM Base

Granular Base

Mr (MPa) Asp

3000

CTB G1

500 2800

G5

350

Mr (MPa)

Base

Subbase

tellenbosch

150

---- >1500 350

Asp BSM1 CTSB G5

200

200 SG

3000 800 >1000

Subgrade

150

SG

Research on BSM Flexibility How can we benefit from?

(Llewellyn, 2016)

Strain-at-break vs Fatigue 25%RA & 0%Cem

1E+07 emulsion A

Number of repetitions

1E+06

emulsion B

4PB Fatigue

1E+05

foamed bitumen C

1E+04 1E+03 1E+02

B

1E+01

Strain at break

1E+00 100

A

C

1,000 10,000 Strain [x 10 -6 ]Stellenbosch University