Post on 08-Apr-2020
transcript
tellenbosch
Cold Recycling & Bitumen
Stabilised Materials BSMs
Research and
Implementation?
tellenbosch
Kim Jenkins
57th Annual Illinois Bituminous
Paving Conference12th December 2016
Outline
1. What is BSM?
2. Mix Design
3. Structural Design
4. Application
5. Where to now?
BSM Binder Options
FOAMED BITUMEN
Mill
Acid or
Caustic Soda
Surfactants
Wat BitumenWater
5 microns
Water
Hot
bitumen
Air
Expansion chamber
BITUMEN EMULSION
Colloidal Mill
Flexibility
Rig
idit
y
320 1
3
4 5
4
2
1
0
Cem
en
t %
Bitumen %6
Cement stabilised
Bound
Granular
Unbound
Non-
continuously
Bound
BSM
Asphalt
Bound
Orientation on BSM
Influence of Active Filler
Strength versus Flexibility
0
100
200
300
400
500
600
700
800
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
Str
ain
-at-
bre
ak
0
500
1000
1500
2000
2500
3000
3500
4000
Un
co
nfi
ned
Co
mp
ressiv
e
Str
en
gth
(kP
a)
Foamed bitumen, Strain
Cement, Strain*
Foamed bitumen, UCS
Cement, UCS*
* 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.
CSIR
BSM
eb
BSM foam
Cement < 1%
BSM Triaxial Tests Shear properties (monotonic tests at 25°C)
Cohesion C
0
100
200
300
400
500
A-7
5C
-0
B-7
5C
-0
C-7
5C
-0
A-7
5C
-1
B-7
5C
-1
C-7
5C
-1
A-7
5M
-0
B-7
5M
-0
C-7
5M
-0
Co
hesio
n [
kP
a]
E E E E E E FFF20
25
30
35
40
45
50
A-7
5C
-0
B-7
5C
-0
C-7
5C
-0
A-7
5C
-1
B-7
5C
-1
C-7
5C
-1
A-7
5M
-0
B-7
5M
-0
C-7
5M
-0
Fri
cti
on
an
gle
[d
eg
rees]
Friction Angle f
E E E E E E FFF
Jenkins, 1999 & Ebels, 2006
25% RAP 25% RAP75% RAP 75% RAP
Resilient Modulus of BSM
Stress dependency: Foamed BC = 2%
150
350
550
750
950
1150
1350
0.0 200.0 400.0 600.0 800.0 1000.0
Sum of Principal Stresses q (kPa)
Re
silie
nt
Mo
du
lus M
r (M
Pa
)
12kPa
24kPa
48kPa
72kPa
s3
HMA > 2500 MPa
GCS
BSM
Research: Visco-elasto-plastic &flexural properties on BSM-foam
Tref = 20C
HMA/WMA
HWFatigue cracks
Rutting
HOT T or
Slow TrafficEquiv
COLD T or
Fast TrafficEquiv
BSM
BSM
BSM test methods
Years
20101990 2000
RealityIndex
Compaction
TestingZ
e
r
o
L
i
n
e
S
l
e
e
v
e
B
a
s
e
P
l
a
t
e
S
t
e
e
l
R
o
d
S
id
e
o
f
M
o
ul
d
V
i
b
r
a
t
o
r
y
H
a
m
m
e
r
W
o
o
d
e
n
b
a
s
e
C,f Mix design to PerformanceDesign BSM layers
h1
h2
h3
>200 project mix designs!
Mix Design Flowchart
Sampling
Sample preparation
Preliminary tests
SUITABLE?
Blend
Effect of active filler
Optimum bitumen addition
Determine shear
properties
Yes
No
ITS
TRIAXIAL
Specification
C (kPa) f (0)
>250 >40
PUGMILL MIXER
FOAMED BITUMEN UNIT
Standardised Mixing Method
Lab Compaction: Vibratory Hammer
Vibratory hammer
Power rating (W)
Frequency (Hz)
Mass (Kg)
PointEnergy (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
2050
2100
2150
2200
2250
2300
2350
2400
G2 G4
Den
sit
y (
kg
/m3)
Material Type
80% OMC, RFR,10kg Surcharge
80% OMC, LFR,10kg Surcharge
80% OMC, RFR,20kg Surcharge
80% OMC,LFR,20kg Surcharge
Refusal Density
Comparison of refusal density for G2 and G4 material
FRAMETYPE
Rigid
Loose
Rigid
Loose
(Stell Univ)
Inter-Layer Roughening (ILR) Device
6 layersX 50mm
2 layersITS
Triaxial
Inventor: Wynand van Niekerk
CT ScansBSM-emulsion
S1A
-5
5
15
25
35
45
55
65
75
85
0 20 40 60 80 100
Volume in %
Sca
n s
lice
nu
mm
er
(bo
ork
ern
le
ng
te i
n m
m).
voids
Mortar
stone
Poor attention to
interlayer preps
tellenbosch
N7 PSPA Mr Analysis over 7 Months
0
500
1000
1500
2000
2500
3000
3500
4000
0 50 100 150 200 250
Time (days)
Mr
(MP
a)
B1-B3 B4-B6 Poly. (B4-B6)
PSPA
Moisture
Mr
Why is curing important?
Mr (field) versus cure
% OMC
100
40
60
80
MC
New Triaxial
Confining Pressure s3
(inflate tube)
Apply Load (stress s1)
Test at
25ºC
tellenbosch
Validation Research Triaxial Test RTT versus
Simple Triaxial Test STT
0
200
400
600
800
1000
1200
1400
0.0 1.0 2.0 3.0 4.0 5.0
Strain [%]A
pp
lied
Str
ess [
kP
a]
RTT
STT
0
200
400
600
800
1000
1200
0.0 1.0 2.0 3.0 4.0
Strain [%]
Ap
pli
ed
Str
ess [
kP
a]
RTT
STT
BSM Crushed Hornfels with 3.3% Emulsion
s3 =50 kPa and 1% Cement s3 = 200 kPa and 0% Cem
APPLY CONFINING PRESSURE (AIR)
APPLY LOAD (3mm/min)
σ1
σ3
t
s
Shear stress
Normal stress
(kPa)
Cohesion
f Friction angle
UNBOUND
BSM
σ1
σ3
σ1
σ3
0 50 100 200
Determine shear properties (C and φ)
Durability of BSMt
s
Shear
stress
Normal
stress
CBSM
Cohesion
f Friction
angle
Retained Cohesion CR = CR*100/CBSM
Effect of
Moisture
Cohesion Loss = 25% max
Structural DesignConsiderations
250mm CIPR:
2.5% Foam 1% Cem
90mm Asphalt
Lab Triaxial Analysis
Permanent deformation (rutting) design for granular material
BSM Design for Max Rut Depth(same principle as Granular Design)
Design Life for 10mm rut
Design Function for BSM
𝑁 = 𝑓 (𝑅𝐷, 𝑅𝑒𝑡𝐶, 𝑃𝑆, 𝑆𝑅)
Relative Density Plastic Strain (a/b)
Retained Cohesion Stress Ratio
ab
Mr change with trafficking (triaxial)
0.0
200.0
400.0
600.0
800.0
1000.0
1200.0
1400.0
1600.0
1800.0
2000.0
100 1,000 10,000 100,000 1,000,000
Resil
ien
t M
od
uli
(M
Pa)
.
Load repetitions
SR=49%SR=57%SR=65%SR=67%
Jenkins et al, IJPE
BSM1-foam (2%)
Jenkins, TU Delft, 1999
In service behaviour of MrInfluence of support & traffic
0
500
1000
1500
2000
0 1 2 3 4 5 6 7 8 9 10
Effe
ctiv
e St
iffn
ess
(Mp
a)
Years or Traffic
1% cem CTSB
1% cem G5SB
1% cem G7SB
Cem % BSM1
TrafficPoor SupportHigh sd/sd,f
Conceptual
N7
Supporttype
Effective Long Term Mr for BSM base Mr from FWD back-calcs
SAPDM - R35 : Theyse, 2015 & Lynch, 2014
1%cem1%cem
2%cem
2%cem
Effective Long Term Mr Stiffness (MPa)for BSM base
BSM Class Cemented Subbase
Granular Subbase
BSM (RAP + GCS)
900 – 1750 700 – 1200
BSM (GCS Grade Crushed Stone)
800 – 1200 600 – 900
ELT Mr = f (aggregate type and quality, RAP %, bitumen %, support, traffic, climate)
Supporting Layer
30
Case Study – Ayrton Senna Highway
Brazil’s most heavily-trafficked highway
8-lanes / divided
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
Key Data
8 HOURS
Results from Pavement Investigation
HMA ± 100mm
SELECTED COARSE GRAVEL (CBR >25) ± 200mm
EMBANKMENT (RIVER LEEVEE) (CBR > 15)Semi-infinite
GRADED CRUSHED STONE ± 200mm
CEMENTED CRUSHED STONE ± 250mm
6% CEMENT
Rehabilitation Options?? (8-hour working window)
HMA ?350mm
BSM-a 200mm
BSM-b 130mm
20mmHMA
50mm
?
100mm
100mm
Step 1. Mill off asphalt layers
Impact crusher (20mm setting)
Grading Correction using Single Stage Crushing
Normal CONTINUOUSAFTER CRUSHINGRAP
Wirtgen KMA 220 plant mixer
2.0% / 2.1% Foamed Bitumen1.0% OPC
Mixed material placed in stockpile
250mm
Step 2. Mill and remove CTB layer
130mm BSM (RAP / crushed stone blend)
Step 5. Import / pave / compact 130mm BSM layer
20mm HMA (gap-graded / fine mix)Temporary surfacing
Step 6. Import / pave / compact 20mm HMA
18th November 2011
31ST January 2012
Currently (3.75 years later)
> 100 lane-km rehabilitated using this method
PROBLEM SOLVED !
Way Forward: ResearchMonotonic Load Cycle (triaxial)
(Bredenhann & Jenkins, 2016)
GCS BSM
Way Forward: ResearchDynamic Conditioning (triaxial)
(Bredenhann & Jenkins, 2016)
GCS BSM
Way Forward: Research(2)
Dynamic Triaxial – Permanent Deformation
(Bredenhann & Jenkins, 2016)
GCS
BSM
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.5 0.6 0.7 0.8 0.9 1
Def
orm
atio
n r
ate
Stress ratio
(ep/N
x 1
0-6
)
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
Flexural Strain-at-break
(Campher, 2014)
Specimen
specification
Material parameter
Average
Maximum Stress
(kPa)
Average Strain-
at-break
(µԐ)
Average
Dissipated
energy (Pa)
Average
stiffness
(MPa)
0.9% Emulsion; 1%
Cement 174.4 376.5 39.1 524.2
2.4% Emulsion; 1%
Cement 254.9 537.2 89.8 473.1
2.4% Emulsion; 2%
Cement 320.4 391.1 78.8 821.6
2.4% Foamed; 1%
Cement 211.6 480.8 68.7 447.4
2.4% Foamed; 2%
Cement 383.8 508.7 151.3 761.9
-40.00 -20.00 0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00
Average Strain-at-break (µԐ)
Average Dissipated energy (Pa)
Average stiffness (MPa)
% Change in parameter value
Fle
xib
ilit
y r
ela
ted
p
ara
me
ters
Increase in bitumen emulsion (specimenscontaining 1% cement)Increase in cement (stabilised with bitumenemulsion)Increase in cement (stabilised with foamedemulsion)bitumen
Flexural Strain-at-break & DE
(Campher, 2014)
Flexibility (triaxial)
(Llewellyn, 2016)
Flexibility (triaxial)
(Llewellyn, 2016)
Factors Influencing BSM FlexibilityAnalysis of Variance
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
P-value
Summary of P values for variables in ANOVA analysis
Strain at Break
DissipatedEnergy
Fenton, 2013
SignificantVariables <0.05
tellenbosch
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
Mr (MPa)
Granular Base
Asp
G1
G5
SG
Asp
BSM1
G5
SG
3000
BSM Base
Mr (MPa)
500
350
150
200
800
3000
350
150
200
Base
Subbase
Subgrade
CTB 2800 >1000
---- >1500 CTSB
Research on BSM FlexibilityHow can we benefit from?
(Llewellyn, 2016)
Strain-at-break vs Fatigue25%RA & 0%Cem
1E+00
1E+01
1E+02
1E+03
1E+04
1E+05
1E+06
1E+07
100 1,000 10,000
Nu
mb
er o
f re
peti
tio
ns
Strain [x 10-6]
emulsion A
emulsion B
foamed bitumen C
Strain at break
AB
C
4PB Fatigue
Stellenbosch University