Upload
vuongthuy
View
240
Download
3
Embed Size (px)
Citation preview
Using the Gyratory Pressure Distribution Analyzer GPDA to Estimate Compaction Resistance of HMA
Hussain Bahia and Andrew HanzUniversity of Wisconsin -
Madison
Francois Malassenet and Tom Brovold Troxler
Background • Best mixture design should include:
–
Volumetrics and resistance to compaction for production, and
–
performance testing for traffic/climate • Difficulty:
–
No current system for compaction resistance–
Performance testing requires more equipment and time.
• Can the SGC be used to address both?–
Compactive Effort - Workability
–
Aggregate Interlock - Stability
History of Using The Gyratory To estimate shear resistance
•McRae –
Gyratory Testing Machine –
1960’s and 1970’s
•Goetz, Ruth, and others recommended using GTM for mix design to measure stability –
1980’s and 1990’s
•France, Australia, and Finland have used the Gyratory for mixture evaluation –
1980’s and 1990’s
• In 1993 the Superpave Gyratory Compactor was adopted in the U.S.
Better Utilization of SGC Since 1996-Not a new topic !•1996: Use densification slope
–
Relationship to Mixture G*
•1998: Use densification curves to define–
Resistance to compaction
–
Resistance to traffic
•2000: Use gyratory with GLPA to measure shear between aggregates –
Resistance to compaction & to traffic
•2002: NCHRP 9-16
(Anderson et al.)–
Gyrations at maximum stress relate to field rutting
Superpave Volumetric Design Criteria
Log
Gyrations
% Gmm
10
100
1000
Nini
NdesNmax
600 kPa
1.16 deg
Construction•CFI•Nini to 92% Gmm
Traffic•TFI•92% -
98%
Gmm
Schematic –
Force Indices
HMA Basics: Rocks + Asphalt + Air Voids
Stability of HMA:1.Rock- to – rock contacts2.Binder rheology
What actually happens in the Superpave Gyratory Compactor?
R
9
R
Mix A
Strong aggregate interlock
Large Moment
Example 1: Behavior of a “Good Mix”
10
Mix B
Less aggregate interlock
Small Moment
R
Example 2: Behavior of a “Bad Mix”
Use of the Shear Plate (GPDA) to Calculate Eccentricity of load
2yy
2x
xy
y
)er(ee
e0M
e0M
x
R = P1
+ P2
+ P3
M(t) = R * e(t)
eR
Ram
GLPA
Mold
HMA Sampleo
1.25
x
y
ey
eO
P2
ex
P3
P1
ry
120o
The Pressure Distribution Analyzer
GPDA Used in the SGC Compaction Mold
2D Eccentricity plots for HV2 and HV5 samples at 6.5 % asphalt content
HV2HV5
Sample of Collected Data and Typical Analysis
Sample of Collected Data and Typical Analysis (continued)
-1.5-1
-0.50
0.51
1.5
-1.5-1
-0.50
0.51
1.50
100
200
300
400
500
600
Ex (in.)Ey (in.)
Num
ber o
f Gyr
atio
ns
HV5
-1.5-1
-0.50
0.51
1.5
-1.5-1
-0.50
0.51
1.50
100
200
300
400
500
600
Ex (in.)Ey (in.)
Num
ber o
f Gyr
atio
ns
HV2
3D Plots for HV2, HV5 (at 6.5% asp. content
0 100 200 300 400 500 6000
200
400
600
800
1000
1200
1400
1600
1800
2000
Number of Gyrations
Load
Cel
l For
ce (l
bs)
HV5-L. Cell Max/Min. Force
0 100 200 300 400 500 6000
200
400
600
800
1000
1200
1400
1600
1800
2000
Load
Cel
l For
ce (l
bs)
Number of Gyrations
HV2-L. Cell Max/Min. Force
Sample of Collected Data and Typical Analysis (continued)
Load Cell force distributions versus number of gyrations for HV2 and HV5 mixtures
Sample of Collected Data and Typical Analysis (continued)
Combine force measurements and volumetrics to calculate workability and stability indices.
The Resistive Effort (ω)
•
Where–
w : the resistive effort (kPa)–
e: the eccentricity of resultant force (m)–
P : the magnitude of resultant force (kN)–
: the angle of tilting (1.16)–
A : the area of specimen (m2)
–
h: the height of specimen at any given gyration (m)
AhePw 4
Stress Analysis: Masad et al
tan21cos)( 12 dWPNNS av
dsdvdu
2G
1G
N
NeN dS EIC
dv= volume change energyds= shear change energy
Masad, et al. “Quantifying Laboratory Compaction Effects on the Internal Structure of Asphalt Concrete.”
Transportation Research Record 1681. Transportation Research Board of the National Academies. Washington D.C., pp 179-185, 1999.
19
Comparing Mixes: Volumetrics vs. GPDA
100
101
102
103
75
80
85
90
95
100
% G
mm
100
101
102
1030
36
72
108
144
180
100
101
102
1030
36
72
108
144
180
Number of Gyrations
Fric
tiona
l Res
ista
nce
(kPa)
Frictional Resistance-HV2-6%Frictional Resistance-HV2-5%% Gmm-HV2-6% % Gmm-HV2-5%
Forc
e
Dens
ity
Δ
Density
Δ
Force
20
Experimental Program
•Four sources of Aggregates•Two gradations•Various levels of fine aggregate angularity•Two PG Grades
•Used PDA to collect shear data
Experimental Plan
0
10
20
30
40
50
60
70
80
90
100
0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00
Sieve Sizes
% P
assi
ng
A05 A01 A02 A03 A04
`
`
12.5mm NM size
19mm NM size
Results-
Construction
(CFI)
Average CFI values for all mixes
A01
A02 A03
A04
A05
B01
B02
C01
C02
D01D02
0
200
400
600
800
1000
1200
CFI
A01 A02 A03 A04 A05 B01 B02 C01 C02 D01 D02
~10
Tim
es D
iffer
ence
eR
Ram
GLPA
Mold
HMA Sampleo
1.25
Measuring Traffic Resistance Index (TFI) with the PDA
A01
A02A03 A04
A05
B01
B02
C01
C02
D01
D02
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
TFI
A01 A02 A03 A04 A05 B01 B02 C01 C02 D01 D02
Average TFI values for all mixes
eR
Ram
GLPA
Mold
HMA Sampleo
1.25
Effects of Warm Mix Additives on Workability (CFI)
050100150200250300350400450
80 100 120 140
CFI
Temperature (?C)HMA Advera ‐ 6%
Revix ‐ 0.5% Foam ‐ 1.5%
0
50
100
150
200
250
300
350400
450
80 100 120 140
CFI
Temperature (?C)HMA Advera ‐ 6%Revix ‐ 0.5% Foam ‐ 1.5%Rediset‐2%
050100150200250300350400450
80 100 120 140
CFI
Temperature (οC)HMA Advera ‐ 6%
Revix ‐ 0.5% Foam ‐ 1.5%
0
50
100
150
200
250
300
350
400
450
80 100 120 140
CFI
Temperature (οC)HMA Advera ‐ 6%Revix ‐ 0.5% Foam ‐ 1.5%Rediset‐2%
PG 64-22 PG 76-22
HMA
WMA
Correlation between GPDA and rutting : TFI vs. Rate of Deformation
y = 5838.6x-0.5927
R2 = 0.7893
0
2000
4000
6000
8000
10000
0 10 20 30 40 50 60
Rate of Deformation
TFI
Rate of Deformation in Rutting Tests
eR
Ram
GLPA
Mold
HMA Sampleo1.25
TFI
26
Correlation between GPDA and Rutting: TFI vs. Flow Number
eR
Ram
GLPA
Mold
HMA Sampleo
1.25
y = 1.0541x + 57.333R2 = 0.809
0
2000
4000
6000
8000
10000
12000
0 2000 4000 6000 8000 10000
FN
TFI
eR
Ram
GLPA
Mold
HMA Sampleo1.25
Proposed Criteria Workability
Stability
Mixture Type Traffic Level (Million ESALS) Maximum CFI
E-3 <3 250E-10 3 to <10 300E-30 10 to <30 400
Mixture Type Traffic Level (Million ESALS) Minimum
TFI
E-3 <3 800E-10 3 to <10 1000E-30 10 to <30 1600
Recommendations
•
The SGC be used as a tool for mixtures:–
Evaluate effect of gradation and WMA additives–
Workability –
Estimate rutting resistance -
Stability
•
It is recommended that –
Workability
and Stability
be included in
evaluation of mix designs to allow for optimum materials selection.
–
Conduct performance testing when possible.
Concluding Remarks
•There is no substitute for performance testing of asphalt mixtures
•We can, however, reduce possible combinations of mixture variables using the SGC and GPDA measurements.
•GPDA results can be better used to study– Workability –
Warm Mix
– Stability –
Modification/Gradation