DSR testing of GTR
Particle size effects
M. Emin Kutay, Ph.D., P.E. Associate Professor - Michigan State University
Anas Jamrah Research Assistant- Michigan State University
DSR Test Plan • Crumb rubber sizes
• #16-#20 (~1mm) • #20-#30 (~0.7 mm) • #40-#50 (~0.4 mm)
• Crumb rubber percentages • 15%, 20%, 25%
• Test geometry • Parallel plate • Concentric cylinders
• PG58-28 base binder
Sample preparation (wet process)
• Mixing temperature: 190C +-5C
• Mixing duration: 1 hr • Mixing speed: 1000 RPM • Two to three replicate
batches
DSR testing
• 25 mm plate • T = 46, 58, 70, and 82oC • ω = 10, 15.84, 25.12, 39.81, 63.09,
100 rad/s • 2 mm gap
• 8 mm plate • T = 15 and 30oC • ω = 10, 15.84, 25.12, 39.81, 63.09,
100 rad/s • 2 mm gap
Effect of Crumb Rubber size
At different percentages of rubber
CR sizes #16-#20
2mm
2mm
#40-#50
#20 - #30
2mm
(1.18 - 0.85 mm) (0.85 – 0.6 mm)
(0.425 – 0.355 mm)
X-ray CT of 15% CR
CR passing #30, retaining #40 sieve
100 101 102 103102
103
104
105
106
107
Angular Frequency (rad/s)
|G*|
(Pa)Temperature = 82oC
#50-15-all#30-15-all#20-15-all
Effect of CR size • For 15% CR content (by binder weight)
3.250#
*20#
*
≅G
G
100 101 102 103102
103
104
105
106
107
Angular Frequency (rad/s)
|G*|
(Pa)Temperature = 70oC
#50-15-all#30-15-all#20-15-all
Effect of CR size • For 15% CR content (by binder weight)
2.250#
*20#
*
≅G
G
100 101 102 103102
103
104
105
106
107
Angular Frequency (rad/s)
|G*|
(Pa)Temperature = 58oC
#50-15-all#30-15-all#20-15-all
Effect of CR size • For 15% CR content (by binder weight)
94.150#
*20#
*
≅G
G
100 101 102 103102
103
104
105
106
107
Angular Frequency (rad/s)
|G*|
(Pa)Temperature = 46oC
#50-15-all#30-15-all#20-15-all
Effect of CR size • For 15% CR content (by binder weight)
65.150#
*20#
*
≅G
G
100 101 102 103102
103
104
105
106
107
Angular Frequency (rad/s)
|G*|
(Pa)Temperature = 30oC
#50-15-all#30-15-all#20-15-all
Effect of CR size • For 15% CR content (by binder weight)
150#
*20#
*
≅G
G
100 101 102 103102
103
104
105
106
107
Angular Frequency (rad/s)
|G*|
(Pa)Temperature = 15oC
#50-15-all#30-15-all#20-15-all
Effect of CR size • For 15% CR content (by binder weight)
150#
*20#
*
≅G
G
|G*| mastercurves (15% CR)
10-2 10-1 100 101 102 103 104 105102
103
104
105
106
107
108
Reduced Frequency (Hz)
|G*|
(Pa)
#20-15-all#30-15-all#50-15-allBase-PG58-28
Tref = 46oC
Effect of Crumb Rubber size
At 20% rubber
Effect of CR size • For 20% CR content (by binder weight)
100 101 102 103102
103
104
105
106
107
Angular Frequency (rad/s)
|G*|
(Pa)
#50-20-all#30-20-all#20-20-all
10-2 10-1 100 101 102 103 104 105102
103
104
105
106
107
108
Reduced Frequency (Hz)
|G*|
(Pa)
#20-20-all#30-20-all#50-20-allBase-PG58-28
|G*| mastercurves (20% CR)
Tref = 46oC
Effect of Crumb Rubber size
At 25% rubber
Effect of CR size • For 25% CR content (by binder weight)
100 101 102 103102
103
104
105
106
107
Angular Frequency (rad/s)
|G*|
(Pa)
#20-25-all#30-25-all#50-25-all
10-2 100 102 104 106102
103
104
105
106
107
108
Reduced Frequency (Hz)
|G*|
(Pa)
#20-25-all#30-25-all#50-25-allBase-PG58-28
|G*| mastercurves (25% CR)
Tref = 46oC
10-2 100 102 104 106102
103
104
105
106
107
108
Reduced Frequency (Hz)
|G*|
(Pa)
Base-PG58-28#20-25-all#30-25-all#50-25-all#50-20-all#30-20-all#20-20-all#50-15-all#30-15-all#20-15-all
|G*| mastercurves (ALL sizes)
Tref = 46oC
Effect of CR percentage & size
|G*| at 10Hz
0
2000
4000
6000
8000
1 104
1.2 104
1.4 104
1.6 104
15 20 25
#20 #30 #50
|G*|
Pa
%CR
82oC
High T versus Low T T = 76oC T = 15oC
Soft binder
Stiff rubber
Stiff binder
Soft rubber
Rubber |G*| of mix
Rubber |G*| of mix
|G*| at 10Hz
0
5000
1 104
1.5 104
2 104
2.5 104
3 104
3.5 104
15 20 25
#20 #30 #50
|G*|
Pa
%CR
70oC
|G*| at 10Hz
0
1 104
2 104
3 104
4 104
5 104
6 104
7 104
15 20 25
#20 #30 #50
|G*|
Pa
%CR
58oC
|G*| at 10Hz
0
5 104
1 105
1.5 105
15 20 25
#20 #30 #50
|G*|
Pa
%CR
46oC
|G*| at 10Hz
0
2 105
4 105
6 105
8 105
1 106
1.2 106
15 20 25
#20 #30 #50
|G*|
Pa
%CR
30oC
Estimated |G*| of swollen rubber
|G*| at 10Hz
0
1 106
2 106
3 106
4 106
5 106
6 106
15 20 25
#20 #30 #50
|G*|
Pa
%CR
15oC
Observations/Conclusions • At low CR% and high DSR temperatures:
• Significant effect of CR size • At low CR%:
• Particle interaction (cushioning) effect becomes visible with increasing CR size
#16-#20 (1.18 - 0.85 mm)
#20 - #30 (0.85 – 0.6 mm)
#40-#50 (0.425 – 0.355 mm)
Observations/Conclusions
• At high CR% and low DSR temperatures: • No effect of CR size • At high CR%
– Regardless of the CR size, the particles are already interconnected (i.e., cushioned)
• At low DSR temperatures – Binder between the CR particles are as stiff or
stiffer than the CR, therefore, no effect is visible » Material acts like a ‘mixture’
Thoughts/Future work
• Mixture |E*| versus |G*| • Is it more appropriate to intentionally
test the “rubber” in DSR? • Rubber modified binder is already
“squeezed” between the aggregates • Does running the CR binder tests in
“loose state” more or less representative of behavior in mixture.
• Repeat the tests using concentric cylinder • Compare with mix |E*|
THE END