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