Post on 13-Apr-2017
Evaluation of Current Modified Asphalt Binders Using the
Multiple Stress Creep Recovery Test
Carl Thodesen, Szabolcs Biro, & John Kay
Introduction
• Idea for research started following work done by Association of Modified Asphalt Producers (AMAP)
• Research entitled: Polymer Asphalt Supply Outlook
• Conduct market research on availability of polymers for use in asphalt modification
Why is SBS Currently in ShortSupply?*
• Styrene-Butadiene-Styrene (SBS) polymer capacity is not short
• Shortage of raw materials
• Ethylene production is the problem
*Slide courtesy of R. Corun: “Asphalt & Polymer Supply Outlook”, NEAUPG Meeting, Atlantic City, NJ October 8, 2008
Why is Ethylene Production the Problem?*
• By-products of Ethylene Production:– Styrene– Propylene– Butadiene– Isoprene– Pentadiene– Cyclopentadienes– Aromatic Resin Formers– Isobutylene– Amylenes– Hydrogen– Benzene
Ethylene
*Slide courtesy of R. Corun: “Asphalt & Polymer Supply Outlook”, NEAUPG Meeting, Atlantic City, NJ October 8, 2008
Ethylene and Butadiene Market Comparison*
• Ethylene Market– 120 million tons per
year– Primary use:
Packaging materials• Plastic wrap• Trash bags• Milk jugs
• Butadiene Market– 14 million tons per
year– Primary use: Tires
(70%)– Multiple other
automotive and durable good uses
– SBS polymer for asphalt (6%)
*Slide courtesy of R. Corun: “Asphalt & Polymer Supply Outlook”, NEAUPG Meeting, Atlantic City, NJ October 8, 2008
Ethylene Production
Issues
• Not possible to use non modified asphalt in lieu of modified asphalt
• Using the wrong grade will lead to poor performance
• Data exists to confirm that modified asphalt improves pavement performance
• Flexibility and creativity necessary to find answers
AMAP Recommendations
• AMAP concludes:– “prudent planners should be working on the
basis that availability of SBS polymers will remain tight for the immediate future. “
– Alternatives should be investigated:• Reacted Ethylene Terpolymer (Elvaloy)• Ethyl Vinyl Acetate (EVA)• Ground tire rubber (GTR)• Hybrid Binders (SBS-GTR)• Polyphosphoric acid (PPA)
Common Modification Agents*
SBS M
odified
SB M
odified
SBR La
tex M
odified
Other Polym
er Modified
(EVA, e
tc)
Chemica
l Modified
(oils,
etc)
Other (G
TR)
PPA
Other Chem
ical (A
ir Blown)
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%80%
45% 45%
19%12%
16% 16%13%
85%
56%53%
15%12%
18%21%
12%
2005 2006
*AMAP , 2006
Research Scope
• Evaluate all AMAP recommended modified binders using MSCR.
• Provide data identifying strengths and weaknesses of various modified binders.
• Identify modifier best suited to use in place of SBS from performance data.
Binders TestedModified Asphalt Additive Used
Concentration (% by weight of total blend)
SBS Calprene 501C 3
Asphalt rubber Ambient crumb rubber 20
SBS-CRM Calprene 501C 1
Ambient crumb rubber 10
EVA EVATENE 3325 6
Elvaloy Elvaloy 4170 1
SBS-PPA Calprene 501C 2
Polyphosphoric acid 0.2
Note: Modifier percentages based on manufacturer recommendation
MSCR (ASTM D7405-08)
• Test developed as procedure for discriminating between modified binders– Performed using DSR on RTFO aged samples
• Possible alternative to PG Grading• Percent recovery and non-recoverable
creep compliance by means of MSCR test determined
MSCR Test Protocol
• Test run at selected temperature (64,70, & 76oC) using constant stress creep of 1.0 second duration followed by a zero stress recovery of 9.0 second duration.
• Test run at two stress levels: 100 Pa and 3200 Pa
• Ten cycles run at each of the two stress levels for a total of 20 cycles.
MSCR: Percent Recovery• Purpose: determine presence of elastic
response and stress dependence of modified and unmodified asphalt binders.
MSCR: Non-Recoverable Creep Compliance (Jnr)
• Non-recoverable creep compliance provides indication of stress dependence of the binder.
Complete loading cycle at 70oC
0 200 400 600 800 1000 12000.1
1.0
10.0
100.0
1000.0
10000.0
AR Elvaloy EVA SBS-CRM SBS-PPA SBS
Time (s)
Stra
in (%
)
Discussion Points
• AR tended to achieve the best results as it consistently yielded the lowest strain values
• SBS, AR, and SBS-CRM:– Less susceptible to the higher stress level– Demonstrate higher capacity to withstand
stress without deforming
First cycle at 70oC and 100 Pa
0 10 20 30 40 50 60 700
2
4
6
8
10
12
14
16
18
20
AR Elvaloy EVA SBS-CRM SBS-PPA SBS
Time (s)
Stra
in (%
)
Percent recovery at 100 and 3200 Pa at 70oC
100 32000
20
40
60
80
100
120
140
160
180
AR Elvaloy EVA SBS-CRM SBS-PPA SBS
Shear Stress (Pa)
Reco
very
(%)
Discussion Points
• AR samples exhibited the highest percent recovery, regardless of stress level.
• SBS-CRM binder yielded high percent recoveries, however, it was seen that at the higher loading rate the SBS-CRM blend did not recover as much as the SBS and asphalt rubber
Percent Recovery versus Temperature
58 64 70 76 820
20
40
60
80
100
120
140
160
180
R² = 0.948710530023546
R² = 0.999329836745937
R² = 0.954210991885703
R² = 0.952131591440598R² = 0.996877366014461
R² = 0.604111959565446
AR Linear (AR) Elvaloy Linear (Elvaloy) EVA Linear (EVA)SBS-CRM Linear (SBS-CRM) SBS-PPA Linear (SBS-PPA) SBS Linear (SBS)Linear (SBS)
Temperature (oC)
Reco
very
(%)
Discussion Points
• Linear relationship between the percent recoveries (64 – 76oC)
• SBS and the SBS-CRM blends are the least temperature sensitive
• AR Yielded highest values
Difference in Recovery
58 64 70 76 82-20
0
20
40
60
80
100
120
R² = 0.265018160217717
R² = 0.995892783383295
R² = 0.99607157576166
R² = 0.999878560813297
R² = 0.998116263330757
R² = 0.226242860034229
AR Linear (AR) Elvaloy Linear (Elvaloy) EVA Linear (EVA) SBS-CRM Linear (SBS-CRM)SBS-PPA Linear (SBS-PPA) SBS Linear (SBS)
Temperature (oC)
Rdiff
(%)
Discussion Points
• SBS: least difference in recovery between 100 and 3200 Pa
• EVA and Elvaloy: greatest differences in difference of recovery
• AR and SBS modified binder are less sensitive to differences in temperature and loading
Jnr Values for 3200 Pa
64 70 760.00
0.10
0.20
0.30
0.40
0.50
0.60
0.05
0.13
0.33
0.04
0.18
0.44
0.00 0.010.03
0.07
0.18
0.40
0.00 0.00 0.000.00 0.00
AR Elvaloy EVA SBS-CRM SBS-PPA SBS
Temperature (oC)
Jnr
0.000.000.00 0.000.00
0.00
Conclusions
• Prudent planners advised to work basis that availability of SBS polymers will remain tight for the immediate future
• Majority of butadiene produced used in tires
• Not possible to use unmodified asphalt for modified asphalt mixes.
Conclusions
• MSCR test developed specifically to discriminate between modified binders.
• Lab results indicate:– AR yielded highest percent recovery values
at both loading settings.– AR and SBS equally adept at withstanding
creep.– AR came the closest to replicating/
exceeding SBS binder properties
Conclusions
• Clear differences can be seen between the various types of modified asphalts in the creep recovery curve
• AR exhibited the least creep, while also demonstrating a very high recovery rate
• AR tended to yield the highest percent recoveries over the range of temperatures
Conclusions
• AR can be considered valid alternative to SBS from performance perspective.
• MSCR testing confirms elasticity of AR binder.
Thank you