Crumb Rubber Modified Bitumen
--- Application vs Specification
__________________________________
Valero Benicia Asphalt plant and Polyphalt Inc.
AMAP CONFERENCE
01-28-03
Crumb Rubber Modified Bitumen (CRMB)
! Overview
! Current Status & Issues
! Feature & Benefit
! Specs vs Applications
What is CRMB ?
Good question … no simple answer
! Diverse recycled rubber sources
! Diverse processes and applications
! Diverse opinions and perceptions
! A moving target
CRMB: An Overview
Recycled
Rubber
Process
Product
- McDonald
WET
Blended w. AC
- On-Site A-R
- Terminal Blend
Modified Bitumen
(CRMB)
- Other Specialty
Crumb Rubbers
(TR Disposal
& Indus. Waste)
DRY
Blended w. AC/Aggregate
-Plus-Ride
-Generic
-Chunk
Rubber Aggregate
(Rubber modified
hot-mix)
Barriers to Market Acceptance
! Performance
! Logistics
! Economics
! Environmental
Performance
Need Ease handling
Logistics /
handling
Crumb Rubber Loading Level
Mandates ???
Background:
! 1992 - ISTEA Mandate passed
! 1995 – Sections 1038 of ISTEA mandate repealed
Impact:
! Confusion
! Industry backlash
! Significant spike in R&D, field work
Issue:
! Role of environmental policy in determining engineering specifications
Market Characteristics
! CRMB Paving Market approaching 400,000 tons
! Undergoing “renaissance” at present
! Regions of high use limited
! Many Countries’ exploring options
! Diverse applications
CRMB Process Comparison
Key Item
Blending Location
At the Same Loading
Levels
Storage Stability
Conventional
CRMB Process
On-Site
15% to 20% by wt
Prone to rapid
settling
Interaction /
Physical / Swollen
Nature of Modification Dispersed phase
Performance
Change during
storing or applying
Process Viscosity
High, varying with
AC &/or TR type, %
Advanced CRMB
Process
Refinery / Terminal
15% to 20% by wet
Compatible
Physical & chemical /
Modified contl. phase
Maintain consistent
Pumpable, Controllable
Morphology of CRMA
Advanced Process
Conventional Process
Advanced CRMA Process
Crumb Rubber Loading at 15 to 20% Level
Advanced CRMB Process
- Conventional CRMB process
with performance uncertainty
- Produce CRMB with
-a desired feature and benefit
-a performance graded product
-CR Liquefied to a type of oil:
miscible with bitumen but
sacrificing CR performance
offering
CRMB Applications
Pavements
! Hot Mix Asphalt
! Hot Applied Surface Treatments
! Crack Fillers / Joint Sealers
! Bridge Deck Coatings
! Tack Coats
! Emulsions
Other Markets
! Waterproofing
! Membranes
! Coatings
CRMB Features & Benefit
Performance:
! Increased rutting resistance at elevated temperatures
! Improved fatigue resistance at intermediate temperatures
! Reduced thermal cracking
! High degree of adhesivity and elastic behavior
Logistics:
! Consistent “end-point” viscosity
! Excellent storage and thermal (performance) stability
! Homogeneous and pumpable
Field:
! Straightforward compaction
! Lower temperatures reduce fuming and odors
Role of CRMB in Its Application
Material Selection
(CRMB)
Design
Construction
End Application and Durability
CRMB Specification
Development
"
"
"
Secure the Role of CRMB in its
Application
Position it into its End Application
Capture its Features and Benefits
“Product” Specification Types
! Functional Specification
-describe end use
-risk of performance is on the seller
! Performance Specification
-specify measurable capabilities
-risk of performance is on the seller
! Detailed (or “Design”) Specification
-quantitative, physical or Chemical description
-industry or commercial standard
-risk of performance is on the buyer
CRMB Specification
!A Detailed (or “Design”) Specification
-quantitative, physical or Chemical description
-industry or commercial standard
-sampling defined
! Minimize Risk on Buyer/User Side
-understand the application
-select relevant parameters as close as possible
-address all major distresses during the
application
Application vs Specification
! Pavements (Specifications)
! Hot Mix Asphalt (MB, MAC-10TR, PG-TR etc)
! Hot Applied Seal Coats (AC15-5TR)
! Crack Fillers / Joint Sealers
! Bridge Deck Coatings
!Tack Coats
CRMB Specification for Hot mix
An Advanced CRMB Spec must address
• Rutting
• Fatigue
• Thermal Cracking
• Aging
• CRMB Stability
Pavement Rutting
Critical Factors
"
Traffic Frequency
"
Traffic Load & Speed
"
Temperature Distribution
"
Traffic Accumulation Rate
Parameters to Address Rutting in
CRMB Specs
• North America:
PG/PG+ & MB:
MAC-10TR :
Dynamic Modulus ( G*/Sin δ )
Absolute Viscosity @ 60°C
Pen & S.P.
• Australia
AB Grade:
Consistency @ 60°C and SP
Pavement Fatigue
Critical Factors
"
Critical Temperature
"
Aging
"
Traffic Load & Speed
"
Traffic Rate & Accumulation
"
Structure (Strain level)
Parameters to Address Fatigue in
CRMB Specs
• North America:
PG-TR:
(Tex-539-C0):
MB:
Dynamic Viscosity (η* ) on PAV
ER @ 50F
SSD: (δ@10rad/s - δ@1rad/s)
SSV: (η*@10rad/s-η*@1rad/s)
• Australia
AB Grade:
Torsional Recovery @ 25 °C
Pavement Thermal Cracking
Critical Factors
"
Cooling Rate
"
Aging
"
Pavement Temperature
"
Temperature Cycle
Parameters to Address Cracking
in CRMB Specs
• North America:
PG-TR & MB:
MAC-10TR:
Creep Stiffness & Rate (on PVA)
PEN @ 4°C (RTFO)
• Australia
AB Grade:
Stiffness @ 15°C
CRMB Storage Issues
"
CR Separation
• CRMB Degradation
Critical Factors
• Storage Temperature
• Storage Time
• CR Type
• CR & Asphalt Interaction
• Process Type
Stability in CRMB Specs
"
Phase Separation
well Addressed
-Storage: 163°C or 180°C for 48 or 72 hours
-Measure: Stiffness Difference in Top & Bottom
Advanced CRMB Spec
Proposed for Hot Mix
AASHTO
Method
Property
PGCR15
(76-22)
RAC
(70-22)
PGCR15
(70-28)
Original CRMB (at 18% at least CR load level)
Flash Point, min., °C
T 48
230
230
230
Rotational Viscosity (RV) @ 135 °C
Cp, max.
TP 48
3,000
3,000
3,000
Dynamic Shear Rheometer
G*/Sin Delta, kPa, min.
TP 5
1.00
at 76°C
1.00
at 70°C
1.00
at 70°C
50
50
ASTM D50
Elastic Recovery (ER), 25°C elongation @
113
10 cm, % min.
CRMB Stored @ 163°C after 48 hrs
Difference in R & B
from Top and Bottom, °C, max
Rotational Viscosity (RV) @ 135 °C
Cp
RV Variation +%
ASTM-D36
2
2
2
TP 48
report
report
report
20
20
20
Advanced CRMB Spec
Proposed for Hot Mix --- Contl.
Property
AASHTO
Method
PGCR15
(76-22)
RAC
(70-22)
PG CR15
(70-28)
1.00
1.00
1.00
CRMB RTFO Residue
Mass loss, %, min.
Dynamic Shear Rheometer
G*/Sin Delta, kPa, min.
TP 5
1.50
at 76°C
1.50
at 70°C
1.50
at 70°C
Elastic Recovery (ER), 25°C
elongation @ 10 cm, % min.
ASTM D113
report
report
report
80
80
80
ER, Retention, %, min
CRMB PAV Residue (100°C)
Creep Stiffness (S)
Mpa @ 300 MPa, max.
TP
-12 °C
-12 °C
-18 °C
Slope (m) 0.300, min
TP
-12 °C
-12 °C
-18 °C
Concluding Remarks
• Properties Measured by an Advanced CRMB Spec Should
Address all Critical Factors Causing Distresses in a Specific
Application
• Current CRMB Specs do not Relate Closely to Real
Pavement Performance
• Quite few Discrepancies of Current CRMB Specs exist in
their Parameters to Predict the Performance
• CRMB Specs Should Take CRMB Storage/Performance
Stability during Handling into Account
Thank You