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Balanced Mix Design: High Recycled Mixes · PDF file 2021. 2. 2. · •The need...

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PowerPoint PresentationCONFIDENTIAL. This document contains Cargill Confidential information. Disclosure, use or reproduction outside Cargill or inside
Cargill, to or by those who do not have a need to know is prohibited. © 2019 Cargill, Incorporated. All rights reserved.
Balanced Mix Design:
Khaled Hasiba, P.E.
Current Pavement Condition
9.96
10.49
10.42
10.77
11.49
11.84
2014
2015
2016
2017
2018
2019
2
Source: Freight volume moved by trucks in the U.S. 2014-2019 (Statista)
© 2021 Cargill, Incorporated. All rights reserved.
Need for Balanced Mix Design
• Some DOTs indicate that cracking and raveling have become
the primary factor controlling service life of asphalt pavement
• Superpave volumetric design is better at addressing rutting than
cracking
changes:
– Binder quality has changed due to evolution of production processes.
– Effect of additives (WMA, Rejuvenators, REOB, polymers, fibers, etc.)
– Impact of recycled materials (RAP and RAS)
Source: pavementinteractive.org
Source: Development of Framework for Balanced Mix Design, R. West
3
• Mix design approach that addresses multiple modes of
distresses
(stability)
location within the pavement structure
• Design property could be binder content, RAP and RAS
content, rejuvenator dosage rate or binder rheology.
Source: Innovation in Asphalt Mix Design Procedures
4
Performance Testing: Cracking
• Evaluates mix durability and resistance to fatigue and thermal cracking
• Involves modes of distresses and aging conditions
DCT IDEAL-CT I-FIT / SCB Overlay Beam Fatigue
Low Temp PG +10 25C or room 25C or room 25C Varies 4-25C
Cut and notched Compacted to height Cut and notched Cut sample Slab compacted, cut
5
Performance Testing: Permanent Deformation
• Function of traffic level and/or mix type and application
Hamburg APA Flow Number
45-65C 45-65C 45-65C
Dry or submerged Dry or submerged Dry
6
Current Use of Rutting Tests
7
Source: Development of Framework for Balanced Mix Design, R. West
7
Case Studies
NCAT Test Track
45% RAP + Rejuvenator
- Air voids allowed to vary (higher density)
9
64 C
30%RAP Control 76.7 -14.6 -9.2 6.1 520 124 296 2.51mm
45%RAP Rejuvenator 75.9 -22.0 -2.0 8.0 565 100 325 2.55mm
No Rutting
Smooth Ride
0 Cracking
Balanced Mix Design for Minnesota
Approval Process
supplier dosage recommendations and HMA producer’s
mix design.
reasonable equivalence to control.
to determine reasonable equivalence to control.
10
Description Extract AC% HT PG LT S PG LT m PG ΔTc DCT -20C HWT at 50C n=5k
25%RAP Control 5.19% 65.1 -29.6 -24.3 -5.2 502.8 7.95mm
45%RAP Rejuvenator 4.51% 66.5 -28.7 -27.2 -1.5 495.0 2.35mm
45% RAP + Anova™ Rejuvenator vs. Control: 25% RAP
“Performance-modified” Volumetric Mix Design:
50% RAP Millings, Wearing Course
Project Highlights: Minnesota
Production Temp. 270-310F
Compaction Temp. 260-280F
Field Density 92.2-93.3% (Nuclear Density Gauge)
Performance Flexibility Index of 9.0±1.5
11
45% RAP 12.5mm Wearing Course
Project Highlights: Minnesota
Performance DCT at -20C 350 J/m2
HWT at 50C <12.5mm
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Project Highlights: Wisconsin
Production Temp. 295-300F
Compaction Temp. 270-275F
Field Density 93.4% (Nuclear Density Gauge)
Performance 620 > 375 J/m2 DCT at -18C
22 > 12 I-FIT Flexibility Index at 19C
4.0 < 12.5mm HWT at 45C
# of Gyrations % AC % Binder Replacement % Voids VMA Gmm
75 6.2% 44.0% 3.0% 14.8% 2.476
Gmb VFA Gse Gsb Dust/AC TSR
2.401 79.7% 2.729 2.644 1.04 96.2%
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Project Highlights: Illinois
Field Density > 350 J/m2 DCT at -12C
< 12.5mm rutting HWT 50C
14
Summary
• The need for a Balanced Mix Design derives from the change in binder quality and the
introduction of recycled materials.
• Balanced Mix Design uses performance-related tests to optimize and select design parameters
• BMD is an effective way to introduce higher recycled content and rejuvenators into the mix
without jeopardizing quality.
already done so.
• Rejuvenation has been used for several years as a practical solution to produce reliable high
recycled mixes for commercial and agency applications.
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