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Characterization of Alaskan Hot-Mix
Asphalt containing RAP
Jenny Liu, Sheng Zhao and Beaux Kemp
06/25/15
Project Update:
Outline
Introduction
Problem Statement
Background
Objectives
Work Completed
Work in Progress
2
Recycled Asphalt Pavement (RAP)
Problem Statement Tendency of greater use of recycled/reclaimed asphalt
pavement (RAP)
Decreasing supplies of locally available quality aggregate
Growing concern over waste disposal
Rising cost of asphalt binder
In Alaska, 15% RAP is allowed in the wearing course, up to 25% RAP in the binder or base course. Projects will see an increased use of RAP
Mechanistic analysis procedures (AKFPD software) require material engineering properties as input
It is essential to properly characterize HMA mixes containing RAP material in Alaska
3
Background
Most recycled material in U.S.
Annually 100 million tons
Recycles aggregates and asphalt binder
4 to 6% binder by weight
Saving 14% to 34%
with 20% to 50% RAP
4Photo credit: http://paving-sacramento-ca.com/
Current Status of RAP Application
Performance
At low or medium content level, Equivalent (or better) performance was expected compared to virgin mix
At high content level, compromised fatigue and low temperature performance
High RAP content is promoted
More than 25% by weight of mix
How to increase RAP content
Using softer binder to compensate aged RAP binder
Adding recycling agents
Combining RAP with warm mix asphalt (WMA)
5
RAP in Alaska
Limited previous research
How RAP contents affect Superpave PG of the blended binder (Saboundjian and Teclemariam 2010)
Effects of 15% RAP on airport runway (Connor and
Li 2009)
Current AK specification
15% in the wearing course, 25% in base
Performance data on HMA containing RAP for surface course application is limited
6
Objectives
To properly characterize Alaskan HMA materials containing RAP, yielding:
Mix modulus (stiffness) values at different temperatures, to be used in pavement design/analysis procedures
Rutting performance at intermediate and high temperatures
Low-temperature thermal cracking performance
7
Work Completed
Task 2 - Development of Materials Collection Plan
Task 3 - Specimens Fabrication and Performance Tests
Development of Testing Plan
HMA mixtures with RAP in Northern Region of Alaska
Materials collection
Sample fabrication and volumetrics verification
Testing for dynamic modulus
Task 4: Characterization of Asphalt Binder with RAP
Preliminary Binder Testing
8
Development of Materials Collection Plan
9
Mix # Region Mix Type Mix Name RAP % Binder PGAggregate
Source
1
Central
Control Type II-B 0 PG 52-28
AS&G (MP 39 Glenn Hwy)
2 Control Type II-B 0 PG 58-34
3 Control Type II-A 0 PG 58-34
4 RAP25 Type II-A 25 PG 58-34
5 RAP25 Type II-B 25 PG 58-34
6 RAP35 Type II-B 35 PG 52-28
7
Northern
Control Type II-B 0 PG 52-28
Tanana Valley
8 Control Type II-B 0 PG 52-40
9 RAP25 Type II-B 25 PG 52-28
10 RAP25 Type II-B 25 PG 52-40
11 RAP35 Type II-B 35 PG 52-28
Development of Binder Testing Plan
10
Properties Parameters EquipmentBinder
statusTesting T (°C) Standard
Binder Grading See standard DSRUn-Aged and
RTFOSee standard ASTM D-7643
Viscoelastic
behavior
complex
modulus (G*)
and phase
angle (d)
DSR RTFO
Three for each
(± 6°C and
high PG)
AASHTO T 315
Master CurveSee standard
DSR RTFOSee standard
AASHTO T 315
MSCR See standard DSR RTFO
Two for each
(-6°C and high
PG)
AASHTO T 350
Low
TemperatureSee standard BBR RTFO and PAV See standard AASHTO T 313
Low
TemperatureSee standard DTT RTFO and PAV See standard AASHTO T 314
Development of Performance Testing Plan
11
Test PropertiesTesting
Temperature (°C)
Dynamic Modulus (lE*l)
Modulus
4.4
21.1
37.8
54
lE*l Master Curve -
Flow Number Rutting 54
IDTLow-TemperatureThermal Cracking
0
-10
-20
Three Replicates
Target Air Voids: 7% ± 0.5%
Materials Collection for Northern Region Mixes
12
Aggregates RAP
Verification of Composition Properties
13
RAP Binder Content Verification RAP and Aggregates Gradation Verification
Development of Mix Design
Based on JMF provided by the same contractor that supplied materials
14
Volumetric Properties
Purpose: target air voids
15
Gmm Testing Mixing HMA in the Lab Sample Compaction
Sample Fabrication
16
Dynamic Modulus Samples IDT Samples
Dynamic Modulus (lE*l) Testing
17
Typical lE*l Results
lE*l tested at 4.4°C
18
Results of PG 52-28 mixes Results of PG 52-40 mixes
Typical lE*l Results
lE*l tested at 21.1°C
19
Results of PG 52-28 mixes Results of PG 52-40 mixes
Typical lE*l Results
lE*l tested at 37.8°C
20
Results of PG 52-28 mixes Results of PG 52-40 mixes
Typical lE*l Results
lE*l tested at 54°C
21
Results of PG 52-28 mixes Results of PG 52-40 mixes
Master Curves of lE*l
22
Results of PG 52-28 mixes Results of PG 52-40 mixes
Findings from lE*l
Higher RAP content, higher modulus
The results are consistent on both PG 52-28 mixes and PG 52-40 mixes produced with materials from Northern Region in Alaska
23
Preliminary Binder Testing
DSR rutting index
Three binders: PG 52-28, PG 52-40, PG 58-34
24
Binder Testing Results
25
DSR rutting indexTested at 10 Hz,within ±6°C of high PG T Spec:|G*|/sinδ,kPa,≥1.00
Properties |G*|(kPa) δ(rad)
Temperature (°C) 46 52 58 64 46 52 58 64
PG 52-28 4.59 1.94 0.81 - 1.51 1.53 1.54 -
PG 52-40 2.64 1.60 0.99 - 1.05 1.00 0.96 -
PG 58-34 - 2.64 1.49 0.90 - 1.25 1.22 1.17
Work in Progress
26
Task 3 - Specimens Fabrication and Performance Tests
IDT tests for Northern Region mixes
Materials collection for Central Region mixes
Task 4 - Characterization of Asphalt Binder with RAP
To complete the binder testing as planned
Task 5 - Data Processing and Analyses
Data analysis using Thermal Stress Analysis Routine (TSAR) software
IDT Tests
27
Central Region Testing Matrix
28
Mix # Region Mix Type Mix Name RAP % Binder PGAggregate
Source
1
Central
Control Type II-B 0 PG 52-28
AS&G (MP 39 Glenn Hwy)
2 Control Type II-B 0 PG 58-34
3 Control Type II-A 0 PG 58-34
4 RAP25 Type II-A 25 PG 58-34
5 RAP25 Type II-B 25 PG 58-34
6 RAP25 Type II-B 35 PG 52-28
TSAR Analysis
Using data collected from BBR test
29Photo credit: TSAR manual
Determine the critical temperature that corresponds to thermal cracking based on BBR for the proposed new AASHTO binder specification
30