Characterization of Alaskan Hot-Mix Asphalt containing RAP Jenny Liu, Sheng Zhao and Beaux Kemp...

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

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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

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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)

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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

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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

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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

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Development of Materials Collection Plan

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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

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Properties Parameters EquipmentBinder status

Testing T (°C) Standard

Binder Grading See standard DSR Un-Aged and

RTFO See standard ASTM D-7643

Viscoelastic behavior

complex modulus (G*)

and phase angle (d)

DSR RTFOThree for each

(± 6°C and high PG)

AASHTO T 315

Master CurveSee standard

 DSR RTFO

 See standardAASHTO T 315

MSCR See standard DSR RTFOTwo for each (-6°C and high

PG)

AASHTO T 350

Low Temperature

See standard BBR RTFO and PAV See standard AASHTO T 313

Low Temperature

See standard DTT RTFO and PAV See standard AASHTO T 314

Development of Performance Testing Plan

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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-

Temperature Thermal Cracking

0

-10

-20

Three Replicates

Target Air Voids: 7% ± 0.5%

Materials Collection for Northern Region Mixes

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Aggregates RAP

Verification of Composition Properties

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RAP Binder Content Verification RAP and Aggregates Gradation Verification

Development of Mix Design

Based on JMF provided by the same contractor that supplied materials

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Volumetric Properties

Purpose: target air voids

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Gmm Testing Mixing HMA in the Lab Sample Compaction

Sample Fabrication

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Dynamic Modulus Samples IDT Samples

Dynamic Modulus (lE*l) Testing

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Typical lE*l Results

lE*l tested at 4.4°C

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Results of PG 52-28 mixes Results of PG 52-40 mixes

Typical lE*l Results

lE*l tested at 21.1°C

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Results of PG 52-28 mixes Results of PG 52-40 mixes

Typical lE*l Results

lE*l tested at 37.8°C

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Results of PG 52-28 mixes Results of PG 52-40 mixes

Typical lE*l Results

lE*l tested at 54°C

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Results of PG 52-28 mixes Results of PG 52-40 mixes

Master Curves of lE*l

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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

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Preliminary Binder Testing

DSR rutting index Three binders: PG 52-28, PG 52-40, PG

58-34

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Binder Testing Results

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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

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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

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Central Region Testing Matrix

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Mix # Region Mix Type Mix Name RAP % Binder PGAggregate

Source1

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

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