Project Update: Characterization of Alaskan Hot-Mix Asphalt containing RAP

Transcription

1 Project Update: Characterization of Alaskan Hot-Mix Asphalt containing RAP Jenny Liu, Sheng Zhao and Beaux Kemp 06/25/15

2 Outline Introduction Problem Statement Background Objectives Recycled Asphalt Pavement (RAP) Work Completed Work in Progress 2

3 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

4 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 Photo credit: 4

5 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

6 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

7 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

8 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

9 Development of Materials Collection Plan Mix # Region Mix Type Mix Name RAP % Binder PG 1 Control Type II-B 0 PG Control Type II-B 0 PG Control Type II-A 0 PG Central 4 RAP25 Type II-A 25 PG RAP25 Type II-B 25 PG RAP35 Type II-B 35 PG Control Type II-B 0 PG Control Type II-B 0 PG Northern RAP25 Type II-B 25 PG RAP25 Type II-B 25 PG RAP35 Type II-B 35 PG Aggregate Source AS&G (MP 39 Glenn Hwy) Tanana Valley 9

10 Development of Binder Testing Plan Properties Parameters Equipment Binder Grading See standard DSR Viscoelastic behavior Master Curve complex modulus (G*) and phase angle (d) See standard DSR DSR Binder status Un-Aged and RTFO RTFO RTFO Testing T ( C) Standard See standard ASTM D-7643 Three for each (± 6 C and high PG) See standard AASHTO T 315 AASHTO T 315 MSCR See standard DSR RTFO Low Temperature Low Temperature Two for each (-6 C and high PG) AASHTO T 350 See standard BBR RTFO and PAV See standard AASHTO T 313 See standard DTT RTFO and PAV See standard AASHTO T

11 Development of Performance Testing Plan Test Properties Testing Temperature ( C) 4.4 Three Replicates Target Air Voids: 7% ± 0.5% Dynamic Modulus (le*l) Modulus le*l Master Curve - Flow Number Rutting 54 0 IDT Low-Temperature Thermal Cracking

12 Materials Collection for Northern Region Mixes Aggregates RAP 12

13 Verification of Composition Properties RAP Binder Content Verification RAP and Aggregates Gradation Verification 13

14 Development of Mix Design Based on JMF provided by the same contractor that supplied materials 14

15 Volumetric Properties Purpose: target air voids G mm Testing Mixing HMA in the Lab Sample Compaction 15

16 Sample Fabrication Dynamic Modulus Samples IDT Samples 16

17 Dynamic Modulus (le*l) Testing 17

18 Typical le*l Results le*l tested at 4.4 C Results of PG mixes Results of PG mixes 18

19 Typical le*l Results le*l tested at 21.1 C Results of PG mixes Results of PG mixes 19

20 Typical le*l Results le*l tested at 37.8 C Results of PG mixes Results of PG mixes 20

21 Typical le*l Results le*l tested at 54 C Results of PG mixes Results of PG mixes 21

22 Master Curves of le*l Results of PG mixes Results of PG mixes 22

23 Findings from le*l Higher RAP content, higher modulus The results are consistent on both PG mixes and PG mixes produced with materials from Northern Region in Alaska 23

24 Preliminary Binder Testing DSR rutting index Three binders: PG 52-28, PG 52-40, PG

25 Binder Testing Results DSR rutting index Tested at 10 Hz, within ±6 C of high PG T Spec: G* /sinδ,kpa, 1.00 Properties G* (kpa) δ(rad) Temperature ( C) PG PG PG

26 Work in Progress 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 26

27 IDT Tests 27

28 Central Region Testing Matrix Mix # Region Mix Type Mix Name RAP % Binder PG 1 Control Type II-B 0 PG Control Type II-B 0 PG Control Type II-A 0 PG Central 4 RAP25 Type II-A 25 PG RAP25 Type II-B 25 PG RAP25 Type II-B 35 PG Aggregate Source AS&G (MP 39 Glenn Hwy) 28

29 TSAR Analysis Using data collected from BBR test Determine the critical temperature that corresponds to thermal cracking based on BBR for the proposed new AASHTO binder specification Photo credit: TSAR manual 29

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