Asphalt Mixtures Containing RAS: Effect of REOB on Laboratory Performance

Louay N. Mohammad Sam Cooper, Jr. Department of Civil and Environmental Engineering LA Transportation Research Center Louisiana State University

William H. Daly Ioan I Negulescu Sreelatha Balamurugan Department of Chemistry Louisiana State University Gaylon Baumgardner Paragon Services

FHWA Asphalt Binder Expert Task Group Oklahoma City, Oklahoma

September 16, 2015

The Story! • Background • Objective/Scope • Methodology

• Mixture Experiment • High, Intermediate, Low Temperatures

• Binder Experiment • Binder Fractionation by MW • SARA

• Results • Summary

Asphalt Mixture Design: Concern • Optimum asphalt cement

content – Quantity – NOT QUALITY – Recycled materials

• Aged binders

VOLUME MASS

air

asphalt

aggregate

Total Mass

Total Volume

aggregate

Objectives of Mixture Design • Perform

– permanent deformation – fatigue cracking – repeated load – low temperature cracking – moisture induced damage

• Safety – Resist skid

• Constructable – Workability

http://pavementinteractive.org/images/f/f2/De-Bonding_Banner.jpg

Objective – Mixture Experiment • Laboratory Performance at Low, intermediate, and

high temperatures – Conventional mixtures – mixtures containing RAS

• With and without REOB as a RA • Effect of REOB as RA

Scope • 12.5 mm Asphalt Mixture • RAS: Post-Consumer • Binder: PG 70-22M

Mix ID Mix Code RAS Recycling Agent Mix 1 70CO 0 None Mix 2 70PG5P_B 5 None Mix 3 70PG5P_B5SK 5 5% REOB Mix 4 70PG5P_B10SK 5 10% REOB Mix 5 70PG5P_B15SK 5 15% REOB

• High temperature Performance • Loaded Wheel Tracking Test • Rutting

• Intermediate temperature Performance • Semi Circular Bend Test • Cracking

• Low temperature performance • TSRST

Lab Performance Tests

Loaded Wheel Tracking Test – 50ºC

Wheel Diameter: 203.5 mm (8 inch)

Wheel Width: 47mm (1.85 inch)

Fixed Load: 703 N (158 lbs)

Rolling Speed: 1.1 km/hr

Passing Rate: 56 passes/min

l AASHTO T 324l rolling steel wheel across the surface of a samplel Specimen Geometry

– Cylindrical: Core or SGC– Slab: 320- L, 260- W, and 80-mm thick

l Wet or dryl Analysis

– Deformation at 20,000 passes is recorded– Indices

Semi Circular Bend (SCB) Test l LA DOTD TR 330l Temperature: 25°Cl Half-circular Specimen

– Laboratory prepared– Field core– 150mm diameter X 57mm thickness– simply-supported and loaded at mid-point

l Notch controls path of crack propagation – 25.4-, 31.8-, and 38.0-mm

l Aging: 5 days, 85°Cl Loading type

– Monotonic– 0.5 mm/min – To failure

l Record Load and Vertical Deformationl Compute Critical Strain Energy: Jc

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0.0 0.5 1.0 1.5 2.0 2.5

Lo

ad (

kN)

Deflection (mm)

Peak Load

notch a1

U1

SCB Test – Analysis l Calculate Energy at failure for each notch

depthl Plot U vs. a and determine slope (dU/da)l Compute CSERR

– Jc

Jc= Critical Strain Energy Release Rate (kJ/m2);b = sample thickness (m);a = notch depth (m); U = strain energy to failure (kilo-Joule, kJ); dU/da = change of strain energy with notch depth,

KJ/m

Results

0

5

10

15

20

Mix 10% RAS

Mix 25% RAS

0% REOB

Mix 35% RAS

5% REOB

Mix 45% RAS

10% REOB

Mix 55%RAS

15% REOB

Rut D

epth

@ 2

0K p

asse

s, m

m

Mixture type

Louisiana Specification 6.00 maximum

REOB

LWT Test Results 50°C

No REOB

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Mix 10% RAS

Mix 25% RAS

0% REOB

Mix 35% RAS

5% REOB

Mix 45% RAS

10% REOB

Mix 55%RAS

15% REOB

Jc, (

kJ/m

²)

Mixture type

Louisiana Specification 0.5 kJ/m²

REOB

Semi Circular Bend Test Results 25°C

No REOB

0.0

5.0

10.0

15.0

20.0

25.0

Mix 10% RAS

Mix 25% RAS

0% REOB

Mix 35% RAS

5% REOB

Mix 45% RAS

10% REOB

Mix 55%RAS

15% REOB

Frac

ture

Tem

pera

ture

, C

Mixture type

REOB

Thermal Stress Restrained Specimen Test Results

No REOB

Mixture High Temp (LWT) Intermediate Temp

(SCB) Low Temp

(TSRST) 70PG5P_B

70PG5P_B5SK

70PG5P_B10SK

70PG5P_B15SK

Summary of Performance Mixes Containing RAS, RAS/REOB as Compared to Control Mixture

Objective / Scope

• Correlate the molecular structure of asphalt binders to fracture property of asphalt mixtures – Asphalt mixtures: Conventional – Asphalt mixtures: RAS with and without REOB

• Binder Experiment

– Extracted from aged asphalt mixtures • 5 days, 85°C

– Gel Permeation Chromatography (GPC) – Saturates (S), aromatics (Ar), and resins (R) Analysis (SARA)

Scope – Binder Experiment

• Gel Permeation Chromatography (GPC)

GPC Analysis Principle GPC Instrument from DOTD Asphalt Lab

Quantification of GPC Curves by Integration

Analysis of Asphalt Binder Composition (SARA )*

• Each binder was deasphaltened to yield asphaltenes (As) and maltenes which are dissolved in the n-heptane soluble portion.

• The maltenes were further fractionated in saturates (S), aromatics (Ar), and resins (R). n-Pentane was used to elute the saturates, and a 90/10 toluene/chloroform mixture was used to elute the aromatics.

• The resins were not eluted and remained at the origin.

Scope – Binder Experiment

0

1

2

3

4PCWS (ALL)

∆RI (

Rela

tive

Units

)

MW (Daltons x 103 )

PCWS ASPHALTENES

7.80 %MW 28,058

25.50 %MW 11,180

12.30 %MW 4,610

54.40 %MW 1,150

15.40 %MW 24,500

32.20 %MW 12,000

52.40 %MW 3,300

0.20.51251020501001000

0.211001000 50 20 10 5 2 0.5

Comparative deconvolution of GPC traces of molecular weight species from PCWS and of n-heptane precipitated asphaltenes (PCWS Asphaltenes).

0

10

20

30

40

50

60

70

80

70PG5P 61.0 % MW 930

5.7 % MW 33,000

21.0% MW 4,300 12.6 %

MW 12,000

∆RI (

Rela

tive

Units

)

MW (Daltons x 10-3)

ASPHALTENES

MALTENES

0.20.51251020501001000

0.211001000 50 20 10 5 2 0.5

A B

MW distribution of molecular species of 70PG5P and 70PG5P_B15SK binders extracted from mixtures containing 5% PCWS (A)

and 5% PCWS & 15% REOB (B) , respectively

-10

0

10

20

30

40

50

60

70

8.40 % MW 11,675

13.80 % MW 3,640

1000

58.00 % MW 1,080

13.50 % MW 9,830

6.30 % MW 41,720

∆RI (

Rela

tive

Units

)MW (Daltons x 103)

ASPHALTENES

MALTENES

0.1

REOB

500 0.20.51251020501000

0.21100 50 20 10 5 2 0.5 0.1

70PG5P_B15SK

Mix Designation

SARA Analysis, %

DECO

NV

ASPH

, %

H

MW

, %

DECO

NV

MAL

T, %

J c, k

J/m

2

Asph

alte

nes

Resi

ns

Arom

atic

s

Satu

rate

s

Sum

resi

ns,

ar

omat

ics,

&

satu

rate

s

70CO 23.2 32.7 42.4 1.7 76.8 30.0 1.0 70.0 0.5

70PG5P_B 22.3 25.5 47.2 5.0 77.7 41.6 5.2 58.4 0.5

70PG5P_B5SK 20.6 26.9 45.4 7.1 79.4 33.5 4.5 66.5 0.3

70PG5P_B10SK 22.3 25.2 47.3 5.2 77.7 42.1 3.2 57.9 0.3

70PG5P_B15SK 24.4 29.3 40.2 6.1 75.6 42.0 6.3 58.0 0.2

Chemical Composition of Extracted Mixture Binders.

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

0 0.1 0.2 0.3 0.4 0.5 0.6

% M

olec

ular

Wei

ght >

20K

Dal

tons

Jc, kJ/m2

Comparison of Jc values versus the content of asphalt fractions with MW>20K Daltons

70PG5P_B5SK

70PG5P_B15SK

70PG5P_B10SK

70CO

70PG5P_B

• In general, mixtures with 5% RAS/No RA exhibited similar performance as conventional mixture

• High Temperature – LWT Rut depth – conventional mixtures = mixtures containing RAS and REOB RA.

• Intermediate Temperature – SCB JC – conventional mixtures was similar to mixtures containing RAS and no

RA – Jc decreased as the % REOB RA increased

• Low Temperature – In general , fracture temperature decreased with an increase in % REOB

RA • Except 5% REOB

Conclusion – Mixture Experiment

• Concentration of RAS asphaltenes exceeds 40% • 25% of these are highly aggregated with apparent MW

approaching 100K • Addition of REAO RA did not significantly dissociated

HMW associated asphaltenes • Evident SCB Jc values

• Extraction of RAS binder increased with an increase in %REOB RA • Increased availability factor

Conclusion – Binder Experiment

• SARA asphaltenes analysis by precipitation did not capture the total amount of associated asphaltenes in the binder as measured by GPC. Some associated asphaltenes may remain in the resin fraction

• Asphaltenes component from the SARA was

considerably smaller than the asphaltenes determined from deconvoluted GPC chromatograms

Conclusion – Binder Experiment

T H A N K

Y O U

Asphalt Mixtures Containing RAS: Effect of REOB on Laboratory Performance The Story!Asphalt Mixture Design: ConcernObjectives of Mixture DesignObjective – Mixture Experiment ScopeLab Performance Tests Slide Number 8Slide Number 9Slide Number 10ResultsLWT Test Results 50°CSemi Circular Bend Test Results 25°CThermal Stress Restrained Specimen Test ResultsSummary of Performance Mixes Containing RAS, RAS/REOB as Compared to Control MixtureObjective / Scope Scope – Binder ExperimentSlide Number 18Slide Number 19Slide Number 20Slide Number 21Slide Number 23Slide Number 24Conclusion – Mixture ExperimentConclusion – Binder ExperimentSlide Number 27Slide Number 28