Mechanical Properties of Recycled Asphalt Shingles at Constant and Elevated

Temperatures

Department of Civil and Environmental Engineering Recycled Material Resource Center (RMRC)

Ali Soleimanbeigi, PEPhD student, University of Wisconsin-Madison

80 % of homes are roofed by asphalt shingles

12 million tons asphalt shingle waste per year in US

400,000 tons in Wisconsin

Current applications reuses 10-20 % of asphalt shingle waste

RAS is a top priory for reuse (EPA, FHWA)

Recycled Asphalt Shingles (RAS)

Reuse application with large volume

Embankment fill

Retaining wall backfill

Shape and component of RAS

Plate like particles Highly angular Rough surface texture

Angular Rough surface texture Porous

RAS Bottom Ash (BA)

Mechanical Properties for Structural Fill

Shear Strength: stability

RAS:BA mixture or stabilized RAS has sufficient shear strength as structural fill (f> 32o)

Compressibility: settlement

Compressibility is limited by adding granular material like BA or by stabilization

Hydraulic Conductivity: drainage capacity

RAS:BA mixture or stabilized RAS has sufficient drainage capacity as structural fill, K > 10-4 cm/s

Effect of seasonal temperature change on mechanical properties of compacted RAS:BA mixture

RAS contains asphalt cement, therefore:

Thermo-mechanical system: Triaxial Cell

tT

T(t)Pump

Temperaturecontroler

Back pressure, u

Thermocouple, Tc

Thermocouple, Tb

Thermocouple, Ts

Heater

Heating bath

RAS:BA specimen

Taygon tubing (6 mm)

Loading cell

Copper coil (6 mm)DifferentialTransducer(Volume change)

Cell pressure, c

Load

LabView

Thermo-mechanical system: Consolidometer

Load Cell

Specimen

Circulating water

Cool/warm water

PVC Cell Consolidation ring

Tc Copper coil

Thermo-mechanical system: Permeameter

Copper tubing

Thermocouples

Heating bath

Effect of temperature change on shear strength of RAS:BA mix and stabilized RAS

9

Effect of Temperature Change on Shear Strength and Volume Change

0 5 10 15 200

100

200

300

400

500

600

700

T=5°CT=22°CT=35°C

Axial strain, ea (%)

Devi

ator

stre

ss, s

'd (k

Pa)

0 5 10 15 20-3

-2

-1

0

1

2

3

4

T=5°CT=22°CT=35°C

Axial strain, ea (%)

Volu

met

ric st

rain

, evo

l (%

)

0 2 4 6 8 10 12 14 16 18 200

150

300

450

600

750

900

T=5°CT=35°C

Axial strain, ea (%)

Devi

ator

stre

ss, s

'df (

kPa)

0 2 4 6 8 10 12 14 16 18 20-3

-2

-1

0

1

2

3

4

T=5 °CT=35 °C

Axial strain, ea (%)

Volu

met

ric st

rain

, evo

l (%

)

RAS Soil

T=5oC1015202530

T=35oC

Shear Strength of RAS:BA mixture at Different Temperatures

Compacted RAS:BA mixtures have sufficient shear strength for typical highway embankment fills

f tanc

c≈0 kPa at different T

Shear strength

Cohesion

Friction

0 5 10 15 20 25 30 35 400

10

20

30

40

50

0

30

60

90

Temperature, T (oC)

Fric

tion

angl

e, f

(deg

rees

)

Cohe

sion

, c (k

Pa)

0 10 20 30 400

100

200

300

400

500

600

Temperature, T (oC)

Com

pres

sive

stre

ngth

s'df

(kPa

)

fff

sin1sin2cos2 '

3'

c

df

Stabilized RAS

Outwash Sand

f

c

Shear Strength of Stabilized RAS at Different Temperatures

Sufficient shear strength at elevated temperatures for structural fill

f tanc

Effect of temperature change on compressibility of RAS:BA mix or stabilized RAS

Long Term Compressibility

v

Time, t (log scale) tp

1Ca

tp : End of primary consolidation time

Ca : Secondary compression ratio

Soil

v

v

h

hh

v

Variation of strain over time under constant load

tc

log

a

Compressibility at Elevated Temperatures

0 5000 10000 15000 200000

1

2

3

4

'v200 kPa T=35°C

Time, t (min)

Verti

cal s

trai

n, e

v (%

)

24 h

Increase of temperature increases the vertical strain and vertical strain rate

0

1

2

3

4

T=35°CT=22°CT=5°C

Time, t (min)

Stra

in (%

)

)(, log

o

o

TTK

TT e

tc

a

0 5 10 15 20 25 30 35 400

0.02

0.04

0.06

0.08

0.1

0.12

Measured, RAS:BA (50:50)Predicted, RAS:BA (50:50)

Temperature, T (oC)

cae

RAS (%) K

25 0.157

50 0.168

Model Verification

0 5 10 15 20 25 30 35 40 45 500.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0.045

'v200 kPa35°C30°C25°C20°C15°C10°C5°C

RAS content (%)

Seco

ndar

y co

mpr

essio

n ra

tio, c

ae

Variation of ca with RAS Content and Temperature

1000 10000 1000000

2

4

6

8

10

12

T=35-22 °CT=22 °C

Time, t (min)

Verti

cal s

trai

n, e

v (%

)

’v=25 kPa

50 kPa

100 kPa

200 kPa100 kPa

200 kPa

50 kPa

25 kPa

Ca= 0.0080

Ca= 0.0004

T=35 oC T=22 oC

Effect of Thermal Preconsolidation-RAS:BA (25%:75%)

Material caClay 0.01Wisconsin outwash sand 0.0003RAS:BA (25:BA)-thermally preconsolidated 0.0004

Construction at warm seasons greatly reduces the long term compressibility of RAS:BA mixture

Effect of Thermal Preconsolidation-Stabilized RAS

0 10000 20000 30000 40000 50000 600000

0.5

1

1.5

2

Time (min)

Verti

cal S

trai

n, e

v (%

)

T=35oCT=22oC

T=22oC

T=22oC

ca=0.0002

ca=0.0016

Material ca

Clay 0.01

Wisconsin outwash sand 0.0003

Stabilized RAS (thermally precompressed) 0.0002

Stabilized RAS 0.0016

Construction at warm seasons greatly reduces the long term compressibility of stabilized RAS

Effect of Temperature on Hydraulic Conductivity

0 10 20 30 400.0000

0.0003

0.0006

0.0009

0.0012

0.0015

0.001835 kPa70 kPa140 kPa280 kPa

Temperature, T (oC)

Hydr

aulic

con

ducti

vity

, K (c

m/s

)

Hydraulic conductivity of RAS:BA mixture increases with increase in temperature

Hydraulic conductivity increases with temperature

Conclusions

Sufficient shear strength of RAS:BA mix or stabilized RAS is maintained due to seasonal temperature change

Thermal cycle increases shear strength and stiffness of RAS:BA mix Secondary compression ratio is an exponential function of temperature

Construction of embankment fills using RAS:BA mix or stabilized RAS is recommended during warm seasons

Use of RAS will contribute to more sustainable roadway construction

QUESTIONS?

0 2 4 6 8 10 12 14 16 18 200

100

200

300

400

(b)

T=22°CT=22-35-22°C

Axial strain, ea (%)

Devi

ator

stre

ss, s

'd (k

Pa)

9% reduction of a

Effect of Thermal Cycle

Thermal cycle increases the shear strength and stiffness of the compacted RAS:BA mixture

0 1000 2000 3000 4000 5000 6000 7000

-8

-7

-6

-5

-4

-3

-2

-1

0(a) T=22°C

T=22-35-22°C

Time, t (min)

Volu

met

ric st

rain

, evo

l (%

)

T=35oC 22oC22oC