Institut für StraßenwesenT U B r a u n s c h w e i g

Experimental Investigation of Wearing Course Mixtures Prepared with Reclaimed Asphalt Pavement and Rejuvenators based

on the BTSV Method

Stephan Büchler

Axel Walther

Augusto Cannone Falchetto

Tokyo, Japan, November 20-21, 2017

Augusto | Experimental investigation of wearing course mixtures prepared with reclaimed asphalt pavement and rejuvenators based on the BTSV method| 20 – 21 Nov, 2017 | 2

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• Introduction

• Materials and Testing

• Results

• Summary and Conclusions

Outline

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Introduction

• RAP is commonly recycled in asphalt pavementconstruction.

• However, for higher RAP content a decrease inpenetration and increase in complex modulus and stiffnessare observed.

• Rejuvenators can be used to improve the characteristics ofthe final mixture.

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Introduction

Objective

• Investigate the possibility of designing mixtures with RAP and

rejuvenators.

Based on:

• Bitumen Typisierungs Schnell Verfahren - BTSV (Binder-Fast-

Characterization-Test)

• Conventional laboratory testing - stiffness modulus, fatigue

behavior and low temperature performance

Augusto | Experimental investigation of wearing course mixtures prepared with reclaimed asphalt pavement and rejuvenators based on the BTSV method| 20 – 21 Nov, 2017 | 5

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Materials and Testing

Materials

Figure 1 Double-shaft paddle mixer

Table 1 Composition and properties of RAP

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Materials and Testing

The BTSV method is based on Dynamic Shear Rheometer (DSR)tests and is used to determine the amount of rejuvenator to achievethe target viscosity for the extracted RAP binder:

• Temperature rate ofΔT=1.2°C/min• Constant shear stress of 500Pa in oscillation mode• Constant test frequency of f=10rad/s

The state of softening is represented through two parameters: thesoftening temperature (TBTSV), obtained at a value of complex shearmodulus of G*=15.0kPa (which is derived from the conventionalring and ball method), and the corresponding phase angle (δBTSV).

Materials

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Materials and Testing

BTSV1.E+04

1.E+03

1.E+02

1.E+01

1.E+00

1.E-01

G*

[kPa

]

δ [°

]

T [°C]

TBTSV = 54.3°C

δBTSV = 82.6°

G* = 15 kPa

Complex shear modulusPhase angle

20 30 40 50 60 70 80 90

90

80

70

60

50

40

30

20

10

0

Figure 2 BTSV Schematic

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Materials and Testing

BTSV

Figure 3 BTSV Plain

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Materials and Testing

Table 2 Composition and properties of laboratory prepared asphalt mixtures 1 to 7

Materials

An average reduction of 13°C is achieved for the extracted RAP binder with all rejuvenatorsstartingfrom the initial 71°C down to 58°C.

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Materials and Testing

Resistance to permanent deformations (EN 12697-25)

© ISBS

Figure 4 Uniaxial cyclic compression test

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Materials and Testing

Stiffness modulus (EN 12697-26)

Cylindrical indirect tensile test mode (CIDT)

Table 3 Number of load cycles to determine the stiffness modulus

[Δ (0.274 )] / [ Δ ]E F h uµ= ⋅ + ⋅E stiffness modulusΔF difference between minimum and maximum loadμ Posson’s ratioh specimen height and Δu difference between minimum and maximum deformation

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Materials and Testing

Stiffness modulus

w absolute modulusz material parameterfR=aT f f is the frequency and αT is the shift factor, such as

( )0log 1/ 1/T m T Tα = ⋅ −

.

00 log( )-| |1 e

Rf xz

wE y −

= +

+

Stiffness modulus master curve:

Figure 5 Example of Stiffness modulus results (T=-10, 0, 10 and 20°C) at different

frequencies

Augusto | Experimental investigation of wearing course mixtures prepared with reclaimed asphalt pavement and rejuvenators based on the BTSV method| 20 – 21 Nov, 2017 | 13

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Materials and Testing

Fatigue behavior (EN 12697-24)

Figure 6 Schematic to obtain the Nmacro based on the maximum value

of EN at f=10 Hz

Figure 7 Example of fatigue function at T=20 °C and f=10 Hz

2.5E+04

2.0E+04

1.5E+04

1.0E+04

5.0E+03

0

ER

[M

Pa]

Loading cycles N

Energy Ratio ERStiffness modulus |E|

|E| [

MP

a]

0 2.E+04 4.E+04 6.E+04 8.E+04 1.E+05

NMacro

1.5E+09

1.2E+09

9.0E+08

6.0E+08

3.0E+08

0

21

CN C ε= ⋅Fatigue functions

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Materials and Testing

Low temperature performance (EN12697-46)

Figure 8 Example of cryogenic stress as function of temperature

Prismatic mixture specimens were subjected to Thermal Stress Restrained

Specimen Tests (TSRST) for evaluating the low temperature behavior.

σ cry

[MPa

]

T [°C]

σcry

Tf = -21.1°Cσcry = 4.09MPa

AC 32 T S5.0

4.0

3.0

2.0

1.0

0.0-25 -20 -15 -10 -5 0 5 10 15 20

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Results

Resistance to permanent deformations

Figure 9 Strain rates at the end of the uniaxial cyclic compression test

It appears that the addition of RAP + rejuvenator positively influences the deformation resistance compared to the virgin mixture with lower strain rates.

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Results

Stiffness modulus

Figure 10 Stiffness modulus from CIDT test at T=20, 10, 0, and -10°C and f=10 Hz

When using Rheofalt and Storflux with a content of 40% of RAP (mixtures 5 and 7) lowerstiffness values are observed.

Augusto | Experimental investigation of wearing course mixtures prepared with reclaimed asphalt pavement and rejuvenators based on the BTSV method| 20 – 21 Nov, 2017 | 17

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Results

Stiffness modulus

Figure 11 Master curves of stiffness moduli obtained from CIDT tests

at f=10 Hz for an AC 11 with a content of 40 M.-% RAP

Table 4 Regression parameters of the mixtures’ master curves

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Results

Fatigue

Figure 12 Loading cycles to fatigue failure Nmacro; initial strain level εelf=10 Hz, T = 20°C and 20 M.-% RAP

Augusto | Experimental investigation of wearing course mixtures prepared with reclaimed asphalt pavement and rejuvenators based on the BTSV method| 20 – 21 Nov, 2017 | 19

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Results

FatigueTable 5 Fatigue functions and R2 for wearing course mixtures at 20 °C

All mixtures prepared with rejuvenators show better fatigue properties thanthe control material, except for mixture 6 (Storflux and 20% RAP) whichpresents fatigue behavior similar to mixture 1.

Augusto | Experimental investigation of wearing course mixtures prepared with reclaimed asphalt pavement and rejuvenators based on the BTSV method| 20 – 21 Nov, 2017 | 20

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Results

Low Temperature PerformanceTable 6. TSRST fracture temperature and corresponding cryogenic stress

Figure 13 Fracture temperature and corresponding cryogenic stress from TSRST

Mixture Rejuvenator RAP [%] Fracture temperature [°C]

Fracture stress [MPa]

1 - 0 -27.3 4.8 2 160/220 20 -25.2 5.1 3 40 -26.7 4.6 4 Rheofalt 20 -24.5 5.4 5 40 -25.9 4.9 6 Storflux nature 20 -26.9 4.7 7 40 -27.6 5.0

Augusto | Experimental investigation of wearing course mixtures prepared with reclaimed asphalt pavement and rejuvenators based on the BTSV method| 20 – 21 Nov, 2017 | 21

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The use of rejuvenators in combination with high reclaimedasphalt pavement (RAP) was investigated based on theanalysis method recently introduced in Germany and knownas Bitumen Typisierungs Schnell Verfahren - BTSV (Binder-Fast-Characterization-Test), and then experimentallyevaluated. The following conclusion can be drawn:

• Rejuvenators and high amounts of RAP have a negligibleimpact on stiffness properties, improve the fatigue response result in comparable low temperature performance, except for a specific rejuvenator.

Summary and Conclusions

Augusto | Experimental investigation of wearing course mixtures prepared with reclaimed asphalt pavement and rejuvenators based on the BTSV method| 20 – 21 Nov, 2017 | 22

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Acknoledgements

Laboratory Team

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Augusto | Experimental investigation of wearing course mixtures prepared with reclaimed asphalt pavement and rejuvenators based on the BTSV method| 20 – 21 Nov, 2017 | 23

Important DatesNov. 27th, 2017 Submission of paper open

Apr. 10th, 2018 Submission of paper due

Jun. 1st, 2018 Notification of papers acceptance

Sept. 17-18th, 2018 RILEM 252-CMB Symposium

Sept. 19-20th, 2018 RILEM Annual Meeting

RILEM-CMB-SYMPOSIUMBRAUNSCHWEIG, GERMANYSEP TEMBER 17–18, 2018CHEMO MECHANICAL CHARACTERIZATION OF BITUMINOUS MATERIALS

SecretariatNina Eßmann, Technische Universität Braunschweig,n.essmann@tu-bs.de

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Thank you!