Effect of Evotherm on Rheological Properties of Modified Binders

Rheological Characteristics of Warm Asphalt Binders

4.2 Effect of Evotherm on Rheological Properties of Modified Binders

Two dosages of WMA additive Evotherm (0.5%, and 0.6% by weight of binder) were used. Binders without Evotherm (i.e. 0% dosage) are referred as control

Chapter 4. Rheological Characteristics of Warm Asphalt Binders

binders. Two modified binders: polymer modified binder (PMB) and crumb rubber modified binder (CRMB), were used as the base binders. Preparation of additive-binder blend consisted of first heating the base binders to about 120°C and then introducing the desired quantity of additive, followed by a thorough stirring to achieve homogeneity. The following sections discuss the effects of varying dosages of Evotherm on the rheological characteristics of PMB and CRMB binders.

Viscosity at 150°C

Viscosity is a measure of consistency of asphalt binder, and reflects the internal resistance of the binder when it flows. Viscosity of both PMB and CRMB binders was measured with and without Evotherm using Brookfield rotational viscometer at 150°C and the results are shown in Figures 4.1 and 4.2. It is observed that viscosity of warm asphalt binders with Evotherm is slightly lower than the control binders. An addition of 0.6% Evotherm reduces the viscosity of PMB and CRMB binders by about 9%. WMA additive Evotherm, which was obtained and added in liquid form during the preparation of warm binders, lead to slight reduction in the viscosity of PMB and CRMB binders.

Failure Temperature

Failure temperature of an original (unaged) asphalt binder corresponds to the temperature at which the Superpave rutting parameter (G*/sinδ) attains a value of 1.0 kPa. Failure temperatures of PMB and CRMB binders with and without Evotherm are presented in Figures 4.3 and 4.4 respectively. It is observed that addition of Evotherm decreases the failure temperatures of both binders, suggesting a decrease in binder stiffness. Decrease in failure temperature is

4.2. Effect of Evotherm on Rheological Properties of Modified Binders

P M B - C o n t r o l P M B + 0 . 5 % E P M B + 0 . 6 % E

6 0 0 7 0 0 8 0 0 9 0 0 1 0 0 0

Viscosity, cP

Figure 4.1: Viscosity results of PMB warm asphalt binders with Evotherm

C R M B - C o n t r o l C R M B + 0 . 5 % E C R M B + 0 . 6 % E

6 0 0 7 0 0 8 0 0 9 0 0 1 0 0 0

Viscosity, cP

Figure 4.2: Viscosity results of CRMB warm asphalt binders with Evotherm

Chapter 4. Rheological Characteristics of Warm Asphalt Binders

slightly higher in case of CRMB binders compared to PMB binders. A maximum decrease of 1.8°C and 4.1°C in the failure temperature is observed, respectively, for PMB and CRMB on addition of 0.6% Evotherm. However, there is no change in the performance grade (PG 76) of both base binders on addition of Evotherm.

P M B - C o n t r o l P M B + 0 . 5 % E P M B + 0 . 6 % E

6 4 7 0 7 6 8 2 8 8 9 4

Failure temperature, °C

Figure 4.3: Failure temperature of PMB warm asphalt binders with Evotherm

Frequency Sweep Test

Frequency sweep test allows evaluation of rheological response of asphalt binders over wide range of frequencies, while the amplitude of the deformation remains constant. Response at low frequencies describes the behaviour at slow changes of stress, whereas the higher frequencies divulge the behaviour at fast moving loads. Figures 4.5 and 4.6 respectively show the elastic (G’) and viscous (G”) moduli of PMB and CRMB warm asphalt binders as a function of frequency from 0.01 to 100 Hz. Results show that the elastic and viscous moduli increase with the increase in test frequency. Both elastic and viscous moduli of PMB and CRMB binders decrease slightly on addition of Evotherm over the frequency

4.2. Effect of Evotherm on Rheological Properties of Modified Binders

C R M B - C o n t r o l C R M B + 0 . 5 % E C R M B + 0 . 6 % E

6 4 7 0 7 6 8 2 8 8 9 4

Failure temperature, °C

Figure 4.4: Failure temperature of CRMB warm asphalt binders with Evotherm range used. Further, an increase in Evotherm content from 0.5% to 0.6% slightly reduces the elastic and viscous modulus of both binders. However, this reduction becomes insignificant at higher test frequencies, indicating that increase in dosage does not produce appreciable changes in the elastic nature of PMB and CRMB binders.

Temperature Sweep Test

Temperature sweep test provides an idea about the rheological changes in the asphalt binders at varying temperatures experienced by the pavement during its service life. The test was performed over the temperature range of 25–80°C, and the two fundamental rheological parameters, namely the complex modulus (G*) and the phase angle (δ), were reported for the modified binders (PMB and CRMB) under varying Evotherm dosages. Figures 4.7 and 4.8 present the results.

Introducing Evotherm into the binders does not show any significant effect on

Chapter 4. Rheological Characteristics of Warm Asphalt Binders

0 . 0 1 0 . 1 1 1 0 1 0 0

1 0 ⁰ 1 0 ¹ 1 0 ² 1 0 ³ 1 0 ⁴ 1 0 ⁵ 1 0 ⁶

G ' : P M B - C o n t r o l G ' : P M B + 0 . 5 % E G ' : P M B + 0 . 6 % E G ' ' : P M B - C o n t r o l G " : P M B + 0 . 5 % E G " : P M B + 0 . 6 % E

Elastic and viscous modulus, Pa

F r e q u e n c y , H z

Figure 4.5: Frequency sweep results of PMB warm asphalt binders with Evotherm

0 . 0 1 0 . 1 1 1 0 1 0 0

1 0 ⁰ 1 0 ¹ 1 0 ² 1 0 ³ 1 0 ⁴ 1 0 ⁵ 1 0 ⁶

G ' : C R M B - C o n t r o l G ' : C R M B + 0 . 5 % E G ' : C R M B + 0 . 6 % E G " : C R M B - C o n t r o l G " : C R M B + 0 . 5 % E G " : C R M B + 0 . 6 % E

Elastic and viscous modulus, Pa

F r e q u e n c y , H z

Figure 4.6: Frequency sweep results of CRMB warm asphalt binders with Evotherm

4.2. Effect of Evotherm on Rheological Properties of Modified Binders

the complex modulus of both binders. A slight increase in phase angle is observed on addition of Evotherm at test temperatures greater than 50°C.

Increase in Evotherm dosage from 0.5% to 0.6% did not show any significant effect on complex modulus and phase angle of both PMB and CRMB binders.

2 0 3 0 4 0 5 0 6 0 7 0 8 0

1 0 ⁰ 1 0 ¹ 1 0 ² 1 0 ³ 1 0 ⁴ 1 0 ⁵ 1 0 ⁶ 1 0 ⁷

G * : P M B - C o n t r o l G * : P M B + 0 . 5 % E G * : P M B + 0 . 6 % E δ: P M B - C o n t r o l δ: P M B + 0 . 5 % E δ: P M B + 0 . 6 % E

T e m p e r a t u r e , ° C

Complex modulus (G*), Pa

4 0 5 0 6 0 7 0 8 0 9 0

Phase angle (δ), °

Figure 4.7: Temperature sweep results of PMB warm mixes with Evotherm

Creep Test

Creep test measures the strain response of binders under a constant shear stress (10 Pa in this study) maintained for a predetermined time (300 s in this study).

The test was performed at 60°C for all binders. The results are reported in terms of compliance, a parameter expressed as the ratio of strain undergone by the binder to the applied stress. The compliance is used as a measure of deformation; higher values denoting higher deformation. Figures 4.9 and 4.10 respectively illustrate the compliance (calculated at conclusion of the test at 300

Chapter 4. Rheological Characteristics of Warm Asphalt Binders

2 0 3 0 4 0 5 0 6 0 7 0 8 0

1 0 ⁰ 1 0 ¹ 1 0 ² 1 0 ³ 1 0 ⁴ 1 0 ⁵ 1 0 ⁶ 1 0 ⁷

G * : C R M B - C o n t r o l G * : C R M B + 0 . 5 % E G * : C R M B + 0 . 6 % E δ: C R M B - C o n t r o l δ: C R M B + 0 . 5 % E δ: C R M B + 0 . 6 % E

T e m p e r a t u r e , ° C

Complex modulus (G*), Pa

4 0 5 0 6 0 7 0 8 0 9 0

Phase angle (δ), °

Figure 4.8: Temperature sweep results of CRMB warm mixes with Evotherm s) for PMB and CRMB warm asphalt binders. There is a slight decrease in the compliance values of both PMB and CRMB binders on addition of Evotherm.

Addition of 0.6% Evotherm increases the compliance values by 7% and 5%, respectively, for PMB and CRMB binders. Results show that addition of Evotherm does not show any significant change in the resistance to deformation of both binders under a constantly applied stress.

Repeated Creep Recovery Test

Repeated creep recovery test involves application of a fixed shear stress for a short time followed by removal of the stress (allowing the binder to recover the deformation), and finally replicating the load-unload cycle for a preset number of times. Results are reported in terms of compliance measured over the complete test duration. In the present study, the test consisted of repeated

4.2. Effect of Evotherm on Rheological Properties of Modified Binders

0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 3 5 0

0 . 0 0 0 . 0 5 0 . 1 0 0 . 1 5 0 . 2 0 0 . 2 5

P M B - C o n t r o l P M B + 0 . 5 % E P M B + 0 . 6 % E

Compliance, Pa-1

T i m e , s

Figure 4.9: Creep results of PMB warm asphalt binders with Evotherm

0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 3 5 0

0 . 0 0 0 . 0 5 0 . 1 0 0 . 1 5 0 . 2 0 0 . 2 5

C R M B - C o n t r o l C R M B + 0 . 5 % E C R M B + 0 . 6 % E

Compliance, Pa-1

T i m e , s

Figure 4.10: Creep results of CRMB warm asphalt binders with Evotherm

Chapter 4. Rheological Characteristics of Warm Asphalt Binders

applications of 10 Pa shear stress over 52 cycles, with each cycle comprising of 1 s loading time and 9 s rest time. Compliance values of PMB and CRMB warm asphalt binders are shown in Figures 4.11 and 4.12 respectively. Addition of Evotherm leads to only a slight increase in the compliance values with both PMB and CRMB binders. An addition of 0.6% Evotherm caused a meagre decrease of 5% and 7% in compliance of PMB and CRMB binders (computed in terms of the compliance at the end of the test). The findings from this test are in agreement with those from failure temperature, temperature sweep, and creep tests. These results show that addition of Evotherm had no appreciable effect on the rheological characteristics of both PMB and CRMB binders, as this additive is designed to work at the aggregate and binder interface rather than influencing the binders’ rheology.

0 2 0 4 0 4 6 0 4 8 0 5 0 0 5 2 0

0 . 0 0 0 0 . 0 0 5 0 . 0 1 0 0 . 0 1 5 0 . 0 2 0 0 . 0 2 5

P M B - C o n t r o l P M B + 0 . 5 % E P M B + 0 . 6 % E

Compliance, 1/Pa

T i m e , s e c

Figure 4.11: Repeated creep recovery results of PMB warm asphalt binders with Evotherm

4.3. Effect of Sasobit on Rheological Properties of Modified Binders

0 2 0 4 0 4 6 0 4 8 0 5 0 0 5 2 0

0 . 0 0 0 0 . 0 0 5 0 . 0 1 0 0 . 0 1 5 0 . 0 2 0 0 . 0 2 5

C R M B - C o n t r o l C R M B + 0 . 5 % E C R M B + 0 . 6 % E

Compliance, 1/Pa

T i m e , s e c

Figure 4.12: Repeated creep recovery results of CRMB warm asphalt binders with Evotherm

4.3 Effect of Sasobit on Rheological Properties of