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The XXVIII International Baltic Road Conference

USE OF REJUVENATORS FOR PRODUCTION OF SUSTAINABLE HIGH

CONTENT RAP HOT MIX ASPHALT

Martins Zaumanis1, Rajib B. Mallick2, Robert Frank3

1,2Worcester Polytechnic Institute (WPI), Worcester, MA, United States

3Compliance Monitoring & RAP Technologies, Linwood, NJ, United States

1100 Institute Road, Kaven Hall, Worcester, MA 01609, jeckabs@gmail.com

2100 Institute Road, Kaven Hall, Worcester, MA 01609, rajib@wpi.edu

3217 Belhaven Avenue, Linwood, NJ 08221, info@raptech.us

Abstract. Aged binder is the main obstacle for increasing the use or Reclaimed Asphalt Pavement (RAP) in production of asphalt

pavements. RAP binder is much stiffer and therefore high RAP content mixes are perceived to be susceptible to fatigue and thermal

cracking failures. Appropriate choice of rejuvenator may allow reducing the binder viscosity to attain the desired mixture workability

and recover the necessary performance properties of the aged binder. Six differently originated rejuvenators were added to extracted

binder at 12% dose including aromatic extract, waste engine oil, tall oil, organic oil, waste vegetable oil and waste vegetable grease.

The rejuvenation potential of these products was evaluated by performing multiple empirical as well as performance tests and the

results compared with a virgin binder. The rejuvenators proved to soften the extracted binder to the level of virgin and the kinematic

viscosity results show that the optimum compaction temperature can be reduced by 15°C to 25°C compared to extracted binder.

Performance Grade (PG) test results showed that none of the rejuvenators reduced the high PG of extracted binder to the level of

virgin binder indicating increased rutting resistance. At the same time most are able to reduce low PG from -12°C of the extracted

binder to at least the required -22°C. The low temperature performance correlated well with penetration index, proving that thermal

cracking should not be an issue at appropriate rejuvenator dose. The binder fatigue performance was evaluated through Linear

Amplitude Sweep (LAS) test. Only waste vegetable products were able to increase the fatigue resistance to the level of virgin binder

at a 12% dose using LAS test while the Superpave G*·sinδ indicated that all rejuvenators pass the minimum fatigue requirement.

Keywords. Rejuvenators, softening agents, waste vegetable oil, linear amplitude sweep test.

INTRODUCTION

Reclaimed Asphalt Pavement (RAP) binder properties depend on the composition of the original

binder and aging during service. If the aggregates are of good quality, then the main obstacle for

increasing the RAP dosage, is the aged RAP binder. The stiff binder has low workability and may

cause fatigue and thermal cracking.

A successful use of rejuvenators should reverse the RAP binder aging process, restore the properties

of asphalt binder for another service period and make the RAP asphalt effectively “available” to the

mix, and hence allow a significant increase in the amount of RAP that could be used in Hot Mix

Asphalt (HMA). However, it is necessary to carefully select the rejuvenator to provide the

necessary short and long term properties, as follows.

1. Short term. Rejuvenators should allow the production of high RAP content mixture by rapidly

diffusing into the RAP binder and mobilizing the aged asphalt in order to produce uniformly

coated mixtures. Rejuvenator should soften the binder in order to produce a workable mixture

that can be easily paved and compacted to the required density without the hazard of

producing harmful emissions. Major part of diffusion process should be completed before the

traffic is allowed to avoid reduction of friction and increased susceptibility to rutting.

2. Long term. Rejuvenators should reconstitute chemical and physical properties of the aged

binder and maintain stability for another service period. The binder rheology has to be altered

to reduce fatigue and low temperature cracking potential without over softening the binder to

cause rutting problems. Sufficient adhesion and cohesion have to be provided in the mix to

prevent moisture damage and raveling.

1 RESEARCH APPROACH AND MATERIALS

1.1 Objective

The objective of the research is to evaluate the use of rejuvenators for restoring the desirable

properties of the aged RAP binder in order to produce very high content RAP hot mix asphalt.

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Fig 1. Research Test Plan

1.2 Test plan and Methods

The test methods used in this study for binder evaluation are summarized in Figure 1. Mixing of

rejuvenators with the extracted binder demonstrates the effects of 100% blending; the penetration

and viscosity tests were carried on unaged samples, but the blended samples for performance

grading (PG) were aged according to standard procedure for virgin binders.

1.3 Binder

The binder was extracted from the RAP using toluene according to ASTM 2172, method A and

recovered using rotary evaporator, according to ASTM D5404. Typically a PG 64-22 binder is used

in this climatic area and therefore this grade was selected as a reference binder.

1.4 Rejuvenators

Six different rejuvenating agents are used in the study. The products have been labeled by generic

descriptors that briefly define the origins of the products. Measured kinematic viscosity and the

specific gravity along with the some basic characteristics obtained from manufacturers are included

in Table 1. The rejuvenator dose selection (12% from binder mass) is based on the author’s

previous study (Zaumanis et al., 2013) as a compromise between all of the rejuvenators. The

research results suggested that this is close to optimum dose for organic products, but lower than

that required for petroleum products.

Table 1. Rejuvenator properties and description

Rejuvenator Viscosity

at 135°C

Specific

gravity

Engineered

or Generic

Petroleum

or Organic

Refined

or Waste

Molecular

structure Polarity Traditional

or Novel

Nustar PG 64-22 474 1.02 Generic Petroleum Refined Ring and Strand Mixed Traditional

Aromatic Extract 9.20 0.995 Generic Petroleum Refined Aromatic Ring Very Traditional

Waste Engine Oil 3.86 0.872 Generic Petroleum Waste Aliphatic Slight Traditional

Distilled Tall Oil 5.60 0.950 Generic Organic Refined Ring and Strand Mild Traditional

WV Grease 4.28 0.924 Generic Organic Waste Ring and Strand Mild Novel

WV Oil 5.17 0.917 Generic Organic Waste Ring and Strand Non Novel

Organic Oil 5.43 0.947 Engineered Organic Refined Ring and Strand Mild Traditional

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1.4.1 Aromatic extract

An aromatic extract is a traditional rejuvenator with dominant polar aromatic rings. Recent findings

show concern with unsaturated polar aromatic ring structure, which have been shown to be

carcinogenic (The Petroleum HPV Testing Group, 2012). This research is not intended to promote

the use of aromatic extract, but rather to allow comparing other products to a rejuvenator, that has

been used historically and has demonstrated acceptable results. Aromatic extracts contain

approximately 75% polar aromatic oils, resin compounds with balance less polar aromatics.

Proponents claim polar aromatics associate with asphaltene molecules and in the process make

binder less brittle, by balancing the chemistry of the oxidized aged binder.

1.4.2 Waste Engine Oil (WEO)

WEO is produced from paraffinic oil with small dose of specialty compounds to improve viscosity

characteristics, stability, cleaning and flammability for use in engines. WEO may contain short

chain polar molecules that break apart during lubricating service. Recent interest in waste engine oil

re-refineries around the world is making WEO increasingly difficult to obtain and more costly.

1.4.3 Refined tall oil

SylvatalTM D30E tall oil is produced by Arizona Chemical. It is a byproduct of paper manufacture

being concentrated from kraft liquors. Tall oil is available either in crude form or as refined

products. Crude tall oil contains fatty acids, resin acids and unsaponifiables in varying ratios

depending on tree type used. Tall oils have a long history of use in hot mix manufacture with many

emulsifiers, antistrip agents and warm mix additives.

1.4.4 Waste Vegetable Oil (WV Oil)

WV Oil is increasingly used for bio-diesel production and has very strict compositional

specifications including low free fatty acid content (<15%), less than 2% MIU (Moisture,

Impurities, Unsaponifiables) (National Renderers Association, 2008). Derived from fast and

convenience food frying oil, it is also referred as “yellow grease”. The product used in this study

consists predominately of peanut, sunflower, and canola oils, with large concentrations of Oleic and

Linolic acids.

1.4.5 Waste Vegetable Grease (WV Grease)

WV Grease is also a food industry organic waste stream but semi solid at ambient temperatures due

to predominance of saturated Lauric and Myristic triglcerides. The product used in study is also

high in free fatty acids (>40%) but with its free glycerin and moisture removed industrially.

1.4.6 Organic oil

Hydrogreen STM is an engineered product by PVS Meridian Technologies, Inc and is designed to be

binder rejuvenator and a low temperature additive. It is composed of fast pyrolysis of pine tree

biomass (Harshavardhan et al., 2012) with other oils added to balance performance. The product is

free flowing most of the year, but slight heating to around 10°C is necessary when used in cold

weather.

2 PERFORMANCE GRADE

The extracted RAP binder was tested for Performance Grade (PG) after addition of each of the

rejuvenators and the results, along with the virgin binder PG 64-22, are illustrated in Figure 2. They

show that RAP binder has aged significantly and grades as PG 94-12. The addition of all products

allowed reducing both the high and low binder grade compared to the extracted binder suggesting

not only decrease in viscosity but also increasing in elasticity. None of the products was quite able

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to reduce the high grade to the level of virgin binder indicating lower susceptibility to rutting. This

shows that, despite the general concern, if adequate dose of rejuvenator is used and good diffusion

occurs in asphalt binder film, there is no danger of increased rutting susceptibility with the use of

rejuvenators. Note that this assumes that there is 100% diffusion of the rejuvenators in the binder.

The required low performance grade (-22°C) was reached in all cases except when using WEO.

Most of the products are actually able to reduce the PG much lower than required, and at the dose of

12%, organic oil and WV oil have provided the lowest cracking temperature.

Penetration Index (PI) was developed to describe the temperature susceptibility of binder. However,

Burke et.al (Burke et al., 2011) in their research on field performance of binder that has been

modified with re-refined waste engine oil residue suggested the use of PI of binder in respect to its

expected thermal and fatigue cracking performance. Their research proposes PI as a good measure

of steric hardening (asphaltene structure formulation over time) that promotes accelerated oxidative

hardening and gel-type structure that retain higher stress levels at low temperatures. According to

their research an increase in PI, despite sufficient low temperature performance grade, indicates low

temperature cracking susceptibility.

PI was calculated from penetration results at temperatures of 10°C and 25°C according to Equations

1 and 2, developed by Pfeiffer and Van Doormaal (Whiteoak et al., 2003). Figure 3 shows good

correlation of rejuvenated binder PG and PI, confirming that low temperature performance has been

in fact improved. The virgin PG 64-22 likely has a different origin and therefore its PI is

significantly different from rejuvenated binders.

PI