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Rejuvenator screening

Rejuvenator screening study

The results of this phase of the research are summarized in article (click to download):
Evaluation of Rejuvenator's Effectiveness with Conventional Mix Testing for 100% Reclaimed Asphalt Pavement Mixtures, Transportation Research Record: Journal of the Transportation Research Board 

Publications

100% Recycled Hot Mix Asphalt: A Review and Analysis, (2014), Resour Conserv Recy 92: 230-245 http://goo.gl/rXFvbr  
Influence of Six Rejuvenators on the Performance Properties of Reclaimed Asphalt Pavement (RAP) binder and 100% recycled asphalt mixtures, (2014), Cons Build Mat 71: 538-550 https://sites.google.com/site/martinszaumanis/publications/publications-pdf-files/Zaumanis%20100%20recycled%20hot%20mix%20asphalt%20Res%20Cons%20Recycl.pdf?attredirects=0&d=1  
Determining optimum rejuvenator dose for Asphalt Recycling Based on Superpave Performance Grade Specifications, (2014), Cons Build Mat 69: 159-166 http://goo.gl/Vtlb3l  
Review of very high-content reclaimed asphalt use in plant-produced pavements: state of the art, (2015), Int J  Pavement Eng 16 (1): 39-55 https://www.researchgate.net/profile/Martins_Zaumanis/publication/261875706_Review_of_very_high-content_reclaimed_asphalt_use_in_plant-produced_pavements_state_of_the_art/links/54688c050cf2f5eb1804d9a9?ev=pub_int_doc_dl&origin=publication_detail&inViewer=true  
Evaluation of Different Recycling Agents for Restoring Aged asphalt Binder and Performance of 100% Recycled Asphalt, (2014), Mater Struct  https://sites.google.com/site/martinszaumanis/publications/publications-pdf-files/Zaumanis%20Recycling%20agents%20Materials%26Structures.pdf?attredirects=0&d=1  
Rheological, microscopic, and chemical characterization of the rejuvenating effect on asphalt binders, (2014), Fuel 135: 162-171 https://sites.google.com/site/martinszaumanis/publications/publications-pdf-files/Zaumanis%20Rejuvenation%20characterization%20Fuel.pdf?attredirects=0&d=1
Evaluation of Rejuvenator's Effectiveness with Conventional Mix Testing for 100% Reclaimed Asphalt Pavement Mixtures, (2013) Transp Res Rec 2370 (1): 17-25  https://sites.google.com/site/martinszaumanis/publications/publications-pdf-files/TRR%202013.pdf?attredirects=0&d=1  
Finite element modeling of rejuvenator diffusion in RAP binder film – simulation of plant mixing process, RILEM symposium 2013, Stockholm, Sweden, 06.12-14.2013    
Low temperature properties of 100% reclaimed asphalt pavement mixtures, 5th European Asphalt Technology Association, Braunschweig, Germany, 06.03-05.2013       
Use of Rejuvenators for Production of Sustainable High Content RAP Hot Mix Asphalt, 28th International Baltic Road Conference, Vilnius, Lithuania, 08.26-28.2013
Interactive presentation of Phase I results and research plans
 

Nine differently originated softening agents were tested with 100% RAP mixtures to evaluate their effect on penetration at two temperatures and low temperature embrittlement. Penetration Index (PI) was evaluated as an indicator for rejuvenation effectiveness and to predict the cracking potential. Low temperature mixture performance was tested at -10°C through determination of indirect tensile strength and creep compliance. The mixture test results confirmed the PI results and showed that the use of six from the tested rejuvenators reduced the binder consistency to the necessary level and reduced the susceptibility of the recycled mixture to low temperature embrittlement.


Select test results

For full research see the article above. 
Nine different rejuvenating agents are used in the study. The products have been labeled by generic descriptor that briefly describes the origin of the product and some or their basic characteristics are included in Table.





Rejuvenator

Spec. gravity

Visc.

135°C, mm2/s

Designed or Generic

Petroleum or Organic

Refined or Waste

Molec. structure

Polarity

Organic blend

0.947

5.4

Designed

Organic

Refined

Ring and Strand

Mild

Refined Tallow

0.891

3.0

Generic

Organic

Refined

Strand

Mild

Paraffinic base oil

0.867

2.7

Generic

Petroleum

Refined

Aliphatic

Non

Aromatic Extract

0.995

9.2

Generic

Petroleum

Refined

Aromatic Ring

Very

Napthenic flux oil

0.940

11.2

Designed

Petroleum

Refined

Ring and Strand

Mild

WEO+FT wax

0.857

40.1

Designed

Petroleum

Refined

Aliphatic

Slight

WEO bottoms

0.917

300.1

Generic

Petroleum

Waste

Aliphatic

Slight

Waste engine oil

0.872

3.9

Generic

Petroleum

Waste

Aliphatic

Slight

Distilled Tall Oil

0.950

5.6

Generic

Organic

Refined

Ring and Strand

Mild


Rejuvenator dosage

 


The target binder penetration at 25°C of the rejuvenated samples was defined as 90 1/10mm which is close to the Nustar PG 64-22 penetration. The dosage of all the rejuvenators was calculated to reach this penetration. The required rejuvenator amount to attain the required penetration for the WEO, aromatic extract and paraffinic base oil was around 18%, while for organic products it is significantly smaller and virgin binder was added to ensure equal binder content with the other mixtures. Figure clearly shows that using napthenic flux oil, WEO+FT wax or Waste Engine Oil (WEO) bottoms it is not possible to reach the penetration level of virgin binder within a reasonable dosage rate. These products were added at a rate of 18,26% in order to reach equal film thickness with the rest of samples.




Compaction temperature




The Viscosity relation plot is created by two values – the penetration at 25C and the kinematic viscosity at 135C.

From this bitumen test data chart it is possible to determine the required mixing and compaction temperature. It is clear that for pure RAP without any rejuvenator it would have to be much higher than for the rejuvenated mixtures. For examples, the use of Valaro V165 allows to reduce the temperature by 25C which is significant reduction bot in respect to the required energy for production and mostly to the oxidation of the binder.


Low temperature properties

Neither stiffness nor strength alone determines when a mixture will crack. A stiff mixture will not crack if its strength is high enough; and a weaker mixture will not crack if it is sufficiently flexible. The mixtures were tested for creep compliance and indirect tensile strength at -10°C for thermal cracking potential since these tests have been recognized as accurate ways of describing mixture properties at low temperatures and the test methodology is standardized by the AASHTO T322-07.
Tensile strength and fracture energy were obtained from IDT strength test. Four rejuvenators have increased the strength while others have decreased it. However, while tensile strength is often used as parameter for evaluation of cracking resistance, it is not a fundamental parameter since it depends on loading conditions and loading mode. It is believed that Fracture energy is more important property for characterizing the cracking potential. It is defined as the energy required to initiate fracture of the mixture and it is not dependent of loading rate. It was derived from the stress tests by calculating the area below the stress-strain curve up to the point of maximum stress. The results in Figure show that all products except WEO+FT wax have the same or higher fracture energy compared to the reference mixture, therefore probably reducing cracking potential. The products that compared to the reference mixture have maintained or increased the creep compliance, without reducing the fracture energy, can be considered to have reduced the embrittlement of the mixture

Summary

The test results are summarized in Table below. They are evaluated based on previous discussions to ensure that addition of rejuvenator has improved low temperature performance:
        *Rejuvenator softening effectiveness to reach penetration of a virgin binder (90 1/10mm) at a reasonable dosage rate (<20% from binder mass) is required, 
        *PI of max 2,23 is required to reduce the cracking potential of the RAP extracted binder, 
        *Creep compliance of more than 0,0151 1/GPa and fracture energy of more than 9.6 kPa are arbitrary requirements to make sure that the use of rejuvenating agent is more effective in improving low temperature performance than simply increasing the AC content. 

The summary of the results in Figure below shows that six rejuvenators - organic blend, refined tallow, paraffinic base oil, aromatic extract, WEO and distilled tall oil, have fulfilled these arbitrary requirements.





















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