ISAET 2012 - Emulsified Asphalt Mixes by Bernard Eckmann

1. EMULSIFIED ASPHALT MIXES OVERVIEW OF THE EMULSIFIED ASPHALT MIXES IN FRANCE B. Eckmann, Technical Department, EUROVIA (France) 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia

2. 0. CONTENTS Background and Introduction Objectives Gravel-Emulsion (GE) Emulsion Asphalt Concrete (EAC) Conclusion – Future perspectives Acknowledgements / Further information 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia

3. 1. BACKGROUND AND INTRODUCTION Emulsion technology is well developed in France (~ 1 Mio tons of emulsions per year) Almost exclusively cationic emulsions More than 65% in spraying applications (bond coats, surface dressings) Micro-surfacing is a well mastered and mature technique Grave-Emulsion (GE) and Emulsion Asphalt Concrete (EAC) cold mixes are the two main emulsion-based alternatives to hot asphalt mixes Grave-Emulsion : - Re-profiling or base course material - Well established products Emulsified Asphalt Concrete : - Wearing course applications - Most technically challenging 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia

4. 2. OBJECTIVES Description of the Grave-Emulsion (GE) and Emulsion Asphalt Concrete (EAC) products Formulation Properties Field of application Perspectives More details on mix design methods, in-situ behaviour and on-going research is given in complementing papers 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia

5. 3. GRAVE-EMULSION (GE) – General description Continuously-graded mix of aggregates and slow-setting emulsion Residual bitumen content is kept between 3.8% and 4.5 % Emulsion breaks preferably on the sand and fine fractions which leads to a mix : With a binder-rich mortar phase Aggregates are allowed to be not completely coated 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia Binder-rich mortar Partially coated aggregate

6. 3. GRAVE-EMULSION (GE) – Properties resulting from its specific structure Plastic behavior Good workability, easy making of joints Accommodates the deformations of substrates and retards reflective cracking A good material for re-profiling purposes, maintenance works and local repairs Yet high friction between larger aggregates once compacted GE can also be used for re-strengthening purposes Full coating of larger aggregates is not ensured  GE needs to be protected from climate and traffic (surface treatment, wearing course) 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia

7. 3. GRAVE-EMULSION (GE) – Main formulation parameters Two main types (French standard XP P98-121) Type R (Re-profiling) - 0/6 or 0/10 - Residual bitumen content : 4.2% – 4.5% - Thickness range : 0 to 8 cm Type S (Structuring) - 0/10 or 0/14 (0/20) - Residual bitumen content : 3.8% – 4.2% - Thickness range : 8 to 15 cm Composition Sand content between 30 and 50%, fines between 6 and 8% Cleanliness (no clay) is an essential requisite Use of RAP (even at high percentages) is possible Slow-setting bitumen emulsion (60 or 65% bitumen – 70/100 or 160/220 Pen.) Total water content at about 7% 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia

8. 3. GRAVE-EMULSION (GE) – Fields of use (1/3) New construction Type S material in base layers or binder course A strong subgrade is required to ensure efficient compaction  Ideal = unbound gravel (also ensures drainage of GE layer) Specific application : prevention of reflective cracking on top of hydraulic layer High proportion of sand (> 40%) – 160/220 bitumen 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia

9. 3. GRAVE-EMULSION (GE) – Fields of use (2/3) Maintenance works and local repair – Type R material GE offer a particular economical and flexible solution Flexibility may be further enhanced by ensuring the GE material a certain storability 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia

10. 3. GRAVE-EMULSION (GE) – Fields of use (3/3) Upgrading and widening of existing roads – Type R material Restoring profiles and adapting roads to increasing traffic 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia

11. 3. GRAVE-EMULSION (GE) – Use of flux-oils Advantages and drawbacks Improves the wetting of aggregates, workability and storability Has of course a negative impact on short term mechanical properties Type S materials Only a “processing aid” - Maximum amount ≤ 2% (vs. emulsion) “Storability” limited to 1 or 2 days Type R materials At high amounts, allows GE to be stockpiled and used for several weeks to months Use to be restricted for local repairs (potholes) and very low to low trafficked roads HSE considerations Strong incentive to switch from “mineral” flux oils to “vegetal” flux oils But “hardening” is slower  experience needs to be built-up ! 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia

12. 3. GRAVE-EMULSION (GE) – Manufacturing Stationary or mobile mixing units May be very simple (adaptation of mixing unit used for hydraulically bound materials) Usually two-shaft paddle-mixer Plants tend to get more and more sophisticated (development of EAC) Different streams for aggregates and sand Multiple and adjustable feeding points for the emulsion(s) 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia

13. 3. GRAVE-EMULSION (GE) – Laying Various equipments are possible depending on the application Grader Paver Fast paver Bond coat Generally not necessary for Type R application (high amount of residual binder) Recommended for Type S applications at low residual binder content 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia Fast paver (re-profiling)

14. 4. EMULSION ASPHALT CONCRETE (EAC) – The challenge 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia Requirements Continuously graded mixes for wearing courses Resistance to water and traffic requests full aggregate coating Targeted residual binder contents are generally between 5.5% and 6% The challenge : Ensure proper coating while maintaining sufficient workability Breaking process of the emulsion Too slow : improper coating, water run-off during hauling Too fast : formation of lumps, insufficient workability Adjustment parameters at hand - Formulation of the emulsion (in relation to aggregate) - Mixing process and equipments - Specific processes to improve workability - Many patents !

15. 4. EMULSION ASPHALT CONCRETE (EAC) – Main formulation parameters 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia Typical formulations Continuous grading 0/10 - Grading curves similar to those of GE Sand between 25 and 35% - Fines around 7% Residual bitumen (70/100 or 160/220) content is defined in relation to aggregate specific surface area (French standard NF P 98-139)  values close to 6% Mineral fractions Aggregates must be suitable for wearing courses Cleanliness (no clay) is an essential requisite Use of RAP (even at high percentages) is possible Emulsion (Usually a 60% cationic slow-setting emulsion) Formulation to be established in relation to aggregates and specific behaviour requirements

16. 4. EMULSION ASPHALT CONCRETE (EAC) – Emulsion and mix design 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia Cold mixes behave differently from hot mixes Material is evolutive and its behaviour changes during the breaking process of the emulsion and the progressive elimination of the water Achievable initial void contents are higher than for hot mixes (but differently structured) Conventional hot mix design procedures are inadequate Emulsion and mix design procedures must address these specific issues Quality of coating (representative laboratory mixing procedures) Workability and compacting ability Manufacturing of representative laboratory test samples (void contents) Mechanical properties after ad-hoc accelerated curing procedures This has triggered :  Development of in-house design and evaluation procedures  Intensive and still on-going research (e.g. at USIRF)

17. 4. EMULSION ASPHALT CONCRETE (EAC) – Mixing processes (1/5) “One-step” process Simplest equipment - Least expensive But only possible with a limited number of aggregates 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia Emulsion Water

18. 4. EMULSION ASPHALT CONCRETE (EAC) – Mixing processes (2/5) Use of a pre-coated sand (0/d) fraction Sand to be pre-coated (emulsion or hot) in a separate process Two separate aggregate feeders on the mixing plant 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia Emulsion Pre-coated 0/d d/D

19. 4. EMULSION ASPHALT CONCRETE (EAC) – Mixing processes (3/5) Use of a pre-treated sand (0/d) fraction Sand is pre-treated with a chemical (aqueous phase) to control its reactivity Two possible ways to introduce the pre-treated 0/d fraction 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia Emulsion treated 0/d + d/D treated 0/d d/D Emulsion

20. 4. EMULSION ASPHALT CONCRETE (EAC) – Mixing processes (4/5) Use of a pre-coated aggregate (d/D) fraction d/D fraction to be pre-coated (emulsion or hot) in a separate process d/D may also be taken as screened RAP material 0/d and pre-coated d/D may be introduced simultaneously 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia 0/d + Pre-coated d/D Water Emulsion

21. 4. EMULSION ASPHALT CONCRETE (EAC) – Mixing processes (5/5) Sequenced coating Two separate aggregate feeders Two separate emulsion inlets (same or different emulsions) Most sophisticated equipment but offers a maximum flexibility 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia 0/d d/D Emulsion Water

22. 4. EMULSION ASPHALT CONCRETE (EAC) – Specific processes to improve workability (1/2) Semi-cold processes The final mix is “warmed-up” (40°C to 60°C above ambient) Use of the heat accumulated in hot pre-coated 0/d or d/D fractions Warming-up of the final mix (dedicated drum mixer) Mix has to be used immediately Better homogeneity of binder film Improved compaction 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia Drum-mix reheating unit

23. 4. EMULSION ASPHALT CONCRETE (EAC) – Specific processes to improve workability (2/2) On-site manufacturing processes Mobile mixing plant close to job-site Mobile equipment trains by which supplied materials are successively mixed and fed to a paving screen Mays also be used for GE 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia Mobile mixing and laying train

24. 4. EMULSION ASPHALT CONCRETE (EAC) – Application (1/2) Ideal for the maintenance of low to medium trafficked road Usual thickness ranges from 3 to 5 cm, sometimes 2 to 3cm (thicker lifts of 5 to 8cm are more seldom) Bond coat is required Due to its flexibility, EAC is well suited for the overlay of deformed pavements.  being directly usable as a wearing course, the re-profiling ability of EAC makes it an economical alternative to two-layer systems (e.g. reprofiling with hot mix or GE + wearing course) 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia

25. 4. EMULSION ASPHALT CONCRETE (EAC) – Application (2/2) Paving Done with conventional pavers Practice has however to be adapted to the particular behaviour of the material (high internal friction) Compacting Usually steel rollers Vibration has to be kept to a minimum (risk of surface cracks) Still a matter of trial and error 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia

26. 5. CONCLUSION – FUTURE PERSPECTIVES (1/2) 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia GE and EAC are still far from their full potential volume of use 40 Mio tons hot mix, ~ 1.5 Mio tons GE, ~ 0.4 Mio tons EAC Cold techniques often restricted to areas where hot mix plants are scarce The need to acquire specific know-how acts as a brake for wider development But circumstances are more favorable than ever Strive for safe and environmentally friendly techniques Growing awareness of the importance of Pavement Preservation Significant technical progress has been made Grave-Emulsion is now a proven technique Specific behavior of cold mixes is now well understood Formulation and evaluation methods have been significantly improved Improved mixing procedures and equipments are now available

27. 5. CONCLUSION – FUTURE PERSPECTIVES (2/2) 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia The future : SUPER – GE ? For the maintenance of slow to medium traffic roads, targeting the composition (in particular the high binder content) and performance of hot mixes for EAC may not be necessary Improved emulsion design and enhanced mixing techniques allow GE to be formulated at higher binder contents, which makes them suitable as wearing course materials. RATHER THAN AIMING AT A HOT MIX EQUIVALENT, AN “OPTIMIZED” GRAVE-EMULSION MAY BE THE TRUE FUTURE FOR EMULSIFIED ASPHALT CONCRETE

28. 6. ACKNOWLEDGEMENTS / FURTHER INFORMATION My acknowledgements go to the members of the USIRF Task Groups dedicated to the development and promotion of cold mix technologies, whose documents and advice helped me in making this overview. SFERB publication, 2008 : Bitumen emulsions Related presentations at the 2012 ISAET Symposium J.P. Serfass Emulsified Asphalt Mixes : Common Points, Advantages, Particularities, Drawbacks Emulsion Asphalt Mixes : Proposed Mix Design Method & Performance-Based Specifications F. Delfosse - Emulsified Asphalt Mixes : Grave-Emulsions Assessment and Design A. Belkahia - Emulsified Asphalt Mixes : Emulsified Asphalt Concrete Assessment and Design 2012 International Symposium on Asphalt Emulsion Technology Oct. 10 - 12, 2012 - Arlington Virginia [email protected] Thank You for your attention