1. The Recycling of Highway Materials: Asphalt - Hot Mix Process
Dr Iswandaru Widyatmoko
Associate – Pavement, Trackbed and Materials Consultancy
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

2. Research on recycling into surfacing Feasibility study
Contents
Research on recycling into surfacing
Feasibility study
Field (full scale) trials
Performance monitoring
Recycling Schemes
The best practice guide
Repave in situ recycling
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

3. Recycling into thin surfacing systems
funded research, since 2001 to 2009
Feasibility study to development of best practice guide
Research led by in collaboration with
, ,
Potential for recycling thin surfacing back into surface course systems
Optimum use of high value end product
Field trials in major trunk roads
Recycling schemes in motorways
Best Practice Guide published in Road Note 43
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

4. Feasibility Study – Laboratory (1/2)
PA from M40 (laid 1994, removed 2001/2)
SMA from A50 (laid 1997, removed 2001)
HRA chippings from A10 (laid 1980s, removed 2002)
UL-M from A12 (laid 1993, removed 2003)
PMB PA ex S Wales for recycling back into PMB asphalt concrete (future work)
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

5. Feasibility Study – Laboratory (2/2)
Maximum theoretical RA proportion (based on grading), % by weight of total aggregate:
Binder types and grades, vary from paving grade to polymer modified binders:
Extraction process? Health and safety?
Residual properties? Compatibility?
Source of RA
Porous Asphalt
HRA Surface Course
DBM Surface Course
DBM Binder Course
DBM Base
SMA
Designation
TAC 35 28 25 30 74
TSMA 47 37 33 40 89
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

6. Constraints with modified binders
Health and Safety
Similar risks associated with recycling SBS polymer modified binder as with unmodified binder
Performance
Severely aged binders can be rejuvenated, benefits of modification retained in recycled material
Compatibility between mixture components an important consideration
“It has been recognised for some time that many polymers are either insoluble or partly soluble in the normal solvents used in the recovery process. This has serious implications for compliance purposes, if anybody wants to check polymer dosage, or binder homogeneity, for instance.” (Poirier et al, Eurobitume Workshop 1999)
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

7. Feasibility Study – Field Trials
Pilot scale, June 2002
Access to quarry
TAC incorporated:
0% RA (Control)
15% RA
30% RA
Visual inspection up to 75 months: M-
Renishaw
Full-scale road trial, Jan 2004
Northbound carriageway exit from tunnel
TSMA incorporated:
0% RA (Control)
10% RA
Visual inspection up to 55 months: G
A1(M) Hatfield
Full-scale road trial, Aug 2004
Northbound carriageway between M1 and M25
TAC and TSMA incorporated:
0% RA (Control)
10% RA
30% RA
Visual inspection – detail later
A405 Bricket Wood
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

8. A405 Bricket Wood Trial
M25 M1
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

9. A405 Bricket Wood Trial
Source: Carswell, I., Nicholls, J.C., Widyatmoko, I., Harris, J.H., Taylor, R., Lee, D., “Development of Best Practice for Recycling Surface Course Materials back into Thin Surfacings”, 9th Annual International Conference on Sustainable Aggregates, Pavement Engineering and Asphalt Technology Liverpool John Moores University, 18 – 19 February 2009
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

10. A405 Bricket Wood Trial (after 49 months)
Visual assessment (27 months) G M
G/M
Source: Carswell, I., Nicholls, J.C., Widyatmoko, I., Harris, J.H., Taylor, R., Lee, D., “Development of Best Practice for Recycling Surface Course Materials back into Thin Surfacings”, 9th Annual International Conference on Sustainable Aggregates, Pavement Engineering and Asphalt Technology Liverpool John Moores University, 18 – 19 February 2009
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

11. A405 Bricket Wood Trial (after 49 months)
Localised fatting up
Re-textured
Laid on various binder course layer
Tar bound slag
Gravel aggregate
Concrete base
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

12. Recycling Scheme M4 Cardiff Constructed in August 2006
6/20mm PA laid 50mm on 4.7km of M4 between J32-33 in 1994
Client (Welsh Assembly) demanded 25% be incorporated in to the new TSC
Selected Cemex proprietary TAC with 80% of aggregate in the 6/18 fraction
Oversized and undersized screened from RA
Site assessed as ‘Good’ by the HA/TRL inspection after 2 years in service
M4 Cardiff
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

13. Recycling Scheme M25 Reigate Constructed in August 2007
PA laid in 1996
Client (Mouchel Parkman) demanded reuse of PA RA in to the new TSC:
23% RA
Masterpave-R
Oversized and undersized screened from RA
Energy audit undertaken by TRL to evaluate any benefits from using RA in this scheme
M25 Reigate
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

14. Best Practice Guide – Road Note 43 (2010)
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

15. Best Practice Guide – Overview
Introduction
Design
Suitability, mix design
Administration
Approach, ownership, approvals
Reclaiming asphalt
Planing, Transport, Storage
Analyses and processing
Gradings and binder contents
Mixing and construction
Asphalt plants, mixing, construction
Quality Control
RA design, HAPAS, long-term monitoring
Conclusions
Planning Advice
Mixture Design Advice
Production Advice
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

16. Recovered chippings may give misleading PSV results
Chapter 2: Design - RA
Mechanical properties of RA aggregate can be assumed at least comply with a set limit for the pavement from which it was taken
Recovered chippings may give misleading PSV results
Effect of mixed PSV?
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

17. Chapter 2: Design – Recycled Mix
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

18. Chapter 3: Administration
Overall Approach
Ownership of Planings
Approvals
Planning Advice
Supplier can plan routine use of 10% RA in their proprietary TS products.
Client can require larger %RA in major schemes
The ownership of planings should be clearly defined in the tender.
The ownership should ne passed on 3rd parties who will use it at the highest level
When working on trunk roads with more than 10% RA, apply departure from standard as practically as possible.
Assume that PSV and AAV are at the set limit for the source if no further information is available.
Mixture Design Advice
For large %RA, get access as early as practicable to meet the deadlines and increasing the opportunities to recycling into surface course layers
Ensure that the HAPAS certificate includes the use of the required %RA if a certificated product is needed.
Ensure that both aggregate sources comply with the requirements, rather than testing blended aggregates if possible
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

19. Chapter 4: Reclaiming Asphalt
Planing
Transport
Storage
Planning Advice
Separate the planings into SC and other layers, as a minimum.
Further classification needs to be justified
Co-ordinate the transport to minimise empty or partial load journeys
Separate storage areas to be made for each classification of RA used
Production Advice
Avoid contamination
No excess water during planing
Carry out routine visual assessment; if noticeable, assess the extent of contaminants.
Avoid contamination and cross-contamination during transit
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

20. Chapter 5: Analyses and processing
Particle Size Distribution
Processing
Binder Content and Condition
Planning Advice
The extent of processing is dependent on the proportion of RA and the RA variability
Mixture Design Advice
Binder film must be allowed for when separating RA fractions
The analysis process (solvent) has to be modified for a majority of the aged soluble bitumen to be extracted.
The binder drainage test can be used as a simple screening test to assess the active binder in the RA.
The requirement for the pen of the added binder can be calculated but will not necessary for 10% RA or less
Production Advice
The removal of oversize particles is essential.
The removal of fine material should reduce moisture content and susceptibility to moisture and is essential where detritus is present
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

21. Chapter 6: Mixing and construction
Asphalt Plants
Mixing
Construction
Planning Advice
Consider mixing plant capacity:
>30% RA in 20% of plants;
10-15% RA in 10-20% of plants;
<10% RA in the rest of plants.
Carry out trials to obtain workable homogeneous recycled mixtures
Production Advice
Plants can be modified to take more RA but it is not always viable economically
RA can be added via cold feed batch mixes;
Some RA may need addition via hot feed for larger proportions;
RA can be added via recycled collar in drum mix plants
No change in technique from laying asphalt mixtures without RA
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

22. Chapter 7: Quality Control
Monitoring of RA
RA Mix Design
HAPAS
Long Term Monitoring
Planning Advice
Aggregate grading and physical properties;
Binder content and physical properties.
HAPA certificates will need to be explicitly extended before addition of RA is permitted within the scheme
Long term monitoring can be used to influence future policy
Mixture Design Advice
The variability of RA needs to be allowed for in any mix design
Change the design if RA properties vary;
The influence of any change will depend upon how much RA is being added;
Changes in binder properties will be more significant for larger RA proportion
The methodology for design, and redesign, will have to be explicitly documented for HAPAS products.
Long term monitoring may lead to improvements in the mixture design procedure.
Production Advice
If RA is added to a mixture without direct reference to the certificate, it will not be a HAPAS product.
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

23. Method Statement for HAPAS Certifications
An example is presented in Appendix B of RN43
Storage of RA – as per RN43 Chapter 4
Particle size distribution – variability & sampling
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

24. Method Statement for HAPAS Certifications
Binder testing – variability & sampling
Mixture design – as per RN43 Chapter 2
Effect of changes in RA grading, binder content and residual pen
Fresh/virgin binder grade and content to be adjusted for:
Variation in RA binder content
Variation in RA residual pen
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

25. Summary of RN 43 Surfacings can be recycled back into surfacings
Routine addition of 10% RA, larger amounts on larger projects where conditions are appropriate
Optimises use of a high value product
Requires:
Better data on pavement history
Improved communication between stake-holders
Separation at source/dedicated stockpiling
Incentives
Best Practice Guide is now available and addresses:
Suitability of source
Regularity of grading & binder property checks
Allowance for “old” binder
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

26. Repave – In Situ Recycling Process
Clause 926 of SHW
DMRB7 HD 31/94
Reclaimed asphalt (typically 25 to 35mm thickness);
New thin asphalt overlay (typically 20 to 30mm thickness);
Both layers are compacted at the same time, whilst they are hot.
Good for sections with uniform material
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

27. Repave – Project Examples (Colas)
Blackburn A6119: 25mm Colrug + 30mm Repave
Resurfacing Blackpool Airport: 20-30mm MA + 30mm Repave
Taxiways B and E at Isle of Man airport: 30mm French BBA + 30mm Repave
Photo taken from: Richardson, J.T.G (2010). “In Situ recycling”, Recyling & Re-using Asphalt, SCI, London, November
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

28. CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

29. CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

30. Benefits In situ recycling – reduced virgin aggregate
Fast application, save time (hence cost)
Stiff composite asphalt mixture
Limited data – comparable fatigue properties
Well bonded with new asphalt layer
Chart taken from: Richardson, J.T.G (2010). “In Situ recycling”, Recyling & Re-using Asphalt, SCI, London, November
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

31. References
Nicholls, J.C., Carswell, I., Widyatmoko, I., Harris, J.H., and Taylor, R., “Best Practice Guide for Recycling into Surface Courses", 5th International Conference on Bituminous Mixtures and Pavements, Thessaloniki, Greece, 1-3 June 2011
Widyatmoko, I., Hakim, B. and Fergusson C., “Pavement Sustainability and Performance Improvement: Case Studies”, XXIVth PIARC Congress – Airfield Pavement Seminar, Mexico, 2011
Richardson, J.T.G. “In Situ recycling”, Recyling & Re-using Asphalt, SCI, London, November, 2011
Carswell, I., Nicholls, J.C., Widyatmoko, I., Harris, J.H., and Taylor, R., “Best Practice Guide for Recycling into Surface Course”, Road Note RN43, Transport Research Laboratory, ISBN
Hakim, B. and Fergusson, C. “Sustainable Pavement Construction at the Isle of Man Airport”. Asphalt Professional, No. 46, November 2010.
Carswell, I., Nicholls, J.C., Widyatmoko, I., Harris, J.H., Taylor, R., Lee, D., “Development of Best Practice for Recycling Surface Course Materials back into Thin Surfacing”, International Journal of Pavement Engineering and Asphalt Technology, December 2009, ISSN
Carswell, I., Nicholls, J.C., Widyatmoko, I., Harris, J.H., Taylor, R., Williams, J., “Recycling Surface Course Materials back into Thin Surfacings”, 4th Eurasphalt & Eurobitume Congress, Denmark, 21 – 23 May 2008
Widyatmoko, I. “Mechanistic-Empirical Mixture Design for Hot Mix Asphalt Pavement Recycling”, Construction and Building Materials, Volume 22, No 2, February 2008, pp , Elsevier, ISSN
Nichols, J.C., Carswell, I., Widyatmoko, I., Elliott, R.C., Harris, J.H., and Taylor, R., “Recycling Surfacings into Thin Surfacing Systems”, Construction Materials 161, Issue CM3, August 2008, pp ISSN X
Widyatmoko, I. and Elliott, R.C, “Asphalt Pavement Recycling for Hong Kong”, Proceedings of the Road Pavement Recycling Seminar, Organised by Polish Road and Bridge Research Institute & PIARC, Warsaw, October 2002
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011

32. URS Scott Wilson becomes URS in January 2012
Contact
URS Scott Wilson becomes URS in January 2012
CIHT Seminar, “The New Economic Realism…Going the Extra Mile for Value”, Cambridge, 16 November 2011