1. A POSITIVE OUTCOME FROM WRAP FUNDED RESEARCH Daru Widyatmoko Associate
Tyre Recovery Association – Forum Day
Grange Hotel, Warwickshire, 15 May 2009
Rubber in Roads?
A POSITIVE OUTCOME FROM WRAP FUNDED RESEARCH Daru Widyatmoko Associate

2. Rubberised Asphalt - Usage
Not a new process worldwide
Has been used in the USA since 1960s
US – AZ, CA, FL, SC, TX, new projects in NJ, NV, WA
Canada – Ongoing in Saskatchewan, projects in Alberta, B.C., Ontario
Europe – Portugal, Spain, Italy, new projects in Germany, Sweden
South Africa - common use since 1980
Asia – China, Taiwan, Malaysia
Australia – NSW, Victoria

3. Rubberised Asphalt - Processes
Two approaches for using reclaimed rubbers in asphalt mixtures
Wet process: dispersing the rubber particles in the bitumen to produce rubberised bitumen, which is then mixed with aggregate to form a mixture
Dry process: rubber particles act as a partial replacement to some of the aggregate sizes

4. Wet Process Rubber component > 15% Rubber component < 15% (10%)
Rubber – bitumen system
ASTM D8 & ASTM D6114
Asphalt rubber ~ a.k.a. rubberised bitumen
Rubber component < 15% (10%)
Rubber ‘dissolved’ in bitumen
More like polymer modified binder
Tire rubber modified asphalt binder, terminal blend, modified binder

5. Rubberised Bitumen (Wet Process)
ASTM D8 definition:
A blend of bitumen, reclaimed tyre rubber and certain additives in which the rubber component is at least 15 percent by weight of the total blend and has reacted in the hot bitumen sufficiently to cause swelling of the rubber particle

6. Production Route

7. Claimed benefits improved durability and resistance to age-hardening;
improved resistance to surface initiated and fatigue/reflection cracking;
reduced temperature susceptibility;
improved resistance to rutting;
[source:

8. Claimed benefits
lower pavement maintenance costs due to improved pavement durability and performance;
reduced construction times due to thinner lifts (layer);
better chip retention due to thicker binder films;
reduced spray and noise (open graded surface course);
improved skid resistance.

9. Perceived Barriers Education Workability Weather dependent
Mix design
Specification
Quality control
Workability
Very temperature sensitive
Hot storage < 48 hours
Handwork not possible
Weather dependent
Surface temperature > 13oC
No rainy days
Emission/odour issues?
Initial construction cost?

10. Suitability for adoption in the UK?
WRAP Funded Projects
Field Trials
Planned for Summer 07 under contract
Cancelled due to mix design not available in time for the “construction season”
Laboratory Testing
Testing contract followed the field trials
Feasibility study prior to introducing the wet process in the UK
October 07 to March 08

11. Scope of the Laboratory Study
Desk Study
Materials and mix design issues
Overseas experience
Practical and environmental issues
Laboratory Testing
Rubberised bitumen
Rubberised asphalt mixtures

12. Materials Variables Source and grade of base bitumen:
40/60 and 100/150; Middle Eastern (ME) crude
40/60 and 100/150; Venezuelan (VE) crude
Type of rubber: reclaimed car and truck tyres
Rubber crumbs production: ambient, cryogenic
Rubber particle sizes
Type of mixtures:
Open graded surface course
Dense graded binder course
Type of aggregates: granite, gritstone, limestone

13. UK Crumb Rubber

14. Grading of Crumb Rubber

15. US Recommendation Binder Design Profile
Rubber and asphalt components are tested in advance
Viscosity test used to validate in the field
Continuous Graded mixes not recommended
Mixes Designed with or for Rubberized Bitumen
Open Grades, SMA, Gap Grade
Make room for the rubber

16. Binder Design Key parameters
The viscosity of a rubber/hot bitumen blend should fall within a narrow band
Lower Bound 1500cP Upper bound 5000cP
Between 15% and 22% crumb rubber addition
Fine grade of crumb rubber so it blends easily
High rubber %
Low rubber %
at 177ºC [350ºF] using a Brookfield rotational viscometer

17. Binder/Crumb Rubber blends
Ambient car rubber
Cryogenic car rubber
VE = Venezuelan 40/60
ME = Middle East 40/60
22 = 22% Crumb Car tyre
Truck rubber proved to be too ‘volatile‘

18. Selected Blends
UK tests
Widely used tests

19. These results are generally comparable with those of PMB
BS EN 14023
These results are generally comparable with those of PMB
Rubberised bitumen blends are known to be susceptible to phase separation and/or devulcanization (thinning due to rubber degradation) after prolonged hot storage!

20. Asphalt mixture tests
Surface Course: Porous Asphalt Binder Course: SMA
Aggregate: GritStone and Granite LimeStone and GRanite
Binder Content PG - 4.5% CR - 9% PG - 5.8% + fibres CR - 8.7% / 9%
Standard designs based on USA data

21. Asphalt Surface Course
Parameter
Weighting Factor*
Surface Course
PA-GS-125 pen
ARSC-GS-1
ARSC-GS-2
ARSC-GS-3
ARSC-GR-1
Workability
Stiffness
Tensile strength 1 3 2
Voids at refusal
Deformation resistance
Crack resistance
Fatigue resistance
Resistance to Moisture Damage
0.5
Binder drainage
Durability
Total 15
7.5
10.5
9.5
Note 1= best performance overall; 3= worst performance overall
The smaller the total score the higher is the overall performance

22. Asphalt Binder Course Parameter Weighting Factor* Binder Course
SMA-LS-50pen
ARBC- LS-1
ARBC- LS-2
ARBC- LS-3
ARBC- GR-2
Workability
Stiffness 1 2 3
Tensile strength
Voids at refusal
Deformation resistance
Crack resistance
Fatigue resistance
Binder drainage
Durability
Total 13 10 11 7
Note 1= best performance overall; 3= worst performance overall
The smaller the total score the higher is the overall performance

23. Key Findings
Middle East and Venezuelan bitumen give very different results
Venezuelan is more adaptable
Car tyres are much more adaptable than truck tyres
A suitable laboratory blending regime was found
Blends satisfy EN PMB and BBA SG4 test regimes
Blends with 16% [ME] and 18.5% [VE] + 40/60 bitumen proved suitable
‘Claimed’ benefits have been largely confirmed
‘Downsides can be overcome

24. Useful Links WRAP Report: US web sites:
US web sites:

25. Latest Developments
Swedish Road Administration (2008) had 2 demo projects
Nr Jonkoping:
Hot in place recycling (Repave) plus 30mm Gap ARFC 0/12mm
Nr Malmo:
40mm Gap AR overlaying CTB
Open graded AR with 15% voids

26. Asphalt Rubber 2009

27. High material & whole life cost for repair – longer life surfacing
Opportunities
High material & whole life cost for repair – longer life surfacing
Urban area – reduced noise
Green agenda – waste and carbon reduction
Hotter summer, wetter climate – rut resistant & reduce spray

28. Opportunity - Products
Surface dressing binder
Bond coat
Membranes SAM, SAMI
Microsurfacing/slurry
Chemically stabilised RA
Warm mix RA

29. Ways forward

30. Acknowledgements
The RiA work was won from WRAP by Scott Wilson in partnership with NTEC, by competitive tender. WRAP helps individuals, businesses and local authorities to reduce waste and recycle more, making better use of resources and helping to tackle climate change; more information on WRAP’s work can be found on
Contributions from Aggregate Industries, Tarmac, Nynas, UK Bitumen, Moncton Rubber Technology, Tyregenics, Allcock and Sons, and Singleton Birch, in providing the materials and the streams of advice from the Technical Advisor to WRAP, Mr Ian Walsh, are greatly appreciated.