1. 3rd International Road Surface Friction Conference
Laboratory Simulation Test Method for Skid Resistance Performance of Chip Seals
By Yuhua Li, Yuying Liu
Associate Professor
Dalian University of Technology
Dalian City, China

2. Outline ◎ Background ◎ Indoor Specimen Molding Methods
◎ Quality Evaluation Test Methods of the Molded Specimen
◎ Skid Resistance Test
◎ Discussion
◎ Conclusions

3. Backgrounds Chip Seal (also called “Seal Coat”, “Sprayed Seal ”,
“Surface Treatment” , etc. )
◎ Protects underlying pavement
◎ Waterproofs the pavement surface
◎ Improves surface friction (safety)
◎ Extends pavement service life
◎ Costs effective surface treatment

4. Backgrounds
◎ Chip seal has been widely used in Australia, New Zealand, America, South-Africa , England and so on. (It has a history of more than 75 years)
◎ Technology regulations or manual on design, construction and quality control have been formed.
◎ In China, the traditional chip seal
is called “surface dressing and seal”.
◎ There has no special regulations or manual on chip seal in China.
Australia
America

5. Backgrounds
◎ In 2007, Liaoning province imported a device of fiber seal coat - SECMAIR.
◎ It is used for wearing course of asphalt pavement in Shenyang, Dalian, Jinzhou city , etc.
◎ Research project, Experiment Study of Fiber Seal Coat , was completed in 2010, by DLUT.
( I am the project leader)
Lack of standard test methods, especially the method of molding specimen.
◎ Field and indoor testing methods
( the main problems to be solved )

6. Backgrounds The Key Difficulties …… How to mold the specimen
How to get the specimen
How to mold the specimen
Multi-layer structure
(Non-uniform mixture)
Early stage – During Construction
Thin!
Thin layer of mixture structure
(Poor uniform mixture)
Main Features
Key Difficulties
Post phase – After Opening Traffic
(about 1~3 months)
◎ Thin layer : H=5~15mm
◎ Non-uniform mixture

7. Construction Simulation
Backgrounds
General Approach
Field - Laboratory Test
(High cost, Inflexible)
(The actual project, Liaoning Province, China )
(Literature: by Jaejun Lee, North Carolina)
(Using MMLS3 device)
Construction Simulation - Laboratory Test
Approach Adopted
(Low cost, Good flexibility)
Construction Simulation
Indoor Specimen
Laboratory Test

8. Quality Evaluation Test Methods
Key Topics
Indoor Specimen
Molding Methods
Quality Evaluation Test Methods
of the Molded Specimen
Skid Resistant Test
in Laboratory

9. Indoor Specimen Molding Methods
Construction procedures
Original pavement surface disease treatment
Spraying emulsion
(+ fiber)
Spreading aggregate
Initial rolling
Early
main-tenance
Long-term natural traffic rolling
Plate specimens made
(Underlay plate )
Spraying emulsion
(+ fiber)
Spreading aggregate
Initial
rolling
Early
curing
Post-rolling
Step-1
Step-2
Step-3
Step-4
Step-5
Step-6
Indoor simulation

10. Indoor Specimen Molding Methods
Step-1: Underlayer Plate Specimens Made
Mould
A plate specimen of asphalt mixture is used as under layer after long-term aging treatment.
300mm×300mm×50mm
◎ Simulate the original asphalt pavement structure
AC-16 Mix
Surface hardness is the most important properties of pavement structure.
Embedment
300mm×300mm×40mm
◎ Simulate technology condition of the original pavement
Pavement surface diseases will be taken
into consideration such as cracks,
surface roughness, etc.
Cracks
Cracks
Pavement Surface
Plate Specimen

11. Indoor Specimen Molding Methods
Step-2: Spraying emulsion / asphalt / (+fiber)
By manual brushing or
by mechanical spraying
Step-3: Spreading aggregate
Uniformity
and
Accuracy!
By manual or mechanical

12. Indoor Specimen Molding Methods
Step-4: Initial Rolling
In chip seal construction, a roller is employed to embed the aggregates into the emulsion film and to ensure an initial bond with the binder film without crushing the aggregate.
Roller width = 50mm
◎ Roller Types
Pneumatic tire roller or Rubber-coated steel drum roller
Roller width = 200mm
Roller width = 200mm
Rolling equipment specially crafted
a) Rubber-coated roller

13. Indoor Specimen Molding Methods
rubber cushion thick
(10mm, 15mm)
b) Steel roller with a underlay rubber cushion
◎ Temperature of initial rolling
(a) from 40°C ~ 70°C or
(b) at room temperature 15°C ~ 25°C
◎ Time of initial rolling
(a) 1min or (b) 3~5 times

14. Indoor Specimen Molding Methods
Step-5: Initial Maintenance
◎ Temperature of initial maintenance
40°C ~ 60°C
◎ Time of initial maintenance
in 4 hours
Oven
Step-6: Post-rolling and post-stage maintenance
In order to simulate the long-term compaction process of natural vehicle after opening to traffic.
◎ Time of post-rolling
30min, interval of 6 hours
◎ Temperature of post-stage maintenance
60°C ~40°C OK
Molded specimens

15. Indoor Specimen Molding Methods
Molded Specimens
By Yuhua Li and Yuxing Liu, DLUT, China,

16. Indoor Specimen Molding Methods
Molded Specimens
By Yuhua Li and Yuxing Liu, DLUT, China,

17. Quality Evaluation Test Methods
Key Topics
Indoor Specimen
Molding Methods
Quality Evaluation Test Methods
of the Molded Specimen
Skid Resistant Test
in Laboratory

18. As comparison , the testing results are assumed to be the true value.
Quality Evaluation Test Methods of the Molded Specimen
◎ Field Testing
As comparison , the testing results are assumed to be the true value.
⊙ Pull out test
No Highway in Liaoning Province,

19. Quality Evaluation Test Methods of the Molded Specimen
◎ Field Testing
⊙ Texture depth test
No.312 Highway in Liaoning Province, China,

20. Quality Evaluation Test Methods of the Molded Specimen
◎ Indoor Testing
⊙ Pullout test
By Li kun, DLUT, China,

21. Quality Evaluation Test Methods of the Molded Specimen
◎ Indoor Testing
⊙ Wet Track Abrasion Loss
By Ye jian,
DLUT,

22. Quality Evaluation Test Methods
Key Topics
Indoor Specimen
Molding Methods
Quality Evaluation Test Methods
of the Molded Specimen
Skid Resistant Test
in Laboratory

23. ⊙ Pendulum Coefficient of Friction Test (BPN)
Skid Resistance Test
◎ Testing Method
⊙ Texture Depth Test
⊙ Pendulum Coefficient of Friction Test (BPN)

24. Discussion
◎ Field texture depth test results
⊙ The TD would decrease greatly in the first 2~3 days after opening to traffic, no matter where the testing sites are, after 7 days the speed reduces.
⊙ When the time is 2-3 months(80days), the speed is going steady.

25. Discussion ◎ Indoor texture depth test results
⊙ Indoor TD test results agree with field TD test results. The value decreases with increasing rolling time, and be more stable after 4 days.
⊙ The smaller values are obtained in high curing temperature conditions.

26. Discussion
◎ Indoor skid resistance test result (BPN)
⊙ The results indicate that friction coefficient also decreases with increasing rolling time, and be more stable after 3 days.
⊙ The smaller values of friction coefficient are obtained in high curing temperature conditions.

27. Conclusions
◎ The chip seal test specimens can be molded by the simulation method, which taking the original pavement structure and the pavement distresses into consideration, and according to the construction process.
◎ The molded specimens indoor can be used to complete Pullout Test, Texture Depth Test, Wet Track Abrasion Loss Test, BPN Test, etc.
◎ The indoor TD test result shows the same trend in compare with the field test result. It is believed that, the indoor BPN test result can approximately predict the chip seal pavement skid resistance.

28. Thank you for your attention.

29. Seal coat is an asphaltic coating, with aggregate, applied to the surface of a pavement structure for the purpose of waterproofing and preserving the surface, reconditioning a previous asphaltic surface treatment, improving the surface texture of the wearing surface, changing the surface color or providing resistance to traffic abrasion. A Chip Seal is generally defined as a surface treatment in which the pavement is sprayed with asphalt (generally emulsified) and then immediately covered with aggregate and rolled.