By Shahin Shabani Transportation Research Institute (TRI) Tehran- Iran Presented on May 16

1. 3rd International Road Surface Friction conference Safer Road Surface – Saving lives Effect of Aggregate Arrangement on Increasing frictional Resistance Through Blending of Stone Material By Shahin Shabani Transportation Research Institute (TRI) Tehran- Iran Presented on May 16

2. Presentation Outline • Introduction • Problem Statement and Main Objectives • General Work Plan • Experimental Procedure • Preparation of Specimens • Testing Process • Results and Discussion • Conclusions Slide 1 of 18

3. Introduction Road Surface Friction Factor 1 Factor 2 Surface Characteristics Factor 3 Factor i Macrotexture Microtexture Slide 2 of 18

4. Introduction • Microtexture: function of surface texture of aggregate particles • Microtexture is Polished under traffic action Polishing Loss of Microtexture Slide 3 of 18

5. Introduction • The ability of different aggregates to resist polishing is measured by PSV index in Lab • Standard BS EN 1097 • There are 3 Categories of Aggregates: • HPA (PSV≥60) • MPA (50≤PSV<60) • LPA (PSV<50) Slide 5 of 18

6. Problem Statement and Main Objectives • The most common rocks being used for road construction are the carbonate rocks • This group of rocks has low hardness and resistance to abrasion and polishing • carbonate aggregates are among LPA • The usage of LPA must be limited in the wearing surfaces Slide 6 of 18

7. Problem Statement and Main Objectives • One way to improve would be in blending two or more types of aggregates with different PSV’s. • Aggregate blending was studied in great detail by Ohio Department of Transportation(Liang 2003). • Research objective: • Finding the best arrangement of two aggregates for achieving the maximum skidding resistance in the laboratory scale. Slide 6 of 18

8. Mechanism of Polishing Two mechanism can occur during an aggregate polishing process: • A general polishing, which tends to remove materials • A differential polishing, which tend to create relief between soft and hard minerals. Slide 7 of 18

9. General Work Plan Collection of Basalt Aggregate Collection of Limestone Aggregate Preparation of Aggregates for polishing test Preparation of test specimens for mounting on the APM ( 50/50 blend of Limestone and Basalt) Accelerated Polishing of Aggregates Using the APM Measurement of Friction Number Using the British Pendulum Tester Determination of PSV Standard BS EN1097 Slide 8 of 18 Conclusions and Recommendations

10. Experimental Procedure Preparation of specimens Slide 9 of 18

11. Experimental Procedure Preparation of specimens (4) (3) (2) (1) Slide 10 of 18 (5) (6) (8) (7)

12. Experimental Procedure Preparation of specimens Slide 7 of 50 Slide 11 of 18

13. Experimental Procedure Testing Procedure Slide 12 of 18

14. Experimental Procedure Testing Procedure

15. Results and Discussion PSV for different specimens Slide 14 of 18

16. Results and Discussion PSV for different specimens Slide 14 of 18

17. Summery and Conclusions • Aggregate arrangement affects friction resistance; the highest change in PSV (about 7 units) has been obtained in this blending. • Transversal alternative arrangement of aggregates provides a better condition for the creation of a new texture. • The least friction is obtained when aggregates are placed in the specimens irregularly and randomly; this is usually the case. Slide 15 of 18

18. Summery and Conclusions • The best aggregate blending arrangement, with a different abrasion property, is achieved when aggregates are arranged regularly and also the conditions have been provided for the creation of a new texture. • The least friction reduction, during the test period, has been found from specimens with alternative non group regular arrangements. Slide 16 of 18

19. Acknowledgements • Friends who helped during this research • Sponsors of this research • Iran University of Science and Technology (IUST) • Transportation Research Institute (TRI) Slide 17of 18

20. Thank you for your attention Slide 18 of 18