EVALUATION METHODS OF ROAD SURFACE PERFORMANCE IN JAPAN Kazuyuki KUBO Public Works Research Institute, Japan Masaru TERADA Public Works Research Institute, Japan Kazuhiro WATANABE Public Works Research Institute, Japan

Contents 1 INTRODUCTION 2 OBJECTIVE 3 SKID RESISTANCE EVALUATION METHODS OF ROAD SURFACE PERFORMANCE IN JAPAN Contents 1 INTRODUCTION 2 OBJECTIVE 3 SKID RESISTANCE (1)Background(DF Tester) (2)Relationship with braking force coefficient determined using Friction Measurement Vehicle (3)Investigation of the limits of using rubber pieces (4)Investigation of the amount of water be sprayed 4 WATER PERMEABILITY (1)Background (2)Investigation on the inside diameter of the valve (3)Investigation on the watertightness of water sealers 5 CONCLUSION

1 Introduction Specification-based Standards EVALUATION METHODS OF ROAD SURFACE PERFORMANCE IN JAPAN 1 Introduction The design guides for pavement were revised in 2001 in Japan Specification-based Standards Performance-based Standards The road administrators require performance for road surface through identifying the functions and needs of the surface of the road. The constructors can select and use materials that meet the required performances. 　The road administrators specify the materials and structures of pavement. 　The constructors produced and applied asphalt mixes that satisfied the regulations in the manual.

Background of this revise … 1.INTRODUCTION EVALUATION METHODS OF ROAD SURFACE PERFORMANCE IN JAPAN Background of this revise … The functions required for pavement have become increasingly diverse as society has developed. The new rules have the freedom of designing pavement and selecting materials, respond to diverse needs, and encourage further technological innovation. Therefore, various performance evaluation methods are being investigated in Japan.

2.OBJECTIVE EVALUATION METHODS OF ROAD SURFACE PERFORMANCE IN JAPAN 2 Objective In this presentation, skid resistance and water permeability will be picked up and investigated toward appropriate evaluation. Skid resistance : great relation to safety for driving a vehicle To investigate the relationship with braking force coefficient determined Friction Measurement Vehicle and rolling skid number (RSN) determined by Dynamic Friction Tester (DF Tester) the limits of using rubber pieces of DF Tester the amount of water to be sprayed of DF Tester Water permeability : road noise reduction, traffic safety by preventing water from splashing during rainfall To investigate the influence of the inside diameter of the valve in testers. the watertightness of water sealers between road surface and testers

3 Skid resistance (1) Background (DF Tester) 3.SKID RESISTNACE EVALUATION METHODS OF ROAD SURFACE PERFORMANCE IN JAPAN 3 Skid resistance (1) Background (DF Tester) In Japan, Skid resistance is measured using… Friction Measurement Vehicle Skid Resistance Tester Based on Rotating Disc (DF Tester) The British Pendulum Tester The second one which was developed in Japan is easy to measure, and has been standardized as an ASTM standard.

Measurement of rolling skid number 3.SKID RESISTNACE EVALUATION METHODS OF ROAD SURFACE PERFORMANCE IN JAPAN Measurement of rolling skid number (RSN) Concept of DF Tester

Braking force coefficient and RSN 3.SKID RESISTNACE EVALUATION METHODS OF ROAD SURFACE PERFORMANCE IN JAPAN (2) Relationship with braking force coefficient determined using Friction Measurement Vehicle Braking force coefficient and RSN In any type of DF Tester, They have good correlation.

Braking force coefficient and RSN at each speed 3.SKID RESISTNACE EVALUATION METHODS OF ROAD SURFACE PERFORMANCE IN JAPAN V=20km/h V=40km/h V=60km/h V=80km/h Braking force coefficient and RSN at each speed Within the range of V=40 to 60km/h, there was a close correlation.

(3) Investigation of the limits of using rubber pieces 3.SKID RESISTNACE EVALUATION METHODS OF ROAD SURFACE PERFORMANCE IN JAPAN (3) Investigation of the limits of using rubber pieces Changes in rubber piece thickness Changes in RSN during repeated measurements These figures showed that it is adequate to express the limit of using rubber pieces not by the number of measurements but by the degree of abrasion.

3.SKID RESISTNACE EVALUATION METHODS OF ROAD SURFACE PERFORMANCE IN JAPAN So, we investigated the relationship between the rubber thickness and RSN. Rubber thickness and RSN (All kinds of pave.) Rubber thickness and RSN (dens graded pave.) These figures showed that rubber pieces should be recommended to be exchanged when they have abraded by 0.5mm.

Water runoff and RSN (dense graded pave.) 3.SKID RESISTNACE EVALUATION METHODS OF ROAD SURFACE PERFORMANCE IN JAPAN (4) Investigation of the amount of water be sprayed ASTM does not prescribe the difference in water head for spraying water during measurements. ( It states that the flow should be kept at 3.6L/min when the tank for supplying water is 0.6m above the tester.) We investigated the relationship between the amount of water be sprayed and RSN. Not great influence on RSN from 2.2 to 4.0 L/min Should be investigated in advance to give a flow of 3.6L/min that ASTM said Water runoff and RSN (dense graded pave.)

4 Water permeability (1) Background EVALUATION METHODS OF ROAD SURFACE PERFORMANCE IN JAPAN 4 Water permeability (1) Background In Japan, porous asphalt pavement is increasingly used mainly on major roads to reduce traffic noise and ensure traffic safety by preventing water from splashing during rainfall. The current evaluation method involves measuring the amount of penetrated water by using an in-situ permeability tester like right side figure.

(2) Investigation on the inside diameter of the valve 4.WATER PERMEABILITY EVALUATION METHODS OF ROAD SURFACE PERFORMANCE IN JAPAN (2) Investigation on the inside diameter of the valve The inside diameters of the valves of the testers sold in Japan were found to be 6.8, 8 and 10 mm. So we investigated the influence by these difference. This figure shows care must be taken on the inside diameter of the valves to be used (the inside diameter of the valves 8 mm or larger).

(3) Investigation on the watertightness of water sealers 4.WATER PERMEABILITY EVALUATION METHODS OF ROAD SURFACE PERFORMANCE IN JAPAN (3) Investigation on the watertightness of water sealers Various kinds of water sealer are used for permeability testers. Because the current evaluation method directly measures the amount of water that flows into pavement, differences in the watertightness of water sealers are likely to strongly affect permeability measurements. So we investigated the influence depends on water sealers. This figure shows highly watertight materials such as putty need to be used to seal in order to correctly evaluate.

5 Conclusion <SKID RESISTANCE> <WATER PERMEABILITY> EVALUATION METHODS OF ROAD SURFACE PERFORMANCE IN JAPAN 5 Conclusion <SKID RESISTANCE> There was a close correlation between RSN determined by DF Tester and the measurement by Friction Measurement Vehicle, especially within the range of V=40 to 60km/h. The rubber pieces which installed on a rotary disk of DF Tester should be exchanged before they abraded by 0.5mm. The amount of water to be sprayed from 2.2 to 4.0L/min in testing didn’t have great influence on RSN. <WATER PERMEABILITY> If the diameter of the valves is 6.8mm that is smaller than the inside diameter of the connecting pipes (=8.0mm), it has great possibility to evaluate performance of water permeability unfairly. Highly watertight materials need to be used between road surface and tester in order to correctly evaluate the seepage of rainwater into pavement.

Thank you for your kind attention. 5.CONCLUSION EVALUATION METHODS OF ROAD SURFACE PERFORMANCE IN JAPAN We will continue to study methods of evaluating various performance indices, aiming to establish methods that can correctly assess the performance requirements for pavement, encourage further innovations of pavement-related technologies, and improve the effects and efficiency of paving works. Thank you for your kind attention. K-watanabe@pwri.go.jp