Shunsuke TANAKA and Kimio MARUYAMA

Transcription

1 Development of a High-performance SMA Suited to the Surface Course of National Highways in Japan s Cold, Snowy Regions 1st International Conference on Stone Matrix Asphalt November 5-7, 2018 Shunsuke TANAKA and Kimio MARUYAMA Civil Engineering Research Institute for Cold Region 2018/11/12 1

2 1. Introduction 0. CONTENTS 2. High-Performance SMA 3. Study about Driving Safety on the Road Surface in Winter 4. Verification of Durability 5. Conclusions 2018/11/12 2

3 1. Introduction 2018/11/12 3

4 1. Introduction In Japan s cold, snowy regions, porous asphalt (PA) has been installed to provide safe driving conditions. Under rainfall conditions... - It improves visibility. - It mitigates hydroplaning. Dense Graded Asphalt Under winter conditions... - It mitigates black ice formation. Dense Graded Asphalt Porous Asphalt Porous Asphalt However, PA has durability problems. 2018/11/12 4

5 1. Introduction The large cities in the cold, snowy regions of Japan are snowier than the large cities in other snowy regions of the world. This means that the pavements in such regions of Japan are exposed to particularly severe environmental conditions. Low temperatures Repeated freeze-thaw of snowmelt in the snowmelt season Abrasion from tire chains and steel snowplow blades City (Country) Pop. (Million) Snowfall (m) Sapporo (JPN) Shenyang (CHN) Montreal (CAN) Vienna (AUT) Munich (GER) Saint Petersburg (RUS) The development of a new asphalt mixture that has high durability and the ability to maintain safe driving conditions High-performance Stone Matrix Asphalt (HP-SMA) 2018/11/12 5

6 1. Introduction Confirming HP-SMA performance 1. Performances conducive to safe driving under wet or icy conditions (HP-SMA vs. PA and DGA) 2. Durability in a cold, snowy environment (HP-SMA vs. PA) It was verified that HP-SMA can be expected to fulfill the required driving safety functions and has higher durability than that of PA. Therefore, HP-SMA is found to be suitable pavement for cold and snowy regions in Japan. Based on this result, HP-SMA has been fully applied for national highways managed by the Hokkaido Regional Development Bureau since /11/12 6

7 2. High-performance SMA 2018/11/12 7

8 2. High-performance SMA HP-SMA was developed for cold, snowy regions. It has high performance in terms of safe driving conditions and durability, at a similar level as that of SMA. The surface course has a texture similar to that of PA, and the pavement body has a dense structure. [Surface] Rough texture achieved by aggregate interlocking [Middle - bottom] Dense, stable, durable Mix proportion Grain distribution (mm) HP-SMA DGA (13F) PA (void content: 17%) Example of asphalt mixtures for HP-SMA Asphalt Filler (%) Screening Coarse Crusher run Crusher run #6 Cellulose (%) sand (%) #7 (%) (%) fiber Total Modified 0.3 (added II-type 5.9 to the total) Straight asphalt Modified H-type /11/12 8

9 2. High-performance SMA HP-SMA was developed for cold, snowy regions. It has high performance in terms of safe driving conditions and durability, at a similar level as that of SMA. The surface course has a texture similar to that of PA, and the pavement body has a dense structure. [Surface] Rough texture achieved by aggregate interlocking [Middle - bottom] Dense, stable, durable Comparison between HP-SMA and SMA11S (Binder and void content) Binder content Void content (Marshall-Specimen) HP-SMA (JPA) % 5.0 ー 7.0% SMA 11S (GER) 6.6% 2.5 ー 3.0% 2018/11/12 9

10 2. High-performance SMA Construction HP-SMA can be compacted by using compaction machines that are ordinarily used in Japan, including three-wheel rollers, tandem rollers and tire rollers. For HP-SMA, sufficient compaction at high temperature is necessary because the optimal temperature for the compaction of HP-SMA in which modified asphalt is used is higher than that for DGA. In cold, snowy regions, it is necessary to investigate and decide the following before construction: the temperature, the combination of compaction machines, and the number of runs of the machine. This is because it may be necessary to conduct work under environmental conditions which may cause a rapid decrease in the temperature of the mixture. 2018/11/12 10

11 2. High-performance SMA Construction An example of compaction condition Breakdown roller compaction Secondary roller compaction Finishing roller compaction Machine Three Wheel Roller Tandem Roller Tire Roller Machine weight 9,300kg 6,800kg 12,600kg Number of runs 6 runs 6 runs 4 runs Target temperature C C C 2018/11/12 11

12 3. Study about Driving Safety on the Road Surface in Winter 3.1 Driving safety assessment test on a freezing road surface 3.2 Driving safety assessment test when an antifreeze agent is spread 2018/11/12 12

13 3.1 Driving safety assessment test on a freezing road surface Russia China Korea Japan Sapporo Cold Region Test Track Ensuring safe road traffic is required even under the specific heavy snow environment in the cold and snowy regions in Japan. For this reason, road surface control in winter is a major issue in this region. Therefore, pavement in this region is required to have sufficient driving safety functions for the road surface in winter. Using the Cold Region Test Track in Hokkaido, which lies in the snowy and cold region, the driving safety function of HP-SMA for road surfaces in winter was assessed. 2018/11/12 13

14 3.1 Driving safety assessment test on a freezing road surface The road surface with a thin ice film generated on it (DGA) Ambient temperature during test Road surface conditions Measured item Measuring equipment Test conditions Test on wet road surface +1 Test on ice film and ice -8 sheet road surface Wet road surface Ice film road surface Film thickness 1mm Ice sheet road surface Sheet thickness 1mm Sliding friction factor Locked-wheel friction tester (LWFT) These tests were performed for HP-SMA, PA, and DGA installed in the Cold Region Test Track. A wet road surface, ice film road surface, and ice sheet road surface were artificially made and measured in terms of sliding friction. 2018/11/12 14

15 3.1 Driving safety assessment test on a freezing road surface F Mt Measurement wheel Running direction μ r Locked-wheel friction tester (LWFT) μ Mt r F μ:coefficients of sliding friction Mt:Tire torque(n m) r:tire radius (m) F:Driving wheel load(kn) The LWFT is a standard device for measuring the skid resistance of the road surface in Japan. The traveling speed was set at 40km/h. 2018/11/12 15

16 3.1 Driving safety assessment test on a freezing road surface Coefficients of sliding friction for wet, ice film and ice sheet surfaces on PA, HP-SMA and DGA With the ice film, the sliding frictions of HP-SMA and PA are much higher than that of DGA. HP-SMA has a performance comparable to that of PA on icy roads. 2018/11/12 16

17 3.2 Driving safety assessment test when an anti-freeze agent is spread At first, an ice film road surface was artificially made on each pavement and an anti-freeze agent was spread. Sodium chloride is used as an anti-freeze agent, and its application rate was 20g/m 2. This application rate is the most regular rate for road surface control in the winter season performed by the Hokkaido Regional Development Bureau. Then, actual road conditions were simulated by having the vehicle run for a specified number of times, and the sliding friction was measured. Test conditions Ambient temperature At the start of the test -3.5 during the test At the end of the test -6.0 Road surface condition Ice film road surface Skid resistance (HFN) Measured items Number of vehicle runs: 0, 50, 100, 150, 200, 250, 300. Measured after each number of runs shown. Measuring equipment Continuous Friction Tester (CFT) Running velocity of CFT 40km/h Anti-freeze agent Sodium chloride 20g/m /11/12 17

18 3.2 Driving safety assessment test when an anti-freeze agent is spread Running direction Angle: 1~2 Measurement wheel Measurement wheel Continuous Friction Tester (CFT) Skid resistance was measured with a Continuous Friction Tester. A CFT can measure skid resistance continuously at a regular running velocity. CFTs also have the merit of not largely disturbing an ice film road surface because, unlike an LWFT, it is not necessary to perform braking action for a CFT s test wheel. The value of skid resistance is called the Halliday Friction Number (HFN). The HFN is indicated by an integer between 0 and 100. The lower the HFN value, the slipperier the pavement. 2018/11/12 18

19 3.2 Driving safety assessment test when an anti-freeze agent is spread Test results HFN values on HP-SMA and PA were greatly improved after salting. In contrast, DGA did not show improved HFN values after salting. Consequently, the anti-skid performance that was achieved after salting of the ice film was greater on the HP-SMA and PA than on DGA. 2018/11/12 19

20 4. Verification of Durability 4.1 Low-temperature Cantabro test 4.2 Raveling test 2018/11/12 20

21 4.1 Low-temperature Cantabro test Before After Los Angeles abrasion testing machine The low-temperature Cantabro test has been used for PA in Japan to assess the degree of aggregate scattering from impact under lowtemperature conditions. Los Angeles abrasion testing machine revolutions: 300 Test temperature: -20 The low-temperature Cantabro loss was calculated as a percentage of weight loss over the initial weight. 2018/11/12 21

22 4.1 Low-temperature Cantabro test Test results The low-temperature Cantabro loss value is lower for HP- SMA than for PA. Therefore, we can say that HP-SMA has superior aggregate interlocking to PA. 2018/11/12 22

23 4.2 Raveling test Test temperature: -10 Wheel-tracking text machine of CERI The machine simulates 10 minutes of driving at 40 km/h. The area of raveling on the specimen is measured at the cross-sections of the specimens with a laser displacement sensor. 2018/11/12 23

24 Test results 4.2 Raveling test HP-SMA has a smaller raveling area than PA has. HP-SMA is superior to PA in the durability of aggregate interlocking. 2018/11/12 24

25 5. Conclusions 2018/11/12 25

26 5. CONCLUSIONS The driving safety function of HP-SMA at the road surface in winter was assessed by the test at the Cold Region Test Track. From the test results, it is found that the driving safety function of HP-SMA is almost equivalent to that of PA and superior to that of DGA. The durability of HP-SMA was assessed by the indoor test. From the results of the test, it is found that the durability of HP-SMA is higher than that of PA. From these findings, it can be said that HP-SMA is a suitable asphalt mixture for national highways in the cold and snowy regions in Japan. 2018/11/12 26

27 Thank you for your attention! Civil Engineering Research Institute for Cold Region (Sapporo, Hokkaido, Japan) Tel: Fax: /11/12 27