Recycling: a circular economy for roads. The Recycle Technology of Asphalt Pavement in Japan

Transcription

1 Recycling: a circular economy for roads. The Recycle Technology of Asphalt Pavement in Japan Osamu KAMADA Japan Road Contractors Association (JRCA), Kajima Road CO., LTD JRCA Member kamadao@kajimaroad.co.jp

2 Table of Contents Introduction Production of Asphalt Mixtures Mix Design Method of Recycled Asphalt Mixture Recycling of Base- Course Material Conclusion Future Work

3 Introduction In Japan, many recycle technologies of asphalt pavement have been actively carried out around 1970 s. The recycling rate of asphalt mixture reached 99.5% in In the past, waste asphalt mixtures were often used as base-course materials. At present, the mixing ratio of RAP used for dense-graded asphalt mixture has increased. More than 60% of waste asphalt mixtures are used for asphalt mixtures containing RAP. 3

4 Production of Asphalt Mixtures ( Million t) Production of virgin and recycled asphalt mixtures in Japan Virgin Mixtures Recycled Mixtures Ratio of Recycled Mixtures (%) year 0 4

5 The mixing ratio of RAP in recycled asphalt mixtures (2016) Hokkaido region; 49.7% Hokuriku region; 38.9% Chubu region; 48.5% Kinki region; 48.5% Chugoku region; 45.2% Shikoku region; 39.0% kyushu region; 46.7% Tohoku region; 48.2% Kanto region ; 61.4% National wide average ; 50.7% 5

6 The mixing ratio of RAP in recycled asphalt mixtures (2016) Saitama Tokyo Kanagawa Chiba Tokyo and surrounding area; 69.1% 6

7 Production of asphalt mixtures in Japan The number of Japanese asphalt plants is about 1,000 and around 90% of them can produce recycled materials. Most of them are batch type, and the manufacturing capacity is mostly between 45 and 120 t/h. Japanese asphalt plant can be divided into three types: drum dryer method, parallel heating method and indirect heating method. 7

8 Typical asphalt mixture plant in Japan Parallel heating method Drum dryer method Additive Asphalt Filler Asphalt Additive Filler Recycled aggregates Surge bin Dryer Hot bin Burner Dryer Virgin aggregates Dryer Burner Mixer Recycled aggregates Virgin aggregates Mixer Mixing ratio of RAP; About 30-60% Mixing ratio of RAP; 60% or more 8

9 Mix design method of recycled asphalt mixture Procedure of design; Sample of RAP and tests of materials Determination of the mixing ratio of RAP and combined grading Mix design of recycled asphalt mixture 9

10 Sample of RAP and tests of materials Quality requirement of RAP Characteristic Asphalt Content Penetration of Characteristic of recover asphalt recovered Indirect tensile asphalt coefficient Percent Passing the 75μm sieve Requirement More than 3.8% More than 20 (1/10mm) Less than 1.7 (MPa/mm) Less than 5% 10

11 The way measuring indirect tensile coefficient Indirect tensile test Using specimens of 100% RAP Test at 20 C The loading speed is 50mm/h Indirect coefficient(mpa/mm) = σ t / X Where: σ t =Indirect tensile strength =(2 P)/(π d L)(MPa) X=Amount of displacement P=Maximum load at break d=thickness of the specimen L=Specimen s diameter 11

12 Determination of the mixing ratio of RAP and combined grading Combined grading is required to adjust the mixing ratio of RAP and the amount of additives is investigated to be satisfied with quality criteria of the recycled asphalt mixture. Virgin asphalts and rejuvenators have been used as additives. Now rejuvenators are more commonly used. Penetration or indirect tensile coefficient have been used determine the target design performance of the recycled asphalt mixture. 12

13 Design ranges of asphalt mixtures containing RAP Area Penetration (1/10mm) General 40/ Cold and snow region IDT Coefficient(MPa/mm) 60/

14 Criteria of rejuvenator Item Standard Kinematic viscosity(60ºc) 80-1,000 (mm 2 /s) Flash point More than 250 (ºC) Ratio of viscosity after thin-film oven test(60ºc) Less than 2 Ratio of mass change on thin film oven test Witin ±3 (%) Density (15ºC) Report Composition Report 14

15 Penetration (1/10mm) Determining the additive amount of the rejuvenator using penetration 100 Designed Penetration 50 Amount of Rejuvenator to Meet Designed Penetration Amount of Rejuvenator(% by Weight of RAP Asphalt) 15

16 Indirect Tensile Coefficient (MPa/mm) Determining the additive amount of rejuvenator using the Indirect tensile coefficient Target Range of Indirect Tensile Coefficient Amount of Rejuvenator to Meet Designed Indirect Tensile Coefficient Amount of Rejuvenator(% by Weight of RAP Asphalt) 16

17 The mix design of recycled asphalt mixtures The Marshall stability test is generally conducted for the design of asphalt mixtures in Japan. The recycled asphalt mixture, which consists of RAP, additives, virgin aggregates and asphalt, is also evaluated by the Marshall stability test. The procedure is the same as virgin asphalt mixture: blend asphalt content of test specimen is centered on the provisional asphalt content and changed every 0.5% when the Marshall stability test is conducted. 17

18 Criteria of Marshall stability test for dense- graded mixture Characteristic Requirement Number of blow 50 Percent of air void (%) 3-6 Voids filled with asphalt (%) Marshall stability (kn) 4.9 or more (7.35 or more) Flow value (1/100mm) The figures in parenthes is applies to the roads, which heavy vehicles pass more than 1,000 a day, and in case 75 blows are required. If the recycled asphalt mixture is satisfied with criteria of virgin asphalt mixture, it is evaluated as equivalent to a virgin mixture. 18

19 Recycling of base- course materials Many other industrial wastes are used as recycled base- course materials. For example; Concrete debris Iron and steel slag Waste glass General waste materials and sewage sludge molten slag etc. 19

20 Recycled concrete aggregate The recycle rate of concrete debris waste was 99.3% in 2012 in Japan. However, the use of recycled concrete aggregates for cement concrete field was about 6% of all in Almost all are used in roads or foundations of structures. As recycled base-course materials, they are widely used for the recycled-graded crushed stone and the recycled crusher-run. 20

21 Iron and steel slag 14.0% Iron and steel slag Blast furnace slag 24 million ton 20.6% 38 million ton Steel slag 41.4% 14 million ton Converter slag 39.2% 11.4 million ton Electric arc furnace slag 43.8% ; Production amount of slag (t) ; Ratio of using as road material (%) 2.6 million ton 21

22 Criteria of iron and steel slag for base course materials Type of Steel and Iron Slag Place of Use Color Development Test Unit Weight (kg/m 3 ) Unconfined Compression Strength(MPa) Modified CBR(%) Immersion Expansion (%) Hydraulic mechanically stabilization slag Base course pass 1,500 or more 1.2 or more 80 or more 1.5 or less Mechanically stabilization slag Base course pass 1,500 or more - 80 or more 1.5 or less Crusher-run slag Subbase course pass or more 1.5 or less 22

23 Conclusion In Japan, The recycling rate of asphalt mixture have been reached 99.5%. The ratio of recycled asphalt mixtures to total shipment quantity is increasing and it reached 76% in More than 60% of waste asphalt mixtures are used for asphalt mixtures, which are mainly dense- graded mixtures, containing RAP. The mixing ratio of RAP in recycled asphalt mixtures is different each area. Especially, the ratio of Tokyo and surrounding areas is higher than that of other areas. 23

24 Conclusion Japan Road Association issued the Manual of pavement recycling in The design methods of recycled asphalt mixture was generally established. Moreover, recycled base course materials are widely used in construction of base course. For base course materials, other industrial waste, such as iron and steel slag and concrete debris waste, are also used. Japanese pavement industry contributes to establish a recycle based society by using various recycling technologies. 24

25 Future work Further usage will be promoted to build recycling-based society. Meanwhile, since the rapidly aging society will arrive in Japan, rational construction, cost reduction and quality assurance are required in pavement works. Furthermore, when using recycled materials, safety to the environment must also be secured. It is necessary to consider using recycled materials, which include these factors. 25

26 Thank you for your attention 26