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August 1, 2000 Aggregate Brought Back to Life from Concrete Waste Production begun of "Cyclite," the first high-quality recycled aggregate that the Building Center of Japan approved
Takenaka Corporation (President: Toichi Takenaka; Head
Office: Osaka), Kurimoto Ltd. (President: Yoshiaki Sakamoto; Head Office:
Osaka) and Aso Cement Co., Ltd (President: Yutaka Aso; Head Office:
Fukuoka Prefecture) have installed equipment in the Kita-Kyushu Ecotown
Practical Research Center (Koyo-cho, Wakamatsu-ku, Kita-kyushu City,
Fukuoka Prefecture) to produce "Cyclite," a high-quality recycled aggregate,
and the first technology to be certified under the
Building Center of Japan's Innovative Building Technology Approval Program*.
Production has begun, looking at the practical use of the material. |
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| "Cyclite" is the name of
the high-quality recycled aggregate jointly developed by Takenaka Corporation,
Takenaka Civil Engineering & Construction Co., Ltd., Professor Masaru
Yamada of the Faculty of Engineering, Osaka City University and Kurimoto
Ltd. To produce "Cyclite," crushed concrete lumps are ground together
using a newly developed processing unit, thereby removing the mortar from
the aggregate surface without crushing the aggregate (sand and gravel).
This gives it the same quality as natural aggregate and crushed stone.
Recycling the aggregate in concrete waste materials generated when a building
is torn down is the first step in cyclical recycling of concrete. Concrete waste, which accounts for the largest percentage of construction by-products, according to a survey of actual conditions carried out by the Ministry of Construction in 1995, has reached 37 percent of the total quantity of construction byproducts emitted, or a weight of approximately 36 million tons. Promoting the recycling of this waste has become extremely important in terms of environmental conservation and resource saving. Generally concrete waste is recycled mainly as roadbed or back-filling materials. Within Takenaka some 81.3 percent of concrete waste was recycled in 1999. However, the recycling of concrete in buildings up until now has been restricted to nonstructural sections of buildings (i.e., not including columns, beams, slabs, etc.) apart from experimental cases of applications. In the research looking at practical use of "Cyclite," quality stabilization of the recycled aggregate and durability of the equipment will be tested, along with verifying transportation costs of the aggregate, initial and running costs of the "Cyclite" production equipment, and the recovery rate and maximum production capacity of "Cyclite." This is to determine in what case the production of "Cyclite" can be begun on a commercial basis. At the present time, "Cyclite" concrete is more expensive than concrete that uses natural aggregate, but adding the cost of disposing of scrap concrete into the equation, there is adequate economic merit in the product if the amount processed reaches a certain level, so the results of these tests are being waited for. Method of Manufacturing "Cyclite" Cyclite was developed based on the understanding that the aggregate in concrete is also an important resource that can be used repeatedly. The system for manufacturing Cyclite comprises two stages: the pretreatment which crushes scrap concrete waste and removes other components in the mixture, and the grinding which processes the surface of the lumps of crushed concrete. Grinding is carried out by an eccentric rotor-type** processing unit. The lumps of crushed concrete input between the outer cylinder and the inner cylinder which rotates eccentrically (eccentric rotor) grind against one another, and only the unnecessary cement and mortar attached to the aggregate surface is removed. The resultant material is then put over a sieve, with Cyclite being recovered. Maximum production capacity is 60 tons/hour. Note ** The concept devised by Professor Emeritus Atsuhiro Honda et. al., Osaka City University was implemented. |
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The Environmental Burden (CO2 Generated) when Cyclite is Manufactured The only energy required for manufacture is the power (electricity) required to move the crushing and grinding machinery; there is no heating or chemical treatment, which means it consumes around the same energy consumption (CO2 generated) as ordinary broken stone production. Quality of Cyclite The quality of Cyclite satisfies the standards for natural aggregate and crushed stone stipulated in JIS (Japanese Industrial Standard) and JASS (Japanese Architectural Standard Specification), and meets all standards stipulated by the Building Center of Japan for certification of technology. Concrete prepared using Cyclite has the same performance of that created using ordinary concrete. |
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| Example of Application Takenaka was the first company to use Cyclite Concrete in the structure of a building (part of the first floor, approximately 100 m2) in Japan, the ACROS Shin-Osaka (Completed in December 1999). Some 30 m3 of concrete was laid, with the weight of Cyclite being 30 tons. Cyclite Experimental Plant Opening Ceremony |
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