Encouraged by more awareness of the environment, use of "Green-Growing Concrete" (developed in 1993, Patent No. 2981071), which has strength and durability of concrete, and can grow things just like soil, has been increasing year by year centered on river and lake embankment work, civil engineering work slopes, car parks and driveways (*2). There are surely a lot of people who have come across these "green-growing concrete" embankments covered in green grass. 
With the new participation of Electric Power Development Co., Ltd. and EPDC Environmental Engineering Service Co., Ltd., the Green-Growing Concrete Group has developed the technology for the effective use of coal ash (*3) in "green-growing concrete." The "green-growing concrete" that uses coal ash effectively uses the coal ash from coal-fired power plants as concrete aggregate, cement paste, filler and surface base material. 
 

(*1) The Green-Growing Concrete Group

The "Green-Growing Concrete Group" was begun in 1998 by Takenaka Corporation, Takenaka Civil Engineering & Construction Co., Ltd., Nippon Chemical Industrial Co., Ltd. and Nisshoku Corporation for the purpose of promoting the use of "green-growing concrete." With the entry of Electric Power Development Co., Ltd. and EPDC Environmental Engineering Service Co., Ltd. in August, 2000, the group presently consists of six companies.

 

(*2) Work record of "green-growing concrete"

Since its development in 1993, green-growing concrete has been used in river embankment and other work at 36 locations throughout the country covering an area of about 12,000 square meters.

 

(*3) Coal ash 

Of the 6.79 million tons of coal ash from coal-fired power plants in 1998, about 75 percent was recycled and 25 percent used in land reclamation.

71 percent of the recycled coal ash was used in the cement area, for example as cement raw material, seven percent was used in civil engineering works, for example as road base material, six percent was used in the construction area, for example as construction boards, two percent was used in the agricultural area, for example as fertilizer, and 14 percent was used in other areas. With the low demand from the construction industry, there is a need for some unique coal ash recycling technology. (Figures taken from material of the Center for Coal Utilization, Japan.)

"Green-growing concrete" consists of two layers. The first is a "porous concrete" layer, which is made by hardening aggregate with low-alkaline high-strength cement paste, has a porosity of 25 to 30 percent, is between 15 to 30 centimeters thick and has a compressive strength between 10 to 15 Newtons per square millimeters. The second is a two to five centimeter-thick sprayed "surface base" layer, which is a combination of organic materials with high water and fertilization retentivity and resistance to erosion, and a mixture of fertilizer and seeds. "Green-fill," a filler mainly composed of organic materials, is used to fill the spaces inside the "porous concrete" to give it the necessary water retentivity and fertilization properties, and to neutralize the alkalis. 
The procedure involves first pouring the "porous concrete," second filling the "porous concrete" with "Green-fill" and third spraying "surface base" layer onto the "surface base" and planting. Grass or tree roots spread into the spaces inside the "porous concrete" and get nutrition from the "filler."

Main features of "green-growing concrete"

1. "Green-growing concrete" has the strength and durability of concrete, as well as the ability to grow plants like soil. 

 
2. Planted bases that cannot be easily eroded by running water or rainwater can be built. 

 
3. The concrete can be poured on-site, so this can be carried out according to the work surface conditions.

 
4. The concrete can also be precast, enabling the work period to be reduced. 

 
5. Not only can lawn or grass be grown on the concrete, but it can also take medium-sized trees. 

About the "green-growing concrete" that uses coal ash

(1) Using coal ash in "porous concrete" 

Fly ash (the small particle contained in the exhaust gas from coal furnaces) is mixed with cement, and clinker ash (the large particles that are taken from the bottom of the furnaces) is used as aggregate to manufacture porous concrete. Forty percent of the cement and ten percent of the aggregate can be replaced with coal ash.

(2) Using coal ash in the "filler" 

Filler with fly ash mixed in is used.

(3) Using coal ash in the "surface base" 

The clinker ash, which has outstanding water retentivity, is mixed into the surface base.

(*4) "Green-growing concrete" is patent-protected (Patent No. 2981071).

Beginning with affiliated companies, the "Green-Growing Concrete Group" will be offering permission for other companies to use this technology.