Kajima and others develop non-standard fly ash CSG, introduce 7,250 cubic meters into Naruse Dam embankment
April 14, 2025
Pour fly ash CSG into the upper section of the embankment (from press release)
Fly ash CSG spreading status (from press release)
Kajima and the other four companies have developed "fly ash CSG," which uses non-JIS standard fly ash (coal ash) in a material (CSG) made from a mixture of on-site soil (stones and gravel), cement, water, etc. The non-JIS standard fly ash replaces part of the normal cement used to make CSG. After confirming that it has the same strength properties as conventional CSG, a total of 7,250 cubic meters was introduced into part of the dam embankment during the construction of the Naruse Dam embankment (Higashinaruse Village, Akita Prefecture). This is said to be the first time in Japan that fly ash CSG has been introduced into a large-scale dam embankment.
Fly ash CSG was jointly developed by the Ministry of Land, Infrastructure, Transport and Tourism's Tohoku Regional Development Bureau, the University of Tokyo, the Dam Technology Center (Chairman Tomari Hiroshi), and Kajima, with the cooperation of Tohoku Electric Power. Compared to conventional CSG, it changes less over time, so the density of the compacted CSG is improved, ensuring the same or better quality. It has effects such as improving resistance to material separation, reducing heat of hydration, and suppressing alkali-aggregate reaction.
Kajima and others introduced a total of 7,250 cubic meters of fly ash CSG into part of the dam embankment. They effectively utilized 435 tons of JIS non-standard fly ash that was treated as industrial waste. When comparing fly ash CSG with conventional CSG, they confirmed that the strength characteristics of fly ash CSG are equivalent to conventional CSG, and that the quality is equal or better.
Because part of the normal cement, which is the raw material for CSG, was replaced with JIS non-standard fly ash, carbon dioxide (CO2) emissions were reduced by 28% compared to when conventional CSG was used.
In the future, the four parties will develop concrete that effectively utilizes not only fly ash CSG but also JIS non-standard fly ash, and actively deploy it in various structures such as dams. They will contribute to the realization of a sustainable recycling-oriented society with zero emissions and low environmental impact.
