Ishikawajima Construction Materials Co., Ltd.

Ishikawajima Construction Materials Co., Ltd. (株式会社ＩＫＫ) is a Japanese company established in December 1974 by Ishikawajima-Harima Heavy Industries (now IHI) in Chiyoda-ku, Tokyo. It designs, manufactures and sells concrete members such as segments used in shield tunneling for subways and expressways, precast products, and engineering materials including soundproof and landscape walls. In October 2025, following a share transfer, it became a consolidated subsidiary of Bertex Corporation and changed its name to 株式会社ＩＫＫ.

The company was established in December 1974 by Ishikawajima-Harima Heavy Industries (now IHI) in Otemachi, Chiyoda-ku, Tokyo, with capital of 200 million yen, and simultaneously opened Osaka and Nagoya sales offices. It moved its head office to Yaesu, Chuo-ku, Tokyo in March 1975, and increased capital to 600 million yen in June 1976. In April 1978 it opened a Fukuoka sales office. In July 1981 it established Chubu Segment Co., Ltd. as a production subsidiary. In September 1985 it acquired shares of Kanto Segment Co., Ltd. from Ishikawajima-Harima Heavy Industries and made it a subsidiary, and in October 1985 increased capital to 915 million yen through a third-party allotment. In March 1988 it issued 1,500 thousand new shares, increasing capital to 1,665 million yen, and listed on the Second Section of the Tokyo Stock Exchange. In May 1989 it issued 1,640 thousand free new shares, and in May 1994 issued 2,706 thousand new shares through a stock split. In September 1996 it moved its head office to Yurakucho, Chiyoda-ku, Tokyo. In March 1997 it acquired shares of Ribcon Engineering Co., Ltd. and made it a subsidiary. In November 1998 it obtained ISO9001 certification. In May 2003 it acquired shares of Tokuho Co., Ltd. as a production subsidiary. In March 2005 it took over all shares of Kanto Segment Co., Ltd. held by Ishikawajima-Harima Heavy Industries (now IHI), making it a wholly owned subsidiary. In June 2006 it opened the Himeji office in Tatsuno, Hyogo Prefecture. In April 2007 it integrated subsidiaries Kanto Segment Co., Ltd. and Tokuho Co., Ltd. In March 2009 it moved its head office to Ryogoku, Sumida-ku, Tokyo. In March 2012, through a tender offer by IHI, it became a wholly owned subsidiary of IHI, reduced capital to 495 million yen, and delisted. In October 2013 it opened a Sendai sales office in Sendai, Miyagi Prefecture. In April 2015 it absorbed subsidiary Kanto Segment Co., Ltd. and changed its name to IHI Construction Materials Co., Ltd. In July 2021 it absorbed subsidiary Ribcon Engineering Co., Ltd., and in October 2021 absorbed subsidiary Chubu Segment Co., Ltd. In October 2025, through a share transfer, it became a consolidated subsidiary of Bertex Corporation and changed its name to IKK Co., Ltd. In February 2026 it moved its head office to Kojimachi, Chiyoda-ku, Tokyo.

Contributing to future urban space creation through segment, precast and engineering technologies.

• Segments for shield tunneling

  Concrete members designed, manufactured and sold for underground tunnels such as subways and expressways.

• Precast concrete products

  Products contributing to shortening construction periods for intersections and railway crossings, and long-life measures for tunnels and bridges.

• Engineering materials

  Soundproof walls, landscape walls and other plant-related materials for domestic and overseas construction projects, mainly in the energy field.

• セメノン® (Cemenon)

  Geopolymer concrete that does not use cement and has high acid resistance.

1. 1株式会社ＩＫＫ 公式ホームページikk.co.jp
2. 2沿革 | 株式会社ＩＫＫ 公式ホームページikk.co.jp
3. 3企業情報 | 株式会社ＩＫＫ 公式ホームページikk.co.jp
4. 4トップメッセージ | 株式会社ＩＫＫ 公式ホームページikk.co.jp
5. 5Ishikawajima Construction Materials Co., Ltd. (Japan)wikidata.org