Unlike in the area of composite cables, where the ACC Club represents all types and forms of composite materials, in the area of external reinforcement there are two associations, based on the type of fiber used:

  1. The Carbon Fiber Repair and Reinforcement Research Association (CFRRA), which considers carbon fiber based applications only
  2. The Society of Aramid Reinforcement Systems (ARS), which considers aramid fiber based applications

The CFRRA was formed in July 1994 to promote the use of, and conduct research into, carbon fiber sheet technology in the retrofit and external strengthening areas. Currently, it has a membership of over 250 companies, most of which are small construction firms. The membership is divided into four classes:

  1. Manufacturers, namely Tonen, Toray and Mitsubishi Chemical
  2. General contractors, comprised of a large number of firms such as Obayashi, Shimizu, Taisei, Kajima, Takenka and others
  3. Design consultants
  4. Submembers belonging to one of three groups (as shown in Fig. 4.11): CRS (or Carbon Fiber Concrete Retrofit System), headed by Obayashi Corp., Mitsubishi Chemical, Toray, and Tonen and emphasizing the use of winding technology; CCA (or Carbon Fiber for Civil Applications), headed by Shimizu, Taisei, Toray and Tonen, and emphasizing the use of tow sheet and Torayca cloth as well as Sho-Bond Technology; and the CFR (or Carbon Fiber Renaissance), headed by Mitsubishi Chemical and emphasizing the use of Replark sheets.

At the time of this WTEC visit, the CFRRA was chaired by a representative of Shimizu Corp. and the secretary was from Tonen. A technical committee charged with establishing standards and overseeing research was chaired by Professor Shoji Ikeda of Yokohama National University, who was assisted by Dr. Asakura of the Railway Technical Research Institute. The activities of the CFRRA are divided among four subcommittees:

  1. Superstructure Committee, dealing with slab and deck related applications
  2. Substructure Committee, dealing with external reinforcement of concrete columns
  3. Tunnel Committee, dealing with the lining of tunnels
  4. Building Committee, dealing with all aspects related to strengthening and seismic retrofit of buildings

Fig. 4.11. Overall structure of the CFRRA.

The CFRRA works in close collaboration with the Public Works Research Institute (PWRI) of the Ministry of Construction, Japan Highways Corp., the Hanshin Expressway Authority, the Building Research Institute (BRI), the Railway Technical Institute, and various expressway and railway corporations. It conducts joint research and demonstration projects, and establishes design guidelines. In many cases, demonstration projects conducted under the aegis of the CFRRA use all three forms of sheet technology (tow sheet, Replark and Torayca cloth) on the same project. CFRRA reported that over 2000 applications/projects have been completed by its members, although it is unclear whether all these were actual demonstrations or commercial projects. Some may have been test programs conducted in laboratories or for purposes of short-term monitoring. Estimates of the use of carbon fiber sheet material in these applications are shown in Figure 4.12.

Fig. 4.12. Estimates of annual consumption of carbon fiber sheet materials for external reinforcement.

The ARS (Society of Aramid Reinforcement Systems) or the Association of Aramid Fiber Reinforcement for Concrete Structures, is a smaller group. It was formed in June 1996 to further the use of aramid fiber sheet products for use in external retrofit of concrete structures. At the time of the WTEC visit, the association had 26 members consisting of 18 general contractors, three repair construction firms, three fiber manufacturers and two design firms. The association was headed by Dr. Sakamoto of Kajima Construction Co., Ltd. Teijin, Ltd., DuPont-Toray Kevlar, Ltd., and Nippon Aramid Co., (a joint venture between AKZO Nobel and Sumitomo Chemical Co.) are its materials suppliers/fiber manufacturers. The construction companies are among the same as those in the CFRRA and include Kajima Construction Co., Obayashi Corp., Sumitomo Construction Co., Mitsui Construction Co., Tokyu Construction Co. and Sho-Bond Construction Co. Although smaller, the ARS group is aggressively promoting the use of aramid fiber-based seismic retrofit and strengthening strategies, emphasizing the higher toughness, strain-to-failure, and non-conductive nature of aramids as advantages compared to the carbon fiber systems. In many cases, ARS also reports that an aramid based system is more economical than a carbon fiber based system for retrofit of columns.

Published: November 1998; WTEC Hyper-Librarian