Establishing mass-production technology for sustainable next-generation concrete products

A research group comprising Senior Scientist Takeshi Yamamoto, Senior Researcher Michio Kikuchi, Senior Researcher Atsushi Shibayama, and other scientists at the Central Research Institute of Electric Power Industry (CRIEPI), in collaboration with Nakagawa Humepipe Industry Co., Ltd. and Japan Coal Frontier Organization, are working toward the realization of a carbon-free society. They developed a next-generation concrete material "EeTAFCON," which can reduce CO₂ emissions by approximately 70% compared to conventional concrete using cement.

For practical use as a precast product, the research group optimized the manufacturing technology according to factory scale and developed a mass-production technology. In addition to this, the research group manufactured precast products such as manholes in various environments and demonstrated their high durability in sewerage systems, where deterioration is an issue encountered with the use of conventional concrete. They also performed a structural experiment with a test piece of the reinforced concrete to apply it to structural members. Through these experiments it was determined that the bending and shear strengths were not inferior to those of conventional concrete, making it applicable to practical use.

EeTAFCON is a concrete product with excellent sustainability because it uses industrial by-products such as fly ash and blast furnace slag (in fine powder form) as raw materials without using cement. While conventional CO₂ emissions related to the production of 1 m³ of cement concrete are approximately 320 kg, these are approximately 90 kg for EeTAFCON, which corresponds to a CO₂ reduction of approximately 70%. On top of these benefits, >500 kg/m³ of by-products such as fly ash and blast furnace slag (fine powder) can be used. By optimizing the manufacturing technology for EeTAFCON developed at the laboratory level based on factory equipment specifications, mass production is possible utilizing existing factory equipment.

EeTAFCON can be applied to various structures because it has a high strength of ≥60 N/ mm², which significantly exceeds the minimum compressive strength standard of 12 N/ mm² for concrete stipulated by the Building Standards Act. Furthermore, various precast products manufactured at the factory were employed in a standard environment, cold environment, and an acid-deterioration environment, and changes in the appearance and strength after construction were monitored for two years. Practicality was demonstrated as the product exhibited sufficient durability without any deterioration in appearance or strength at all construction sites. Particularly in the sewerage environment, which is an acid-deterioration environment, higher durability was observed compared to that of conventional cement concrete products. Approximately 40 reinforced concrete beams with dimensions of one-half to one-third of an actual structure were manufactured, and the structural performance was tested. Results proved that the reinforced concrete member composed of EeTAFCON could be utilized as a structural member because the bending strength and shear strength, which are important parameters for structural design, were comparable to those of the conventional reinforced concrete member comprising cement.

It is expected that the wider implementation of this concrete material will contribute to addressing important issues related to the achievement of SDGs, such as the establishment of a low-carbon society and recycling-oriented society. In the future, the researchers intend to collect additional data on the durability and structural performance and promote the application of EeTAFCON in the field.

■ Fly ash: A type of ash produced by the combustion of coal at coal-fired power plants. In "Act on the Promotion of Effective Utilization of Resources", recyclability is required in the design of new products.

■ A video showing the development and testing process of EeTAFCON products, including a shear test, can be seen at the following link: https://www.youtube.com/watch?v=Lj2AIrBsy3M