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Production of recycled cement ‘Cem R3®’ from returned concrete generated at several ready-mixed concrete plants

Kajima has established a system to manufacture recycled sludge cement ‘Cem R3®’ from returned concrete generated at several ready-mixed concrete plants in Kanagawa Prefecture.

Furthermore, Ecocrete R3, an environmentally friendly concrete using Cem R3, has been adopted for the columns, beams and floors of an apartment block under construction in Yokohama City, Kanagawa Prefecture. Ecocrete R3 is an environmentally friendly concrete that reduces CO2 emissions while promoting resource recycling, and is the first time it has been used in a residential building.

Instead of cement, which generates a large amount of CO2 during the production process, Ecocrete R3 uses Cem R3, a recycled sludge cement produced by dewatering and grinding the aggregate after removing it from the returned concrete, as a raw material.
Until now, Cem R3 has only been manufactured at Sanwa Seisan’s Fujisawa Plant from returned concrete. The company has now set up a new manufacturing base for Cem R3 at its plant in the coastal area of Kawasaki City, and established a system to collect returned concrete from multiple ready-mixed concrete plants and manufacture Cem R3.

The new system can handle up to seven plants’ worth of returned concrete generated at nearby ready-mixed concrete plants, increasing the manufacturing capacity of Cem R3 by about seven times compared to the previous system. In addition, by setting the conditions for receiving returned concrete and ensuring quality through quality control during production, Ecocrete R3 has obtained a technical performance certificate (GBRC Material Certificate No. 16-10 Revision 3) from the Japan Building Research Institute, while each ready-mixed concrete plant has obtained ready-mixed concrete JIS certification.

Ecocrete R3, made from Cem R3 manufactured under the new system, has been adopted for the first time in an apartment block being built by Kajima in Yokohama City. Ecocrete R3 can be used in a wide range of applications by adjusting the content of Cem R3. This time, the content of ‘Cem R3’ was set at 10% in accordance with the legally stipulated standard*4 to suit residential applications. As a result of its adoption for building columns, beams and floors, it was confirmed that it is easy to construct and has sufficient strength.