Researchers go green by mixing wood to recycle concrete

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Researchers have developed an environmentally friendly method of recycling concrete waste by mixing in wood and other materials.

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The new method makes it possible to “recycle concrete waste without using cement,” Yuya Sakai, a lecturer at the University of Tokyo’s Institute of Industrial Science, who led the research team, said at a news conference on Feb. 6.

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“It will help reduce carbon dioxide and reuse wood building materials and plants that would otherwise be scrapped,” Sakai said.

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Every year, 33 million tons of concrete waste, such as debris from demolished buildings and bridges, are generated in Japan.

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In many cases, such concrete waste is pulverized and reused as sub-base gravel for road surfaces.

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Some of the waste will be recycled into concrete by adding cement. However, since cement is produced by burning limestone at 1,500 degrees, the cost is high.

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In the new method, researchers crushed concrete waste to a powder. Then they added wood powder and water into the mixture and applied pressure equivalent to five atmospheres at a temperature of 160 degrees.

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The mixture became concrete again, without the use of cement.

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The flexural strength of the recycled concrete exceeded regular concrete, researchers said.

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Lignin, a chemical compound richly contained in plants, played a role as an adhesive bond and helped connect particles of the pounded concrete, according to the researchers.

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The durability of the recycled concrete seemed inferior to regular concrete. However, researchers are confident that the recycled concrete can be sufficiently utilized for parking blocks and temporary facilities.

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