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Fixing Waste Plastic in Concrete: Aizawa High Pressure Concrete Jointly Develops the Technology with a US Company

Aizawa High Pressure Concrete (Headquarters: Tomakomai) has signed a joint development agreement with MiCon Technology in the United States for immobilization technology with which waste plastic modified with gamma rays is used as a substitute for sand when making concrete. They are targeting practical use by the spring of 2023. Since waste plastic is reused as a material rather than being used as fuel, CO2 emissions can be expected to be reduced. It is likely to attract attention as a technology that will lead to decarbonization and environmental improvement.

Applying plastic reforming technology developed from basic research at the Massachusetts Institute of Technology (MIT), waste plastic is fixed inside concrete. MiCon Technology is a MIT startup, where Professor Olar Bucasterk, who is an authority on the development of sustainable cement-based materials, serves as CTO (Chief Technology Officer), and Dr. Cave Bactary, who conducts research on material processing technology, serves as CEO (Chief Executive Officer).

MiCon Technology has strengths in basic research on waste plastic use in concrete production. Crushed waste plastic is irradiated with gamma rays in a special method to modify the surface, and thereby the waste plastic can be used as a substitute for fine aggregate without impairing the physical characteristics. Aizawa High Pressure Concrete started technical exchanges with MiCon Technology in 2019 and has proceeded with technical verification and commercialization surveys through the Aizawa Institute of Technology.

Technical verification has revealed that about 5 kg of waste plastic (equivalent to 200 500 ml PET bottles) per m3 of concrete can be used as a substitute for fine aggregate. It reportedly leads to semi-permanent fixation of 13 kg of CO2 generated during incineration.

When crushed plastic with deteriorated quality is added to concrete, it adversely affects the freshness of concrete, causing a concern that the strength may deteriorate after curing. The Aizawa Institute of Technology has confirmed the potential to bring out the same or higher concrete strength by using MiCon’s reforming technology and a mixture with materials such as silica fume, which can be expected to increase strength.

In the future, they plan to develop a container-type module equipped with an electron beam irradiator that has the same modification effect as gamma ray irradiation and has a high processing speed. The dimensions of containers are set as world standards, and it is easy to install, move and combine containers. They are considering increasing or decreasing the number of modules according to the amount of waste plastic collected, or reusing the modules according to the operating rate.

About 8.5 million tons of waste plastic are collected annually in Japan, of which 69% is incinerated. Meanwhile, China announced a ban on imports of waste plastics in 2017, and regulations have also been introduced in Southeast Asia and Taiwan. As a result, there are increasingly fewer places for Japan to send its waste plastics.

President Yoshihiro Aizawa says, “We will be able to flexibly develop a waste plastic material recycling system in which residents, collectors, and concrete manufactures work together. By increasing the strength, it is possible to strategically reduce the amount of cement used, and it is expected that CO2 will be reduced during cement manufacturing.”

(Excerpt from an article on July 15, 2021)

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