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Engineers create greener concrete using waste clay

When it comes to man-made materials, concrete is the most consumed product on Earth. Each year, about three tons of concrete are consumed per person. The environmental impact of concrete is much less publicized than the impact of other man-made materials, such as plastic. Concrete is made of water, cement and filling materials such as sand. The researchers say the concrete industry alone is responsible for about 8% of carbon dioxide emissions worldwide.

Concrete production also consumes approximately 10 percent of the world’s industrial water. Researchers at the National University of Singapore have shown that they can reduce the amount of sand needed to make concrete by replacing common clay material easily obtained as a residue from excavation work on construction sites around Singapore.

The clay is heated to about 700 degrees Celsius to activate it and increase the bonding capacity in the concrete. The activated clay was then used to replace up to half of the fine sand powder normally used in the manufacture of concrete. The result was ultra-high performance concrete, an extremely resistant type of concrete that can reduce the size of structural elements and potentially reduce the amount of concrete needed in a construction project.

The researchers say that tunnels and foundation works are common in Singapore and generate a lot of excavation waste. Disposing of the material is difficult because land is scarce in Singapore, offering limited space for landfill. The project marks the first time that low-grade clay waste is used as a concrete filler.

The team is currently studying the use of clay waste for additional concrete applications. The research group is also exploring the use of other waste materials to replace concrete fillers and the use of sea water and sand to reduce dependence on freshwater and river sand imports into Singapore. Researchers are also studying the use of concrete as a carbon capture material to reduce their carbon footprint.

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