Biochar blend makes concrete more environmentally friendly

In a proof-of-concept work, the researchers infused regular cement with biochar that had been strengthened with concrete wastewater. The biochar was able to absorb up to 23 per cent of its weight in carbon dioxide from the air while still reaching a strength comparable to ordinary cement.   

The work, led by doctoral student Zhipeng Li, is detailed in Materials Letters.

“We’re very excited that this will contribute to the mission of zero-carbon built environment,” said Xianming Shi, professor in the WSU Department of Civil and Environmental Engineering and the corresponding author on the paper.

Researchers have tried adding biochar as a substitute in cement to make it more environmentally friendly, but adding even three per cent of biochar reduced the strength of the concrete. After treating biochar in the concrete washout wastewater, the WSU researchers were able to add up to thirty per cent biochar to their cement mixture.

After 28 days the biochar-amended cement is said to have reached a compressive strength comparable to ordinary cement of about 4,000 pounds per square inch.