Concrete samples (IMAGE) University of Tokyo Caption Two samples of calcium carbonate concrete, one using hardened cement paste (left) and the other using silica sand. Both raw materials are common construction and demolition waste products. Credit © 2021 Maruyama et al. Usage Restrictions Credit © 2021 Maruyama et al. License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.