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The increase in carbon emissions is a growing concern for the sustainability in our society, particularly as energy consumption rises, leading to annual CO2 releases into the environment. The construction sector, responsible for utilizing a significant portion of the Earth's yearly extracted raw materials, significantly contributes to this issue. After the life cycle of a structure, this one is often transformed or demolished for new developments, generating large amounts of construction debris. Most concrete debris is further processed to create recycled aggregates, which are commonly used for road construction or as filling material. Nonetheless, efforts are underway to promote material circularity by reusing these aggregates back into concrete, reducing concrete downcycling and disposal in landfills. Hamburg's "Musterbude" project in 2022 stands as an example of material circularity, showcasing the sustainable use of recycled aggregates in concrete. Seven concrete mixes were formulated; two conforming to German recycled concrete standards with 45% and 35% recycled aggregate replacement. Others, including the so-called "Hamburger Mische," departed from these standards, incorporating varied recycled materials like crushed bricks and 100% mixed C&DW aggregates. The findings provided valuable insights for policymakers, engineers, and researchers, fostering a transition towards a more circular economy in the construction sector while minimizing environmental impact.
Rapallo et al. (2024) studied this question.