Carbonation of recycled concrete aggregates for new concrete and concrete fines to make cement-free hollow blocks

Jef Bergmans, Hadi Kazemi Kamyab, Debabrata Ghosh, Peter Van Mierloo, Hilde Carens, Peter Nielsen

Research outputpeer-review


Mineral carbonation provides a way to increase the recycling of concrete waste in added-value products, and contributes to the principles of the circular economy. At present, most concrete waste is still downcycled. The high water absorption of recycled concrete aggregates, among other factors, impedes their recycling in the concrete industry. The quality of coarse recycled concrete aggregates (RCA) can, however, be enhanced by carbonation. Even when starting with high-grade RCA obtained from a selective demolition process, the carbonation process can decrease the water absorption of the RCA to as low as 3.0%. Concrete with a 50% replacement rate of carbonated RCA can be produced without a significant compressive strength reduction. The research further shows that carbonation can be performed at atmospheric pressure and low CO2 concentrations (e.g., 10%). The recycled concrete fines (RCF, 0–4 mm) in combination with 25% stainless steel slag were used to make zero-cement hollow blocks (39 × 19 × 9 cm) by carbonation curing without using any hydraulic binder. The hollow blocks have a compressive strength of 15.4 MPa at the lab scale. Both technologies were demonstrated on a pilot scale. In both processes, CO2 is immobilized in the resulting construction product. The developed production processes use less primary raw materials and cause less greenhouse-gas emissions than the production of traditional concrete products.

Original languageEnglish
Article number3494
Number of pages20
JournalSustainability (Switzerland)
Issue number8
StatePublished - Apr 2024


This research was funded by the EU Horizon2020 project ICEBERG \u201CInnovative Circular Economy Based solutions demonstrating the Efficient recovery of valuable material Resources from the Generation of representative End-of-Life building materials\u201D (No. 869336).

FundersFunder number
Horizon Europe869336

    ASJC Scopus subject areas

    • Computer Science (miscellaneous)
    • Geography, Planning and Development
    • Renewable Energy, Sustainability and the Environment
    • Environmental Science (miscellaneous)
    • Energy Engineering and Power Technology
    • Hardware and Architecture
    • Computer Networks and Communications
    • Management, Monitoring, Policy and Law

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