Preparation of artificial aggregate using waste concrete powder and CO2 fixed by microorganisms.

High carbon emissions, shortages of natural aggregates and environmental pollution of waste concrete powder (WCP) have become open issues for the traditional concrete industry. Aggregates prepared by crushing and screening waste concrete usually possess poor mechanical properties. Meanwhile, the WCP cannot be effectively utilized. This paper proposes a novel approach based on microorganisms for strengthening mechanical properties and improving CO₂ sequestration of 'newly' artificial aggregates prepared by cold-bonding pelletization of WCP. Specifically, the microorganisms enhanced the artificial aggregates, resulting in their apparent density, crushing strength and water absorption increasing to 2620 kg/m³, 9.1 MPa and 4.8%, respectively. With the increase of well-crystallized mineralization products, the artificial aggregates exhibited a denser microstructure where the porosity decreased from 20.9 to 13.9%. The CO₂ fixation of artificial aggregates increased from 7.4 to 16.0 wt. % due to the existence of microorganisms. The compressive strength of concrete indicated that artificial aggregate could partially substitute the natural aggregates without affecting its strength, and a better substitution rate should be controlled within 50%. This method improves waste resource utilization and CO₂ emission reduction, showing good potential for future applications. Preparation process of the artificial aggregate and its application. [ABSTRACT FROM AUTHOR]