Producing Carbon-Negative Bricks by Regenerating C-S-H from Carbonated Recycled Concrete Fines

Abstract

This study proposes the production of bricks utilizing underutilized fine powders, predominantly consisting of old cement paste derived from the recycling of demolished and waste concrete. Four brick designs were developed and manufactured using a hydraulic press, incorporating recycled concrete fines (RF) or carbonated recycled concrete fines (CRF) as both filler and binder materials. The experimental study revealed the self-cementing ability of RF, exemplified by a compressive strength exceeding 13.8 MPa in the RF-based brick. However, a substantial portion of this self-cementing ability is lost after carbonation of RF. Nevertheless, the carbonated RF can be activated by introducing Ca(OH)2. New calcium silicate hydrate gels can be regenerated between the carbonated RF and Ca(OH)2, resulting in a brick with a compressive strength surpassing 19 MPa, suitable for certain structural applications. Significantly, this brick boasts a truly carbon-negative carbon footprint, owing to the substantial sequestration of CO2 in the carbonated RF.