Overview

The need of today’s society to reduce emission of greenhouse gases and resource consumption is currently prevailing in discussions and media more than ever. The construction sector is a massive contributor to global CO₂ emissions, with cement production alone accounting for approximately 7-8% of total anthropogenic CO₂ emissions. The integration of supplementary cementitious materials (SCMs) into cement can significantly reduce these emissions. However, conventional SCMs, such as fly ash and slag, are becoming scarce, causing the need for the development of alternative materials. The re-CEM project addresses this critical challenge by exploring the potential of carbon capture and utilization (CCU) technologies to convert recycled concrete paste (RCP) into a viable SCM. RCP, a by-product of concrete recycling, presents a promising solution due to its high availability and potential for CO₂ sequestration when subjected to wet carbonation. Despite this potential, RCP is currently underutilized, with much of it ending up in landfills. The wet carbonation of RCP can enhance its reactivity by forming a reactive Si-Al gel, transforming it into a pozzolanic SCM. Analyses before and after carbonation include thermogravimetric analysis (TGA), X-ray powder diffraction (QXRD), inductively coupled plasma optical emission spectrometry (ICP-OES), ²⁹Si and ²⁷Al solid-state nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), and the R³ test. TGA quantifies mass loss and carbonate formation; QXRD determines crystalline and amorphous phase assemblages; ICP-OES assesses elemental composition and potential alkali incorporation or leaching. NMR and FTIR probe the structure of the Al–Si gel. The R³ test will be applied to evaluate the reactivity. Together, these techniques aim to clarify the complex relationships between the chemical composition, the amorphous Si-Al gel structure, and the pozzolanic reactivity of the resulting carbonated RCP (cRCP) for use in cement and concrete.

This project is part of the SPP 2436 Net-Zero Concrete