Isotope chemistry to trace carbon mineralization in construction materials

Abstract

This contribution presents an overview of the current literature and application potential of carbon isotope analysis in cementitious systems. Stable carbon isotope ratios (¹³C/¹²C) offer powerful insights for tracking carbonation processes, especially in the context of carbonation hardening and the characterization of recycled concrete fines. Isotope methods can help determine the extent of carbonation and to distinguish between naturally formed carbonates and those resulting from enhanced carbonation by fossil CO₂. This approach offers a valuable tool in circular construction strategies.

Alongside published studies, we highlight recent experimental work that further demonstrates potential applications of this method. However, to fully exploit carbon isotopes as a diagnostic tool, several questions remain open. In particular, isotope fractionation during carbonation is not yet fully understood. Key factors of influence include temperature, pH, relative humidity, porosity of the carbonated material and the isotope composition of the CO₂ source. Moreover, differences between aqueous and gaseous carbonation must be evaluated, as they may result in different isotope fractionation. 

Understanding these fractionation mechanisms is essential to establish robust interpretation frameworks for isotope-based approaches in cement and concrete research and applications.