Verification Method of Direct Air Capture by Cementitious Material Using Carbon Isotopes

Capturing atmospheric CO₂ into cement-based materials is a way to set off the CO₂ emissions of concrete production. This study proposes an experimental method to track the origin of cement paste that fixes CO₂ directly from the air under natural conditions. By exposing powders of well-hydrated cement paste to air, carbonated cement paste powders are obtained with different carbonation degrees. The inorganic carbon of these carbonated samples is extracted by dissolution in phosphoric acid, and the isotopic characteristics related to ¹³C and ¹⁴C are measured. The experimental results show that the ¹⁴C value of carbonated cement paste can be used as an indicator for tracing the origin of carbon.