Microstructure and chemical properties for CO2 concrete

Mineralisation of CO2 into cementitious materials improves upon material quality by densifying and reducing water absorption of such materials whilst permanently imprisoning CO2. This paper aims to semi-quantitatively and qualitatively demonstrate ability of CO2 injection on microstructure and chemical composition of concrete, cement and recycled aggregate. The injection of CO2 into recycled aggregate creates CO2 Aggregate. Furthermore, the mixing of CO2 aggregate into concrete is referred as CO2 Concrete. The investigations utilise in the completion of objective include concrete petrography, scanning electron microscopy, x-ray diffraction and thermogravimetric analysis. The petrography as well as scanning electron microscopy reveal that the carbonation treatment, or carbon-conditioning, of recycled aggregate greatly increases the amount of calcium carbonate when compared alongside untreated recycled aggregate or the fresh cement paste CO2 Concrete itself. The x-ray diffraction semi-quantitatively demonstrates that a lower carbonation pressure of 25 kPa and a longer duration of 120 min produces the greatest amounts of calcium carbonate crystals. This paper provides insight on the mineralisation of CO2 into cementitious materials, which provides a great opportunity to create sustainable concrete products