Natural fibre-enhanced CO2 transport and uptake in cement pastes subjected to enforced carbonation

Mineral carbonation is an effective CO 2 sequestration approach and can be applied to cement-based materials through enforced carbonation curing. To accelerate this process, this study investigated the use of natural fibres (hemp, jute, cotton, and wool) to enhance CO 2 transport in cement composites. Spun fibre yarns were added to cement pastes and subjected to enforced carbonation (20 vol% CO 2 ) at 25 °C and 1 atm for 24–168 hours. Carbonation profiles were evaluated using two methods: phenolphthalein indicator coupled with image analysis, and thermogravimetric analysis (TGA). A novel image analysis method, based on colour deconvolution of phenolphthalein-stained images, was developed. Results from this method were consistent with those from TGA, offering a reliable and rapid technique for quantitatively assessing carbonation profiles of cement-based materials. The results confirmed that the natural fibre yarns created preferential CO 2 transport pathways to facilitate CO 2 uptake. Hemp yarns led to the most significant acceleration of CO 2 transport, with carbonation fronts reaching 50 mm depths within 24 hours. Samples without fibres only showed superficial carbonation at the exposure surface. The findings of this study indicate the feasibility of using natural fibres to improve CO₂ sequestration in cement-based materials. • Spun natural fibre yarns can achieve targeted CO 2 transport and mineralisation in cement paste samples. • The porous structure of natural fibre yarns enhances the surface area for CO 2 mineralisation and increases CO 2 uptake. • A novel image analysis method is developed to quantify carbonated areas in phenolphthalein-stained cement pastes.