Enabling carbon dioxide mineralization and active set control in portlandite-based cementitious suspensions

The real-time control of concrete's stiffening allows users to better control pumping and extrusion during 3D-printing processes. Here, a portlandite-based cementitious formulation (i.e., slurry or suspension) that features the potential for rapid CO₂ uptake is adapted for 3D-printing applications. In particular, we showcase a portlandite-fly ash binder system combined with a thermoresponsive polymer, wherein precise control via thermal activation allows set control and rapid solidification. Through the thermally induced polymerization of polyacrylamide, the hybrid binder system rapidly undergoes stiffening at trigger onset temperatures ranging from 60 °C to 80 °C, exhibiting average stiffening rates of up to 2600 Pa s⁻¹. The addition of fly ash is noted to extend the open time, reduce the yield stress, and improve pumpability. The polymerization process contributes to initial strength gain. Subsequently, portlandite's carbonation and fly ash's pozzolanic reaction enhances mechanical strength. By combining set control and CO₂ mineralization, this work pioneers the development of CO₂-cured 3D-printed construction materials.