Foam Stability of 3D Printable Foamed Concrete (2021-12)¶

This study investigates the susceptibility of precursor foam in 3D printable foamed concrete (3DP-FC), particularly in aspects of rheology. The relatively higher yield stress, film liquid withdrawal from unsaturated cement grains and the pumping process raises a concern of considerable foam degradation. Foam stability under the static and dynamic environment is investigated with a wide yield stress range of the base mix (200–1500 Pa) and foamed concrete density range (700–1400 kg/m3) is investigated in this study. No major foam instability was found in the static environment with comparison of various wet-to-dry density and porosity models, while the pumping process caused densification for the higher density 3DP-FC. Other than the gravimetric measurements, the X-ray CT scans were performed to analyse the porosity, sphericity and pore distribution changes between the pre- and post-pumped samples. This paper addresses the effect of fluidity on foam stability due to physicochemical interaction on microstructural level, and the producibility of a stable 3DP-FC with a density as low as 700 kg/m3