Rheological parameters and building time of 3D printing sulphoaluminate cement paste modified by retarder and diatomite

Recent advances have proposed new requirements on the controlling of the hydration, the rheology, and the structural build-up of 3D printing (3DP) sulphoaluminate cement (SAC) paste. In this study, the boric acid (BA), the sodium gluconate (SG), and the diatomite were used to control these behaviors of 3DP SAC paste, and the printed structures could be well built based on the extrusion system. The results show that the building time and printability can be improved by the introduction of BA and SG into SAC paste, but the excessive dosage will cause the structural failure. To decrease the structural deformation of 3DP SAC paste, the diatomite was applied to increase the static yield stress and elasticity modulus. Meanwhile, a paste sample with the structural deformation less than 10% can be achieved when the static and dynamic yield stress was controlled in the range of 590-895 Pa, and 509-722 Pa, respectively. In conclusion, the 3D printed structures and rheology could be well controlled by the introduction of retarders and diotomite in the 3DP SAC paste. (C) 2019 Elsevier Ltd. All rights reserved.