Accelerating Early Age Properties of Ultra-Low Clinker Cements for Extrusion-Based 3D Printing

In this study, we investigated the influence of commercial sodium nitrate/thiocyanate accelerator compared to calcium sulfoaluminate cement addition on setting time, rheology and reaction kinetics of ultra-low clinker composite cement for extrusion-based 3D printing application. CEM I 52.5 N and a ternary composite cement with 70% clinker replaced by slag and limestone were evaluated. Results indicate that final setting time of 30 min and buildable yield stresses can be attained with less than 5% addition of calcium sulfoaluminate, with ettringite and C-(A)-S-H as main reaction products. This demonstrates the synergy between slag and calcium sulfoaluminate cements can be harnessed to control rheology and hardening. This is significance for evidencing suitability of ultra-low clinker composite cements for extrusion-based 3DCP, thus helping to fulfil its wider potential as a low-carbon concrete technology.