Set-On Demand Concrete by Activating Encapsulated Accelerator for 3D Printing (2022-06)¶

In-line activation of cementitious materials by introducing the accelerators at the print head is a promising solution to attain the conflicting rheological requirements in 3D concrete printing. However, there are many challenges associated with this technique including, difficulty in achieving good mixing homogeneity, formation of dead zones during in-line mixing etc. This study investigates a method to attain in-line activation of cementitious materials by encapsulating the accelerator and introducing it in the initial mixing. This is followed by thermal activation at the printing head to destroy the encapsulation and subsequently mix the accelerator with the cementitious materials. Agelatine-based capsule was used as the shell material for the encapsulation, which dissolves when the temperature is exceeded above 30 °C. The encapsulated accelerator was used at different dosages and the fresh properties of 3D printable mixes were assessed. The results showed that the in-line activation of encapsulated accelerator at 2.5 wt% dosage transformed the highly pumpable fresh concrete to a stiffened concrete with high yield strength development. For instance, the yield strength of concrete after activation was increased by fivefold, compared to control printable mix (CPM).Meanwhile, before activation, the fresh concrete mixes with encapsulated accelerator showed excellent flowability for long durations.