On-demand setting of extrusion-based 3D printing gypsum using a heat-induced accelerator

Abstract

While powder bed binder jetting (PBBJ) based 3D printing of gypsum is industrialized, development of extrusion-based 3D printing of gypsum is still challenging due to fast setting of the material. This study introduced a heat-induced accelerator (HIA) to control gypsum setting on-demand to promote the printability of the extrusion-based 3D printing gypsum. The gypsum was first retarded to acquire pumpability and extrudability, then setting time of retarded gypsum with HIA at different temperature was examined. The hydration heat, TG-DTA, electrical conductivity and viscoelasticity of the gypsum plaster were characterized. Besides, collapse ratio and shape retention index of a 3D printed cylinder were used to evaluate the buildability of the plaster. It was found that HIA had little effect on setting time of retarded gypsum plaster at room temperature, but accelerated hydration and shortened setting time from 65 ~ 75 min to less than 15 min when temperature exceeded 40 ℃. When the temperature further raised to 80 ℃, the collapse ratio decreases from 21.83% to 0.97% and the shape retention index decreases from 25.96% to 1.17%, showing effective on-demand control of setting and shaping for extrusion-based 3D printing gypsum.