Evaluating the Effect of Methyl-Cellulose on Hardened State Properties in Selective Cement-Activation (2022-06)¶

Compared with other 3D printing techniques used in construction, particle bed 3D printing by Selective Cement Activation (SCA) offers unique possibilities regarding the fabrication of high-resolution and freeform components. The printed geometry is determined by the fluid distribution in the particle bed, consisting of a dry mixture of fine aggregates and cement. The fluid intrusion behaviour and thus the shape accuracy of the printed object can be actively controlled by adding additives such asmethyl cellulose (MC) to the particle bed. In this research the goal is to fundamentally understand the effect ofMCvarying in degree of polymerization (DOP), size and dosage on hardened state properties of SCA printed objects. Therefore, dissolution experiments of MC in the rheometer, capillary induced fluid intrusion into the particle bed as well as printing experiments are conducted. As hardened state properties of printed components, geometric precision, density as well as compressive strength are assessed. It was found that MC granules in the particle bed increases the geometric precision and the mechanical performance of SCA objects to a certain extent. This is explained by a modified fluid intrusion behaviour in the particle bed. Here, the effect of the DOP is low compared to the effect of the particle size of the dry granules and the amount of MC. When using too much MC, the geometric precision is not further increased while the mechanical performance even decreases, which is attributed to an increase in porosity in the printed specimen.