(519e) Quantitative Analysis of Hydrogel-Based Cement Pastes for 3D Printing Applications

Robust cement-based printing pastes for extrusion-based 3D printing have been developed using hydrogel-forming polymers. Not all gel-forming polymers, however, produce good outcomes. Gel rheology, pore structure and the nature of confined gel-water are being studied in an attempt to discover physical reasons for printing efficacy. In addition, despite growing interest in 3D printing by the construction industry, there is still a lack of quantitative metrics to assess the quality of 3D printed objects. Three printability metrics were developed to assess deviations from target objectives. Regression analysis were performed to obtain the most influential mix formulation effects. Conjectures based on objective measures of printability and gel and paste rheological characteristics are emerging that could help target better printing aid selection and design. The class of hydrogels explored exhibit time-independent shear stability, a characteristic that may be a pre-requisite for printing aid applications. These particular gels are also highly shear thinning and produce workable, but cohesive pastes when mixed with cement. While notable differences in gel-pore structure and the amount of confined water are quantifiable, it is not so clear how or if these factors are directly related to printability.