Case Study: Measuring Flow and Setting Time for Three-Dimensionally Printed Mortar

The authors explored the influence of ingredients on fluid consistency and setting behavior of mortars for three-dimensional (3D) printing using standard test methods typically employed to monitor postdepositional flow and setting time of pastes and mortar from one to several hours after batching. With minor modifications in method and reanalysis of results, readily available standard tests can characterize some behaviors of plastic mortar as early as half an hour or sooner following printing. The work also showed the behavioral sensitivity of the 3D-printed mortar to changes in ingredients, including conversion of a prebagged commercial mortar mixture to a sand, cement, and lime mixture and isolating the impact of hydrated lime, high-range water reducer, calcium chloride set accelerator, and polypropylene fibers. Fluidity and setting behavior were monitored with the ASTM C1437 mortar flow, ASTM C403 time of setting, modified C403, and ASTM C807 Modified Vicat Needle tests. Keywords: additive manufacturing; mortar; mortar flow; setting; threedimensional (3D) printing.