Drying Behavior of 3D Printed Cementitious Pastes Containing Cellulose-Nano-Crystals (2022-06)¶

This study uses neutron radiography to evaluate the drying of printed cement paste samples containing cellulose nanocrystals (CNCs). CNCs have previously been used in printed cement paste to decrease the extrusion pressure and increase the degree of hydration (DOH) of the samples. Three different mixtures were prepared consisting of a plain mixture and mixtures containing two different types of CNCs. The influence of the sample surface to volume ratio (S/V) on the drying of cement paste samples and their DOH was examined. Exposing 3D printed samples to drying immediately after preparation can lead to high levels of water evaporation, which can limit the hydration evolution in the system and increase the porosity. The DOH and the drying behavior of cement paste are found to be dependent on the S/V of the element. The DOH decreased with an increase in the S/V of the sample. The addition of the CNCs to the mixture design did not substantially alter the DOH of poorly cured 3D printed samples. Previous work has shown that CNCs addition to the mixture design can lead to an increase in DOH only if water remains in the sample.