(174e) Molecular Dynamics Simulations to Study the Tribological Behavior of Gel-Forming Polymers for Cement-Based 3D Printing Applications

Molecular dynamics simulations to study the
tribological behavior of gel-forming polymers for
cement-based 3D printing applications

Hajar
Taheri Afarani¹, Babajide Y Onanuga¹, Venkat
Padmanabahan¹, and Joseph J. Biernacki¹

¹Department
of Chemical Engineering, Tennessee Technological University, Cookeville,
Tennessee

Additive
manufacturing (AM), also known as 3D printing (3DP), offers new horizons to the
construction industry. 3DP in construction promises reduced construction time, elimination
of form work and hence greatly reduced cost, free-form shape and design and
reduced waste.  To make portland cement-based pastes printable, additional
ingredients such as gel-forming polymers are required.  However, not all
gel-forming polymers provide the necessary properties for effective 3D
printing. This work aims to address key questions, including: What molecular
features are critical? What forms of water-polymer-cement interactions are
desirable, and how do gel-forming polymers respond with cement particles under
shear?  To answer these and other questions, molecular dynamics simulations
(MD) of various hydrogels with the (040) surface of the tricalcium silicate
crystal (the primary component of portland cement) were performed. The
distribution of water molecules between two cement surfaces at different
concentrations of gel-forming polymers was characterized and the effect of
shear rate on tribological properties computationally determined.  Finally, the
effect of polymer chemistry on the printability of cement pastes was also
investigated.