Joseph James Biernacki

This research endeavors to link the physical and chemical characteristics of select polymer hydrogels to differences in printability when used as printing aids in cement-based printing pastes. A variety of experimental probes including differential scanning calorimetry (DSC), NMR-diffusion ordered spectroscopy (DOSY), quasi-elastic neutron scattering (QENS) using neutron backscattering spectroscopy, and X-ray powder diffraction (XRD), along with molecular dynamic simulations, were used. Conjectures based on objective measures of printability and physical and chemical-molecular characteristics of the polymer gels are emerging that should help target printing aid selection and design, and mix formulation. Molecular simulations were shown to link higher hydrogen bond probability and larger radius of gyration to higher viscosity gels. Furthermore, the higher viscosity gels also produced higher elastic properties, as measured by neutron backscattering spectroscopy.

The use of up to 20 % clinoptilolite-Ca zeolite replacement of portland cement was investigated. The as-received Ca zeolite exhibited reduced monosulfate associated heat of hydration. Blended samples had a higher initial chemical dissolution of calcium and aluminate; but subsequently, the consumption of both were higher compared to the neat cement control. Clinoptilolite-Ca zeolite exhibited a transformation into clinoptilolite-Na zeolite in NaOH and NaCl solutions and showed a distinct monosulfate formation heat flow. Micro-chemical analysis suggests a different hydration reaction mechanism for both calcium and sodium-based zeolite along with the possibility of reduction in the formation of C-S-H, ettringite, and monosulfate due to the formation of new hydration products. The clinoptilolite-Ca zeolite consumed higher aluminate forming amorphous calcium-aluminum-silicate-hydrate (C-A-S-H) gels. In contrast, the clinoptilolite-Na zeolite released sodium ions and produced sodium aluminosilicate hydrate (N-A-S-H), and did not interfere with the monosulfate formation reaction.