Date of Award

2013

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Mohan, Dr. Ram

Abstract

Cementitious materials have complex hierarchical structures with random features that range from nanometer (nm) to millimeter (mm) scale. Processes occurring at the nanometer scale affect the performance at larger length scales. The present work employs molecular dynamics (MD) simulations as the computational modeling methodology to predict mechanical properties for both hydrated and unhydrated cementitious materials at the molecular/nano scale level. A detailed study on the effect of increasing MD simulation cell size, dynamics time duration on the predicted mechanical properties was performed. Further studies focused on understanding the effect of higher thermodynamic pressure states on predicted mechanical properties using MD based material modeling. High strain rate behavior of materials undergoing shocks, detonations and other dynamic failure modes are characterized via an Equation of State (EOS) and Hugoniot curves to account for the associated adiabatic effects. A MD modeling methodology for the characterization of Mie Gruneisen EOS and Hugoniot curves based on molecular structures is developed and presented. This method is demonstrated for cement hydrated product (C-S-H Jennite) and the associated adiabatic longitudinal stress – specific volume relationship is developed. This method is based on the assumption that cementitious molecular constituents are confined and subjected to plane longitudinal shock waves. This allows their response to be investigated based on the estimation of shock Hugoniot curves.

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