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Title: Non-Equilibrium Thermodynamic Modeling Framework for Ordinary Portland Cement/Supplementary Cementitious Material Systems

Author(s): Deborah Glosser, O. Burkan Isgor, and W. Jason Weiss

Publication: Materials Journal

Volume: 117

Issue: 6

Appears on pages(s): 111-123

Keywords: amorphous silica; dissolution kinetics; hydration; ordinary portland cement; supplementary cementitious materials; thermodynamic modeling

Date: 11/1/2020

Abstract:
Thermodynamic modeling is an established tool that can use binder composition to predict reaction products and pore solution chemistry in hydrating cementitious systems. Thermodynamic simulations rely on the assumption that all reactions reach equilibrium; however, reacting systems are inherently dynamic. An established kinetic model exists and is used in conjunction with thermodynamic Gibbs free energy minimization software (GEMS) to provide quasi-equilibrium inputs for modeling hydrating cement clinkers. However, no similar model has existed to explicitly model the non-equilibrium reactions of cement with supplementary materials. Here, a framework to compute kinetic inputs for use in time-dependent thermodynamic calculations of cement/amorphous silica systems is demonstrated. Reaction products, pore solution composition, and pH are modeled and compared with experimental measurements for multiple ordinary portland cement (OPC)/SiO2 binders at varying replacement levels and water contents. The results show that when time-dependent clinker and SiO2 reactions are modeled together, the hydraulic reactions and the pozzolanicity of SiO2 can be accurately predicted.


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