The effect of statistical fluctuation, finite size error, and digital resolution on the phase percolation and transport properties of the NIST cement hydration model

• Published in: Cement and concrete research 2001-10, Vol.31 (10), p.1501-1514
• Main Authors: Garboczi, E.J., Bentz, D.P.
• Format: Article
• Language: English
• Subjects: Applied sciences; Buildings. Public works; Cement concrete constituents; Cements; Electrical properties; Exact sciences and technology; Hydration; Hydration products; Materials; Miscellaneous; Modeling; Properties of anhydrous and hydrated cement, test methods; Structural analysis. Stresses; Transport properties
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/S0008-8846(01)00593-2

The National Institute of Standards and Technology (NIST) cement hydration model starts with a three-dimensional digital image of cement particles, and then uses cellular automaton rules to simulate the reaction of cement with water and the development of cement paste microstructure. This stochastic model uses a digital image with a certain resolution to represent the reality of continuum shapes in a fairly small periodic unit cell. As such, it is potentially subject to statistical fluctuation, finite size error, and the effects of digital resolution. This paper evaluates the model in light of these potential sources of error, along with the effects of cement particle size distribution (PSD), water/cement (w/c) ratio, and cement chemistry, by focusing on the phase percolation and transport property predictions of the model. Statistical fluctuation and finite size error are shown to be of minor importance in the model. The effect of digital resolution is significant, however, but different from the case of a finite element or finite difference model. Unlike these cases, the “best” resolution is not necessarily the finest resolution, but must be chosen based on comparison with experiment and various physical length scales present in cement paste.