Reference: Reprinted from Innovations in Portland Cement Manufacturing, Chapter 10.3, J.I. Bhatty, F.M. Miller and S.H. Kosmatka, eds., Portland Cement Association, 5420 Old Orchard Road, Skokie, IL 60077, pp. 1311-1331 (2004).PDF Version of Original Paper
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Cementitious materials, including cement paste, mortar, and concrete, possess great chemical and
structural complexity. Chemically, cement pastes contain many chemical components and mineral
phases. Many of these phases can be amorphous or poorly crystalline, with metastable solid solution
compositions varying over a fairly wide range. Dozens of chemical hydration reactions may
occur simultaneously at rates that vary from region to region within the material. Structurally, a
cementitious material is a random composite structure on length scales from nanometers to
millimeters, and the contrast in various physical properties among the different composite phases
is often quite large. One would be hard pressed to find a system that even approaches this range of
complexity from among other classes of engineering materials such as ceramics and metals.
Figure 10.3.1. Pictorial representation of the current VCCTL software modules, showing the range of input specifications and predicted properties.
One consequence of this complexity is that the hydration, properties, and long-term field performance of cement and concrete are difficult to predict; simple empirical relations cannot be universally applied with confidence. As a result, mix design and optimization for tailored applications is a long, arduous, and expensive proposition.
A promising alternative is to use scientifically based models to guide testing and development efforts. To be accurate and reliable, such models must account for all the relevant chemistry and physics that influence cementitious systems. Because of the complexity of these materials, these models must take the form of computer simulations. Computer hardware has advanced to the point that sufficient computational power for most relevant simulations can be obtained on a standard personal desktop computer. Therefore, computer modeling potentially could supplant much of the current empirical design and testing procedures with relatively inexpensive and quick simulations. Computer modeling applied to materials is usually called "computational materials science," which is a term that will be used extensively throughout this chapter. What is meant by "computational materials science of concrete" is this: computer-based models of microstructure at the relevant length scale, operated on by algorithms that give accurate measures of physical properties.