Towards Computer-Based Microstructure Models for Cement-Based Systems
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TOWARDS COMPUTER-BASED MICROSTRUCTURE MODELS FOR CEMENT-BASED SYSTEMS
HAMLIN M. JENNINGS Building Materials Division, National Bureau of Standards, 20899
Gaithersburg,
MD
ABSTRACT Computer-based models represent an important development that should provide a scientific basis for in-depth predictions of the behavior of materials. Aspects of microstructure models for cement-based systems are A computer model is described that can incorporate many assumpdescribed. Specific algorithms are selected to solve tions in the form of sub-models. specific parts of the problem. The algorithm chosen depends on specific problem requirements at each stage of calculation, and these problem reAn important part of these quirements may not be anticipated in advance. computer models is that they incorporate a file of numbers, representing the microstructure, which can be operated on to effect an incremental change in the system.
INTRODUCTION There are indications that cement science is likely to be revolutionModelling ized by the development of comprehensive mathematical models. cement-based systems, however, has proven to be particularly difficult because a large number of processes are involved and because many of the processes are incompletely understood. Several recent reviews [1-3] have summarized the mathematical models developed for the kinetics of hydration. There is, however, no general agreement on a conceptual basis for such a model. Some models have several adjustable parameters that have not been As yet, there is no model that can be assigned a physical interpretation. elevated to the status of a theory. A new type of computer model for cement-based materials is being The basis of this type of model is a detailed description of developed. This paper discusses some microstructure during the hydration of cement. features of two [4-6] microstructure models. Because they are in the developmental stage, it is not yet possible to analyze these models comprehensively.
BRIEF BACKGROUND The term model has been introduced into almost every branch of science. An exact definition of a model within the context of scientific investigation is elusive, but generally it is considered to be an alternative, usually simpler, representation of a real object, concept, or process [7]. Study of the model produces information about the original. Models may be An example of a divided into two types [7]: physical and conceptual. physical model is a small boat, which provides useful information for An designing a large boat by testing its performance in a tank of water. example of a conceptual model is a mathematical model that predicts the This has performance of a physical system under many different conditions. been described [3] as a "representation of a system or its components in terms of mathematical formulas." Mathematical models have inputs and outputs that are connected by functional relationships, and when the
Mat. Res. Soc. Syrup. PrOc. Vol. 05. -1967 Materials Research Society
292
relationship between inputs and outputs is conf
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