Developing improved relationships between microstructure and creep and shrinkage of cement-based materials. Final report for the period September 9, 1998 - July 31, 2000

The shrinkage of concrete that occurs on drying is a complex function of age of concrete, rate of drying, temperature, and composition of concrete. This project investigated the fundamental relationships between microstructure and shrinkage. In order to accomplish this goal a new quantitative image analysis technique was developed to analyze the distribution of strain throughout the microstructure during drying. The technique has been verified at NIST and the results have provided new insights. A major result of this effort has been the redefinition of microstructure of cement paste. Large deformations, both expansive and compressive, occur throughout the microstructure. These large deformations can be best explained by considering the calcium silicate phase to be a colloid. A new model for calcium silicate hydrate was developed