MODELING DRYING SHRINKAGE OF CEMENT PASTE AND MORTAR .1. STRUCTURAL MODELS FROM NANOMETERS TO MILLIMETERS

The nanostructure of calcium silicate hydrate (C-S-H) gel contributes to many physical properties of concrete, including the important engineering properties of creep and shrinkage. A set of structural models for this gel and computational techniques for their validation have been developed. The basic nanostructure of C-S-H is conceived as a self-similar agglomeration of spherical particles at two levels (diameters of 5 nm and 40 nm). Computational techniques are presented for simulating transmission electron microscopy images and computing sorption characteristics of the model nanostructures. Agreement with available experimental data is reasonable. The development of these nanostructural models is a first step in a multi-scale approach to computing the drying shrinkage of model cement-based materials. Such an approach will provide a better understanding of the relationships between microstructure and the shrinkage behaviour of these systems.