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 engin eering properties of creep and shrinkage. A set of structural models f or this gel and computational techniques for their validation have bee n developed. The basic nanostructure of C-S-H is conceived as a self-s imilar agglomeration of spherical particles at two levels (diameters o f 5 nm and 40 nm). Computational techniques are presented for simulati ng transmission electron microscopy images and computing sorption char acteristics of the model nanostructures. Agreement with available expe rimental data is reasonable. The development of these nanostructural m odels is a first step in a multi-scale approach to computing the dryin g shrinkage of model cement-based materials. Such an approach will pro vide a better understanding of the relationships between microstructur e and the shrinkage behaviour of these systems.