Examining the relationship between the microstructure of calcium silicate hydrate and drying shrinkage of cement pastes

Cement paste undergoes a volumetric contraction called drying shrinkage when placed in a low relative humidity (RH) environment. Only a portion of this shrinkage is reversible upon rewetting. In order to understand better the mechanisms responsible for the irreversible portion of drying shrinkage, a quantitative comparison was made between shrinkage values and microstructural properties of cement pastes. Drying shrinkage, surface area and pore volume were manipulated using curing temperature and chemical admixtures. It was observed that total and irreversible drying shrinkage increase with surface area and pore volume as measured by nitrogen (1-40 nm pore radius range), when degree of hydration and water-to-cement ratio (w/c) are held constant (0.55 and 0.45, respectively).