Shrinkage, cementitious paste volume, and wet packing density of concrete

Abstract

AbstractShrinkage of concrete refers to the volumetric change of concrete due to cement hydration (i.e., self‐desiccation) and environmental drying (i.e., water evaporation). It creates dimensional instability and induces tensile stress when the concrete is restrained that may be large enough to cause cracking. The most fundamental way to mitigate concrete shrinkage is to decrease the shrinkage of cementitious paste in the mix design. Some major factors of concrete mix design affecting the shrinkage include water‐to‐cementitious material (W/CM) ratio, dosage of superplasticizer (SP), concrete strength, and cementitious paste volume (CPV). While the effects of concrete strength and CPV on shrinkage are straightforward, those of W/CM and SP are more complicated because they also affect the pore size and distribution that influence the moisture movement. In this paper, it is advocated to study the concrete shrinkage by its wet packing density (WPD). Considering that the shrinkage of concrete is associated with the moisture movement in capillary pores and that the WPD accounts for the void ratio in fresh concrete, it will be shown in this paper that the shrinkage can be correlated negatively to the WPD with the consideration of CPV. The paper thus provides a new insight to the interdependence amongst shrinkage, CPV, and WPD of concrete.