Kenji Sakata

A study on moisture diffusion in drying and drying shrinkage of concrete

Abstract It is the purpose of this paper to clarify the behavior of moisture existing in concrete as drying occurs, and the relationship between moisture loss and drying shrinkage. Assuming that the behavior of moisture existing in concrete when drying was governed by nonlinear diffusion equation, the diffusion coefficient was expressed as a function of the moisture content by the experiment. The surface factor was also determined by the experiment. The relationship between diffusion coefficient or surface factor and the water-cement ratio of concrete were given. It was shown that the shrinkage strain was closely related to moisture loss.

Influence of urea in concrete

Urea can substantially reduce the temperature of concrete both at casting stage and during hydration process. However, not much is known about what effects urea can likely bring in concrete. In this study the influence of urea in concrete on flowability, heat of hydration, setting time, strength, shrinkage strain, and carbonation resistance are discussed. The results of the experiment show that apart from the fact that urea can reduce the hydration temperature in concrete, it can also enhance both flowability and durability of concrete.