The Damage of Concrete Structures Due to Coupled Moisture Transfer and Drying Shrinkage

The coupling effect of moisture diffusion and drying shrinkage is an important factor in the durability design of concrete structures. The internal damage in concrete due to excessive shrinkage accelerates the diffusion of moisture. On the other hand, the drying shrinkage of concrete occurs due to moisture loss. Thus, drying shrinkage and moisture diffusion are two coupled processes and their interactive effect is very important for the durability of concrete structures. The moisture diffusion is modeled based on Ficks' laws and the drying shrinkage is modeled based on a multiscale method. The effect of drying shrinkage on the moisture diffusion is introduced by the scalar damage model based on the concept of the continuum damage mechanics (CDM). The coupled problem of moisture diffusion and drying shrinkage is solved using a finite difference method. The influential parameters such as water-cement ratio and aggregate volume fraction are analyzed by several numerical applications. In recent years, many researchers have investigated the interactive effect of the mass diffusion and the cracking resulted from moisture gradient, temperature gradient and mechanical loading. All the research work on this area indicated that the microcraking produced during hardening, drying and heating of concrete and the cracking resulted from the mechanical loading could increase the diffusivity and thus, accelerate the mass diffusion process.