An implicit consideration of fluid flow in the calculation of drying shrinkage of porous materials: Case of saturated concrete in low humidity environment.

The drying shrinkage of porous materials is significantly dependent on external relative humidity (RHe$RH^{e}$). The perspective of temperature increase due to the climate change will accentuate the drying phenomenon in structures in lands and cities. The evolution of shrinkage can be determined by equivalent pore pressure consisting of capillary pressure Pc$P_c$, disjoining pressure and pressure caused by interfacial energy. For concrete structures, up to RHe=70%$RH^{e}=70 \%$ condition, standard models can reproduce the drying shrinkage experiments accurately. However, as the RHe$RH^{e}$ decreases to 30%, these models seem to be limited because the measured relationship (Pc−Sw${{P}_{c}}-{{S}_{w}}$) differs from the corresponding static equilibrium relationship as the drying occurs rapidly and the dynamic fluid flow effects on capillary pressure have been neglected. In this paper, the standard shrinkage model has been improved to take into account the dynamic flow effect and the viscoelastic behaviour of the solid skeleton. The dynamic and standard models have been compared with experimental results of drying shrinkage of concrete with two different relative humidity conditions. The standard model clearly showed its limitations at low external relative humidity RHe=30%$RH^{e}=30 \%$. However, the dynamic model showed good prediction of mass loss and shrinkage strains at high and low humidity conditions. Furthermore, the numerical and experimental investigations indicate that not only the dynamic effects but also the additional pressure induced by surface energy should be taken into account to quantify the drying shrinkage of cement‐based materials at low RHe$RH^{e}$ condition. [ABSTRACT FROM AUTHOR]