Can the dual-permeability model be used to simulate unsaturated moisture flow in damaged mortar and concrete?

Abstract

Moisture is one of the main contributors to the majority of the deterioration processes that occur in reinforced concrete structures. Moisture ingress, very often, occurs in unsaturated concrete structures. In addition, some level of damage is usually present in structural concrete, for example, due to mechanical or environmental loading. Therefore, for a more accurate service life prediction of reinforced concrete structures, methods for modeling unsaturated flow in damaged cement-based materials are needed. Previous works have shown that the classical isothermal unsaturated flow modeling fails to adequately describe the long-term moisture ingress in damaged cement-based materials since this method of modeling neglects air diffusion/dissolution and does not explicitly account for the matrix-fracture interaction. In the present paper we (1) investigate whether the dual-permeability modeling approach can be used to more accurately model unsaturated moisture flow in damaged cement-based materials especially at later stages of moisture ingress, (2) propose methods of obtaining the transport modeling parameters of the fracture phase that cannot be directly measured, and (3) propose a model for moisture transfer coefficient across matrix-fracture interface and discuss the effect of this parameter on the results. We compare the results of dual-permeability and classical isothermal modeling against experimental results for damaged mortar and concrete. Finally, we discuss modeling challenges that may arise in applications of the dual-permeability model in simulating unsaturated moisture flow in damaged mortar and concrete.