New method to investigate the permeability of stressed concrete

Permeability is the most important property of concrete governing the strength and long term durability. The coefficient of concrete permeability can be significantly affected by pore structure developed due to concrete composition. It is also influenced by the interconnectivity of those pores and micro cracks. Even though an extensive research work has been performed in the aspects of porosity and cracking effect, the investigations based on how the concrete microstructure, as a 3-phase material (i.e. aggregate-cement paste-Interfacial Transition Zone (ITZ)), could affect the permeability when subjected to loading is at scarce. In particular, ITZ, which is said to be the weakest link of concrete, can play a significant role in determining the changes to concrete permeability during the operational life cycle of a structure. The current study investigates how the behaviour of ITZ, due to an applied load could affect the concrete permeability using numerical analysis. A new method has been proposed to investigate the permeability of stressed concrete. A two dimensional Finite Element (FE) model has been developed of the 3-phases including their interactions to investigate how the operational loads on the structure can impact the failure of ITZ and hence the changes in concrete permeability. Aggregates of similar size are randomly placed at arbitrary locations with surrounded ITZs of constant thickness. The outcomes from the study reveal that the adopted modeling approach is effective when estimating the concrete permeability changes induced by applied loads. The proposed methodology can be useful for developing a closed form solution for permeability against the applied loading.