Investigation on water absorption in concrete after subjected to compressive fatigue loading.

• The cumulative water content rises when loading cycles and stress level increase. • An improved test apparatus is used to record in real time the cumulative water absorption of specimens after fatigue loading. • The initial sorptivity and secondary sorptivity increases generally with an increase of loading cycles and stress level. • A theoretical model for predicting water absorption of concrete damaged by compressive fatigue loading is developed in terms of the residual strain. For reinforced concrete (RC) structures in coastal regions, fatigue loading is a common loading type, which has the potential to progressively promote micro-cracks generation and development, and in turn, greatly to facilitate the water and aggressive agents (such as chloride and sulfate ions, which are usually sucked by water) penetration in concrete. Therefore, it is imperative to investigate the behavior of water movement in concrete after fatigue loading. This paper presented an experimental investigation on the influence of fatigue stress level and loading cycles, which may induce different degree of damage for concrete, on the transport rate and volume of water absorbed by concrete after compressive fatigue loading. The residual strain was measured by strain gauges to represent the damage evolution of concrete and estimate the water absorption in concrete under cyclic loading. Moreover, the cumulative water content of specimens under fatigue loading was recorded in real time through an improved test apparatus. The results show that the residual strain and cumulative water content of concrete increase with the increase of stress level and loading cycles. The initial and secondary sorptivities, i.e., the slope of the two linear parts of the cumulative water content-time1/2 curves, both increase dramatically when stress level and loading cycles increase because of the development of the cumulative pore volume in concrete corresponding to various pore radius. In addition, a theoretical model for predicting water absorption of concrete damaged by compressive fatigue loading was developed in terms of the residual strain, which shows good agreement with experimental data. [ABSTRACT FROM AUTHOR]