Permeability of concrete with fiber reinforcement and service life predictions

Abstract

In the context of its long-term durability, permeability of concrete to water remains one of the most important characteristics. In the study reported here, water permeability of plain and fiber reinforced concrete (FRC) was measured with and without an applied compressive stress. For the stressed specimens, two levels of the applied stress, 0.3f _u and 0.5f _u , where f _u is the ultimate strength of concrete in compression, were investigated. A collated cellulose fiber at volume fractions of 0.1, 0.3 and 0.5% was used. Results indicate that for the unstressed concrete, fiber reinforcement reduces the permeability. For the stressed concrete, initially as the applied stress was increased, a reduction in the permeability for both plain and fiber reinforced concrete was observed. This reduction, however, occurred only to a certain threshold value of stress. Beyond this threshold, a rapid increase in the permeability occurred for plain concrete. For fiber reinforced concrete, while an increase in the permeability was noticed beyond the threshold value of stress, the magnitude of the increase remained small and the permeability remained well below the unstressed level. In the later part of the paper, some Service Life Predictions were carried out by first relating the measured permeability coefficients to chloride diffusion coefficients and then using available mathematical models. Results from the modeling exercise indicate that at least in qualitative terms, fiber reinforced concrete will depict a better durability in service than plain concrete.