Chloride penetration and material characterisation of carbonated concrete under various simulated marine environment exposure conditions.

Concrete carbonation has an important influence on chloride penetration. The chloride distribution profiles found in carbonated concrete are often different from those found in uncarbonated concrete even when they have the same exposure conditions. In this paper we present an experimental study on chloride penetration in carbonated concrete specimens when they are subjected to stationary, splash, submerged, and pressured exposure conditions. Free chloride concentration profiles were measured in the specimens to examine the effect of carbonation and exposure condition on chloride diffusion. In addition, material characterisations were carried out using x-ray radiography imaging tests and thermogravimetric analysis to understand the influence mechanism of concrete carbonation on chloride penetration in concrete. The experimental results showed that the chloride distribution curve in carbonated concrete exhibits a second peak under marine exposure conditions. The exposure condition can significantly affect the position and value of the second peak point in the profile. It is also shown that concrete carbonation can drastically change the distribution of pores in concrete, leading to a sudden change in porosity, which is the reason for the carbonated concrete to have the zone-dependent chloride variation profiles. • The chloride distribution curve in carbonated concrete exhibits a second peak under marine exposure conditions. • The exposure condition can significantly affect the position and value of the second peak point in the profile. • The different carbonation zones can be identified based on the distribution curve of the calcium carbonate. • Change in porosity caused by carbonation leads to a zone-dependent chloride variation profiles. [ABSTRACT FROM AUTHOR]