Resumen de Assessment of chloride corrosion in steel fibre reinforced cementitious composites
High performance steel fibre reinforced cementitious composites (HPSFRCCs) show enhanced structural performance and durability. The improved properties favour its use in agressive conditions (such as marine environment) prone to corrosion. Despite the remarkable advances in the knowledge about corrosion of conventional reinforced concrete structures, questions still remain about its effects on the durability of HPSFRCC. The governing mechanisms of corrosion, the presence of cracks, the high steel fibre content, and the long-term chloride exposure still need to be properly evaluated. Given the increased application of HPSFRCC with structural responsibility and the high steel fibre content commonly used in the mixes, it is of great importance to understand the main mechanisms governing the chloride corrosion and its effects on the durability of the real-scale structures constructed with the material. To overcome these barriers and the uncertainty mentioned, this doctoral thesis adresses the following key issues: the effect of chlorides in uncracked HPSFRCCs under constant conditions; the influence of chloride corrosion in uncracked HPSFRCCs under wet-dry cycles with chlorides; the effect of corrosion in pre-cracked HPSFRCCs subjected to the same cycles and the proposal of a simplified model to consider the structural effects of corrosion. The first subject concerns the assessment of chloride corrosion on the aesthetic aspect and on the mechanical behaviour of HPSFRCCs by means of an accelerated test. For that, HPSFRCCs specimens with and without chlorides added to the mixes and with different fibre contents were tested. The preliminary experimental programme shows that, in general, the chlorides produce a level of surface corrosion with aesthetic consequences but have small influence on the mechanical performance. In the second subject, the influence of cycles was assessed in accelerated tests with uncracked HPSFRCCs prisms. The results reveal that, for uncracked HPSFRCCs elements, the corrosion affects the surface aspect but has no influence on the post-cracking response. The third subject focuses on the analysis of pre-cracked HPSFRCCs prisms under cyclic chloride exposure, considering different pre-crack widths and fibre contents. The study shows that the corrosion affects significantly the mechanical behaviour of the fibres for all specimens. The last subject covers a proposal of a simplified model to consider the effect of corrosion in the ULS design of HPSFRCC elements under cyclic chloride exposure. The model proposed was capable of reproducing the influence of the corrosion process over the cycles, being compatible with the current philosophy proposed in codes for the design of HPSFRCC structures.
