Effectiveness of techniques for the appraisal of degradation of concrete exposed to a marine environment

Abstract

Reinforced concrete is widely used for the construction of marine structures for it is a costeffective material with inherent mechanical and durability properties that make it appealing to use for construction in this hostile environment. Notwithstanding that different means could be used to increase the structure’s durability, parts of the structure could still start showing signs of degradation early during its service life, since aggressive ions, such as chlorides and carbonate, marine organisms, and temperature fluctuations of the marine environment accelerate the degradation of these structures. Consequently, an appraisal of the structure would be required to analyse the progressive severity of the degradation and to determine whether the structure could still be of service. Hence, this study intends to survey the effectiveness of techniques, selected for an appraisal of a concrete structure. Besides, this study endeavours to highlight the indicative factors of these tests and techniques, such as their possibilities and limitations, amongst others. These indicative factors are beneficial to select the appropriate techniques to obtain the most effective and reliable information from the appraisal. The techniques, reviewed in this study, comprise of Non-Destructive techniques and Destructive techniques, as well as Laboratory tests that further supplement the findings from the visual inspection. Furthermore, the effectiveness of the above-mentioned tests and techniques will be tested on the Terminals of the Malta Freeport for a practical on-site appraisal of a marine structure. This harbour structure has been expanded by various extensions and construction of new terminals since its establishment in the late nineteen-eighties. Therefore, this structure was chosen not only because it needs an appraisal to monitor the effects of deterioration mechanisms but also for it provides the opportunity of testing the effectiveness of these techniques on Terminals, which were constructed at different ages, using various concrete mixes, and exposed to different marine exposure zones. The effectiveness of the NDTs and DTs was tested further on concrete test slab specimens, cast using a known mix. These concrete test slab specimens deliberately included steel reinforcement with variable spacing, voids and delaminated areas, of which their locations and specifications were known. The results, obtained from this study, recommend that multiple techniques should be selected rather than one technique on its own for a combination thereof produces a more effective and reliable appraisal of a marine concrete structure.