Study on concrete deterioration and deterioration indicators in marine environments

In order to investigate the deterioration of concrete in marine environments, both concrete cores sampled from existing structures and test specimens exposed in an outdoor pool of natural seawater are used. These specimens were examined using the Vickers hardness test and EPMA (Electron Prove Micro Analyzer). The following behaviors were observed: 1) The penetration depth of Mg²⁺ was correlated with both the neutralization depth and the depth of SO₄ ^2- penetration. 2) Deteriorated areas in concrete specimens determined by Vickers hardness were correlated with the penetration depth of Mg²⁺. One reason for this deterioration is considered to be the phase change of C-S-H (Calcium silicate hydrate) to M-S-H (Magnesium silicate hydrate), which has a lower strength than C-S-H. 3) The penetration depth of Mg²⁺ can be an indicator of concrete deterioration progress in marine environments.