Effects of CEA on the microstructure evolution and chloride ion migration of marine concrete

• The addition of CEA resulted in the self-healing of partial damage for marine concrete in the later stage. • The effect of CEA dosage on the chloride migration coefficient was significantly weakened and the loss of compressive strength decreased in the later stage. • When the dosage of CEA was no more than 6%, the marine concrete behaved a good volume stability and chloride penetration resistance in the later stage. In this paper, autogenous shrinkage, compressive strength, microstructure evolution and also chloride migration coefficient of marine concrete with CaO-based expansive agent (CEA) were investigated. The results showed that the autogenous shrinkage of marine concrete was effectively compensated by adding CEA, especially in the early stage. However, as the CEA dosage increased to 12%, re-expansion of concrete in the later stage was observed to cause the problem of poor volume stability of marine concrete. The re-expansion of 12% CEA was due to the rehydration of unreacted CEA. While, Ca(OH) 2 produced by CEA hydration accelerated the hydraulic reaction and pozzolanic reaction the of slag in the later stage. As a result, more C-S-H gel was generated to fill the pore and micro-cracks and refine the pore structure, which can partially repair the inner damage of marine concrete in the later stage. Although the chloride migration coefficient gradually increased and the compressive strength decreased with the increase of CEA dosage, the self-healing of partial damage for marine concrete made the chloride ion more difficult transport into the marine concrete. Thus, the impact of CEA dosage on chloride migration coefficient of marine concrete was significantly weakened in the later stage. When the dosage of CEA was no more than 6%, the marine concrete behaved a good volume stability and chloride penetration resistance in the later stage.