Cl- attack resistance of marine concrete with nano-particles under the combined action of flexural fatigue load and freeze-thaw cycles

Abstract

This paper investigated the role of nano-particles in the resistance of marine concrete to chloride ion (Cl-) corrosion under the combined influence of flexural fatigue load and freeze-thaw cycles. We analyzed the nano-particles to improve the mechanism of Cl- attack resistance of the concrete. The results indicated that the combined effect of freeze-thaw cycles and flexural fatigue load promoted the migration of Cl- into the concrete. The free Cl- content in the compressive zone of concrete initially decreased and subsequently increased with the increasing stress level and combined action stage. In the tensile zone of concrete, the free Cl- content increased significantly with the stress level and combined action stage. The nano-SiO2 and nano-CaCO3 could effectively improve the Cl- attack resistance of concrete and the optimal amounts of nano-CaCO3 and nano-SiO2 were 1% and 2% (Nano-particles were substituted for equal amount of cement), respectively. According to the SEM and XRD results, nano-particles could help cement hydrate and lower the size and orientation of Ca(OH)2 in the interfacial transition zone (ITZ). Nano-SiO2 exhibited a good pozzolanic effect, while the pore structure and ITZ of concrete with nano-SiO2 was denser compared to the concrete with nano-CaCO3.