Study on the durability of marine concrete with nanoparticles under the coupling action of bending fatigue load, dry-wet cycles and Cl−corrosion

The combination of multiple factors in the marine environment will accelerate the corrosion of concrete structures. Unlike earlier studies, who employed alternate experiments to evaluate the endurance of marine concrete with nanoparticles under the combined impacts of bending fatigue load, dry-wet cycles, and Cl- erosion, this paper integrates three elements in each cycle to accomplish the effect of coupling. The dry-wet cycle test of the optimal amount of nano-concrete was simulated in seawater with a concentration of 5% NaCl solution and bending fatigue loads at stress levels of 0.5, 0.6, 0.7 and 0.8 were applied. X-ray diffraction was used to observe the physical phases of the concrete before and after the experiment and to analyse the reasons for the increased durability of the concrete. The results indicated that the nanoparticles enhance the resistance to Cl- erosion during dry-wet cycles and bending fatigue load by making the nano-concrete more durable under the coupling impact of bending fatigue load, dry-wet cycles, and Cl- erosion. The improvement effect is the most obvious when the nano-TiO2 content is 1% and the improvement effect is most obvious when the nano-SiO2 content is 2%, and the improvement effect is better when the nano-TiO2 content is 1% than when the nano-SiO2 content is 2%. In comparison to the compressive zone of concrete, the free Cl- in the tension zone is larger. Microscopic tests showed that nanoparticles increase the content of hydrated calcium silicate in concrete, change the orientation of calcium hydroxide and improve the durability of concrete.