Durability of concrete with nano-particles under the influence of both Cl- penetration and alkali aggregate reaction

Abstract:

In marine environment, chloride-ion (Cl^-) penetration and alkali aggregate reaction are important factors affecting the durability of concrete. In this paper, an appropriate amount of nano-SiO₂ or nano-Al₂O₃ was added to ordinary marine concrete to study the durability of concrete with nano-particles under the combined influence of Cl^- penetration and alkali aggregate reaction. The experimental results showed that Cl^- penetration and alkali aggregate reaction promoted the durability of the concrete mutually. Nano-SiO₂ or nano-Al₂O₃ of different amounts could inhibit the Cl^- penetration and alkali aggregate reaction of concrete to different degrees so that the durability of the concrete under the interaction of the two factors was improved. The optimum amount of nano-SiO₂ and nano-Al₂O₃ in concrete was both 2.0%. When the total content of Cl^- in concrete was basically stable, the total amount of Cl^- in concrete with nano-SiO₂ or nano-Al₂O₃ was decreased by 18.04% and 11.60%, respectively. In the 39th week, the expansion rate of concrete with nano-SiO₂ or nano-Al₂O₃ was reduced by 28.75% and 16.87%, respectively. The addition of nano-particles could improve the pore structure of concrete, enhance the Cl^- penetration resistance of concrete, inhibit the generation of Friedel’s salt, thereby mitigating the expansion of concrete. Additionally, nano-particles can promote secondary hydration of cement, reduce the aggregation degree of Ca(OH)₂ crystal in the transition zone, and restrain the formation of CaCl₂ complex compound and alkaline environment required for alkali aggregate reaction.