The effect of Caspian Sea water on mechanical properties and durability of concrete containing rice husk ash, nano SiO2, and nano Al2O3

Various studies have been recently conducted aiming at developing more sustainable cementitious systems so that concrete structures may not have a negative effect on the environment and are decomposed. It has been attempted to build sustainable binders by substituting silica fume, cement with fly ash, nano-silica, nano-alumina, and rice husk ash. In this paper, a series of experiments on concrete with different contents of rice husk ash (10%, 15%, and 20%), nano SiO2 (1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%), and nano Al2O3 (1%, 2%, 3%, 4%) are performed to analyze the durability and mechanical properties of samples under the curing condition of Caspian seawater. The workability, density, water penetration, chloride ion penetration, and compressive strength (at 7, 14, 28, and 90 day) of the samples were determined. The experimental results showed that workability decreased gradually with increasing additives content, while the compressive gradually increased. Among the additives, adding 8% of the nano SiO2 had the most significant effect on the improvement of compressive strength. Adding 8% nano SiO2 and 4% nano Al2O3 reduced the depth of water permeability by 53% and 30%, respectively. Furthermore, adding 8% nano SiO2 reduced chloride ion penetration by 85%.