# Development and Evaluation of Nano-Silica Sustainable Concrete
###### Abstract
All durability indicators of the SCC studied (conductivity, chloride migration and diffusion coefficients, and freeze-thaw resistance) were significantly improved with the addition of 3.8% of both types of the nano-silica [16]. Compared to the powder nano-silica SCC mix, the colloidal nano-silica SCC mix showed slightly better performance in terms of durability properties. [PERSON] and [PERSON] [17] studied the behavior of ground granulated blast-furnace slag (GGBS) and nano-silica on the strength properties of concrete. The properties of nano-silica used in this experiment are 23.6 pH (1.08-1.11). It used specific gravity and a 219 nm particle size. Eight different mixes were tested, in which mixes 1, 2, 3, and 4 contained zero nano-silica and 0%, 10%, 20%, and 30% GGBS, respectively, and mixes 5, 6, 7, and 8 contained 1%, 2%, 3%, 2% nano-silica and 0%, 0%, 0%, and 30% GGBS, respectively. Based on the test results, multiple conclusions were obtained. First, mix #8 (30% GGBS and 2% nano-silica) achieved the highest seven-day and 28-day compressive and split tensile strength results. Similarly, mix 8 had the highest flexural strength compared to the other mixes. Second, the SEM test shows that the microstructure of nano SiO\({}_{2}\) concrete was more uniform and compact than the normal concrete [17]. Third, the silica nanoparticles addition improved the pore structure of concrete. [PERSON] and [PERSON] [18] conducted an experimental investigation on the strength properties of concrete containing micro-silica and nano-silica. The properties of nano-silica used in this experiment are 39.5-41% nano solids, 9-10 pH, 1.29-1.31 specific gravity, and milky white liquid texture. Seven different mixtures were tested in which the mixes contain 0, 19, 38, 19, 38, 19, and 38 kg micro-silica and 0, 0, 0, 14.25, 14.25, 28.5, and 28.5 L colloidal nano-silica, respectively. The addition of 1.5% nano-silica to the 5% and 10% micro-silica mixes had better mechanical properties compared to the addition of 3% nano-silica to the 5% and 10% micro-silica mixes. Overall, in terms of its strength performance, the addition of 1.5% nano-silica and 10% micro-silica achieved the highest results compared to the other mixes. [PERSON] et al. [19] investigated the mechanical properties of silica and GGBS incorporated cement mortar. The properties of nano-silica used in this experiment are 2.4 specific gravity, 2200 kg/m\({}^{3}\) bulk density, 640 m\({}^{2}\)/g fineness, and white color. Eleven different mixes were tested consisting of different dosages of GGBS, densified silica fume, and nano-silica. Numerous conclusions were obtained from this experiment. First, the initial and final setting times were directly proportional to the GGBS content. The increase in initial setting time of GGBS incorporated cement paste was higher than the increase of final setting time for cement paste [19]. Therefore, the incorporation of GGBS retarded the initial hydration of cement. Second, the compressive strength of silica added mortar mixes showed good improvement in the early age's compressive strength as compared with the GGBS cement mix [19]. [PERSON] et al. [20] studied the modification effects of a nano-silica slurry on microstructure strength and strain development of recycled aggregate concrete applied in an enlarged structural test. Three concrete groups were prepared in this study, i.e., the commercial natural aggregate concrete (CNAC), the original recycled aggregate concrete (ORAC), and the modified recycled aggregate concrete (MRAC) [20]. For both ORAC and MRAC, the percentage replacement of recycled aggregate was 50%. The strengthening slurry prepared for this experiment contains 100 kg cement, 50 kg water, 1 kg super-plasticizer, and 1 kg nano-silica dispersant. Multiple conclusions were obtained during this experiment.