# Development and Evaluation of Nano-Silica Sustainable Concrete
###### Abstract
First, mechanical properties of ORAC and MRAC, i.e., the compressive strength and the splitting strength, were inferior to those of CNAC, given the mixture proportions employed in this study, i.e., the dosage of water, cement, and aggregates were kept the same among the three concrete groups [20]. Second, at an early age (before 28 days), the resistance of CNAC to shrinkage caused by deformation in the target beam was found to be inferior to ORAC and MRAC. However, after 90 days, CNAC showed long-term superiority to ORAC and MRAC in its deformability against loads, given the loads applied to the target beams similar [20]. Third, the employed nano-slurry had verified a beneficial role in the deformability against shrinkage and loads of MRAC, which were applied in RC beams in a real project. [PERSON] et al. [21] studied the modification effects of nano-silica on the interfacial zone in concrete. At macro-scale level, compressive and flexural strength tests showed that the addition of nano-silica is beneficial for the improvement of the interfacial transition zone (ITZ) performance in particular [21]. On the other hand, at the micro-scale level, the addition of nano-silica accelerated the hydration process, which played a major role in improving the interfacial transition zone (ITZ) at an early age. [PERSON] et al. [22] studied the nano-modified fly ash concrete as a repair option for concrete pavements. Numerous outcomes were obtained from this research. The incorporation of 6% nano-silica in concrete with up to 30% fly ash significantly shortened the dormant period and accelerated the rate of hydration reactions, which discounted some of the retarding effect of class F fly ash on the rate of hardening concrete [22]. Furthermore, the addition of nano-silica improved the early-age and the long-term compressive and tensile strength. Moreover, it refined the pore structure of the fly ash concrete. Hence, the nano-modified fly ash concrete presented a viable option for a suite of repair applications in concrete pavements [22]. [PERSON] and [PERSON] [23] conducted an experimental study on nano-silica improving concrete durability of bridge deck pavements in cold regions. The materials used in the study were OPC grade 42.5, fine aggregate, coarse aggregate, water reducer agent, defoaming agent, and nano-silica. The technical parameters of the used nano-silica are 15 nm average grain diameter, 99.5% purity, globospheric crystal form, 300 m\({}^{2}\)/g specific surface area, 0.05 g/cm3 apparent density, and white color. It was found out that the addition of nano-SiO\({}_{2}\) in bridge deck pavement concrete improved the durability of the concrete effectively, prolonged the service life of the bridge deck pavement, reduced the early onset of damage to bridge deck pavement, and reduced repair and maintenance costs; consequently, using it has significant social and economic value [23]. Furthermore, the incorporation of nano-silica greatly improved frost resistance, resistance to CI\({}^{-}\) ion permeability, and abrasion resistance of concrete. Nano-silica incorporated into concrete effectively absorbed Ca(OH)\({}_{2}\), which is released in the early stage of hydration of cement and increased the content of hydrated calcium silicate, which improved the interface between the hardened cement paste and aggregate [23].