A comprehensive review of cementitious composites modified with nano silica: Fabrication, microstructures, properties and applications.

• Evaluate the nano silica (NS) types, dispersion methods and fabrication methods of utilizing NS in cementitious composites. • A small content of NS can significantly enhance the mechanical properties and durability of cementitious composites. • NS can also improve the multifunctional properties of cementitious composites. • The modification mechanism of NS on cementitious composites is nano-core effect. • NS has a potential to develop the low carbon cementitious composites. To reduce the life-cycle carbon emissions of cementitious composites, potential pathways are to use more low-carbon raw materials, enhance the composites' performance and further extend the service life of their structures. Nano silica (NS), dividing into powder and colloid, and colloidal NS is less harmful to human than that of powdery NS. NS holds nanomaterial characteristics, pozzolanic activity, and more reactive compared with traditional supplementary cementitious materials (SCMs). Therefore, a small content of NS can significantly improve in the mechanical properties, durability, and multifunctionalities, expected to achieve carbon emission reduction of cementitious composites. This paper provides a comprehensive review on the fabrication (NS, mix proportion, and fabrication method), microstructures (hydration products and microstructures), and properties (early performance, mechanical properties, durability, volume stability and functional properties), and applications of cementitious composites modified with NS. The paper also concludes with an outline of some future risks, challenges, and future development of cementitious composites modified with NS. [ABSTRACT FROM AUTHOR]