Properties of ultra-lightweight cement composites with nano-silica

Abstract Nano-silica was used to improve the microstructures, mechanical properties and durability performances of ultra-lightweight cement composites (ULCC) in this paper. The combined expanded glass particles and cenospheres were used as fine aggregates to facilitate the ULCC mix with a density of 1075 kg/m 3 and 28-day strength of 20 MPa. With small addition of colloidal nano-silica (CNS), ULCC strength increased to 27 MPa as a result of the increased packing density of solid particles and the modification of microstructures at the interface between fine aggregates and cement paste. The greatest improvement was observed at CNS dosage of 2%, beyond which CNS particles agglomerate and the higher air content compromised the advantages. ULCC obviously exhibited higher resistance against water and chloride penetration with the incorporation of CNS. Similar findings were observed for the other ULCC mix with different water-binder ratio, verifying the beneficial influences of CNS on transport properties.