Sodium　carbonate　activated　slag　mortar　(SCASM)has　the　advantages　of　low　carbon　emissions,　high　long-term　strength　and　excellent　durability,　but　its　disadvantages　such　as　long　setting　time　and　low　early　strength　limit　its　practical　application.　Nano-silica　sol　(NSS)is　a　colloidal　solution　formed　by　the　stable　dispersion　of　nano-SiO2　particles　in　water,　exhibiting　high　activity　and　dispersibility.　In　this　work,　the　effect　of　various　NSS　contents　on　the　workability　and　mechanical　performance　of　SCASM　was　investigated,　and　its　mechanism　was　explored　by　hydration　heat,　Fourier　transform　infrared　spectroscopy　(FTIR),　scanning　electron　microscope　and　energy　dispersive　spectrometer　analysis　(SEM-EDS).　The　results　show　that　NSS　can　effectively　improve　the　setting　speed　and　mechanical　properties　of　SCASM.　NSS　provides　nucleation　effect　and　nano-filling　effect　to　effectively　accelerate　the　hydration　rate,　increase　the　polymerization　degree　of　SCASM,　and　densify　the　matrix　microstructure.　Under　alkaline　action,　the　Si-O　bond　of　nano-SiO2　particles　in　NSS　is　further　opened　to　form　monomer　[SiO4]4-　in　the　early　stage,　providing　more　nucleation　sites.　This　is　prior　to　the　reaction　of　CO32-　with　Ca2+　and　Al3+　in　the　slag　to　form　C-(A)-S-H　gel,　which　plays　an　important　role　in　the　early　strength.　The　gel　formed　has　lower　Al　/　Si　ratio　and　denser　structure.　At　the　same　time,　the　unreacted　SiO2　particles　could　fill　the　pores　and　further　optimize　the　pore　structure.　With　the　increasing　of　NSS　content,　the　setting　time,　bleeding　rate　and　fluidity　of　SCASM　gradually　decrease,　while　the　mechanical　properties　and　the　ratio　of　flexural　to　compression　firstly　increase　and　then　decrease.　When　the　NSS　content　is　11%,　the　initial　setting　time　and　final　setting　time　of　the　pastes　can　be　shortened　by　96.　0%　and　93.　1%,　respectively.　When　the　NSS　content　is　5%,　the　mortar　sample　has　the　highest　flexural　strength,　compared　with　mortar　sample　without　NSS,　its　7　d　and　28　d　flexural　strength　significantly　increases　by　75.　4%　and　24.　7%,　respectively.　When　the　NSS　content　is　8%,　the　mortar　sample　has　the　highest　compressive　strength,　and　its　7　d　and　28　d　compressive　strength　significantly　improve　by　91.　7%　and　21.　6%,　respectively.　However,　when　the　NSS　content　is　too　high,　the　mechanical　properties　of　SCASM　will　reduce　due　to　the　decreased　dispersibility　of　NSS.　©　2025　Cailiao　Daobaoshe/　Materials　Review.　All　rights　reserved.