Effects of colloidal nanoBoehmite and nanoSiO2 on fly ash cement hydration

• NanoBoehmite and nanoSiO2 have accelerating effect on cement hydration at early stage.
• Higher addition of CNB and CNS decreases the compressive strength in the later age.
• CNB and CNS can accelerate the appearance of CH at early age.
• CNB–CNS can compact the ITZ and result in dense coating around FA particles.

The influences of colloidal nanoBoehmite (CNB) and colloidal nanoSiO2 (CNS) on fly ash cement mortar hydration and microstructure development of fly ash cement pastes were investigated. The results revealed that fly ash cement hydration was accelerated by CNB and CNS at early age thus enhancing the early age strength of the materials. Although higher content of nanoparticles significantly hindered cement hydration, adding appropriate amount of CNB and CNS benefited the development of compressive strength both at early and later age.