Role of nanofillers for high mechanical performance cementitious composites

Using nanofillers, such as nano-Fe₂O₃, nano-Al₂O₃ and nano-SiO₂, in the design of ultra-high-performance cementitious composites is widely practised, but there is a lack of quantitative understanding of the role these nanofillers play at molecular or micro levels. In the present study, we proposed a framework to offer an insight into molecular failure mechanics, microscale characterisation and the mechanical performance of cement with nanofillers. Results from the multiple-scale investigation showed good consistency and supported each other. Reactive molecular dynamic simulations indicated that the mechanics of molecular failure between nanofillers and cement primarily depends on their interfacial bonding, transitioning from adhesive failure at the interface to cohesive failure within adjacent cement hydrates. Results from microscale characterization further confirmed that mineral nanofillers in cement strengthened the surrounding cement hydrates, generating around 63.64–161.97% increase in high-density hydrates, while also expediting the reduced the porosity from 17.62% to 39.51% relative to reference samples. Consequently, the mechanical properties of the cement paste were improved. These findings quantify the role of nanofillers in cement systems and provide fundamental understanding of key material design parameters for mechanical property enhancement of cementitious nanocomposites.