Abstract: By replacing cement with Al₂O₃ of 1 μm and 10 nm, respectively, cement-based materials with low water-binder ratio were prepared for researching the modification effect of micron-Al₂O₃ and nano-Al₂O₃ on the mechanical properties and durability of cement-based material. Macro-and-microscopic approaches were adopted to examine the change law of mechanical performance and durability and to analyze the modification mechanism. Results demonstrated that both micron-Al₂O₃ and nano-Al₂O₃ at a dosage of 0.5%-4.0% could enhance the mechanical performance while reducing the drying shrinkage of cement-based material. Micron-Al₂O₃ at a dosage of 0.5%-2.0% or nano-Al₂O₃ at a dosage of 0.5%-4.0% could reduce the permeability coefficient; however, a 4.0% micron-Al₂O₃ would increase the permeability coefficient. The modification effect of nano-Al₂O₃ is superior to that of micron-Al₂O₃. SEM result and previous research findings prove that in the process of cement-based material’s hydration and hardening, micron-Al₂O₃ and nano-Al₂O₃ ameliorate the mechanical performance and durability through size effect, filling effect and surface activity effect.

Key words: cement-based material, micron-Al₂O₃, nano-Al₂O₃, modification, mechanical properties, durability, mechanism