Effects of nano-SiO2 and nano-Al2O3 on mechanical and durability properties of cement-based materials: A comparative study

Abstract In order to explore the all-round influence of nano-SiO2 (NS) and nano-Al2O3 (NA) on cement-based materials, especially the small dosage and compound effect, the single and combined effects of NS and NA on mechanical and durability properties of cement-based materials were investigated. The contents of nanomaterials were 0.5%, 1.0%, 2.0% and 3.0% of the binder by weight, respectively. Results show that setting time could be shortened by introducing NS and NA except single-doped 2% and 3% NA and binary combination NS+NA at 3%. In addition, all hardened mortar systems with nanomaterials exhibited positive strength growth rate compared to control group. Especially, the compressive strength growth rates of mortars containing NS after 3 days were 10.5%, 27.09%, 26.78% and 42.13%, respectively, with the increase of NS content from 0.5% to 3%. In terms of durability, the charge passed, weight loss and capillary permeability coefficient decreased by adding small amount (0.5%) of NS and NA. And then the introducing of 0.5%NS + 0.5%NA powders at 1 % reduced capillary permeability coefficient of concrete samples compared to that of 0.5%NS and 0.5%NA samples. Among all groups, the best performance was provided from NS at 1%, NA at 0.5%, and the binary combination NS+NA at 1%. Finally, the relationships between the drying rate/water absorption rate and time were given, which was conductive to study the moisture transport of nano-concrete.