Investigating mechanical and bonding properties of micro/nano filler containing epoxy adhesives for anchoring steel bar in concrete

In this study, effect of incorporating different sizes of silica microparticles (i.e. with mesh sizes of 100, 200, 400 and 600) and their hybrids on the properties of the epoxy composite adhesives was investigated. To determine the performance of the micro silica-based epoxy adhesives, their mechanical (i.e. the compressive, tensile and flexural) properties and adhesion to concrete and steel bar (i.e. pullout test) were evaluated. Meanwhile, the effect of surface humidity of micro silica particles on the mechanical properties of the epoxy adhesive were assessed. Hereafter, SiO2 and CaCO3 nanoparticles at 1, 3 and 5 wt% were applied to the micro silica-based composites and the mechanical and pull-out properties were determined. Results showed that moisture content were negligible in micro silica particles but it caused 7, 40 and 25% decline in the tensile modulus, flexural strength and flexural modulus of the epoxy samples compared to the samples with dried micro silica. Using micro silica particles with mesh 600 in epoxy binder caused the best performances in the epoxy composites and improved 266, 205, 60 and 102% the compressive strength, compressive modulus, tensile and flexural modulus, respectively. Hybridizing micro silica particles with different sizes had significant effect on the adhesive mechanical properties. Incorporating nano CaCO3 to the composites containing micro silica just improved compressive strength but had small impact on other properties. Finally, using nano SiO2 along with micro silica due to its incompatibility with epoxy resin caused considerable diminution in the mechanical and bonding properties especially at higher loading contents. (C) 2020 Elsevier Ltd. All rights reserved.