Influence of nano-SiO2 and nano-Al2O3 additions on steel-to-concrete bonding

The research on nanoparticles is quite recent and potentially relevant in different contexts, including the concrete field. Fiber reinforced concrete presents several advantages, one of which its capacity to best control cracking. In this scope, the bond between steel rebars and/or fibers and the binding paste plays a most relevant role. The study herein described was developed aiming at analyzing the influence on the latter, and as a consequence on cracking, of nano-Al2O3 and nano-SiO2 additions. In the experimental analysis, the following materials were adopted: both plain and ribbed rebars, eight different concrete mixtures, two types of nanoparticles additions, namely nano-Al2O3 and nano-SiO2, and, in some mixtures, steel fibers. Overall, thirty-two pull-out tests, plus sixteen tensile tests on reinforced concrete ties, were performed. It was concluded that adding nanoparticles to the concrete paste leads to an increase of the steel-to-concrete bond, for mixtures with higher percentage of cement. It was also concluded that Al2O3 nanoparticles induce a beneficial effect in terms of cracking, decreasing the width of these when plain rebars are used. (C) 2016 Elsevier Ltd. All rights reserved.