Influence of Nano-SiO₂, Nano-Al₂O₃, and Nano-ZnO Additions on Cementitious Matrixes with Different Powder and Steel Fibers Content

Abstract

In the study herein presented three types of nanoparticles, with different dosages, were used, namely nano-SiO₂, nano-Al₂O₃ and nano-ZnO, which were combined with different concrete formulations. The main goal is to improve the eco-efficiency of concrete, using simultaneously a partial replacement of Portland cement by industrial by-products and reduced amounts of nanoparticles, aiming to avoid the reduction, or even enhance, both mechanical and durability properties of the final mixtures. The interaction between the steel fibers added to the matrixes and the nanoparticles is also addressed. To analyze the effects of nanoparticles additions in the properties of both mortar and concrete mixtures, several tests were performed in fresh and hardened states. Durability indicators were also evaluated, namely, capillary absorption, immersion water absorption and carbonation depth. It was concluded that an increase of both flexural and compressive strengths can be obtained with nanoparticles additions, but that effect depends on the powder dosages used in the binder matrixes and on the type and dosages of nanoparticles. Regarding the matrixes with steel fibers, no additional gains were obtained combining simultaneously nanoparticles with those fibers. It was also concluded that the nano-ZnO addition significantly delay the concrete hardening and show a negative effect when combined with the steel fibers.