Resistência à tração e à carbonatação de argamassas fabricadas comnanotubos de carbono sintetizados diretamente sobre clínquer

Abstract

With the advent of innovations in science and engineering offered by nanotechnology, carbon nanotubes emerge as an excellent candidate for improving the performance of cement-based materials. The carbon nanotube structure consists of a tubular arrangement of carbon atoms,with diameters in the order of nanometers (billionth of a meter). Its high tensile strength and modulus of elasticity have attracted researches to investigate the effects of its addition to Portland cement composites. These studies have shown significant gains in performance when compared to ordinary Portland cement pastes and mortars; however the physical mixing process of these materials is unfeasible for being implemented on a large scale. In this investigation carbon nanotubes were synthesized in a continuous process directly over the cement clinker, which will allow its large-scale production. This research aims to analyze the resistance to carbonation and the tensile strength of Portland cement mortars with carbon nanotubes. In order to evidence the carbonation phenomenon, the mortars were subjected to accelerated tests in chamber and, after a certain period, the carbon dioxide penetration is measured and analyzed. Splitting tensile tests were performed to evaluate the tensile strength of carbonated as well non-carbonated specimens. For both investigations, different ages ofspecimens and carbon nanotube contents are analyzed in order to verify the influence of this material on the mortar behavior. Aiming to complement the results, scanning electron microscopy images and thermogravimetric analyses were carried out. Compared to ordinaryPortland cement mortars, the results indicated gains in tensile strength for nanostructured mortars, which also offered greater resistance to carbon dioxide penetration. Thus, this type of composite is a promising high performance material, contributing to the durability of reinforced concrete structures.