Avaliação do uso de óxido de grafeno como tratamento superficial em fibras sintéticas para utilização em concretos reforçados com fibra

Abstract

One of the ways to enhance the mechanical properties of concrete, especially in relation to tensile strength, is through the use of synthetic fibers. However, this use will only be efficient enough when there is a strong interaction between the cement paste and the surface of the fiber used. Better fiber-matrix interaction can be achieved with the surface treatment of polymeric fibers using graphene oxide (GO). This research sought to evaluate the GO surface deposition methods present in the literature and their effect on fiber-reinforced concrete, developed in two stages, the first which sought to evaluate the importance of temperature in the treatment of synthetic microfibers and subsequently its effect on the microstructure. and physical properties of concrete, and the second stage sought to evaluate the effect of treatment on synthetic macrofibers and its effect on microstructure and pullout resistance. To evaluate the quality of GO deposition, scanning electron microscopy (SEM-FEG) and energy-dispersive spectroscopy (EDS) tests were performed, with the same technique used to assess the fiber-matrix transition zone. Thermal analyses (DSC) were conducted to evaluate the treatment effect on microfibers and macrofibers. Mixtures of concrete reinforced with microfibers (FRC) were evaluated in both fresh and hardened states, while mixtures of concrete reinforced with macrofibers (MFRC) were assessed through single-fiber pull-out tests. Results from the first stage demonstrate, through SEM-FEG images and the identified C/O ratio in EDS, that microfibers treated at 80°C increased the C/O ratio. Changes in the microfiber-matrix transition zone were identified in FRC/GO samples through SEM-FEG, showing denser regions of cement hydration products, which did not translate to mechanical property gains but showed reduced water absorption compared to FRC samples. In the second stage, SEM-FEG images indicated that polypropylene macrofiber with higher C content achieved greater surface deposition homogeneity of GO, and the microstructure of macrofiber-reinforced concretes showed alterations with the presence of GO. In the pull-out test, treated macrofibers exhibited higher resistance over the analyzed displacements, demonstrating better behavior for a displacement of 3.5 mm, and the shear stress of synthetic macrofibers could be determined for displacements fR0,5, fR1,5, fR2,5 e fR3,5. [resumo fornecido pelo autor]