Efeitos da adição de nanofibras de celulose e nanossílica em pastas de cimento para poços de petróleo

Abstract

Cellulose nanofibers (NFC) are a promising alternative as sustainable additives in cementitious matrices. This is because its fibrillar morphology can result in composites with high tensile strength and flexibility. However, some studies suggest loss of NFC performance in alkaline matrices and has little influence on compressive strength. One possibility is the addition of a highly reactive material that decreases the alkalinity of the cementitious matrix and provides good compressive properties, such as Silica Nanoparticles (NS). Thus, this work aims to analyze the synergistic effect of NFC and NS on the mechanical properties of cementitious pastes for oil wells. For this, six formulations, with a specific mass of 1,797 g/cm3, were developed with a fixed concentration of NS (0,1 gpc), varying only the concentration of NFC (0,0 to 0,5%). Initially, a mixture analysis of the nanoadditives added to the cementitious paste was carried out, dividing them into groups of low (without dispersant) and high concentration (with dispersant) of NFC. With this, stability and rheology tests were realized in all formulations, as well as compressive and Brazilian tensile test. In addition, cement hydration cured for 28 days was analyzed with Field Emission Gun - Scanning Electron Microscope (FEG-SEM) and X-Ray Diffraction (XRD). These results showed that progressive increase of NFC affect stability and rheology properties. However, mechanical properties results showed limited influence with NFC addition. In turn, the morphological analyses indicated a high adhesion of the NFC with the cementitious matrix, as well as possible agglomerations between the nanomaterials. Therefore, NFC have promising characteristics as an additive in cementitious pastes for oil wells, making further adjustments of NFC and NS concentrations necessary.