Matriz cimentícia reforçada com celulose microfibrilada tratada com álcool furfurílico

Abstract

The addition of nanocellulosic products, such as microfibrillated cellulose (MFC), in cementitious composites can improve some mechanical properties of this material, however, it can also impair other characteristics, such as workability, water consumption and setting time. Many of these problems are linked to the high hydrophilicity of MFC, originated from its large number of OH- groups. In order to mitigate the negative effects and enhance the already known reinforcement function of MFC, a furfuryl polyalcohol graft was performed on its surface. The MFCs produced were introduced into a cement paste (0.4 w/c) with a ratio of 0.2% in relation to the cement mass. MFCs were studied by optical microscopy, infrared spectroscopy (FTIR), contact angle and thermogravimetric analysis (TGA). The composites studied were submitted to tests in the plastic state regarding their rheology and affinity with water, and in the hardened state regarding physical properties, hydration, mechanical properties and durability. The results pointed to a good compatibility between furfuryl alcohol (FA) and MFC, reducing the hydrophilicity of MFC and not interfering with its thermal degradation. In the tests of fresh pastes, the furfurylation of MFC mitigated all the negative effects related to its addition in cementitious matrices, improving workability, reducing water consumption and reducing the setting time when compared to untreated MFC composites. In the hardened state, the addition of MFC reduced the porosity and water absorption of the cement pastes, however, this effect was mitigated in the MFC treated with AF (MFC25 and MFC50) due to the increase in hydrophobicity caused by the treatment. In the hardened state, the introduction of MFCs improved the hydration of cement pastes, causing increases of up to 200% in mechanical strength at early ages.