Análise de tratamentos químicos em fibras de coco para uso em argamassas : avaliação das propriedades físico-mecânicas e microestruturais

Abstract

In Brazil, the industry extracts coir fiber by mechanically crushing the fibrous mesocarp, from which the husk and powder are removed, and the coir fiber is made commercially available. Several studies are being carried out to use coir fibers as reinforcements in cementitious materials. The present study evaluated the effect of three chemical treatments: the first treatment using 5% w/w sodium hydroxide (considering two time variations: 1h and 2h), oxalic acid with the same concentration and exposure time. The third treatment consisted of 10% w/w sodium bicarbonate (with a time variation of 120h and 168h). Investigations were carried out into extractive, lignin, hemicellulose and cellulose content, tensile strength, modulus of elasticity, elongation, Fourier transform infrared spectroscopy (FTIR), contact angle using the sessile drop method, atomic force microscopy, scanning electron microscopy, X-ray diffraction and thermogravimetric analysis. After the chemical treatments, different mortar mixes were made with 1 and 2% coir fiber content in the cement paste. Compressive and tensile strength tests, capillary water absorption and accelerated carbonation were then carried out. X-ray micro tomography and scanning electron microscopy tests were also carried out. The best results were obtained by treating the fiber with oxalic acid for one hour, which led to a 22.9% increase in tensile strength compared to the untreated fiber. The increase in fiber roughness due to the use of chemical treatments can promote better interaction with the cement paste and be used as reinforcement in cementitious matrices.