Painéis de cimento Portland produzidos com fibra de mesocarpo do açaí

Abstract

In the Amazon, the açaí residue is an abundant biomass that presents superficial fibers, whose potential for the production of agglomerated cement panels can be studied. In case of chemical incompatibility with the cement, the fibers may have their chemical structure modified to improve the quality of the product. This work investigates the compatibility between Portland cement and açaí seed mesocarp fibers under in natura conditions and submitted to physical and chemical pre-treatments for application as reinforcement in CBPB-type agglomerated cement panels. Treatments were performed in a muffle of 180 ° C, 200 ° C and 220 ° C, with hot water (90 ° C), cold water (21 ° C), alkaline treatment twice, alkaline treatment twice and bleaching one and two times. The fiber characterization was performed using X-ray diffraction, scanning electron microscopy (SEM) for analysis of morphology and pH measurement in deionized water. The analysis of the compatibility between cement and fibers was performed by calorimetry, X-ray diffraction and mechanical tests. Panels produced with in natura fibers were characterized by water absorption (AA) and swelling in thickness (IE) after 2 and 24 hours of immersion in water, apparent density (DA) and modulus of elasticity (MOE) and modulus of rupture (MOR) in static bending. With the exception of cold and thermal water treatments, other treatments increased the crystallinity index of the in natura fibers from 27.93% to up to 57.42% (bleached fibers). In natura fibers are cylindrical, with approximately 210.4μm of diameter and channels of points in the surfaces, being the diameter altered by the chemical treatments. The disappearance of the hemicelluloses peak was verified only for chemical treatments. The fiber cement pastes had a lower reaction temperature than cement paste without fiber addition, but a low inhibition rate of açaí fibers was observed for all conditions, including in natura. The diffractograms of the pulps show that the in natura fiber causes delay in the formation of the portlandite phase, however this treatment presents a higher peak referring to the formation of this phase after 28 days. In the compression tests of the cylinders, in natura fibers resulted in superior average resistance with respect to the treated fibers. It was concluded that the morphology and chemistry of açaí fibers could be advantageously modified by the proposed chemical and physical treatments. However, these do not result in better chemical compatibility with the cement, so that the fiber can be applied in the in natura condition for the production of the panels. The açaí mesocarp fiber has great potential for the production of CBPB panels considering its low inhibition on cement cure, but the variables of the production process proposed in this work should be adjusted so that the panels reach, in addition to the physical, similar mechanical properties commercial CBPB panels