Desenvolvimento e caracterização de compósito cimentício híbrido reforçado com fibras curtas de malva e resíduos madeireiro

Abstract

This research presents the development and characterization of hybrid cementitious composites reinforced with mallow fibers and wood industry residues. To increase the durability of these materials, a matrix free of calcium hydroxide was used, through the partial replacement of Portland cement by 40% of industrial metakaolinite (MK), 15% of setting accelerator additive was added to the mixture (on the weight of the cement), in order to combat the delay and/or inhibition of the cement hardening time, caused by the amount of polysaccharides present in the wood. Short mallow fibers of 50 mm were used, randomly placed in the composite, 4% in fiber volume, and wood residues, with a 10% content, randomly dispersed in the composite, whose determination was carried out through a previous study. The composites were physically and mechanically characterized, after natural aging of 236 days, by means of 4 point bending tests, permeability of the composites, bulk density and fire propagation resistance, with the characterization of these composites after incineration through the test of 4 point bending. Fibers were characterized by scanning electron microscopy and wood residues were chemically characterized to determine the amount of chemical constituents of lignin, cellulose, hemicellulose and inorganic material. Composites with treatment (M1FM) had lower permeability than composites without treatment (M0FM), about 15.39% more permeable. The results of bending at 4 points indicated that the partial replacement of cement by MK influenced the resistance capacity when cracked, as the composites M1FM showed a cracking zone (figures 40 and 41) and the composites M0FM showed only the zone in the graphic behavior elastic. The composites with the addition of MK showed toughness resistance results higher than 18 MPa. The fire resistance test results indicated that the composites did not propagate flames instantly, however, there was a loss of 74.23% in the resistance of the lignocellulosic material, observed through the 4 point bending test.