Estudo da durabilidade de compósitos cimentícios com polpa de eucalipto modificados com microssílica e látex

Abstract

Modifications in cementitious composites reinforced with plant fibers is an advance on the way to materials innovation. In this research, the study of composite durability was analyzed by mechanical and physical tests, scanning electron microscopy (SEM), X-ray diffraction (XRD), contact angle, among other characterization tests, at 28 days and after natural aging in 90 and 180 days. The materials used for formulations of the composites include Portland cement, mineral addition (silica fume), natural rubber latex and natural fiber reinforcement (eucalyptus kraft pulp). The composites were produced by a vacuum suction process of the mixture and subsequent pressing, according to the contents specified in the central composite design. Micrographs showed an adequate synergy between the fiber and the latex and, in addition, the cellulose fibers were predominantly stripped from the matrix at the earliest ages and after the aging due to its preservation. The experiments showed a decrease in the toughness and elevation of the modulus of rupture due to the densification in the matrix and fiber-matrix interface, with the continuous hydration and carbonation of the matrix. The results indicated that higher amounts of fibers in the composites allowed the reinforcement of the fragile matrix. The presence of silica fume and latex provided greater preservation of the fibers to natural aging. Diffractograms at initial ages showed the decrease of the portlandite in mixtures with the presence of silica fume and rubber latex. The latex allowed a greater volumetric stability of the composite against the hydrophilic character of the fibers. Statistical models were validated and an ideal composite (E3 experiment) could be obtained, with 2,9% silica fume and 1,4% latex, by mass, and 13.5% cellulose, by volume, with mechanical properties such as the modulus of rupture (12,38 MPa) and modulus of elasticity (18,76 MPa)