Resíduos lignocelulósicos como alternativa de reforço em compósitos cimentícios extrudados

Abstract

Cement-based materials are characterized by their brittle and brittle behavior. For this reason, the use of reinforcement materials helps in the absorption of energy by the composite, providing greater resistance to traction and deformation efforts. Asbestos and polymeric fibers are commonly used to modify the brittle nature of cement-based materials, but they do not represent an ecological solution, and asbestos causes lung disease. Alternative means are evidenced by the increase in research evaluating the benefits of using vegetable fibers. However, the main challenge is the compatibility between the fiber and the matrix, due to the hydrophilic nature of the fiber, and also due to the alkaline environment of the cement matrix, which degrades the vegetable fiber. An alternative to overcome this challenge is accelerated carbonation, which acts by reducing the alkalinity of the cement matrix, providing a favorable environment for better adhesion between fiber and matrix. Thus, this research aimed to evaluate the physical, mechanical and microstructural properties of extruded fiber-cements compounds with sorghum or rubberwood fibers, as an alternative for reinforcement and the correct use of these waste materials. The research consisted of two proposals for the use of natural fibers. In the first proposal, composites using sorghum fibers were produced by the extrusion process. In the second proposal, in order to reduce the influence of extractives on cement hydration, the rubberwood fibers underwent alkaline treatment with sodium hydroxide (NaOH) (10% m/v), in addition, the influence of curing composites by accelerated carbonation was evaluated. Both types of composites remained in the curing process in a saturated environment for 2 days, after this period, the composites produced with rubberwood fibers underwent accelerated carbonation for a period of 12 h, then remained in wet curing until completing the period of 28 days. The use of lignocellulosic fibers as reinforcement in cement matrix proved to be viable, as it presented satisfactory behavior with regard to the physical and mechanical properties of the fiber-cements produced. In general, the cementitious composite with the best mechanical performance was achieved by replacing cement with sorghum fibers in the percentage of 1%. In the composites produced with rubberwood fibers, the accelerated carbonation caused the reduction of the mechanical properties, with the exception of the tenacity, resulting in the improvement of the mechanical energy absorption of the composites. Thus, the production of cement composites using lignocellulosic waste adds value to these wastes, reducing environmental pollution caused by burning or improper disposal, as well as employing the principles of the circular economy.