Influência de diferentes tipos de fibras nas propriedades de compósitos cimentícios

Abstract

The development of cementitious composites reinforced with plant fibers has been highlighted as an alternative technology for the production of new materials that provide a

lower environmental impact. There are two ways to improve the properties of the fiber- reinforced cementitious composite, namely the surface treatment of the vegetable fiber and

the insertion of surfactant additives, improving the properties of the cementitious matrix. The ideal condition to carry out the surface treatment was studied based on research in the literature, in which the alkaline medium used was sodium hydroxide (NaOH) 5% (w/v), heated and stirred for 2 h. The fibers were evaluated in terms of density, humidity and morphology and the composites in terms of physical, mechanical and microstructural properties. The results showed that the alkaline treatment chemically modified the surface morphology of the fibers, in addition to extracting impurities, resulting in an increase in surface roughness, which confers better adhesion between fiber and cementitious matrix, hydration reaction and internal curing. Through the analyzes carried out by SEM, XRD, TG and tests of physical and mechanical properties in the composites, a better interaction capacity of the treated fibers with the matrix can be verified. There was a reduction in water absorption of the treated fiber composites, with these results confirming that the treatment was efficient in improving fiber/matrix adhesion. The second purpose of the research was to evaluate the effect of surfactant additives (lignosulphonate plasticizer and air entrainer) in fiber cement extruded with in natura sisal fiber. For this, mechanical, physical and microstructural analyzes of fiber cement composites were performed. It should be noted that the proposed lignosulphonate plasticizer (FSADR0.6) proved to be more efficient than the air entrainer (FSA0.8) and reference (FSA) in relation to the volume of incorporated air and the stability of the formed pore system. In addition, the apparent density did not have a significant reduction as expected, however the combination of additives provided an increase in mechanical properties. Thus, the present study based on tests can prove that treated vegetable fibers improve the performance of cementitious mortar and that untreated surfactant additives can be added to improve the mechanical and physical properties of the cementitious composite reinforced with in natura sisal fiber.