Characterization of lignocellulosic fibers from pineapple leaf with alkaline treatment for application in geopolymeric mortars

Abstract

Geopolymers are binding materials with potential applications in civil construction. The use of natural lignocellulosic fibers stands out over synthetic fibers because they are renewable and offer desirable technological properties such as high tensile strength and low specific gravity. These fibers also have a lower cost than other reinforcements, such as synthetic fibers. In this context, the objective of this study was to investigate the physical and mechanical properties of fibers extracted from the pineapple leaves, a waste widely generated in producing areas. The fibers were characterized in their natural form and after treatment by immersion in a 5% alkaline solution/1 h (mercerization). Parameters such as average diameter, water absorption, density, tensile strength, deformation and modulus of elasticity were obtained. Several analyses such as XRD, FTIR, DSC and SEM were performed to compare treated and untreated fibers for a more efficient application in geopolymers. A thermal behavior study, with 28 days of exposure at 60 °C, was carried out to analyze the possibility of thermal curing in a possible application in geopolymers. The treated fibers obtained a considerably superior performance in all properties analyzed. In this context, geopolymer composites were prepared using treated fibers to evaluate the fresh and hardened state of the mortars, obtaining the consistency index, flexural strength and compression. The composites had the addition limited by the workability of 3% and reached approximately 17 MPa of mechanical resistance to compression, with the addition of fibers being beneficial to the context studied. It is concluded that the use of pineapple leaf fiber after mercerization treatment in geopolymers is a viable alternative.