Coir fiber as reinforcement in cement-based materials

Abstract

The disposal of coconut waste in many coastal habitats worldwide is an enormous environmental problem. A valorization alternative suggests coir fibers as attractive reinforcements of many kinds of cement-based composites. The features of the raw or enhanced fibers, the compatibility between the matrix and the reinforcement phases, and the production parameters are critical for developing high-performance composites. Coir technological fibers consist of fiber bundles, phloem, and parenchyma cells. The relatively high lignin level (27%-35%) provides coir fibers great weather, fungal and bacterial resistance, and elongation at break. It has natural compatibility with cement because of relatively low levels of soluble sugars. However, water or NaOH soaking pretreatments of coir fibers release soluble sugars that hinder cement hydration, keep cellulose integrity, enhance fiber morphology, and improve chemical compatibility and interface between the matrix and reinforcement. Pressed coir-reinforced cemented-bonded fiberboards and wool boards exhibit remarkable physical strength compared to commercial products and based on quality standards. Still, the production process demands adjustments to meet mechanical strength requirements. Extruded composites reinforced with 1% and 2% of coir fibers were compared to neat cement regarding rheological, mechanical, and physical properties. The 2% coir fiber reinforcement exhibited ram pressure 38% higher compared to the neat cement paste. Accelerate aging by 200 cycles improved the modulus of rupture and water absorption of the extruded 2% reinforced composites because of the effective cement hydration, which filled the pores and densified the material structure, improving the fiber/matrix ratio.