Effect of Coir Fiber Reinforcement on Properties of Metakaolin-Based Geopolymer Composite

Abstract

This study explored the use of coir fibers extracted from coconut husks, an agro-waste material that constitutes sanitation and environmental pollution problems, as a reinforcing element in the production of metakaolin-based geopolymer composites with improved properties. A series of sample formulations were produced with varying coir fiber content (0.5, 1.0, 1.5, and 2.0 percent weight of metakaolin powder). The investigation was conducted using a 10 M NaOH alkaline solution with a 0.24 NaOH:Na2SiO3 mass ratio. Samples were cured for 28 days and tested for bulk density, ultrasonic pulse velocity (UPV), and compressive and flexural strength. Microstructural examinations such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) were also performed on samples. Compressive strength values up to 21.25 N/mm2 at 0.5% fiber content and flexural strength values up to 10.39 N/mm2 at 1% fiber content were achieved in this study. The results obtained showed a decreasing bulk density of geopolymer samples (2113 kg/m3 to 2045 kg/m3) with increasing coir fiber content. The geopolymer samples had UPV values varying from 2315 m/s to 2717 m/s. Coir fiber with 0.5–1.0% fiber content can be incorporated into metakaolin-based geopolymers to produce eco-friendly composite materials with improved mechanical properties for sustainable development.

Alkaline Degradation of Plant Fiber Reinforcements in Geopolymer: A Review

“…The toughness of the composite material increases, and the matrix and fiber also show a good bond without significant degradation. Hemicellulose and lignin cause the porosity of the composites, and their alkaline degradation reduces the degree of polymerization of the composites [ 27 , 28 ].…”

“…In general, excess plant fibers adversely affect the compressive strength of the matrix. However, an appropriate amount of plant fibers can be evenly distributed in the matrix to enhance the compactness of the matrix, thus reducing porosity and cracks and improving compressive strength [ 28 , 29 ].…”

The Mechanical Properties of Plant Fiber-Reinforced Geopolymers: A Review

“…An appropriate amount of PFs content distributed evenly in the matrix can enhance the compactness of the composite, reduce the porosity and crack, and thus improve the compressive strength. Ayeni et al [ 91 ] studied geopolymer composites of 0.5, 1.0, 1.5, and 2.0% different weight of coir fibers contents. The compressive strength was increased from 16.91 N/mm 2 to 21.25 N/mm 2 by adding coir fibers with 0.5% fibers content.…”

“… Relationship between fibers content and compressive strength of composites [ 87 , 90 , 91 , 92 , 94 , 97 , 101 ]. …”

“…Different types of PFs also affect the flexural properties of the PFRGs. Ayeni et al [ 91 ] added different proportions of coir fibers to improve the flexural strength of PFRGs. When the fibers content is 0.5%, the flexural strength is 9.74 N/mm 2 .…”