Microwaved cement boards with alkali-treated pineapple and water hyacinth fibers

Pineapple fibers (PFs) and water hyacinth fibers (WHFs) were treated with sodium carbonate (Na₂CO₃) and sodium hydroxide (NaOH) solutions for soaking times of 0·5, 1·0, 1·5 and 2·0 h. Analyses showed that the best treatment parameters for PFs were 2·0 M sodium carbonate for 1·5 h and 2·0 M sodium hydroxide for 0·5 h; those for WHFs were 1·5 M sodium carbonate for 0·5 h and 1·0 M sodium hydroxide for 1 h. The untreated and treated PFs showed similar Fourier transform infrared spectra ranging from 2924 to 2926 cm⁻¹, which signify the presence of acidic oxygen (O)–hydrogen (H) stretching vibrations on a carbonyl group. The sodium hydroxide-treated WHFs had the 2926 cm⁻¹ transmittance peak absent compared with the untreated WHFs. The acetylation process on both fibers resulted in increased roughness of fibers, which were analyzed under scanning electron microscopy of 10 μm magnification. The fibers treated under the determined best parameters were then used in the fabrication of cement boards. The specimens underwent microwave curing with regimes under 119 and 280 W. The cement board with aligned sodium carbonate-treated combined PFs and WHFs performed 16–41% better than the cement board with non-woven oriented fibers in terms of flexural strength.