Rice husk and coir fibers as sustainable and green reinforcements for high performance gypsum composites

Abstract

Reinforcing gypsum with coir and rice husk enhances the flexural properties, acoustic and thermal insulation and resistance to environmental degradation. Coir and rice husks are agricultural coproducts available in large quantities at low cost and are renewable and sustainable source. In addition, coir provides excellent strength increase and rice husks have low density and good thermal resistance. In this study, rice husk and coir were used as reinforcement for gypsum as individual components and also as blends. Up to 30 % of reinforcement was possible with enhanced properties. Compared to pure gypsum, up to 187 % increase in flexural strength, reduced moisture absorption and excellent thermal resistance were achieved. Highest flexural strength of 1.5 MPa was obtained when 10 % rice husk was added compared to highest strength of 5.6 MPa when 30 % coir fibers were added into gypsum. An equal proportion of 50 % ricehusk and 50 % coir fibers provided the highest flexural strength for the hybrid composites. Addition of ricehusk and coir also improved the acoustic resistance particularly between 2500 and 4000 Hz whereas there was no major difference in the thermal conductivity of the samples with and without the reinforcement. The extent of increase in properties could be controlled by varying the proportion of ricehusk and coir in gypsum ceiling tiles. Developing hybrid composites particularly in equal proportion of ricehusk and coir was found to be better in terms of improving the performance of gypsum. Being byproducts of major food crops, ricehusk and coir provide sustainable and renewable source for developing composites. Reinforcing gypsum with ricehusk and/or coir will also assist in decreasing the environmental burden and increasing the sustainability of buildings.