Development of lightweight concretes using agricultural by-products

Abstract

Agricultural wastes; rice straw and coconut coir fiber, which are found in large quantity in Thailand, were utilized as main materials for reinforcing concretes and making concretes lighter than cement mortar 25-40%. The total fiber content was varied in the range 30-50 vol%. Coarse rice straw fibers (1-5 mm) and fine fibers (<1 mm) were treated with 15% sodium hydroxide and found effective for removing hemicellulose, lignin and fatty acids. This improved the surface roughness and hydrophobicity of the cellulose fibers. The distribution of natural fibers in the matrix became more uniform and the adhesion between the fiber surface and cement phase was greatly improved. Lightweight concrete containing 20% fine rice straw fiber and 10% fine coconut coir in the composition showed high compressive strength value of 140 kg/cm2 with bulk density reduced by 30% compared to cement mortar. Hydration of concrete specimens for more than 28 days resulted in the improvement of compressive strength.