Mechanical behaviour of Composites based on Diss and Aflfa fibres in different matrices

Abstract

The use of natural fibers in cementitious matrices has an incompatibility, which results considerable retardation of setting and very low resistances during the composite tests with natural crushed Diss, despite the fact that the fibers have considerable tensile strengths, because of the sugars and water- soluble components contained in natural plants. To improve the fibers contribution in cementitious composites, we have carried out a treatment by boiling the natural fibers to extract the substances responsible for the bad connection between fibers and the cement paste. This phenomenon of incompatibility disappears with the use of clay matrix or lime, which allows using the fibers without any treatment. We were able to determine the mechanical behavior of composites in flexion and compression by measuring stresses and deformations. Through our vast experimental program on the composites of natural fibers of Alfa and Diss in different matrices (cement and clay) and different sizes ranging from 2 to 8 cm, we have found: 1) The best resistance in bending and compression are generally reached for the composites with fibers having the dimensions between 4 and 6 cm. 2) The best bending strengths are achieved for composites with cementitious matrices, because of the good adhesion of the fibers to the matrix. 3) The best compressive strengths are achieved for clay matrix composites, which are due to the good compressibility of the clay. 4) The composites of Alfa and Diss fibers presented a very ductile behavior as well in flexion as in compression, contrary to the pure binder paste which has a brittle behavior. 5) The composites obtained have a very low density, which makes it possible to classify them as lightweight materials and have a very ductile behavior, which suggests using these materials as filling in the seismic zones.