Role of homogenization and surface treatment of flax fiber on performance of cement-based composites

Abstract

The incorporation of natural fiber in cementitious matrices can lead to several problems in fresh and hardened phases, such as fiber clumping and shrinkage. This paper investigates the effects of mixing methods and treatment of flax fiber on the fresh and mechanical properties of mortar mixtures. A mixing method is proposed to achieve a better homogenization of flax fiber mortar by adjusting the speed and time of mixing. Different fiber volumes (0.3, 0.6, 0.9, 1.2, 1.5, and 1.8 by weight of cement) and various treatments (hydrothermal and alkali) were incorporated into the experimental program. The influence of mixing parameters of flax fibers is investigated by evaluating flowability, setting time, compressive and flexural strengths, drying shrinkage, and mercury porosity. The results were compared to similar mixtures made with polyvinyl alcohol (PVA) fibers. Introducing flax fibers in a cementitious matrix in pre-saturated conditions was found to improve the rheology and reduce the volume change. Mixing of high speed (183 rpm) for a duration of 6 min can secure a well- homogenization of natural flax fiber into the matrix, leading to enhance mechanical performance.

Keywords

• Flax-fiber mortar composites
• Homogenization
• Fiber treatment
• Flowability
• Mechanical performance
• Drying shrinkage