Construction materials made of polymeric fibres  (geosynthetics) are a viable alternative to traditional materials (concrete, granular materials) as proven the last years. Their use in association to mineral materials as soils or granular fills leads to composite materials having improved physical and mechanical properties and allowing to build more efficient structures both from structural and environmental point of view.  Paper presents the main aspects related to physical and mechanical properties of geosynthetics, the main applications, focusing on reinforcement, filtration and drainage functions. It presents the various interactions between geosynthetics and mineral materials and the properties of the resulted composite material.