What are concrete noise barriers made of?
Concrete noise barriers can either be manufactured as absorptive or reflective barriers and are made of wood fiber concrete material. They are normally relatively heavy, ranging from 100-300kg/m², especially compared to timber and plastic barriers. However, this is important as they will not degrade as quickly when large wind and aerodynamic loads are applied. They also have a life cycle of over 30 years and require no maintenance.
A concrete noise barrier usually consists of a combination of a porous sound absorbing face and a standard concrete to increase the mechanical properties of the barrier. Porous concrete is made using large aggregates with either very small or no fine aggregates and contains continuous voids and withholds high permeability compared to normal concrete. As a result, the pores absorb a lot of the sound energy through internal friction. Glass Fibre Reinforced Concrete (GRC) noise barriers have also be used worldwide since the 1970s. The acoustic performance of GRC depends on three physical properties; the surface mass, the stiffness, and the damping, where the most important of these properties is the surface mass. According to the Mass Law Curve, as can be seen in Figure 2.12, it is shown how a 10mm thick panel of GRC with a mass of 20kg/m² performs. It provides a noise reduction of 30dB.