VALORISATION OF COARSE RIGID POLYURETHANE FOAM WASTE IN LIGHTWEIGHT AGGREGATE CONCRETE

The mechanical properties and the durability parameters of lightweight aggregate concretes (LWAC) incorporating rigid polyurethane (PUR) foam waste as coarse aggregates (8/20 mm) were studied. The influence of both the increasing incorporation of PUR foam waste and the presence of superplasticiser on the workability, bulk density, mass loss, drying shrinkage, compressive strength, dynamic modulus of elasticity, total porosity, gas permeability and chloride diffusion coefficient of the different concretes was analysed. The use of PUR foam waste enabled the dry density of concrete to be reduced by 29-36% compared to that of the normal weight concrete (made without foam waste). The reduction of density was due to the increase of total porosity in the lightweight concretes, which also induced higher gas permeability and chloride diffusion coefficient. These negative effects on durability of concrete were lowered by improving the characteristics of the cementitious matrix. The mechanical properties of the LWAC ranged between 8 and 16 MPa for the compressive strength and between 10 and 15 GPa for the dynamic modulus of elasticity; the concrete mixture with the higher performances almost satisfied the mechanical and density criteria of structural lightweight concrete. These results show the potential of the use of PUR foam waste for the manufacture of lightweight aggregate concretes.