Mechanical properties of concrete made with fluff

A detailed investigation on the use of automotive shredder residues, the so-called fluff, as an alternative aggregate of structural lightweight concrete, is the subject of the present paper. Specifically, a new granulated fluff, obtained through a granulation process already used to treat returned concrete, substitutes the traditional gravel made with expanded clay. Slump values are measured with the slump cone test on fresh concrete, whereas the depth of penetration of water under pressure, and the uniaxial compressive tests as well, are performed on hardened concrete cylinders. As a result, a new parameter, herein called “inconsistency parameter”, is introduced and used to define both the mechanical properties (i.e., the strength and ductility) and the workability of the lightweight concretes made with virgin or plastic waste aggregates. According to the required structural performances in service, the optimal value of the inconsistency parameter can be defined as a function of both the water/cement ratio and the content of the granulated fluff.