Green public procurement applied to partially precast reinforced concete slabs

To build environmentally friendly public constructions, authorities impose tailoring concrete mixtures with a minimum content of recycled materials. To satisfy this green public procurement (GPP) in frame structures, whose mass is mainly distributed on horizontal diaphragms, it is necessary to draw attention to the slabs of floors. As ready-mixed concrete with recycled materials is not easily available on the market, partially prefabricated one-way slabs, composed by both cast-in-situ concrete and precast plates (generally called predalles) were investigated. Only the precast concrete of predalles contained recycled materials, such as supplementary cementitious materials (SCM) in place of CEM I, recycled concrete aggregate (RCA) and rubber to replace stone aggregate, and recycled steel fibers (RSF). These materials were used to cast full-scale one-way slabs, subsequentially tested in three-point bending. A three-stage model, based on the equivalence between the traditional rebar and RSF, was also introduced to predict the load-deflection responses of the slabs. As results, both numerical and experimental analyses revealed the effectiveness of RSF, which can be added to concrete mixtures to compensate the loss of flexural strength that the substitution of virgin materials produces. Thus, if large quantities of SCM, RCA, rubber, and RSF are in the concrete of predalles, slab can satisfy both GPP and the mechanical performances, though the cast-in-situ concrete does not contain any recycled material.