Experimental bond behaviour of reinforced concrete with recycled plastic aggregates

In this work, the performances of an innovative concrete produced by partially replacing coarse and/or fine aggregates with recycled plastic grains are experimentally investigated. More in detail, the research is focused on the production of structural concrete, suitable to be used with steel reinforcement. The plastic used for this study derives from industrial processing waste, usually disposed of in landfills but for this study recycled in the form of grains from a mixture of 50% low-density polyethylene and 50% polyamide. Since as known the substitution of natural with plastic aggregates determines a mechanical strength reduction, proper admixtures are formulated so to guarantee the reaching of a minimum strength class also for concrete with recycled plastic aggregates. The experimental program aims to find out the influence of recycled plastic aggregates in particular on the bond-slip behaviour of the innovative concrete produced, by performing a set of pull-out tests on reinforced concrete specimens specially designed to this scope. Two steel bar diameters are considered, and the observed different failure modes are properly discussed. By comparing the obtained experimental results to those of a traditional concrete, some interesting considerations can be derived to evaluate possible uses of this sustainable concrete developed in the perspective of circular economy