Properties of Recycled Polystyrene and Polypropylene Bounded Concretes Compared to Conventional Concretes

Abstract

Thermoplastic recycled polystyrene (rPS) and polypropylene (rPP) bounded concretes were formulated by thermal curing. Mechanical properties, thermal crack-healing efficiency, and moisture and temperature susceptibility of the rPS-bounded and rPP-bounded concretes were evaluated with respect to portland cement and asphalt concretes (PCCs and ACs, respectively). The rPS-concrete exhibited a compressive strength slightly higher than that of the ACs. In contrast, rPP-concrete possesses much higher compressive strength, approximately threefold that of the ACs, which is almost equivalent to the strong PCC. However, rPS-concrete demonstrates the highest bending resistance, more than the ACs and twice as rigid as the PCCs, while rPP-bounded concrete was only stiffer than the ACs. The rPS-concrete exhibited flexural strength greater than both the PCCs and the ACs, and the rPP-bounded concrete showed approximately threefold and fivefold bending strength of the PCC and ACs, respectively. A simple crack-healing efficiency assessment test was proposed. Results indicate the high feasibility of utilizing heat treatment to successfully repair cracks at early formation for the thermoplastic recycled plastic concretes (TRPC). The rPP-bounded and rPS-bounded concretes showed better moisture resistance and much lower thermal sensitivity than the ACs.