Impact of recycled plastic waste on the corrosion behaviour of steel rebar in concrete

This study examines the corrosion behaviour of steel rebar in concrete with recycled plastic waste (RPW) from single-use plastics as a partial replacement for conventional fine aggregate. The use of RPW in concrete helps reduce environmental impact and reliance on natural sand. To improve bonding between RPW and the cement matrix, RPW was chemically treated. Five RPW content levels (0, 5, 10, 15 and 20%) and two RPW types (treated and untreated) were considered. Concrete permeability was evaluated through water absorption, sorptivity and chloride ion penetration tests. Corrosion behaviour of embedded steel rebars was assessed using electrochemical impedance spectroscopy and potentiodynamic polarisation techniques under accelerated conditions with 3.5% NaCl solution in alternating wet-dry cycles. Open circuit potential was monitored throughout. The study revealed that using T-RPW fine aggregate reduced water absorption by 16.1% and increased resistance to chloride ion penetration by 17.3% compared to UT-RPW at a 20% replacement level. Additionally, the corrosion rate for T-RPW (0.0144 mm/year) was 50% lower than that of UT-RPW (0.0288 mm/year), highlighting its effectiveness in enhancing concrete durability. This study highlights both the benefits and limitations of using treated RPW as a sustainable alternative in concrete.