Prospects of using chars derived from mixed post waste plastic pyrolysis in civil engineering applications

Pyrolysis provides a sustainable solution for managing post-consumer mixed plastic waste (PC-MPW) streams by producing valuable mixtures of liquids and gases, which have potential for use as fuels. Compared with landfilling, gasification and incineration processes, pyrolysis has the smallest environmental footprint. Waxes produced as an intermediate product of controlled pyrolysis conditions have been used as viscosity-reducing additives in modified asphalts, which reduce energy requirements for heating and mixing on site. The chars produced from PC-MPW pyrolysis have been used to produce activated carbon (adsorbents), additives in epoxy resins and fuel briquettes. These chars have proven to increase the conductivity, thermal stability and non-flammability of epoxy resin composites. Furthermore, the chars also have potential as additives in concretes to reduce the carbon footprint associated with Portland cement production. Albeit PC-MPW-chars have not been used in civil engineering applications to date, chars derived from other organic sources (e.g. wood) have been successfully used in cement admixtures and demonstrated their atmospheric carbon sequestration and strength gaining capabilities. The material properties of the chars that are responsible for producing such promising performances include high porosity (which enables water absorption and retention capacities), high surface area and reactivity (particularly for chars produced at higher pyrolysis temperatures) for promoting the formation of cementitious gels. Furthermore, pulverised chars act as a “micro-filler” within cementitious materials, whereby they fill pore spaces and increase material strength and stiffness. This study highlights the promise of PC-MPW chars as a low carbon additive for use in cement-based construction materials. •Pyrolysing plastic waste has lower CO2 emissions than other energy recovery methods.•Waxes from plastic pyrolysis are used to reduce rubber modified asphalt viscosity.•Replacing cement with biochar has microfiller effects and contributes to hydration.•Pyrolysed plastic chars can be used as additives in epoxy resins and fuel briquettes.•Plastic chars have prospects as sustainable additives in cementitious materials.