Use of irradiated PET plastic waste for partially replacing cement in concrete?

Portland cement used in the manufacture of concrete is responsible for an estimated 5-8% of the global CO₂ emissions. Recently published work (Schaefer et al., 2018) claims that γ-irradiated PET waste powder can be used as a partial replacement of cement in concrete for reducing its CO₂ footprint. More specifically, exposure of PET to γ-irradiation at a dosage of 100 kGy alters its crystal structure and chemical composition, which in turn leads to a smaller reduction in concrete strength compared to non-irradiated PET waste. Hence, making it possible for irradiated PET waste to be used as a raw ingredient in the manufacture of concrete while at the same time diverting significant quantities of PET waste from landfills. The aim of this research was to independently assess and verify the above claims. For this purpose, the effect of different low irradiation dosages (0, 10 and 100 kGy) and different replacement levels (2.5 %, 5 % and 10 % by volume) of cement by PET waste on the consistency and mechanical strength of pastes and mortars was determined in a laboratory investigation. XRD, TGA and DSC were also used to study the effect of irradiation on the microstructure of raw PET waste and the microstructure of paste and mortar samples containing irradiated PET waste powder. Our results indicate that use of γ-irradiated PET waste (exposed to an irradiation dosage of up to 100 kGy) for partially replacing cement does not lead to a significant recovery of mechanical strength lost when non-irradiated PET waste is used.