Influences of photovoltaic waste glass and alkaline activator content on microstructure, engineering performance, and CO ₂

Abstract

The application of photovoltaic waste glass (PVWG) in the production of geopolymers provides a sustainable route for the recycling of solar panel waste at the end of their lives and for the reduction of the use of conventional raw materials. In this study, the effects of the PVWG content (5–40 wt.%) and alkaline activator dosage (10–30 wt.%) on the engineering properties, CO ₂ uptake, and microstructural development of fly ash (FA)‐based geopolymer were investigated. Geopolymer specimens were prepared from class F fly ash and finely ground PVWG activated by a solid NaOH‐Na ₂ SiO ₃ system and cured under combined thermal and ambient conditions. Results show that the geopolymer performance is strongly dependent on the balance between PVWG addition and alkali activation. The optimum formulation containing 25 wt.% PVWG and 20 wt.% activator exhibited the highest compressive strength and the lowest water absorption and porosity. Microstructural analyses showed a dense aluminosilicate gel network with a stronger amorphous phase in X‐ray diffraction (XRD) patterns, a shift of SiOT band to lower wavenumbers in Fourier‐transform infrared spectroscopy (FTIR) spectra and a homogeneous elemental distribution in scanning electron microscopy with energy‐dispersive X‐ray spectroscopy (SEM‐EDS). In contrast, insufficient activator resulted in incomplete geopolymerization, and excess activator caused Na‐rich heterogeneous domains. CO ₂ uptake was strongly related to pore structure and residual alkali distribution. These results show that the optimized inclusion of PVWG can improve the performance of geopolymers and offer a promising way for the valorization of photovoltaic waste and the production of low‐carbon construction materials.