A thermodynamic perspective on wind turbine glass fiber waste as a supplementary cementitious material

By the year 2050, glass fiber reinforced polymer (GFRP) material from decommissioned wind turbine blades is expected to generate 40 million tons of waste worldwide. Managing GFRP waste is a vexing problem since the materials cannot be easily recycled. One potential waste management solution is to use the glass fiber (GF) component of GFRP as a supplementary cementitious material (SCM) to replace cement in concrete, which has the additional benefit of reducing CO₂ emissions from cement clinkering. The chemical composition of wind turbine GFs is variable, but is predominantly calcium, silicon, aluminum, and iron, with trace amounts of light and heavy metals, making it an attractive candidate for use as SCM. In this study, thermodynamic modeling was used to evaluate the reaction products, pore solution chemistry, and trace metal immobilization potential of three GF compositions (high silica; high calcium; median calcium/median silica) at varying cement replacement levels. These factors influence pore size and structure, which control mechanical properties, freeze-thaw behavior, transport properties, and corrosion potential. For all GF compositions, replacement levels up to 60% produce cementitious materials with higher volumes of C-S-H (and higher alkali and trace metal binding potential) than control mixtures; pore solution pH values appropriate for mixture designs optimized for either ASR or corrosion prevention; and, at replacement levels below 10% and above 40%, reaction of some trace metals to form insoluble precipitates. While further experimental investigation is essential, these models present evidence that the use of wind turbine GF as an SCM is a viable solution for managing this expanding waste stream.