Valorization of e-waste as a novel supplementary cementitious material in LC³ system

With the global proliferation of electronic devices, the accumulation of electronic waste (e-waste) has become a critical issue, and the most challenging component to manage in e-waste is printed circuit boards (PCBs). This study systematically analyzed the characteristics of waste PCBs and proposed high-efficient modification methods to mitigate their adverse effects when incorporated into cementitious materials. The pulverized modified PCBs were used to develop a low-carbon cementitious material—PCB calcined clay cement (PC³), aiming at reducing the carbon emissions of cement and disposal of e-waste. Through mineral composition analysis, microstructural characterization, and leachate testing, it was found that pre-soaking of PCB in alkaline solutions effectively reduced the air content in PC³, and low-temperature heat treatment removed most organic compounds, thereby exposing reactive SiO₂ and enhancing its pozzolanic reaction. This resulted in refined pore structures and improved the mechanical properties. Compared to limestone calcined clay cement (LC³), PC³ prepared with PCB powder treated with alkaline solution and heat treatment exhibited smaller threshold pore size and lower porosity. Moreover, the heavy metal concentration in the leachate of pretreated PCB powder was significantly reduced, and the leaching behavior of both the raw material and the PC³ paste complied with the limits specified by the TCLP. This low-carbon cementitious material provides a new pathway for e-waste management and the sustainable development of construction materials.