The effect of melted-spherical and crushed CRT funnel glass waste as coarse aggregates on concrete performance

Waste management regarding discarded cathode ray tube (CRT) funnels glass has become a major concern worldwide due to its potential toxicological threat on the environment and surrounding population health. Conventional recycling process of CRT funnel glass waste typically involved a method of crushing and reutilization as fine aggregates for concrete works. However, this approach has been facing serious repercussions in terms of lead (Pb) leaching and concrete expansion due to the accompanying alkali-silica reaction (ASR). Hence, this study investigates the potential of exploiting alternative recycling method which incorporate the technique of melting and annealing in producing spherical CRT funnel glass (GS). CRT concrete containing GS and crushed CRT funnel glass (GC) as coarse aggregates in various ratios were tested for its properties concerning; workability, voids, mechanical strength, water absorption, drying shrinkage, alkali-silica reaction (ASR), leaching of Pb, and microstructure. Findings from this study had discovered the utilization of GS to have decreased the Pb leaching rate (0.516 mg/L) and ASR expansion (0.035%), which may be attributed to the minimal formation of micro-cracks as evidenced in the scanning of electron micrograph. Despite its strength reducing properties, combination of GS and GC at a specified ratio of 0.6:0.4 was found capable to achieve the highest CRT concrete strength of 64 MPa, only 12% lower than the control concrete specimen. Essentially, this research findings underpin the opportunities in the exploitation of recycling the CRT funnel glass as aggregate in the form of melted-spherical glass.