A novel approach for the development of sustainable hybridized geopolymer mortar from waste printed circuit boards

Printed circuit boards (PCB) contain metallic and non-metallic fractions (NMF) that are hazardous and toxic when disposed of in a landfill. This paper emphasizes the feasibility of using NMF reclaimed from waste PCB's as a replacement to fly ash (FA) and metakaolin (MK) in a geopolymer mortar. Geopolymer mortar mixes were prepared with five FA-MK replacement ratios of 100-0, 90-10, 80-20, 70-30 and 60-40 and for each mix FA was also replaced with NMF by 5%, 10%, 15%, and 20%. The compressive strength and microstructures of geopolymer mortar were investigated and it was found that the addition of NMF enhanced the compressive strength. Maximum strength gain was found with 30% of MK and 15% of NMF in FA. The pozzolanic action of alumino-silicates was studied through SEM and XRD which reflected the formation of C-S-H gel with a dense geopolymer matrix along with the formation of CaCO3 crystals resulting in strength gain. The experimental studies provide a practical and sustainable recycling approach for the use of NMF in geopolymers for the construction industry.