Valorization of spent Zn-C battery and construction and demolition waste (CDW): Fabrication and characterization of geopolymer composites for radiation shielding applications

There is a serious threat of pollution due to the high waste of energy and materials worldwide that needs to be decreased. One way is to reduce waste or use them in secondary processes. New eco-friendly geopolymer binders were fabricated using metakaolin, CDW, and battery waste (BW) powders as starting materials and a mixture of potassium silicate and sodium hydroxide as activation solutions. 5 formulations with BW powder replacements ranging from 5 to 40 wt% were prepared and subjected to heat curing at 80 °C for 24 h. The effect of Zn-C battery waste content on the phase composition, densification, microstructure, mechanical, and gamma shielding properties of the obtained geopolymer composites was investigated. The results revealed that incorporating battery waste reduced the density and mechanical strength of the geopolymer composites. Additionally, microstructural analysis indicated that synthesized geopolymers consisted of unreacted CDW and BW particles embedded in a geopolymer matrix with a low degree of compactness. The effect of BW replacement on the shielding capacity was also evaluated experimentally and theoretically. The gamma transmission experiments proved that the addition of BW caused a reduction in the radiation shielding ability of the composites when they were exposed to 137Cs and 60Co gamma-ray sources. Finally, the variation of the main attenuation parameters (MAC, HVL, EBF, and EABF) with photon energy was also obtained theoretically. The outcomes of this investigation can provide a basis for the design of new CDW-based geopolymers for radiation shielding applications in the context of a circular economy.