A preliminary investigation on gamma-rayattenuation of alkali-activated concrete waste based-geopolymer modified with pozzocrete-fly ash

Abstract

In the current investigation, pozzocrete fly ash (PFA) was employed to assess its effects on physical, mechanical and radiation shielding properties of alkali-activated geopolymer mixtures prepared using calcined concrete waste-based dolomite aggregate (DCW). Two series of geopolymer samples comprising 6% and 10% sodium hydroxide as alkaline activator were designed. Concrete waste was partially substituted by PFA at levels of 0%, 10%, 15%, 20% and 30%, by weight. Bulk density, compressive strength, attenuation coefficients (μ & μm) as well gamma transmission factors (half-value layer, HVL; tenth-value layer, TVL and mean free path, MFP) of studied samples were determined at different hydration times. The gamma attenuation coefficients of the blend were experimentally conducted with NaI (Tl) scintillation detector utilizing radiation sources namely Cs-137 with photon energy of 0.662 MeV and Co-60 with photon energies of 1.173 and 1.333 MeV. The inclusion of 15% PFA in DCW-geopolymer system alkali-activated with 10% NH has resulted in the enhancement of both physical and mechanical properties. In a similar fashion, this geopolymer composite demonstrated superior performance in terms of attenuation of gamma rays through a 5 cm thickness shield over the corresponding mixtures.