*Kaolin, *Quartz, *Size reduction of materials, *Slag, *Polymer-impregnated concrete, *Radiation shielding, *Astrophysical radiation, *Fast neutrons

In this study, metakaolin based geopolymer mixtures using granulated blast furnace slag and different sizes of quartz aggregate were thermally cured at 30–60–90°C for 4, 6, and 8 h. Sodium hydroxide and sodium silicate were used as alkali activators in the experiments. Early (1 d), and 28-days mechanical strengths, transport (capillarity) properties, unit weights at hardened stage, microstructural features of the mixes obtained at different curing time and curing temperature were observed. The compressive strength of the geopolymer mixtures was measured between 41.7–106.5 MPa, at early ages; and the 28 days compressive strength between 23.6–80.5 MPa. The flexural strengths varied between 7.2–22.9 MPa for 1 d. Increased the curing temperature and curing time tended to surge the mechanical properties of the mixtures while increasing aggregate size tended to decrease these properties. The unit weights of the samples at hardened stage are between 2256–2358.4 kg/m3. The capillary water absorption coefficient of the produced samples was measured as 0.015–0.059 kg/m2.min0.5. In matrix of the geopolymer mixture zeolitic phases and NASH structures were observed in XRD, SEM and FT-IR results. It was observed that quartz aggregate, blast furnace slag and metakaolin-based geopolymer with an early compressive strength of 106.28 MPa can be observed at short curing time as little as 6 h. Moreover, using experimental and theoretical approaches, photon and fast neutron radiation shielding properties of geopolymer mixtures were examined. Our results showed that the particle size reduction of Quartz aggregate improves the photon and neutron attenuation abilities of the mixture. Since the reduction in particle size enhances the radiation shielding properties as well as the mechanical strength, the produced geopolymer mixtures can be useful materials in the design of nuclear radiation facilities and spaces where advanced radiation applications are made. [ABSTRACT FROM AUTHOR]

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