Abstract
The use of geopolymer-based concrete has become a viable alternative for mitigating of the ecological and socioeconomical issues related to the production and utilisation of Ordinary Portland Cement (OPC) in radiation shielding concrete. However, geopolymer preparation can be achieved through different alumina-silicate precursors whose chemical composition are not the same, hence, shielding competence of the geopolymer-based concrete could vary widely. This study was aimed at evaluating the gamma photon shielding competence of blast furnace slag-based geopolymer concrete. Geopolymer concrete was prepared using aggregates and geopolymer gel. The geopolymer was prepared using metal slag as precursor and a solution of NaOH and Na2SiO3 as the alkali activator. The prepared concrete was prepared and oven and ambient air for 7, 14-, 21-, and 28-day periods. The cured concrete was then subjected to density measurement, compressive strength (CS) test, chemical composition analysis, and shielding characterisation. The density and CS increased from 2.56 g/cm³ to 2.79 g/cm³ and 21.34 MPa to 39.67 MPa for OPC-based control concrete (OPC-CC), respectively, while the corresponding ranges for geopolymer-based concrete (GP_CC) were 2.81 g/cm3 –3.87 g/cm³ and 23.32 MPa –43.52 MPa as the curing period increased. OPC-CC had higher CaO content, while the silicate content of GP_CC was relatively higher. For OPC_CC the mass attenuation coefficient (MAC) and linear attenuation coefficient (LAC) decreased from maximum values of 17.2368 cm²/g and 38.145 cm^-1 to 0.0232 cm²/g and 0.0513 cm^-1, respectively. On the other hand, the range of MACs and LACs for GP-CC are 0.0225 cm²/g – 14.5582 cm²/g and 0.0546 cm^-1– 35.2455 cm^-1. The fast neutron removal cross-section of GP_CC was higher than that of OPC_CC. The gamma photon and fast neutron interacting abilities of GP_CC was better than that of OPC_CC for gamma energies above 0.40 MeV. The shielding ability of GP_CC was comparable to some traditional shielding materials. The GP_CC can be used for radiation shielding concrete in radiation facilities.

Key words: Compressive strength; Concrete; Geopolymer; Metal furnace slag; Radiation shielding