Effect of hybrid nanoparticles additions to normal weight concrete on its microstructures and mechanical properties before and after exposure to gamma-rays

•Adding nanomaterials to NWC improves the hydration process and decreases the pores.•The pozzolanic nature of nanomaterials increased the CSH and decreased CH.•Hybrid nanomaterials showed a positive effect on the mechanical properties of NWC.•Adding nanomaterials to NWC increases the resistance to Gamma irradiation.•Nano-silica showed the best nanomaterials for improving concrete behavior. The present work adopts the synergistic effect of improving concrete radiation shielding using three different nanoparticles. This research aims to add single or hybrid nanoparticles, i.e., nano-silica, ceramic, and metakaolin (NS, NC, and NMK), to normal-weight concrete to reduce the effect of gamma radiation. The weight percentages of nanomaterials as a cement replacement were 3% NS, 6% NC, and 2% NMK. Two combinations of nanoparticles, namely, 3% NS + 2 %NMK and 3% NS + 6% NC, were made to examine the synergistic effect of the present hybrid nanoparticles. Irradiated specimens were exposed to a source of Cobalt 60 (Co−60) for 250 days at a rate of 2 Mrad/day. Adding single or hybrid nanoparticles to concrete improved its compressive, tensile, and flexural strength. After exposure to gamma radiation, the residual compressive strength of different concrete types ranged between 63% and 73%. The microstructural characterizations of un-irradiated and radiated showed that concrete with hybrid nanoparticles had a high radiation shielding due to a significant decrease in the percentage of pores.