Abstract: Concrete nuclear reactors could be improved in terms of life safety by adding boron carbide. This study presents an experimental investigation of the physical, mechanical and microstructural properties of Portland cement concrete containing boron carbide (B4C) as a neutron radiation-absorbing material for nuclear reactor applications. The boron carbide powder additions were 5 and 20% of the cement weight. The water-to-cement ratio of the concrete design mix was 0.4. The results show that the concrete density decreased as the percentage of boron carbide content increased. The results also show that concrete with a 0% content of B4C produced the highest compressive strength (32.73 MPa) and that the addition of 5 and 20% B4C produced a negligible reduction of strength (<2% compared with 0% B4C concrete). Scanning Electron Microscopy (SEM) results confirm that the addition of boron carbide to Portland cement concrete reduces the strength and density of concrete because the morphology of samples containing 5 and 20% B4C by weight (wt.) shows a more porous concrete microstructure compared with the control samples. Energy Dispersive X-ray (EDX) analysis was used to conclude that the higher content of B4C results in a lower percentage of calcium in the concrete which in turn reduces the strength. Up to 20% B4C powder by weight can be added to concrete which produces minimal strength reduction.