Influence of High-Z Filler Chemistry on the Energy-Dependent Gamma-Ray Shielding of Cement-Board Composites.

Cement-board composites were prepared at a fixed nominal filler loading to compare the attenuation response of different high-Z additives under a common mass-fraction condition. A commercial cement board was used as the host matrix, and five formulations containing 30 wt% Bi2O3, BaSO4, HfO2, WO3, or Fe were fabricated and compared with a pure pressed control. X-ray diffraction (XRD) was used to examine phase-related structural features, while gamma-ray transmission was measured with 241Am (59.5 keV) and 137Cs (661.7 keV) using a collimated NaI(Tl) spectrometric arrangement. At 59.5 keV, the linear attenuation coefficient increased from 0.3909 cm-1 for the control to 0.6423, 1.8127, 2.5464, 2.6205, and 2.7828 cm-1 for Fe-, HfO2-, WO3-, BaSO4-, and Bi2O3-containing specimens, respectively. The corresponding half-value layer decreased from 1.773 cm to 1.079, 0.382, 0.272, 0.265, and 0.249 cm. At 661.7 keV, the modified specimens remained more attenuating than the control but clustered within 0.1731-0.1842 cm-1. Within the tested conditions, the fabricated formulations showed much stronger discrimination at 59.5 keV than at 661.7 keV, with Bi2O3-, BaSO4-, and WO3-containing specimens forming the strongest low-energy group. Because the pressed-disc densities differed between the formulations, these linear-attenuation differences are interpreted as the combined response of additive identity and the resulting bulk density/compaction rather than as a chemistry-only effect. This study is a fixed-loading, two-energy screening comparison rather than a concentration or structural optimization study.