This research partially replaced cement with coconut shell ash (CSA) to produce seven concrete samples, assessing the influence on the thermal, structural and mechanical characteristics of the resulting concrete for radiation shielding application. 3.8 kg of coconut shell was washed, dried and burnt (in muffle furnace at 200 °C) into ashes of total weight 0.38 kg at 10% yield/weight. The resulting ash was pulverized and sieved to fine powder. The control concrete (cement, sand and granite) was mixed with varying percentages of ordinary-CSA and barite-lime-modified-CSA to form seven samples. The sample's densities which ranged between 2.2 g/cm3 to 2.40 g/cm3 were obtained by Archimedes’ method. The XRD results revealed the presence of albite, muscovite, quartz and orthoclase feldspar across our samples. A good thermal stability against high temperatures, as well as improved mechanical strength were noticed with increased barite-lime-modified-CSA. Compared to the control concrete CSA-0.00, the LAC of CSA-0.05, CSA-0.10, and CSA-0.15 decreases by 4.43%, 5.28%, and 3.03% at γ-ray energies of 0.081 MeV, while that of CSA-CH-B-0.05, CSA-CH-B-0.10, and CSA-CH-B-0.15 respectively increased by 8.77%, 10.20%, and 14.65% at the same γ-ray energies. Sample CSA-0.15 and CSA-CH-B-0.15 showed greatest waste-management (WM%) with 90% cost-effectiveness. Therefore, the introduction of barite-lime-modified-CSA to concrete matrix increases the mechanical, thermal and γ-ray shielding properties of the concrete materials, with CSA-CH-B-0.15 as optimum combination for concrete in shielding application, indicating that barite-modernized-CSA additive have positive impact on the γ-ray shielding performance of concrete compared to ordinary CSA additive.