Improving the strength of radiation shielding concrete and the safety of corresponding structures is crucial. However, radiation shielding ultra-high performance concrete (RS-UHPC) often faces the issues of high volume shrinkage and easy cracking. Using barium alumino-silicate-based ceramic as aggregate in concrete is a promising solution for its internal curing effect and excellent radiopacity. In this study, a barium alumino-silicatebased ceramsite (BASC) was developed using bauxite, coal gangue, and barite. The effects of boric anhydride (2 %, 5 %, 8 %), barite powder dosages (20 %, 40 %, 60 %, 80 %), and sintering temperature (1260 degrees C, 1280 degrees C, 1300 degrees C, 1320 degrees C) on the apparent density, compressive strength, and water absorption of the ceramsite were investigated. The microstructure and reaction mechanism of the BASC were analyzed using TG-DSC, XRD, SEMEDS, and low-field NMR techniques. The results showed that the addition of barite increases the apparent density of ceramsite but decreases its strength. The ceramsite with 60 % barite calcined at 1320 degrees C has a density of 3120 kg/m3, water adsorption of 11.19 %, and a cylinder compressive strength of 11.2 MPa. The prepared BASC ceramsite exhibits a highly connected pore structure and good water retention capacity at this temperature. The ceramsite has many closely packed celsian and corundum crystallites, which give it good mechanical strength. Finally, the gamma-ray attenuation and autogenous shrinkage of UHPC prepared with this ceramsite was tested. The linear attenuation coefficient of the BASC-UHPC is 0.176 cm-1, comparable to UHPC prepared with lead glass. The BASC replacement for quartz sand reduces the 28d autogenous shrinkage of UHPC by 55.0 %. The research results can guide the application of BAS-based ceramsite in radiation-shielding ultra-high performance concrete.
