Experimental Investigation of Radiation-Shielding, Mechanical and Thermal Properties of Colemanite-Modified Gypsum-Based Composites

In this study, the radiation-shielding, mechanical, microstructural, and thermal properties of gypsum-based composites modified with thermally treated colemanite were investigated. Composite samples containing 1, 2.5, 5, and 10 wt.% colemanite were prepared, and the additive was pre-treated at 650 °C to improve its stability and compatibility with the matrix. Gamma-ray attenuation was evaluated at different photon energies, and neutron attenuation was determined using a 241Am–Be source. The results showed that colemanite addition improves gamma-ray attenuation, particularly at low and medium energies, with the best performance observed at 2.5–5 wt.%. Neutron attenuation increased with an increasing colemanite content due to the presence of boron. Compressive strength exhibited a non-linear trend, reaching its maximum at 2.5 wt.% and decreasing at higher contents due to microstructural changes. Thermal conductivity also showed non-linear behavior, with the lowest value obtained at 5 wt.% colemanite. SEM and FTIR analyses confirmed the incorporation of colemanite and its influence on the microstructure. Overall, the results indicate that colemanite-modified gypsum composites provide a balanced combination of radiation-shielding, thermal insulation, and mechanical performance.